What Solar Panel To Charge 12V Battery?

What size solar panel do I need to charge a 12v battery? Authors Note: This has been updated on Feb 9, 2022 with updated information, links, and resources. What to know about using 6 volt batteries in your solar installation If you live in an RV, van, or cabin, solar with battery storage is a great way to meet your energy needs.

Once you’ve selected your solar panel kit, you’ll need to purchase a battery to store that energy produced from your panels. But how do you make sure that battery gives you the power you need and how do you know that solar panel will charge that battery effectively? Let’s break it down. What are deep cycle batteries? Deep cycle batteries may look similar to the batteries used in your car, but they are actually very different.

In contrast to car batteries which only provide short bursts of energy, deep cycle batteries are designed to provide sustained energy over a longer period of time. Deep cycle batteries can be discharged up to 80%, but most manufacturers recommend not discharging below 45%. How do you charge batteries with solar panels? Can you charge solar batteries without charge controller? The answer is necessary and obvious, solar panels with batteries need a charge regulator which will be responsible for maintaining the charge of the batteries and keeping them in good condition.

Solar batteries store the energy that is collected from your solar panels. The higher your battery’s capacity, the more solar energy it can store. In order to use batteries as part of your solar installation, you need solar panels, a charge controller, and an inverter. When using batteries for solar panels as part of a home solar system, you’re able to store the excess electricity your panels produce instead of sending that energy back into the grid.

Electricity will be sent to the grid if your batteries are fully charged and your panels are still producing energy. Your solar panels will first need to be connected to a charge controller which will help monitor how much energy is stored in the batteries to prevent overcharging.

Charge controllers will also shut down a system if the batteries become too depleted. Before powering your appliances, your batteries will need to be connected to an inverter to convert the DC energy collected from solar panels and converted to AC energy. What are amp hours? Deep cycle batteries have a specific amp hour rating.

This refers to the amount of current that is supplied from the battery over a certain period of time. If you have a 200ah battery, it can supply 20 continuous amps for 10 hours or 10 amps for over 20 hours. How many amps does a 100 watt panel produce? Calculate the current in amps by dividing power in watts by the voltage in volts.

When a 12V solar panel is rated at 100W, that is an instantaneous voltage rating.
So if all of the test conditions are met, when you measure the output, the voltage will be about 18 volts.
Since watts equals volts times amps, amperage will be equal to 5.5 amps (100 watts divided by 18 volts),
So your panel will produce 5.5 amps per hour.

How many panels would I need to charge a 200ah battery? If you have a 200ah battery, only 80% of that is usable due to depletion limitations, so you really only have 160 amp-hours of energy to draw on. If you learn that you typically can last two days with energy from that battery, that means you consume 80 amp hours a day.

Based on the earlier calculation, a 100 watt panel will produce an average of about 30 amp-hours per day (based on an average sunny day).
This means you would need three 100 watt solar panels or one 300 watt panel to fully recharge your battery on the average day.
How long will it take to charge a battery? Total charging time depends on the weather, as well as state and type of battery.

If a battery is completely drained, a panel can typically charge the battery within five to eight hours. The total charging time will vary depending on the state of a battery. If a battery is totally drained, a solar panel can energize the cells within five to eight hours.

The position of the sun in the sky can impact a panel’s charging speed.
When sunlight shines directly on a panel in the middle of summer, the charging speed will be faster.
Charging cycles are slower on cloudy days.
How many solar panels does it take to charge a 100ah battery? Again we use the same calculation dividing power in watts by the voltage in volts to find amps.

Charging your battery at 12 volts and 20 amps will take five hours to charge a 100 amp hour battery. By multiplying 20 amps by 12 volts, 240 watts is how big of a panel you would need, so we’d recommend using a 300w solar panel or 3 100 watt solar panels. What are the best conditions to charge a battery? You’ll find that all of Renogy’s deep cycle batteries have a normal operating temperature, storage temperature, and operating charge temperature specifications listed. Most batteries have a normal operating temperature of 77°F plus or minus 5.4°F.

Most batteries have an ideal operating temperature between 50°F and 85°F. Batteries typically lose about 10% of their capacity for every 15°F to 20°F below 80°F. Their internal chemistries slow down, resistance increases and capacity and charge acceptance drop. This reduced capacity is temporary. Does it matter what kind of battery you use? Yes! Different batteries can have a huge impact on how your solar installation operates.

There are three main types of deep cycle batteries used in solar systems: flooded lead acid, sealed lead acid, and lithium iron phosphate batteries. Each of these batteries vary in price, battery capacity, voltage, and cycle life. For example, battery capacity is important because it measures the amount of energy you can store.

If you need to power certain appliances for long periods of time, you’ll need more batteries to carry a bigger load. Capacity is measured in total amp hours. Look at cycle life to learn about the number of discharge and charge cycles a battery can provide before the capacity drops below the rated capacity.

This varies sharply from technology to technology and is measured in a number of cycles. For more information about battery types and how to choose the best battery for your system, refer to our blog post, Do lithium batteries charge faster than flooded lead acid batteries? Lithium iron phosphate batteries are more efficient than sealed and flooded lead acid batteries.

They also have a faster rate of charge. This is because they can typically handle a higher amperage, which means they can be recharged much faster than flooded lead acid batteries. Lead-acid batteries are limited in how much charge current they can handle, mainly because they will overheat if you charge them too quickly.

In addition, the charge rate gets significantly slower as you approach full capacity. How do I size my battery bank and why is it important? It’s very important to properly size your deep cycle battery bank. The amount of battery storage you need is based on your energy usage.

Energy usage is measured in kilowatt hours.
For example, if you need 500 watts for 8 hours per day, then your energy usage is 4kWh per day.
A battery capacity of 4 to 8 kWh is usually sufficient for an average four-person home.
Your energy needs may greatly differ from that depending on what you’re powering in your household.

To size a system that will best fit your needs, we recommend making a list of all the devices you plan on running. Get the wattage information, or the amps and volts of the product, and provide an average run time per device. The Renogy solar panel calculator is a great tool that makes it a quick and easy process to help determine your specific needs.

Battery Capacity Sizing your solar panels to charge a 12v battery depends on several factors. You must consider your battery capacity and your expected discharge rate before sizing your solar panels to suit your needs. After you’ve determined these two factors, you can determine what size solar panel will be sufficient to charge your 12v battery.

