What size solar panel do you need to charge a 12V battery? Enter your battery specs, solar charge controller type and desired charge time into our solar panel size calculator to find out:
Calculate Solar Panel Size to Charge 12V Battery
Note: If you already have a solar panel size in mind and want to estimate how long it will take to charge your battery, check out our solar panel charge time calculator.
Calculator Assumptions
- The solar charge controller is the only load connected to the battery
What Size Solar Panel to Charge 12V Battery?
To find out what size solar panel you need to charge your 12V battery, you’ll need to enter the following info into our solar panel size calculator at the top of this page:
- Battery Voltage (V): What is your battery’s voltage? We’ve gone ahead and entered 12 volts already, but you can always change it if your battery has a different voltage.
- Battery Amp Hours (Ah): What is your battery’s capacity in amp hours? (If you only know its capacity in watt hours, first convert watt hours to amp hours)
- Battery Type: Is your battery a lead acid or lithium (LiFePO4) battery?
- Battery Depth of Discharge (DoD): What level of discharge is your battery at? 100% means fully discharged and 0% means fully charged.
- Solar Charge Controller Type: Will you be using a PWM or MPPT solar charge controller?
- Desired Charge Time (in peak sun hours): How quickly do you want your solar panel to charge your battery, in peak sun hours?
Once you’ve entered the above info, click “Calculate Solar Panel Size” to get an estimate of what size panel you need to charge your 12V battery at your desired speed.
Example
Let’s say you have a 12V 100Ah lead acid battery and a PWM charge controller in your campervan. You want a solar panel that will charge your battery in 10 peak sun hours.
To find out what size solar panel you need, you’d simply plug the following into the calculator:
- Battery Voltage (V): 12
- Battery Amp Hours (Ah): 100
- Battery Type: Lead acid
- Battery Depth of Discharge (DoD): 50%
- Solar Charge Controller Type: PWM
- Desired Charge Time (in peak sun hours): 10
Turns out you need a 120 watt solar panel to charge a 12V 100Ah lead acid battery in 10 peak sun hours with a PWM charge controller.
What Size Solar Panel to Maintain 12V Battery?
Maintaining a battery, also called trickle charging, is when you charge a fully charged battery at a rate equal to its self-discharge rate to keep it topped off.
Here is a chart showing what size solar panel you need to maintain 12V batteries of various capacities with a PWM charge controller.
Note: Many factors affect a battery’s self-discharge rate — such as age of the battery and ambient temperature — so to keep things simple I just used a desired charge time of 1000 peak sun hours for these calculations.
| Battery Amp Hours (Ah) | Battery Type | Estimated Solar Panel Size |
|---|---|---|
| 50Ah | Lithium (LiFePO4) | 3 watts |
| 60Ah | Lithium (LiFePO4) | 3 watts |
| 80Ah | Lithium (LiFePO4) | 3 watts |
| 100Ah | Lithium (LiFePO4) | 4 watts |
| 120Ah | Lithium (LiFePO4) | 4 watts |
| 140Ah | Lithium (LiFePO4) | 4 watts |
| 200Ah | Lithium (LiFePO4) | 5 watts |
| 50Ah | Lead acid | 2 watts |
| 60Ah | Lead acid | 2 watts |
| 80Ah | Lead acid | 3 watts |
| 100Ah | Lead acid | 3 watts |
| 120Ah | Lead acid | 3 watts |
| 140Ah | Lead acid | 3 watts |
| 200Ah | Lead acid | 4 watts |
Summary
- You would need a 3-5 watt solar panel to maintain the most common sizes of 12V lithium batteries with a PWM charge controller.
- You would need a 3-4 watt solar panel to maintain the most common sizes of 12V lead acid batteries with a PWM charge controller.
What Size Solar Panel to Charge 12V 100Ah Battery?
