What Size Solar Panel To Charge 100Ah Battery? (Calculator + Chart)

Let’s say you have a 100Ah battery and want to charge it with solar panels. What size solar panel do you need to charge a 100Ah battery? We will show you exactly how to calculate the solar panel wattage you need to charge a 100Ah battery. To make things even easier, we have created:

  1. 100Ah Battery Solar Size Calculator. You just input how many volt battery you have (12V, 24V, 48V) and type of battery (lithium, deep cycle, lead-acid), and how quickly you want the battery to be charged, and the calculator will automatically determine the solar panel size (wattage) you need.
  2. Chart Of What Size Solar Panel Is Needed To Charge Your 100Ah 12V Battery. We have calculated what size solar panel you need to charge any 100Ah battery in 1, 2, 3, … 20 peak sun hours (or up to 4 days). You will find all the results summarized in the neat chart at the end.
What Size Solar Panel To Charge 100Ah Battery
Solar panel charging a 100Ah 12V lithium battery via the charge controller.

Alright, let’s set up this task properly. Pretty much any solar panel will be able to charge a 100Ah battery. It just depends on how long it will take. Here are some examples we calculated along the way:

  • A 100-watt solar panel will charge a 100Ah 12V lithium battery in 10.8 peak sun hours (or, realistically, in little more than 2 days, if we presume an average of 5 peak sun hours per day).
  • A 400-watt solar panel will charge a 100Ah 12V lithium battery in 2.7 peak sun hours (or, realistically, in about half a day, if we presume an average of 5 peak sun hours per day).
  • A 10kW solar system will charge a 100Ah lithium battery in 6.48 peak sun minutes. That’s quick!

To adequately calculate the size of the solar panel to fully charge any 100Ah battery, we have to take a 2-step approach.

  1. Calculate how much juice solar panels have to add to the battery. This will depend on 100Ah battery voltage and type (lithium, deep cycle, lead) and related discharge rate.
  2. Calculate how much time it will take for 100W, 200W, 300W, 400W solar panels, and so on, to add that juice to the 100 Ah battery.

100Ah Battery Capacity Calculation (1st Step)

Let’s start by calculating the battery capacity we need to add to the 100Ah battery (in watt-hours or Wh). This will depend on these two factors, namely:

  • Battery voltage. Most 100Ah batteries will have 12V, 24V, or 48V voltage. At a 100% discharge rate, the battery capacity is calculated by multiplying 100Ah with voltage (Battery Capacity (Wh) = 100Ah × Voltage). That means that a 100Ah 12V battery has a 1,200 Wh capacity, a 100Ah 24V battery has a 2,400 Wh capacity, and a 100Ah 48V battery has a 4,800 Wh capacity.
  • Type of battery and related discharge rate. We can never use 100% of the juice in the battery (that would equal a 100% discharge rate). In general, lithium LiFeP04 batteries have a 90% discharge rate, deep cycle batteries have an 80% discharge rate, and lead-acid batteries have a 50% discharge rate. That means that, out of 100Ah of available electricity, the actual usable battery capacity will be 90Ah (lithium batteries), 80Ah (deep cycle batteries), and 50Ah (lead-acid batteries).
100ah 12v lithium battery to be charged with solar panels
No battery can be exhausted fully (100%). Lithium batteries are great because they have 90% discharge rate (you get 90Ah of useful electricity from them).

Here is a chart of how much electricity solar panels have to add to 100Ah batteries (12V, 24V, 48V lithium, deep cycle, and lead-acid batteries), based on these two factors:

Battery Type (And Discharge Rate): 12V Usable Battery Capacity (Wh): 24V Usable Battery Capacity (Wh): 48V Usable Battery Capacity (Wh):
100Ah Lithium LiFePO4 Battery (90% Discharge Rate): 1,080 Wh 2,160 Wh 4,320 Wh
100Ah Deep Cycle Battery (80% Discharge Rate): 960 Wh 1,920 Wh 3,840 Wh
100Ah Lead-Acid Battery (50% Discharge Rate): 600 Wh 1,200 Wh 2,400 Wh

Alright, let’s take a 100Ah 12V lithium battery since this is the most commonly used 100Ah battery. As we see from this chart, a solar panel will need to add 1,080 Wh of electricity to this battery in order for it to be fully charged.