Your 12v battery capacity should be listed on your battery’s specification sheets or printed on the outside of your unit. Typically, capacity is listed in amp-hours (Ah). A battery that has a 100Ah capacity will be able to provide 100 amps of power for one hour or 10 amps for 10 hours.

If you have multiple batteries working together in a system, you may need to do some calculations to determine your battery bank’s total capacity and voltage. If you have multiple battery banks wired together in parallel, you simply add the Ah ratings together to determine your total capacity and keep the voltage the same.

For example, if you have three 100Ah 12v batteries wired in parallel, you would have a total battery bank capacity of 300Ah at 12 volts. If your batteries are wired together in series, you are instead adding the voltages of the battery together while capacity remains the same. Expected Discharge Rate Calculating your discharge rate is important if you intend to continue using your batteries while they are charging. If you have appliances that run around the clock — such as a refrigerator, air conditioner, or lights — determining their expected power draw will help you to ensure that your solar panels are powerful enough to both keep your appliances operating and charge your battery banks.

Power draw is typically expressed in watts, just like solar panel production capacity.
It may be easier to understand how your battery capacity can handle power draw by converting amp-hours to watt-hours.
Using a 300Ah 12v battery system as an example, multiply the amp hours by the voltage to determine your capacity in watt-hours; in this case, 3600 watt-hours (Wh).

A battery bank of this size can operate an appliance that consumes 300 watts for approximately 12 hours. Determining the draw of your appliances can be done similarly. Most appliances will give you some indication of their expected power consumption. Look at the charging cord, the bottom or back of your appliance, or the charging block — it should indicate either wattage or show you a voltage and amperage rating.

Refrigerator: 150 Watts x 4 Hours = 600 Wh Six LED Lights: 6 x 5 Watts x 6 Hours = 180Wh Air Conditioner: 1000 Watts x 2 Hours = 2000 Wh Total Expected Daily Discharge: 600+180+2000 = 2780Wh

Now that we have our expected discharge rate of 2780Wh, we can determine the size needed for our solar panels. Sizing Your Solar Panels Continuing with our example of a 300Ah 12v battery (with a 3600Wh capacity) and an expected daily discharge of 2780Wh, we can determine what size solar panels we need to both keep our appliances operating and fully charge our battery banks.

To operate these devices alone, you will need 2780Wh of power.
Ideally, your solar panels will provide more than enough power to the system than needed to meet your daily needs alone, allowing your batteries to charge to maximum capacity for overnight use or periods in the shade.
If you add your total battery capacity to your expected daily usage for a total of 6380Wh, you can fully charge your 12v batteries from empty while simultaneously running all of your appliances.

Working with the 6380Wh estimate, we can calculate the power required from the solar panels. Solar panels are sold by watt, so this calculation is relatively straightforward, but there are certain components to keep in mind. The main consideration is that solar panels don’t always operate at their peak efficiency, so estimating a 70% power production from each panel will give you a more accurate representation of their power production in typical use.

To reach 6380Wh in a typical 12 hour day, we follow a simple calculation: 6380Wh (desired energy production) / 12 hours (average hours of daily sunlight) = 531.67 Watts.
In this example, we need the solar panels to produce 532 watts per hour for 12 hours to meet our energy goals.
Using our 70% power production estimate from earlier, we can further calculate: 531.67 Watts / 0.7 = 759.52 watts.

This calculation brings us to the size of the solar power system we would need to appropriately power our 12v battery system while including daily consumption. Combining Solar Panels for 12-Volt Battery Systems If there isn’t a single solar panel that meets your energy needs, you can combine multiple panels to reach the desired wattage.

For our above example, you could combine four 200 watt solar panels into an 800-watt system to exceed the desired output of 759.52 watts, or you could combine two 400 watt panels.
When connecting solar panels in parallel or series, you need to consider what the total output voltage and amperage are so that you can select an appropriate solar charge controller.

If connecting solar panels in series, the total system voltage is the sum of each individual panel’s voltage, while the amperage remains the same. In parallel, the total amperage is the sum of each panel’s, while voltage remains the same. Conclusion It can be intimidating when you first start navigating the solar and battery options out there.

From deciphering amp hours from volts, sealed lead acid from flooded lead acid, there’s definitely a lot to consider. But by doing some simple math, properly calculating your energy needs, and learning a bit about the different battery options available to you, you’ll be well on your way to a battery bank to fit you and your household’s needs.

Now it’s time to select your own solar storage system. Whether you want a 12 volt deep cycle battery, 48v battery, marine battery, or other type of batteries, you can find a suitable one at Renogy store!

Contents

1 Can any solar panel charge a 12V battery?
2 How do you match a solar panel to a battery?
3 Will a 100 watt solar panel keep a 12 volt battery charged?
4 Can you use house solar panels for 12V?
5 How much solar power do I need for a 12V fridge?
6 What will a 30 watt solar panel run?

Can any solar panel charge a 12V battery?

How Many Solar Panels Do I Need to Charge a 12V Battery? – Me happily charging a 12V battery with one 100W solar panel You only need one 12V solar panel to charge a 12V battery. For instance, a 100 watt solar panel is a common solar panel size you could use to charge some of the most common 12V battery capacities.

What size solar panel do I need to trickle charge a 12V battery?

How Many Solar Panels Would You Need to Charge a 12V 200Ah Battery? – It is important to remember that solar panels will not function at 100% efficiency at all times. Not only are weather conditions and the way the panels are installed factors, a certain level of efficiency is lost as the power flows through your charge controller and power inverter.

Then, of course, most batteries do not hold a full charge, as their storage capabilities deplete over time.
If, for example, you were using a 200Ah 12V battery and it was only able to store 80% of that power due to depletion issues, the battery might only be capable of storing 160Ah worth of electricity.

Given that a typical 100 watt solar panel can produce an average of roughly 30Ah per day (check 100 watt solar panel specifications ), which is based on an average sunny day, you would need three 100 watt solar panels, or a single 300 watt solar panel to fully recharge your battery.

How long will a 100 watt solar panel take to charge a 12V battery?

How long does it take a 100 watt solar panel to charge a battery? – For charging batteries with solar you should gather the following information:

What is battery capacity when fully charged?Depth of discharge in regular operationIrradiance in your location? (If not known, use 4 peak sun hours as an average value.)The type solar controller to be used (MPPT is more efficient and reommended.)