12V 100Ah Lithium Battery
| Charge Time | Charge Controller Type | Estimated Solar Panel Size |
|---|---|---|
| 5 peak sun hours | MPPT | 310 watts |
| 10 peak sun hours | MPPT | 160 watts |
| 15 peak sun hours | MPPT | 110 watts |
| 20 peak sun hours | MPPT | 80 watts |
| 25 peak sun hours | MPPT | 70 watts |
| 5 peak sun hours | PWM | 380 watts |
| 10 peak sun hours | PWM | 190 watts |
| 15 peak sun hours | PWM | 130 watts |
| 20 peak sun hours | PWM | 100 watts |
| 25 peak sun hours | PWM | 80 watts |
Summary
- You would need around 310 watts of solar panels to charge a 12V 100Ah lithium battery from 100% depth of discharge in 5 peak sun hours with an MPPT charge controller.
- You would need around 380 watts of solar panels to charge a 12V 100Ah lithium battery from 100% depth of discharge in 5 peak sun hours with a PWM charge controller.
12V 100Ah Lead Acid Battery
| Charge Time | Charge Controller Type | Estimated Solar Panel Size |
|---|---|---|
| 5 peak sun hours | MPPT | 220 watts |
| 10 peak sun hours | MPPT | 100 watts |
| 15 peak sun hours | MPPT | 70 watts |
| 20 peak sun hours | MPPT | 50 watts |
| 25 peak sun hours | MPPT | 40 watts |
| 5 peak sun hours | PWM | 270 watts |
| 10 peak sun hours | PWM | 120 watts |
| 15 peak sun hours | PWM | 80 watts |
| 20 peak sun hours | PWM | 60 watts |
| 25 peak sun hours | PWM | 50 watts |
Summary
- You would need around 220 watts of solar panels to charge a 12V 100Ah lead acid battery from 50% depth of discharge in 5 peak sun hours with an MPPT charge controller.
- You would need around 270 watts of solar panels to charge a 12V 100Ah lead acid battery from 50% depth of discharge in 5 peak sun hours with a PWM charge controller.
What Size Solar Panel to Charge 12V 50Ah Battery?
12V 50Ah Lithium Battery
| Charge Time | Charge Controller Type | Estimated Solar Panel Size |
|---|---|---|
| 5 peak sun hours | MPPT | 160 watts |
| 10 peak sun hours | MPPT | 80 watts |
| 15 peak sun hours | MPPT | 60 watts |
| 20 peak sun hours | MPPT | 50 watts |
| 25 peak sun hours | MPPT | 40 watts |
| 5 peak sun hours | PWM | 200 watts |
| 10 peak sun hours | PWM | 100 watts |
| 15 peak sun hours | PWM | 70 watts |
| 20 peak sun hours | PWM | 50 watts |
| 25 peak sun hours | PWM | 40 watts |
Summary
- You would need a 160 watt solar panel to charge a 12V 50Ah lithium battery from 100% depth of discharge in 5 peak sun hours with an MPPT charge controller.
- You would need a 200 watt solar panel to charge a 12V 50Ah lithium battery from 100% depth of discharge in 5 peak sun hours with a PWM charge controller.
12V 50Ah Lead Acid Battery
| Charge Time | Charge Controller Type | Estimated Solar Panel Size |
|---|---|---|
| 5 peak sun hours | MPPT | 120 watts |
| 10 peak sun hours | MPPT | 60 watts |
| 15 peak sun hours | MPPT | 40 watts |
| 20 peak sun hours | MPPT | 30 watts |
| 25 peak sun hours | MPPT | 30 watts |
| 5 peak sun hours | PWM | 140 watts |
| 10 peak sun hours | PWM | 70 watts |
| 15 peak sun hours | PWM | 40 watts |
| 20 peak sun hours | PWM | 30 watts |
| 25 peak sun hours | PWM | 30 watts |
Summary
- You would need a 120 watt solar panel to charge a 12V 50Ah lead acid battery from 50% depth of discharge in 5 peak sun hours with an MPPT charge controller.