Now, let’s take a look at the sizes of solar panels that can generate this electricity:

Solar Panel Batteries That Can Charge 100Ah Batteries

The most common solar panel sizes are 100-watt, 200-watt, 300-watt, and 400-watt panels. This is a specified solar panel wattage that is generated during peak sun hours. In the US, we get a daily average of about 3 peak sun hours (Alaska) to 7 peak sun hours (Arizona). We will take an average of 5 peak sun hours, and calculate how much electricity we get.

Here’s how this works – A 100-watt solar panel will generate:

  • 100 Wh in 1 peak sun hour.
  • 200 Wh in 2 peak sun hours.
  • 300 Wh in 3 peak sun hours.
  • 400 Wh in 4 peak sun hours.
  • 500 Wh in 5 peak sun hours.

Alright, we can see that a 100-watt solar panel can (on average, given 5 peak sun hours per day) produce 500 Wh of electricity. The 100Ah 12V lithium battery will need (we have calculated this in the previous chapter) 1,080 Wh to be fully charged. That means that a 100W solar panel can fully charge a 100Ah 12V lithium battery in a bit more than 2 days (10.8 peak sun hours, or 2 days, 3 hours, and 50 minutes, to be exact).

Here is a glimpse at what size solar panel you need to charge a 100Ah 12V lithium battery in 1-20 peak sun hours (for the full story, use the calculator and the chart further on):

Peak Sun Hours: Solar Panel Size To Charge 100Ah 12V LiFePO4 Battery):
1 Peak Sun Hour: 1.080 Watt Solar Panel
2 Peak Sun Hours: 540 Watt Solar Panel
3 Peak Sun Hours: 360 Watt Solar Panel
4 Peak Sun Hours: 270 Watt Solar Panel
5 Peak Sun Hours: 216 Watt Solar Panel
6 Peak Sun Hours: 180 Watt Solar Panel
7 Peak Sun Hours: 154 Watt Solar Panel
8 Peak Sun Hours: 135 Watt Solar Panel
9 Peak Sun Hours: 120 Watt Solar Panel
10 Peak Sun Hours: 108 Watt Solar Panel
11 Peak Sun Hours: 98 Watt Solar Panel
12 Peak Sun Hours: 90 Watt Solar Panel
13 Peak Sun Hours: 83 Watt Solar Panel
14 Peak Sun Hours: 77 Watt Solar Panel
15 Peak Sun Hours: 72 Watt Solar Panel
16 Peak Sun Hours: 68 Watt Solar Panel
17 Peak Sun Hours: 64 Watt Solar Panel
18 Peak Sun Hours: 60 Watt Solar Panel
19 Peak Sun Hours: 57 Watt Solar Panel
20 Peak Sun Hours: 54 Watt Solar Panel

As you can see, the bigger the solar panel you use, the quicker your 100Ah battery will be 100% full.

For example, in 2 days, most Americans get about 10 peak sun hours of sunlight. To fully charge a 100Ah 12V lithium battery using these 10 peak sun hours of sunlight, you would need a 108-watt solar panel. Practically, you would use a 100-watt solar panel, and in a little bit more than 2 days, you will have a full 100Ah 12V lithium battery.

Alright, let’s inch a little bit closer to the calculator and the all-encompassing chart:

Time It Takes To Charge A 100Ah Battery With Solar Panels

This is the overhaul equation we can write for how many peak sun hours it takes for 100W, 200W, 300W, 400W solar panels, and so on, for any 100Ah battery:

Time To Charge 100Ah Battery = 100Ah × Voltage × Battery Discharge Rate / Solar Panel Wattage

Let’s take a 100Ah 12V lithium battery (0.9 discharge rate). We want to charge it with a 400-watt solar panel. How will that take? Just insert everything in the equation like this:

Time To Charge = 100Ah × 12V × 0.9 / 400 Watts = 2.7 Peak Sun Hours

As we can see, a 400-watt solar panel will need 2.7 peak sun hours to charge a 100Ah 12V lithium battery. If we presume that we get 5 peak sun hours per day, we can actually fully charge almost two 100Ah batteries (or one 200Ah battery).

Now, there are many different 100Ah batteries, and you can use many different solar panel sizes to charge them. To help you figure out what size PV panels you need to charge 100Ah in a certain time, we have designed the following 100Ah Battery Solar Size Calculator.

You have to choose battery voltage (usually 12V, 24V, or 48V), battery type (lithium, deep cycle, lead-acid), and how quickly you want the 100Ah battery to be charged (in peak sun hours). The calculator will automatically give you the adequate solar panel size (wattage) you need for that. PS: Don’t forget to check out the all-encompassing 100Ah battery solar panel size chart below the calculator:

100Ah Battery Solar Size Calculator

Hint: Play around with the 2nd slider (peak sun hours) to see how the solar panel size changes.