As a general rule, a typical size 12v 50Ah auto battery at 20% discharge will need 2 hours to fully recharge with a 100 watt solar panel. A lead-acid deep-cycle 12v 50Ah battery at 50% discharge will take about 4 hours to fully recharge using a 100 watt solar panel. Both examples above assume a solar panel current output of 5.75 amps using an MPPT controller.

Will a 80 watt solar panel charge 12V battery?

Below is a list of 30 of the most common Solar related questions we receive from customers that could help answer some of the queries you may have. Click to view more information or contact our Support team and discuss with a REDARC team member today.

What are Watts? The Watt is the basic unit of power.
It is named after the eighteenth-century Scottish inventor James Watt.
Power = Voltage x Current, so Watts = Volts x Amps.
What are Volts? Volts is a unit of electromotive force, the volt measures how much “potential” there is in an electric circuit.

The higher the voltage, the more electrical current will flow in the circuit. What are Amps? Amperes (or Amps), is the measure of electric current. One Amp is equal to a number of electrons passing a point in a circuit each second at a certain voltage.

What are Amp hours? Amp hours is a measure of stored power. Amp hours is the number of Amps drawn, for the amount of time in hours that you draw that current. Amps x hours = AH How are Solar panels created? Solar panels (Mono or Poly crystalline) are created from multiple ‘wafers’ of silicon connected together in series and/or parallel to form a solar ‘module’.

These wafers are created from silicon ingots. The ingots are either block-cast from multiple silicon crystals (poly-crystalline) or grown to form a single crystalline structure (mono-crystalline). The ingots are cut into slices around 180 to 350 micrometers thick to form the wafers.

The ingots are generally made from p-type doped silicon, and n-type silicon is then applied as a surface layer to the wafer. This creates the n-p junction which allows the flow of electrons. Anti-reflective layers are then applied to the wafer before metallic connections are made in a grid-like pattern on the front side of the panel and a plate across the full area of the wafer on the back side.

These metallic connections are screen printed using a silver paste on the front and an aluminium paste on the back. The wafer is then fried at a few hundred degrees celsius to create contact between the silicon and the metal electrodes. The wafers are now ready to be connected to form the solar module.

How many watts do I need? The number of watts or the amount of Power you need is determined by the requirements of your system with regards to both charging and to running particular loads. The power rating or wattage of your panels determines the rate at which you can deliver charge to your system. You need to ensure that you have enough solar panels to cope with the amount of power you plan to use.

A good rule is to overrate your system so that it can cope with cloudy days and unexpected power usage. The power rating of your inverter determines what appliances you can run from your inverter. If you want to run a1800W microwave from your inverter you would need at least an 1800W inverter.

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It is important to keep in mind that running an appliance such as this from an inverter will drain your battery bank considerably. As a general rule of thumb, if you divide the amount of watts an appliance uses by 10 for a 12V system or 20 for a 24V system, this will give you the current draw on that system.

For example, an 1800W microwave will draw 1800/10 = 180A from a 12V system. What is the difference between amorphous and crystalline silicon panels? Amorphous type solar technology uses Silicon in a non-crystalline, random form. It can be deposited onto many different substrates to give effects like flexibility for use in different applications.

Amorphous type solar technology falls under the ‘thin-film’ category of solar modules. Amorphous type solar panels have a typical efficiency of around 6 – 7%. Crystalline silicon type solar technology refers to monocrystalline and polycrystalline panels. These panels are created from silicon in a tetrahedral lattice type structure.

This structure gives crystalline silicon type solar modules a higher efficiency per square meter than amorphous type modules. How many solar panels do I need? The amount of solar panels you require will be determined by the amount of charge that you need to return to your system during the sunlight hours of each day.

For a 12V system, if you need to replace 100A/h of charge to your batteries each day, and you have 8 sunlight hours in each day you will need.100AH x 12V = 1200WH 1200WH / 8H = 150W of solar panels. In reality it is recommended that you always overrate your requirements by at least 20%, therefore you would need 180W of solar panels.

How do I connect my panel to my battery? Your solar panels should always be connected through a regulator and then the regulator connected to the battery/s. A regulator is required to ensure that none of the high voltages present at the output of a solar panel during good light level conditions can damage the battery/s.

Each panel/regulator comes with a set of instructions outlining how the panel/regulator should be connected to the system.
If after reading the instructions you are still unsure of how to connect your devices please contact a qualified auto-electrician or REDARC electronics on (08) 8322 4848.
What sized wiring do I need for my system? The wiring size for your system is determined by the overall length of cable involved in the system, and the amount of current drawn over that length of cable.

The amount of current drawn by the system is related to the amount of current your solar panels can output for the cable between the solar panels and the battery, and is related to the amount of load you are planning to use for the cable between the battery and your loads.

Required cable thickness can be easily worked out using our cable size and voltage drop calculator.
What type of battery do I need for my solar setup? The type of battery you choose depends on the application for which you are using it.
It is recommended that a deep cycle battery be used as an auxiliary battery because generally an auxiliary battery is discharged to a lower level and then recharged as opposed to a starter battery which is generally kept at a particular charge level.

It is important to ensure that your regulator is designed to charge the type of battery you plan to install in your setup. Most regulators will have specific charging profiles for the four different types of automotive batteries commonly used today. It is also important to consider where the battery is mounted.

If you plan to have the battery inside a caravan for example, you must get a sealed battery because an unsealed battery will generate harmful gases during charging. Your best bet is to contact a battery supplier and discuss your requirements with them. Why do I need a regulator? A 12V solar panel is designed to output at least enough voltage to charge a 12V battery under worst case conditions (low light level, high temperature etc).

A 12V battery needs at least 13.6 volts to charge, therefore under worst case conditions a solar panel needs to output at least 13.6 volts. This means that in perfect conditions a 12V solar panel may output around 17V or more. If you plug a solar panel, which is generating 17V, straight into your battery it is easy to understand how this can cause damage.

Solar regulators are designed to accept the voltage from the solar panel, and output a voltage that is safe and useable to charge a battery.
A good regulator will incorporate a 3 stage charging output.
What can I run on my 80 Watt Panel? An 80W solar panel can realistically supply between 4 and 5 Amps on a sunny day, for most of the sunlight hours of the day.

If we assume that only 1/3 of the day is sunlight hours then it is safe to assume that the panel can supply between 4 and 5 Amps for this period. Given that there are 24 hours in a day, an 80W panel can effectively run a load of around 1.5A continuously throughout the day/night running at no loss.

