- Alex Beale
- UpdatedAugust 24, 2022
- DIY Solar Power
What size solar panel do you need to charge a 100Ah 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 100Ah Battery
Estimated solar panel size:
watts
Warning: We estimate that a solar power system with these parameters would have a maximum charge current of . Many battery manufacturers recommend a maximum charge current of for lead acid batteries with this capacity. To maximize your battery’s lifespan, consider using a smaller solar panel or a bigger battery. Or increase your desired charge time.
Warning: We estimate that a solar power system with these parameters would have a maximum charge current of . Many battery manufacturers recommend a maximum charge current of for lithium iron phosphate batteries with this capacity. To maximize your battery’s lifespan, consider using a smaller solar panel or a bigger battery. Or increase your desired charge time.
Error: We estimate that it is impossible to charge your battery this quickly. The typical absorption time for batteries is around hours, which is greater than (or equal to) your desired charge time. Increase your desired charge time and try again.
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 100Ah Battery?
To find out what size solar panel you need to charge a 100Ah 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?
- Battery Amp Hours (Ah): What is your battery’s capacity in amp hours? We’ve gone ahead and entered 100 amp hours already, but you can always change it if your battery has a different capacity.
- 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 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 battery at your desired speed.
Example
Let’s say you have a 12V 100Ah lithium battery and an MPPT charge controller in an off-grid cabin. You want a solar panel that will charge your battery from 100% DoD in 15 peak sun hours.
To find out what size panel you need, you’d enter the following into the calculator:
- Battery Voltage (V): 12
- Battery Amp Hours (Ah): 100
- Battery Type: Lithium (LiFePO4)
- Battery Depth of Discharge (DoD): 100%
- Solar Charge Controller Type: MPPT
- Desired Charge Time (in peak sun hours): 15
Turns out, you need a 110 watt solar panel to charge a 12V 100Ah lithium (LiFePO4) battery in 15 peak sun hours with an MPPT charge controller.
What Size Solar Panel to Charge 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 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 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.
What Size Solar Panel to Charge 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 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 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 24V 100Ah 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 need around 610 watts of solar panels to charge a 24V 100Ah lithium battery from 100% depth of discharge in 5 peak sun hours with an MPPT charge controller.
- You need around 760 watts of solar panels to charge a 24V 100Ah lithium battery from 100% depth of discharge in 5 peak sun hours with a PWM charge controller.
What Size Solar Panel to Charge 24V 100Ah 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 need around 430 watts of solar panels to charge a 24V 100Ah lead acid battery from 50% depth of discharge in 5 peak sun hours with an MPPT charge controller.
- You need around 540 watts of solar panels to charge a 24V 100Ah lead acid battery from 50% depth of discharge in 5 peak sun hours with a PWM charge controller.
What Size Solar Panel to Maintain 100Ah 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 are charts showing what size solar panel you need to maintain 100Ah batteries of various voltages using a PWM charge controller. I recommend PWMs for trickle charging because they generally have lower power consumption (which makes a small difference during long charging cycles). Also, MPPTs often require a PV voltage of 4-5 volts above battery voltage to start charging. That’s easy to achieve with a large solar panel, but not with a small one.
Note: Many factors affect a battery’s self-discharge rate — such as age of the battery and ambient temperature. To keep things simple I just used a desired charge time of 1000 peak sun hours for these calculations.
What Size Solar Panel to Maintain 100Ah Lithium Battery?
| Battery Voltage | Estimated Solar Panel Size |
|---|---|
| 12V | 4 watts |
| 24V | 6 watts |
| 36V | 7 watts |
| 48V | 9 watts |
Summary
You need a 5-10 watt solar panel to maintain a 100Ah lithium battery.
What Size Solar Panel to Maintain 100Ah Lead Acid Battery?
| Battery Voltage | Estimated Solar Panel Size |
|---|---|
| 12V | 3 watts |
| 24V | 4 watts |
| 36V | 5 watts |
| 48V | 6 watts |
Summary
You need a 3-6 watt solar panel to maintain a 100Ah lead acid battery.
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Alex Beale is the founder and owner of Footprint Hero. As a self-taught DIY solar enthusiast, Alex has spent 4 years producing educational solar content across YouTube, TikTok, Instagram, and the Footprint Hero blog.During that time, he's built Footprint Hero to over 7 million blog visits and 18 million YouTube views. He lives in Tennessee.
Hi, I'm Alex. I’m a DIY solar power enthusiast on a journey to learn how to solar power anything. Footprint Hero is where I’m sharing what I learn – as well as the (many) mistakes I’m making along the way.
