What size solar panel to charge 70ah battery? Use our solar panel size calculator or follow the steps mentioned below to find out.
6 steps to calculate solar panel size to charge 70ah battery
I come across several methods for calculating the size of solar panels required to recharge a battery online, but unfortunately, many of them result in inaccurate information.
In my experience, I found this method to be the most accurate as it considers a majority of real-world factors.
Let's begin!
Steps
1. Multiply the battery capacity amp-hours (ah) by battery volts to convert the battery capacity into watt-hours (Wh). let’s suppose you have a 12v 70ah battery.
70ah Battery capacity in Wh = 70 × 12 = 840 watt-hours2. Multiply the battery watt-hours by the battery depth of discharge limit. Lead-acid, AGM, and gel batteries come with a 50% depth of discharge limit, and lithium batteries with 100% DoD. let’s suppose you have a lead-acid battery.
Discharged Battery capacity in Wh = 840 × 0.5 = 420 watt-hours3. Multiply the battery capacity after DoD by 1.15 for lead acid and 1.01 for a lithium battery to take into account battery charge efficiency rate (source). Lithium: 99%; Lead-acid: 85%;
Solar power required to charge 70ah battery = 420 × 1.15 = 483wh
4. Divide the battery capacity value by the desired number of charge peak sun hours. let’s suppose you want to recharge your battery in 5 peak sun hours.
Solar power required in peak sun hour = 483 ÷ 5 = 96 watts
5. Multiply the solar power required in peak sun hour by 1.2 if you’re using a PWM charge controller or 1.02 for an MPPT charge controller to take into account the charge controller efficiency. Charge controller efficiency, PWM: 80%; MPPT 98%. Let’s suppose you’re using an MPPT charge controller.
Solar power required after charge controller = 96 × 1.02 = 98.5 watts6. Now multiply the value by 1.2 to consider the solar panel's efficiency.
Solar panel Required = 98.5 × 1.2 = 118 wattsYou need a 120 watt solar panel to charge a 12v 70ah lead acid battery in 5 peak sun hours using an MPPT charge controller.
Charging or discharging your deep cycle battery at a higher will cause pause power and can damage the battery's internal cells. Read the below to find out how fast can you recharge your lead acid or lithium battery. Must Read: Maximum Charging Current For 12v Battery
What are peak sun hours?
Peak sun hour is equal to when the intensity of the sunlight averages about 1kw/meter2.
We use peak sun hours as a reference when estimating the solar panel output. Use PV watts calculator to find out how many peak sun hours your location receives daily.
What Size Solar Panel To Charge 70ah Battery?
Here are some charts on what size solar panel you need to charge 70ah battery in desired time.
12v 70ah lead acid battery
| Charge Time | Charge Controller Type | Required Solar Panel |
|---|---|---|
| 4 peak sun hours | PWM | 170 watts |
| 5 peak sun hours | PWM | 140 watts |
| 6 peak sun hours | PWM | 115 watts |
| 10 peak sun hours | PWM | 70 watts |
| 15 peak sun hours | PWM | 50 watts |
| 20 peak sun hours | PWM | 35 watts |
| 4 peak sun hours | MPPT | 145 watts |
| 5 peak sun hours | MPPT | 115 watts |
| 6 peak sun hours | MPPT | 100 watts |
| 10 peak sun hours | MPPT | 60 watts |
| 15 peak sun hours | MPPT | 40 watts |
| 20 peak sun hours | MPPT | 30 watts |
Summary
- You need around 140 watts of solar panels to charge a 12V 70Ah lead-acid battery from 50% depth of discharge in 5 peak sun hours with a PWM charge controller.
- You need around 115 watts of solar panels to charge a 12V 70Ah lead-acid battery from 50% depth of discharge in 5 peak sun hours with an MPPT charge controller.
12v 70ah Lithium battery
| Charge Time | Charge Controller Type | Required Solar Panel |
|---|---|---|
| 4 peak sun hours | PWM | 310 watts |
| 5 peak sun hours | PWM | 250 watts |
| 6 peak sun hours | PWM | 200 watts |
| 10 peak sun hours | PWM | 120 watts |
| 15 peak sun hours | PWM | 80 watts |
| 20 peak sun hours | PWM | 60 watts |
| 4 peak sun hours | MPPT | 255 watts |
| 5 peak sun hours | MPPT | 200 watts |
| 6 peak sun hours | MPPT | 170 watts |
| 10 peak sun hours | MPPT | 100 watts |
| 15 peak sun hours | MPPT | 70 watts |
| 20 peak sun hours | MPPT | 55 watts |
Summary
- You need around 250 watts of solar panels to charge a 12V 70Ah lithium battery from 100% depth of discharge in 5 peak sun hours with a PWM charge controller.
- You need around 200 watts of solar panels to charge a 12V 70Ah lithium battery from 100% depth of discharge in 5 peak sun hours with an MPPT charge controller.
24v 70ah lead acid battery
| Charge Time | Charge Controller Type | Required Solar Panel |
|---|---|---|
| 4 peak sun hours | PWM | 350 watts |
| 5 peak sun hours | PWM | 280 watts |
| 6 peak sun hours | PWM | 230 watts |
| 10 peak sun hours | PWM | 140 watts |
| 15 peak sun hours | PWM | 90 watts |
| 20 peak sun hours | PWM | 70 watts |
| 4 peak sun hours | MPPT | 290 watts |
| 5 peak sun hours | MPPT | 230 watts |
| 6 peak sun hours | MPPT | 190 watts |
| 10 peak sun hours | MPPT | 115 watts |
| 15 peak sun hours | MPPT | 80 watts |
| 20 peak sun hours | MPPT | 60 watts |
Summary
- You need around 280 watts of solar panels to charge a 24V 70Ah lead-acid battery from 50% depth of discharge in 5 peak sun hours with a PWM charge controller.
- You need around 230 watts of solar panels to charge a 24V 70Ah lead-acid battery from 50% depth of discharge in 5 peak sun hours with an MPPT charge controller.
24v 70ah Lithium battery
| Charge Time | Charge Controller Type | Required Solar Panel |
|---|---|---|
| 4 peak sun hours | PWM | 610 watts |
| 5 peak sun hours | PWM | 490 watts |
| 6 peak sun hours | PWM | 410 watts |
| 10 peak sun hours | PWM | 250 watts |
| 15 peak sun hours | PWM | 160 watts |
| 20 peak sun hours | PWM | 120 watts |
| 4 peak sun hours | MPPT | 510 watts |
| 5 peak sun hours | MPPT | 410 watts |
| 6 peak sun hours | MPPT | 340 watts |
| 10 peak sun hours | MPPT | 200 watts |
| 15 peak sun hours | MPPT | 135 watts |
| 20 peak sun hours | MPPT | 100 watts |
Summary
- You need around 490 watts of solar panels to charge a 24V 70Ah lithium battery from 100% depth of discharge in 5 peak sun hours with a PWM charge controller.
- You need around 410 watts of solar panels to charge a 24V 70Ah lithium battery from 100% depth of discharge in 5 peak sun hours with an MPPT charge controller.
70Ah Battery: FAQs
How many watts is a 70Ah battery?
12v 70ah battery is equal to 840 watt-hours. calculate the watts in a battery using this formula ( battery ah × battery volts )
How many solar panels does it take to charge a 70AH battery?
12v 70ah battery will need about 110 watts of solar panels to charge in 10 peak sun hours from 0-100%.