Let’s assume that the solar panels are charging a 100A/h battery.
You wish to run a 50L Fridge which draws on average 3A, and 2 x LED camp lights which draw 0.25A each when running.
You want to run the fridge 24 hours a day, and the camp light for 6 hours each night.
Fridge: 3A x 24h = 72Ah Lights: 0.25A x 6h = 1.5Ah x 2 lights = 3Ah Total: 75Ah per day.

Your panels can supply: 4.5A x 8h = 36Ah each day. Therefore the battery is being discharged by: 75Ah – 36Ah = 39Ah each day. So you could run your fridge and lights for: 100Ah / 39Ah = 2.5 days without any other form of charge. What can I run on my 120 Watt Panel? A 120W solar panel can supply between 6 and 7.5 Amps on a sunny day, for most of the sunlight hours of the day.

If we assume that only 1/3 of the day is sunlight hours then it is safe to assume that the panel can supply between 6 and 7.5 Amps for this period.
Given that there are 24 hours in a day, a 120W panel can effectively run a load of around 2.75A continuously throughout the day/night running at no loss.

Let’s assume that the solar panels are charging a 100A/h battery. You wish to run a 50L Fridge which draws on average 3A, and 2 x LED camp lights which draw 0.25A each when running. You want to run the fridge 24 hours a day, and the camp light for 6 hours each night.

Fridge: 3A x 24h = 72Ah Lights: 0.25A x 6h = 1.5Ah x 2 lights = 3Ah Total: 75Ah per day.
Your panels can supply: 6.75A x 8h = 54Ah each day.
Therefore the battery is being discharged by: 75Ah – 54Ah = 21Ah each day.
So you could run your fridge and lights for: 100Ah / 21Ah = just under 5 days without any other form of charge.

What do I need to run my Fridge? This depends on the size of your fridge, how long you plan to stay away from any other power sources and the size of your battery bank. Please refer to the Typical Usage Calculator for more accurate information. What do I need to run my Inverter? This depends on the size of your inverter, how long you plan to stay away from any other power sources and the size of your battery bank.

Please refer to the Typical Usage Calculator for more accurate information.
What is a typical setup for my camper trailer? The typical setup for a camper trailer would involve a 80L fridge and a couple of LED lamps.
We would recommend 2 x 80W solar panels mounted on the roof of the camper trailer if the space is available.

If not we would recommend a solar kit such as a 2 x 120W Folding Solar panels. What is a typical setup for my caravan? The typical setup for a caravan would involve a fridge, inverter, television, lighting and possibly some other equipment. We would recommend 3 x 120W solar panels mounted on the roof of the caravan.

What is a typical setup for camping? Typically a camper would require a 40 – 50L fridge and a couple of camp lights. We would recommend an 80W solar pane l, or a 112 watt Amorphous folding blanket How long will it take to recharge my battery? The time needed to fully recharge your battery with solar depends on 1) how much stored energy you need to replace in your battery/battery bank, 2) the efficiency of your solar regulator and the charging method it uses and 3) the amount of solar energy you can provide.

For the following example we will assume the regulator is 100% efficient. Let’s say you need to replace 50A/h of stored energy into your battery via 300W of solar panels.300W @ 12V = 300/12 = 25A 50A/h @ 25A = 50/25 = 2 hours So as a rough estimate it would take around 2 hours to recharge your battery.

In a real life situation you would need to take into account the efficiency of your regulator and its ability to charge the battery to 100% (multi-stage charging), and the fact that the charger will output at least 13V to charge the battery (not 12V).
Where do I place my panel with regards to the sun? Ideally your solar panel should be in direct sunlight for best performance.

This means that as much as possible your solar panel should be perpendicular to the direction of the sun rays. In practice this is not easily achievable or convenient and so we recommend that you orient your panels so that they are facing north at about a 45° angle.

What’s the best time of day to use my panel? Your panels will provide the most power at peak sunlight.
This requires no cloud cover and occurs at the middle of the day.
Your panels will continue to provide power at a reduced rate before and after this peak sunlight period at any time whilst the sun is out.

Your panels will obviously not provide any power before dawn or after dusk. Can I leave my panel out in the weather? Both REDARC thin film and rigid type panels are protected against the elements and will be fine if left out in the weather. REDARC solar panels are tested to handle rain and hail, and our portable panels can be tied or pegged down so as not to lose them in windy conditions.

Having said that, generally when the weather is stormy, rainy or there is hail, sunlight levels are not high enough to generate power from your solar panels.
Therefore if possible it would be best to bring your panels out of the weather during these conditions.
Will my panel work when it’s cloudy? Solar panels do generate electricity in cloudy weather although their output is diminished.

The output can drop to as low as 10% of the full sun intensity. The use of a MPPT regulator will help get the most out of your panels during these conditions. How do I clean my solar panels? You should clean your solar panels on a regular basis for best performance as anything that may be blocking sunlight from the photovoltaic material will reduce the efficiency of the panel.

Panels should be cleaned using a microfiber cloth as scratches may reduce the performance of your panels.
Can I upgrade my solar system? REDARC solar modules are designed to be upgradable and expandable.
All REDARC panels, thin film, portable or fixed, are designed to be interconnected regardless of their type.

There is also adaptor plugs available should you wish to add REDARC solar modules to an existing non-REDARC solar setup. My panel has stopped working, what do I do? If your panel has stopped working please run through the steps outlined in the troubleshooting guide.

If after completing the troubleshooting guide you have not solved the problem, please contact REDARC on (08) 8322 4848 for further assistance. Can I charge with my solar panels partially in the shade? When a solar panel is partially shaded the cells that are in the shade will not output any power. A solar panel with bypass diodes will ensure that if a cell is in the shade and not providing any power, the other cells and therefore the panel as a whole will still provide an output.

Panels without bypass diodes will lose all power when partially shaded. Each cell in an 80W solar array provides about 0.5V output. Therefore every 2 cells lost will mean a 1V drop in output. An 80W panel will output around 16V – 18V, which means that if more than about 6 cells are shaded the panel is less likely to charge a 12V battery.

How long will my solar panel last? REDARC rigid solar panels are designed to resist environmental conditions such as rain, hail and strong winds.
REDARC rigid panels come with a 5 year warranty to back up this claim.
REDARC rigid panels also offer a 12 year 90% efficiency warranty and a 25 year 80% efficiency warranty to ensure a useable output for years to come.