 

Here is how this solar panel size calculator for 100Ah batteries works:

Let’s say that you have a 100Ah 24V deep cycle battery. You want the solar panel to charge it in 5 peak sun hours (that’s 1 normal day in the states). What size solar panel do you need for that? Just slide the voltage slider to ’24’, pick ‘100Ah Deep Cycle Battery’, and set the peak sun hours slider to ‘5’.

You get the result: You need a 384-watt solar panel to charge this battery. Basically, if you get one 400W Tesla solar roof panel, it should do the trick.

Now, let’s look at all the various battery types and the solar panel sizes that can fully charge these 100Ah batteries in 1-50 peak sun hours:

100Ah 12V Solar Panel Size Chart

Peak Sun Hours (And Normal Hours, Days): 100Ah 12V Lithium Battery Solar Panel Size: 100Ah 12V Deep Cycle Battery Solar Panel Size: 100Ah 12V Lead-Acid Battery Solar Panel Size:
1 Peak Sun Hour
(4.8 Normal Hours):
1.080 Watt Solar Panel 960 Watt Solar Panel 600 Watt Solar Panel
2 Peak Sun Hours
(9.6 Normal Hours):
540 Watt Solar Panel 480 Watt Solar Panel 300 Watt Solar Panel
3 Peak Sun Hour3
(14.4 Normal Hours):
360 Watt Solar Panel 320 Watt Solar Panel 200 Watt Solar Panel
4 Peak Sun Hours
(19.2 Normal Hours):
270 Watt Solar Panel 240 Watt Solar Panel 150 Watt Solar Panel
5 Peak Sun Hours
(1 Normal Day):
216 Watt Solar Panel 192 Watt Solar Panel 120 Watt Solar Panel
6 Peak Sun Hours
(1.21 Normal Days):
180 Watt Solar Panel 160 Watt Solar Panel 100 Watt Solar Panel
7 Peak Sun Hours
(1.42 Normal Days):
154 Watt Solar Panel 137 Watt Solar Panel 86 Watt Solar Panel
8 Peak Sun Hours
(1.63 Normal Days):
135 Watt Solar Panel 120 Watt Solar Panel 75 Watt Solar Panel
9 Peak Sun Hours
(1.83 Normal Days):
120 Watt Solar Panel 107 Watt Solar Panel 67 Watt Solar Panel
10 Peak Sun Hours
(2 Normal Days):
108 Watt Solar Panel 96 Watt Solar Panel 60 Watt Solar Panel
11 Peak Sun Hours
(2.21 Normal Days):
98 Watt Solar Panel 87 Watt Solar Panel 55 Watt Solar Panel
12 Peak Sun Hours
(2.42 Normal Days):
90 Watt Solar Panel 80 Watt Solar Panel 50 Watt Solar Panel
13 Peak Sun Hours
(2.63 Normal Days):
83 Watt Solar Panel 74 Watt Solar Panel 46 Watt Solar Panel
14 Peak Sun Hours
(2.83 Normal Days):
77 Watt Solar Panel 69 Watt Solar Panel 43 Watt Solar Panel
15 Peak Sun Hours
(3 Normal Days):
72 Watt Solar Panel 64 Watt Solar Panel 40 Watt Solar Panel
16 Peak Sun Hours
(3.21 Normal Days):
68 Watt Solar Panel 60 Watt Solar Panel 38 Watt Solar Panel
17 Peak Sun Hours
(3.42 Normal Days):
64 Watt Solar Panel 56 Watt Solar Panel 35 Watt Solar Panel
18 Peak Sun Hours
(3.63 Normal Days):
60 Watt Solar Panel 53 Watt Solar Panel 33 Watt Solar Panel
19 Peak Sun Hours
(3.83 Normal Days):
57 Watt Solar Panel 51 Watt Solar Panel 32 Watt Solar Panel
20 Peak Sun Hours
(4 Normal Days):
54 Watt Solar Panel 48 Watt Solar Panel 30 Watt Solar Panel

Alright, now you can fully see what size solar panel you need to charge a 100Ah 12V solar panel (be it lithium, deep cycle, or lead-acid).

Example: If you want to charge a 100Ah 12V lead battery in 15 peak sun hours (that’s usually 3 days worth of sunlight), you need only a 40W solar panel.

We hope that this article illustrates well how to go about sizing a solar panel for 100Ah battery charging. If you have any questions or would need our help, just give us some numbers in the comment section below, and we will help you out.

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