- You would need a 140 watt solar panel to charge a 12V 50Ah lead acid battery from 50% depth of discharge in 5 peak sun hours with a PWM charge controller.
What Size Solar Panel to Charge 12V 120Ah Battery?
12V 120Ah Lithium Battery
| Charge Time | Charge Controller Type | Estimated Solar Panel Size |
|---|---|---|
| 5 peak sun hours | MPPT | 370 watts |
| 10 peak sun hours | MPPT | 190 watts |
| 15 peak sun hours | MPPT | 130 watts |
| 20 peak sun hours | MPPT | 100 watts |
| 25 peak sun hours | MPPT | 80 watts |
| 5 peak sun hours | PWM | 460 watts |
| 10 peak sun hours | PWM | 230 watts |
| 15 peak sun hours | PWM | 150 watts |
| 20 peak sun hours | PWM | 120 watts |
| 25 peak sun hours | PWM | 90 watts |
Summary
- You would need around 370 watts of solar panels to charge a 12V 120Ah lithium battery from 100% depth of discharge in 5 peak sun hours with an MPPT charge controller.
- You would need around 460 watts of solar panels to charge a 12V 120Ah lithium battery from 100% depth of discharge in 5 peak sun hours with a PWM charge controller.
12V 120Ah Lead Acid Battery
| Charge Time | Charge Controller Type | Estimated Solar Panel Size |
|---|---|---|
| 5 peak sun hours | MPPT | 260 watts |
| 10 peak sun hours | MPPT | 120 watts |
| 15 peak sun hours | MPPT | 80 watts |
| 20 peak sun hours | MPPT | 60 watts |
| 25 peak sun hours | MPPT | 50 watts |
| 5 peak sun hours | PWM | 330 watts |
| 10 peak sun hours | PWM | 150 watts |
| 15 peak sun hours | PWM | 100 watts |
| 20 peak sun hours | PWM | 70 watts |
| 25 peak sun hours | PWM | 60 watts |
Summary
- You would need around 260 watts of solar panels to charge a 12V 120Ah lead acid battery from 50% depth of discharge in 5 peak sun hours with an MPPT charge controller.
- You would need around 330 watts of solar panels to charge a 12V 120Ah lead acid battery from 50% depth of discharge in 5 peak sun hours with a PWM charge controller.
What Size Solar Panel to Charge 12V 200Ah Battery?
12V 200Ah Lithium Battery
| Charge Time | Charge Controller Type | Estimated Solar Panel Size |
|---|---|---|
| 5 peak sun hours | MPPT | 610 watts |
| 10 peak sun hours | MPPT | 300 watts |
| 15 peak sun hours | MPPT | 200 watts |
| 20 peak sun hours | MPPT | 150 watts |
| 25 peak sun hours | MPPT | 130 watts |
| 5 peak sun hours | PWM | 760 watts |
| 10 peak sun hours | PWM | 380 watts |
| 15 peak sun hours | PWM | 250 watts |
| 20 peak sun hours | PWM | 190 watts |
| 25 peak sun hours | PWM | 150 watts |
Summary
- You would need around 610 watts of solar panels to charge a 12V 200Ah lithium battery from 100% depth of discharge in 5 peak sun hours with an MPPT charge controller.
- You would need around 760 watts of solar panels to charge a 12V 200Ah lithium battery from 100% depth of discharge in 5 peak sun hours with a PWM charge controller.
12V 200Ah Lead Acid Battery
| Charge Time | Charge Controller Type | Estimated Solar Panel Size |
|---|---|---|
| 5 peak sun hours | MPPT | 430 watts |
| 10 peak sun hours | MPPT | 200 watts |
| 15 peak sun hours | MPPT | 130 watts |
| 20 peak sun hours | MPPT | 100 watts |
| 25 peak sun hours | MPPT | 80 watts |
| 5 peak sun hours | PWM | 540 watts |
| 10 peak sun hours | PWM | 240 watts |
| 15 peak sun hours | PWM | 160 watts |
| 20 peak sun hours | PWM | 120 watts |
| 25 peak sun hours | PWM | 90 watts |
Summary
- You would need around 430 watts of solar panels to charge a 12V 200Ah lead acid battery from 50% depth of discharge in 5 peak sun hours with an MPPT charge controller.