My solar panel gets very hot when I leave it out in the sun, is this normal? Solar panels when left in the sun will get hot for two reasons. Firstly, the sun beating down on the surface of the panel will cause the panel to increase in temperature, as it will with most surfaces.

How long will a 20W solar panel take to charge a 12V battery?

What Size Solar Panel Do You Need to Charge a 12V Battery? – You can charge a 12V battery with many different solar panel sizes. Knowing this, the question then becomes: “How fast do I want to solar charge my 12V battery?” Based on the above charge times, we can draw some conclusions: 5W and 10W solar panels are good for slow, trickle charging 12V batteries.

They’re a good size solar panel for maintaining a 12V battery’s charge, and will slowly charge it up over the course of weeks — maybe even months depending on the weather and size of the battery.20W and 50W solar panels are good for fast charging small 12V batteries. For example, a 20W solar panel can charge a 20Ah 12V battery in around 17 hours of direct sunlight.

A 50W panel can do it in around 8 hours.80W and 100W solar panels are good for fast charging large 12V and car batteries. If it’s a 50Ah battery, they can fully charge it in around 12 hours or less of direct sunlight. For more help on finding the right size solar panel for your solar charging setup, check out my post on what size solar panel will charge a 12V battery quickly,

How long will it take a 25 watt solar panel to charge 12V battery?

How Long Does It Take A 25-Watt Solar Panel To Charge A 12V Battery? – How long it takes for a 25-watt panel to charge a 12 V battery depends on the battery capacity. As a 25-watt panel produces 25 watts at 12 V, this translates to around 2 Amps of power to store. With 6 hours of sunlight, it takes that amount of time for your panel to charge a 12 V, 12 Amps battery.

How do you match a solar panel to a battery?

Wind/Solar Hookup Basics and Beyond. Matching the solar panels to the battery Page 8 The image above shows the typical routing of the energy in a alternate energy system. This system uses a battery bank and inverter. Our sun makes renewable green energy that is economically captured via solar panels. This energy can be used directly by small D/C appliances; however almost always, the use of of some basic components are required in a typical household (or cabin) environment, to fully benefit from the solar energy.

Many of these components are discussed in great detail elsewhere in this document.
This article focuses on how to properly match the solar panels to your battery bank, as well as the various electrical specifications you should be familiar with when purchasing your panels.
Please note: The image above is very simplified, many of the images elsewhere in this document offer more instructive wiring information,

Solar Panels convert the sun’s energy into electricity via small wafers of silicon. These super thin slices of silicon are actually comprised of even smaller layers of silicon wafers that are “Doped” with positive or negative impurity. The silicon is then refereed to as “P” type silicon and “N” type silicon The arrangement of these layers in wafers in just right manner causes electrons to flow from one layer to the next when the sun’s energy (photons) hits the wafer.

This energy is quite small in each single cell (each cell is generally a rectangle or square of wafers); however when many cells are used in a single solar panel, the voltage and current (power) is increased.
When multiple panels are combined, the energy (power) is again increased, resulting in a very useful amount of power.

How the solar panel actually works is not generally of the greatest concern to us, but we do need to know something about the panels so we can purchase the correct panels, and then install them correctly into our system. In order to achieve the maximum performance from your solar panels, you should design your system such that the VOC (Voltage Open Circuit), of your solar panel(s) are between 1.4 and 1.8 times your nominal battery bank voltage.

The Vmpp of your array (or single panel) should be 1.15 to 1.3 times the nominal battery voltage.
Tip: Solar panels loose their efficiency when they become hot.
The sun’s rays loose much of their power in even a slightly overcast day.
Dirt, dust and other buildup on the panels will cause loss of power.

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Panels (by most manufactures) are rated at 25 centigrade (77 Fahrenheit in the panel interior, not ambient air temperature), for a 1000m/w2 (bright sunny day, no clouds), and no dust or dirt on the panels! Let’s take a look at the specs of two different 220 watt panels. Panel 2: Let’s take a look at some terms. Voc = Voltage open circuit. This is the maximum amount of voltage a solar panel will produce, in bright sun, on a cold day, when measured with a volt meter, and the panel is not hooked up to anything (open circuit). Isc = Short circuit voltage, this is the maximum amount of current a solar panel can produce in bright sun, on a cold day, when measured with an amp meter, and the panel wires are shorted together (short circuit).

Voc and Isc, can never occur at the same time, so we can not use these figures directly to determine how many watts a panel produces, but they are very important values in properly matching our solar panels and batteries. As we put a load on a solar panel, the voltage drops and the current goes up. There is a point in this load curve where the panel is producing its most power.

This point is the Vmpp Vmpp or MPV = Voltage Maximum power point, or Maximum power voltage (same thing.) This is the voltage that would be read by a meter, when the panel is in bright sun, on a cold day, and the panel is loaded (by hooking it up to a battery or D.C.

Appliance), such that the load causes a current draw (flow) of Impp. Impp = Current (“I” stands for current in electrical jargon), Current maximum power point. This is the maximum amount of current a solar panel can produce in bright sun, on a cold day, when it is producing its most amount of power (It maximum wattage, not maximum voltage) When Vmpp and Impp come together, then the panel is producing its maximum power,

This should not be confused with a MPPT controller. All quality controllers work well when your batteries and panels are properly matched. So what is properly matched, or how do we achieve this match? For our examples, we are looking to purchase panels that will work in a 24 volt, battery based system.

The best performance will be achieved if the solar panels produces a VOC of 1.4 to 1.8 times the nominal battery voltage. So in a 24 volt system, we want the VOC to be between 33.6v and 43.2 volts (a little higher or lower is fine here). The Voc of the panel 1 (220 watts) shows 36.6v, so this panel will work for us,

This panel can be considered a “24 volt panel”. But how about panel 2? – It shows a VOC of 58V – This panel will waste more than 1/2 of its power in a 24 volt system, and will not produce enough voltage in a 48 volt system to charge the batteries beyond about 50 volts (1/2 of what is needed).

Panel 2 will only work for direct grid tie applications (no battery bank), or with an MPPT controller to downshift the high voltage down to the voltage required to properly match the battery.
This panel is not a good choice for a battery based system.
This does not mean the panel is not a good panel, in-fact we know nothing about either panel’s quality or reputation.

We are strictly looking at how the two panels match up to our 24 volt battery bank. Panel 1 matches quite well, panel 2 does not! Let’s do some more math, first on panel 1. How well will panel 1 work andhow many watts can we actually expect? It’s time to look at the Vmpp a little closer.

The spec. tag shows a Vmpp of of 28.7v. Remember, this is the voltage we can expect when the panel is producing is best power. So in our 24 volt system, our panels will produce their maximum power when our batteries are at 28.7 volts (not including loss in the wires). This is not bad, and in fact it may be just about perfect depending on how long your wire run is, how hot the panels are are etc.

We might prefer to have a panel that produces its maximum power a little lower in colder climates and if our wires are short, say 27.5 volts. Why? Let’s do the math. The Vmpp of the panel is 28.7 volts, the Impp is 7.7 amps. Power (watts) = volts x amps.

So, 28.7 volts x 7.7 amps = 220.99 watts. So this is where the panel manufacturer derives the 220 watts from. Now this figure is in a perfect world, where the sun is very bright and is it is a very cold day. This may occur a few times a year, but in reality, the brighter the sun, the hotter the day. The hotter the panels, the lower the voltage output, so the lower the wattage.

Also, it does not matter how good your connections are and how short the wires are to your batteries, there is some loss between the panel and the battery. So let’s take a more realistic approach to the possible power we can expect. Let’s assume it’s not quite as bright as we would like, and it’s not anywhere close to cold enough to keep the panels at 25c, so we’re going to say that our best power point (Vmpp) of this panel is probably closer 28 volts on a normal day (The panel is not changing, it’s just the environment is not perfect).

We might expect to see the VOC drop off to 33 volts or so in bright sun on a hot day.
Now let us also say that we also have a 2% loss in our cable run.
At 28 volts, we will lose about,6 volts.
Now we have some loss in connections and the path through breakers and controllers.
We need to add another,25 volts or so.

This leaves us with a Vmpp voltage when measured at the battery of about 27.15 volts. What this means is; this panel, in more real world conditions will produce its maximum power when the battery is at 27.15 volts. If we de-rate the Impp for the heat, less than perfect sun, and wire loss, we can hope for closer to 6.25 amps (this is possibly a bit optimistic).

So, 27.15 volts, times 6.25 amps, we might see 169 (to 172) true charging watts, or about 80% of our panels nameplate. Hotter days, longer runs and this may be closer to 50%. The charge stage of the batteries also play into the the Vmpp. If our batteries are very low, we would see something like 23.5 volts x 7 amps (the amperage would be a little higher as the voltage drops).

Or 164 watts. If our battery is very high (being equalized), we might see: 30v x 4.2 amps (the amperage will drop off as we approach the VOC), or 126 watts. What all this means is these panels (panel 1) are a pretty darn good match for a 24 volt battery based charging system, in real world conditions, where most of us live.

But let’s just say you live in the north, and you have some very bright days and the wind has still got a cold bite to it. Then a panel with a little lower Vmpp might match your system a little better. There is another reason why you might want to use a panel with a lower Vmpp, (and this is applicable to us here at Coleman Air), and that is our batteries are often lower than 27 volts because we constantly have a load on them, day and night.

So in this case, if the batteries are likely to be at 26 volts most of the time, then a panel with a little lower Vmpp, might improve your total performance. Our system (here at ColemanAir.us), is designed around a battery bank that is kept constant at about 26.5 volts, our wire runs are very short and our controllers (the Coleman Air C150-SMA’s) have very little loss.

So we have chosen panels with a little lower Vmpp.
The downside is when it gets VERY hot, we have a little lower performance, but the sun shines longer in the summer.
The net affect is a system that is tuned to our location, our batteries, wiring and or course to our controllers, netting a very useful power curve, day in and day out.

How about panel 2? Panel 2 has a Vmp of 46v (a 24v battery bank is never at 46v, neither is a 12v or properly charging 48v battery bank). It has a Impp (Current Mpp) of 4.8 amps. Remember this occurs at the voltage of 46v (where our battery bank will never be).

To be very optimistic, we will simply multiply the normal battery bulk charge voltage of 28 volts x the 4.8 amps, yielding 134 watts.
This is the maximum this panel can deliver without any losses, including wire loss, heat loss, connection loss etc.
In reality, as described above, this panel will probably only produce about 75% of the 134 watts, so perhaps 100 watts is a closer figure.

This is less than 1/2 the stated power. Remember, this is not because the panel is not a good panel, it simply does not match any particular battery bank. It must be used without a battery, or in conjunction with an expensive MPPT controller to match the panel to a battery bank.

The MPPT controller is required in this case, since the panel is not a good match.
To keep it simple, purchase panels for your system using the following guidelines 12 volt system: with a Voc between 16.8 and 21.6, with 18 volts being about the best for colder areas, and 20-21.5 volts being better for hot conditions or long wire runs.24 volt system: with a Voc between 33.6 and 43.2, with 36 volts being about the best for colder areas, and 40-41 volts being better for hot conditions or long wire runs.48 volt system: with a Voc between 67.2 and 86.4, with 72 volts being about the best for colder areas, and 80-82 volts being better for hot conditions or long wire runs.

(There is less power loss in the wires in a 48 volt system, then there is in a 12 volt system) When you follow these simple design rules, then you will achieve the real world, maximum power available from your panels. Any quality charge controller will pass the power from your panels to the batteries, no downshifting or up-shifting of voltage is necessary; and in fact, when properly matched, a PWM controller will work very efficiently and at a fraction of the cost of a MPPT controllers. HOME

Will a 100 watt solar panel keep a 12 volt battery charged?

How Long To Charge 12v battery With 100 Watt Solar Panel? How Long To Charge 12v battery With 100 Watt Solar Panel? If you’re looking for an off-the-grid way to power your devices, you may be wondering how long it takes to charge a 12V battery with a 100W solar panel.

Can you use house solar panels for 12V?

Residential solar panel voltage – Residential solar panels typically have a voltage of 24 volts. You can use them to charge a 12-volt battery, but it is not considered good practice. This is because a 24-volt panel produces more power than a 12-volt battery can store.

How much solar power do I need for a 12V fridge?

How Many Solar Panels Do I Need to Run a Refrigerator? – At home, you probably have an average household refrigerator. In order to power that fridge using solar power, you would need about two to three solar panels. Average solar panels produce approximately 250 to 400 Watts of power.