- You would need around 540 watts of solar panels to charge a 12V 200Ah lead acid battery from 50% depth of discharge in 5 peak sun hours with a PWM charge controller.
How to Charge a 12V Battery with a Solar Panel
You’ve got your 12V battery. ✔
You’ve got your perfectly sized solar panel. ✔
Now you need to connect them together to start solar charging the battery.
Here’s a quick tutorial:
Note: For more in-depth instructions, check out my full tutorial on how to connect a solar panel to a battery.
Parts
- 12V solar panel
- 12V battery
- Solar charge controller (one that’s compatible with 12V batteries)
- Battery cables
- Solar panel to charge controller adapter cables
Step 1: Connect the 12V Battery to the Charge Controller
Insert the stripped end of the negative battery cable into the negative battery terminal on the charge controller. Screw the terminal shut with a screwdriver. Repeat the process for the positive battery cable.
Connect the ring terminal on the negative battery cable to the negative terminal on the 12V battery. Repeat the process for the positive battery cable.
Your charge controller should turn on to indicate the battery and charge controller are properly connected. Mine has a battery indicator light that turned on.
Now you need to program your charge controller for your battery type. This lets the charge controller know which voltage to charge the battery to.
Consult your instruction manual for how to do this. In this example, I’m using a sealed lead acid battery, so I programmed my charge controller for that battery type.
Check!
Step 2: Connect the Solar Panel to the Charge Controller
Connect the positive solar panel adapter cable to the positive solar panel cable. Repeat the process for the negative solar panel cable.
Insert the negative solar cable into the negative solar PV terminal on the charge controller and screw the terminal shut. Repeat the process for the positive solar cable.
Your charge controller should indicate that the solar panel is properly connected. Mine has a PV indicator light that turned on.
Done!
Step 3: Put the Solar Panel Outside in Direct Sunlight
Your solar panel and battery are connected…
…but the solar panel isn’t charging the battery yet because the panel isn’t in direct sunlight.
That’s an easy fix.
Take your solar panel outside and angle it towards the sun.
Once you do, your charge controller should indicate that the solar panel is charging the 12V battery. For example, the PV indicator light on my charge controller starts blinking green when the battery is charging.
There ya go!
You’re charging a 12V battery with a solar panel.
(Simple, no?)
Now all you have to do is wait for the solar panel to charge the battery. The charge controller will automatically stop the charging once the battery is fully charged.
Solar Charging 12V Batteries FAQ
What Size Solar Panel Do I Need to Charge a 12V Battery?
Short answer: Use the calculator at the top of this page.
Long answer: What size solar panel you need depends mainly on 2 things:
- Battery capacity in amp hours (Ah)
- Desired charge time in peak sun hours
If you want to charge a big battery quickly, you’ll need a big solar panel or solar array. Like how you’d need a big hose to quickly fill up a big bucket.
Alternatively, if you want to slowly charge a small battery, you can use a small solar panel. A small hose will eventually fill up a small bucket.
Want to charge a big battery slowly? Or a small battery quickly?
Your solar panel size will fall somewhere in between.
There is no single solar panel size that will be perfect for every scenario. Depending on your battery size and how fast you want to charge your battery, you could get away with using a small 5W solar panel, or you might need a 400W solar array.
How Many Solar Panels Do I Need to Charge a 12V Battery?
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.
But if you have a big battery and you want to charge it quickly, you’ll likely need to buy multiple solar panels and connect them together to create a solar panel array.
If you just want to maintain a 12V battery, you can get away with a small 12V solar panel, such as a 5W or 10W panel. That’s right — a 5W solar panel will charge a 12V battery.