But you are not using an average refrigerator in your RV. Most likely, you need to power a 12V fridge, which is smaller. The best size solar panel to run a 12V fridge is 150 Watts into 200 Watts of batteries. That’s why a 300-Watt panel system is a great choice since you can be sure to collect and store more than enough energy for a continuous power supply.

That way if the forecast is not calling for sunny days, you can store more energy. You may want to read our article on best portable solar panels for RV, When shopping around for a solar energy system, be sure to check its wattage rating so that you get exactly what you need.

Also factor in the amount of sunlight you typically get when traveling.
Same with the time of year.
The sun is closer and produces more solar energy in the summer, than in winter.
And it’s stronger in southern states than northern.
Truth is, only between 11 Am and 1 PM local time is when solar panels are most effective.

Super fancy systems angle themselves to catch more rays as the sun moves. Or if you are using portable panels, you can manually adjust their angle at various times. If you love to RV in dense forests or northern locations, you are going to get much less energy.

What will a 30 watt solar panel run?

BSP3012 12 Volt 30 Watt Solar Panel This 30 watt solar panel has an output of 1.6 amps of DC power during peak solar hours. This panel must be used with a controller, as it is large enough to overcharge batteries without one.30 watts of solar can be used for charging and maintenance of 12 volt batteries up to about 250 amp hours of capacity and replace energy consumption, giving from 6 to 12 amps or more in a day.

This can be appropriate for remote telemetry, radio repeaters, LED signs, RV battery maintenance, and other such applications where the amp draw fits the output. The BSP3012 solar panel is an aluminum framed, commercial grade unit for long term exterior use, and has 15 feet of UV resistant cable permanently attached.

Click image for larger picture, “Back” button to return

Part#: BSP301230 WattSolar Panel $140

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Specifications: Features: Dim (LxWxH): 26.2 x 16.2 x 1.30 Aluminum Frame Actual Weight: 8.5 Exterior Grade Ship Weight: 11.0 Weatherproof Open Circuit: 22.1 VDC 15 Foot Output Cable Output: 30 watts Output Current: 1.6 Amps Warranty: 10 Years

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This 30 watt panel is used for battery recharging in small solar systems where the current draw is small (2 to 10 amps total in a day). A solar controller such as the Morningstar SunSaver 6 should be used with this panel, or any solar panel over 5 watts output.

Can a 18v solar panel charge a 12V battery?

To charge a 12V battery, you need at least 14V. And voltage drops over distance, so the plug in the very back of my SUV only outputs 10V, meaning it will need a higher voltage (at least 16V) to be sure it will still charge the battery. You’re right that, if this was a high-speed charger with more power (amps/watts) 18V could potentially do some damage.

But at just 5W (which is 0.28amps at 18V) it really doesn’t output enough power to hurt a big car battery. At worst, you might lose water quicker. With a tiny wheel-chair or UPS/FIOS battery, you might have to be a bit more cautious of overcharging with this solar panel.4 of 5 found this helpful. Do you? | Report abuse Solar panels can put out any voltage, up to some maximum “open circuit voltage”.

If you put the panel in the sun, and measured the voltage across the leads without connecting it to anything, you would measure 18v, which is the open circuit voltage. Solar panels also have some voltage at which they will generate maximu see more Solar panels can put out any voltage, up to some maximum “open circuit voltage”.

If you put the panel in the sun, and measured the voltage across the leads without connecting it to anything, you would measure 18v, which is the open circuit voltage.
Solar panels also have some voltage at which they will generate maximum power, this is the “Max Power Point”, hopefully this is about 12v for this panel.

The solar panel will match the voltage of any battery that you connect it to, but if the battery voltage is above the “open circuit voltage” (18v), it will not generate any electricity, and will not charge the battery. Ignore the other answers here, they are not accurate.

See less Solar panels can put out any voltage, up to some maximum “open circuit voltage”.
If you put the panel in the sun, and measured the voltage across the leads without connecting it to anything, you would measure 18v, which is the open circuit voltage.
Solar panels also have some voltage at which they will generate maximum power, this is the “Max Power Point”, hopefully this is about 12v for this panel.

Do you? | Report abuse You are correct; 18vdc is too much voltage for charging your car battery. Other answers on here are unfortunately misinformed by the difference between watts and volts. Using a water analogy, it’s like a pressure washer filling a bucket. Even though a pressure washer puts out LESS OVERALL WATER than the hose on the s see more You are correct; 18vdc is too much voltage for charging your car battery.

Other answers on here are unfortunately misinformed by the difference between watts and volts. Using a water analogy, it’s like a pressure washer filling a bucket. Even though a pressure washer puts out LESS OVERALL WATER than the hose on the side of your house (overall water in this case is watts) it shoots that water in a stream that can eventually damage the bucket.

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It would be far better to have a FIREHOSE that’s turned way way down so even though it’s putting out much more water it’s Not under as much pressure. Too many volts can damage your battery. This should have a charge controller between it and the 12v battery. That would keep it around 13-14v see less You are correct; 18vdc is too much voltage for charging your car battery.

It would be far better to have a FIREHOSE that’s turned way way down so even though it’s putting out much more water it’s Not under as much pressure.
Too many volts can damage your battery.
This should have a charge controller between it and the 12v battery.
That would keep it around 13-14v 1 of 3 found this helpful.

Do you? | Report abuse The 5W is not real for this size solar panel. This is about a 2W panel. While charging your car this will be loaded down to a little less than 14V and current limited to less than 0.2A so figure 2.5W max. Amps are what matters because W is just a function of Voltage at the moment.

A typical car battery is around 55 amp-hrs so 0.2A will take 50hrs just to charge 20%. And those are 50 bright hours. Most locations average less than 5 peak hrs of sunshine per day, so 10 days to charge 20%. You can see this will never damage a car battery by overcharging.2 of 3 found this helpful. Do you? | Report abuse The output of the solar cell is only 5 watt, so on a good day it might out out half an amp and on average about 100 mA.

Given the cell current, voltage will be clamped down by the internal resistance of the battery. A car battery is designed for hundreds of amps, so the charge current will be tiny compared to the bat see more The output of the solar cell is only 5 watt, so on a good day it might out out half an amp and on average about 100 mA.

Given the cell current, voltage will be clamped down by the internal resistance of the battery. A car battery is designed for hundreds of amps, so the charge current will be tiny compared to the battery capacity. Batteries tend to self discharge and there are auto electronics that are always drawing current.

Most battery manufacturers allow a constant trickle charge of up to 1% of the battery rated AH capacity (e.g. if the car battery is rated 100 AH, then under 1 amp trickle charge would be acceptable). This maintainer is probably 0.1% of the battery rated capacity and less considering the load of the electronics.

see less The output of the solar cell is only 5 watt, so on a good day it might out out half an amp and on average about 100 mA. Given the cell current, voltage will be clamped down by the internal resistance of the battery. A car battery is designed for hundreds of amps, so the charge current will be tiny compared to the battery capacity.

Batteries tend to self discharge and there are auto electronics that are always drawing current. Most battery manufacturers allow a constant trickle charge of up to 1% of the battery rated AH capacity (e.g. if the car battery is rated 100 AH, then under 1 amp trickle charge would be acceptable).

This maintainer is probably 0.1% of the battery rated capacity and less considering the load of the electronics.0 of 1 found this helpful. Do you? | Report abuse It’s like needing 60 lbs of force to lift a 50 lb weight on a rope and pulley. The extra force is there to overcome friction in the system and get things to move.

Electrical resistance is the friction that makes some extra voltage necessary to move electrical charge and charge the battery up.18 volts makes sure the 12 volt system charges as fast as 5W can fill it.3 of 4 found this helpful. Do you? | Report abuse this is not a charger.

This just maintains the batteries charge. I wrote to the company and they explained to me that, in my case, while I am on the boat and not running but playing the radio or any other electronics, this will help keep the battery charge and it will not put a drain on the battery.and it works. I use it all of the time.

we are sitting sometimes for 4/5 hours listening to the radio and using radios and the battery charge does not go down when this is hooked up. you must have direct sun though 2 of 3 found this helpful. Do you? | Report abuse

Can a 24v solar panel charge a 12V battery?

Yes, you could do it. The voltage isn’t too much of a concern, it is the current the panel can provide.

How do you match a solar panel to a battery?

Many of these components are discussed in great detail elsewhere in this document. This article focuses on how to properly match the solar panels to your battery bank, as well as the various electrical specifications you should be familiar with when purchasing your panels. Please note: The image above is very simplified, many of the images elsewhere in this document offer more instructive wiring information,

This energy is quite small in each single cell (each cell is generally a rectangle or square of wafers); however when many cells are used in a single solar panel, the voltage and current (power) is increased.
When multiple panels are combined, the energy (power) is again increased, resulting in a very useful amount of power.

The Vmpp of your array (or single panel) should be 1.15 to 1.3 times the nominal battery voltage.
Tip: Solar panels loose their efficiency when they become hot.
The sun’s rays loose much of their power in even a slightly overcast day.
Dirt, dust and other buildup on the panels will cause loss of power.

Voc and Isc, can never occur at the same time, so we can not use these figures directly to determine how many watts a panel produces, but they are very important values in properly matching our solar panels and batteries. As we put a load on a solar panel, the voltage drops and the current goes up. There is a point in this load curve where the panel is producing its most power.

Appliance), such that the load causes a current draw (flow) of Impp. Impp = Current (“I” stands for current in electrical jargon), Current maximum power point. This is the maximum amount of current a solar panel can produce in bright sun, on a cold day, when it is producing its most amount of power (It maximum wattage, not maximum voltage) When Vmpp and Impp come together, then the panel is producing its maximum power,

The best performance will be achieved if the solar panels produces a VOC of 1.4 to 1.8 times the nominal battery voltage. So in a 24 volt system, we want the VOC to be between 33.6v and 43.2 volts (a little higher or lower is fine here). The Voc of the panel 1 (220 watts) shows 36.6v, so this panel will work for us,

Panel 2 will only work for direct grid tie applications (no battery bank), or with an MPPT controller to downshift the high voltage down to the voltage required to properly match the battery. This panel is not a good choice for a battery based system. This does not mean the panel is not a good panel, in-fact we know nothing about either panel’s quality or reputation.

The spec. tag shows a Vmpp of of 28.7v.
Remember, this is the voltage we can expect when the panel is producing is best power.
So in our 24 volt system, our panels will produce their maximum power when our batteries are at 28.7 volts (not including loss in the wires).
This is not bad, and in fact it may be just about perfect depending on how long your wire run is, how hot the panels are are etc.

We might expect to see the VOC drop off to 33 volts or so in bright sun on a hot day.
Now let us also say that we also have a 2% loss in our cable run.
At 28 volts, we will lose about,6 volts.
Now we have some loss in connections and the path through breakers and controllers.
We need to add another,25 volts or so.

So, 27.15 volts, times 6.25 amps, we might see 169 (to 172) true charging watts, or about 80% of our panels nameplate. Hotter days, longer runs and this may be closer to 50%. The charge stage of the batteries also play into the the Vmpp. If our batteries are very low, we would see something like 23.5 volts x 7 amps (the amperage would be a little higher as the voltage drops).

But let’s just say you live in the north, and you have some very bright days and the wind has still got a cold bite to it.
Then a panel with a little lower Vmpp might match your system a little better.
There is another reason why you might want to use a panel with a lower Vmpp, (and this is applicable to us here at Coleman Air), and that is our batteries are often lower than 27 volts because we constantly have a load on them, day and night.

So we have chosen panels with a little lower Vmpp. The downside is when it gets VERY hot, we have a little lower performance, but the sun shines longer in the summer. The net affect is a system that is tuned to our location, our batteries, wiring and or course to our controllers, netting a very useful power curve, day in and day out.

To be very optimistic, we will simply multiply the normal battery bulk charge voltage of 28 volts x the 4.8 amps, yielding 134 watts. This is the maximum this panel can deliver without any losses, including wire loss, heat loss, connection loss etc. In reality, as described above, this panel will probably only produce about 75% of the 134 watts, so perhaps 100 watts is a closer figure.

The MPPT controller is required in this case, since the panel is not a good match.
To keep it simple, purchase panels for your system using the following guidelines 12 volt system: with a Voc between 16.8 and 21.6, with 18 volts being about the best for colder areas, and 20-21.5 volts being better for hot conditions or long wire runs.24 volt system: with a Voc between 33.6 and 43.2, with 36 volts being about the best for colder areas, and 40-41 volts being better for hot conditions or long wire runs.48 volt system: with a Voc between 67.2 and 86.4, with 72 volts being about the best for colder areas, and 80-82 volts being better for hot conditions or long wire runs.

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