How long to charge a 50ah battery with solar power will depend on these factors
- Battery depth of discharge
- The size of the solar panel
- Charge controller type
To make this easy for you! i have made a battery charge time calculator “Enter the battery specs, depth of discharge, the size of solar panel, and select the charge controller type”
Also, you’ll learn:
- How long to charge a 50ah battery with a charger? (2 amp, 5 amp, 10 amp… )
- charging efficiency of lead-acid or lithium battery
- How fast can you recharge your 50ah battery?
Battery charge time calculator
Note! Use this solar panel size calculator if you want to find out what size solar panel you need to charge your battery in desired peak sun hours.
Some instructions about calculator
The battery charging time will be according to peak sun hours. if you’re not sure “What are peak sun hours?” click here to read the post in which I’ve explained it in detail. In short,
- 1 peak sun hour = 1000 watts per meter square (1kw/m2) of sunlight intensity
- use this calculator to determine how many hours of peak sunlight your location receives per day.
What is Battery Depth of Discharge or DoD? is the percentage of the battery that has been discharged from its total capacity
Example: how long to charge 50ah lithium battery
Let’s suppose you have a 12v 50ah lithium battery with 100 depth of discharge, and a 200-watt solar panel system using an MPPT charge controller.
12v 50ah lithium battery will take about 4 peak sun hours to get fully charged with 200 watt solar panel system using an MPPT charge controller
How many watts is a 50Ah battery?
First of all, let’s calculate the battery capacity in watts because solar panels are measured in watts. This step is to make the calculation easy
To calculate the battery capacity in watts, we use this formula
Battery capacity in watts = Battery Ah * Battery volts
let’s take a 12v, 24v, and 48v 50ah battery as an example
50ah * 12v = 600 watts, 50ah * 24v = 1200 watts, 50ah * 48v = 2400 watts
12v 50ah battery is equal to 600 watts, 24v 50ah battery is equal to 1200 watts, 48v 50ah battery is equal to 2400 watts.
Calculate 50Ah battery charge time (2 methods)
I have seen many simple ways to calculate the battery charge time online. But they are the most inaccurate way of determining how long it will take to charge the battery.
So in this post, I’ll share the two methods, starting from the most common and easy but the most inaccurate one.
And also I’ll share the method to calculate the charging time of a battery with the charger as well.
⚠️ This is the most common but inaccurate way of measuring the battery charge time!
Step 1: convert the battery in watt-hours, which we have done in the above session, so we’ll take 12v 50ah battery as an example (600 watt-hours)
Step 2: Multiply the battery capacity in watt-hours by the battery depth of discharge. So we’ll take a lead-acid battery as an example with 50% DoD.
600 * 50% = 300 watts
Step 3: Divide the battery capacity after DoD by the solar panel wattage. let’s say you have a 200 watt solar panel
300 / 200 = 1.5 hours
This method doesn’t take into account the charging efficiency of the battery, charge controller inefficiency, and the solar panel efficiency
This is the most accurate way to determine how long it will take to charge the battery with a solar panel
Step 1: convert the battery in watt-hours
which we have done in the above session, so we’ll take 12v 50ah battery as an example (600 watt-hours)
Step 2: Multiply the battery capacity in watt-hours by the battery depth of discharge.
So we’ll take a lead-acid battery as an example with 50% DoD.
600 * 50% = 300 watts
Step 3: Multiply the battery capacity after DoD by 1.15 for lead-acid type battery or by 1.02 for lithium (LiFePO4) battery type.
As we have considered lead-acid battery
300 * 1.15 = 345 watts
Step 4: multiply the solar panel wattage by 0.8 if you’re using a PWM charge controller or by 0.98 if you’re using an MPPT charge controller.
let’s say you have a 200 watt solar panel and a PWM charge controller
200 * 0.8 = 160 watts
Step 5: Take into account the solar panel efficiency in peak sun hour by multiplying the solar panel rated wattage by 0.8
160 * 0.8 = 128 watts
Step 6: Divide the battery capacity after charging efficiency by the average solar panel output in peak sun hour
345 / 128 = 2.5 peak sun hours
How long to charge 50ah battery with charger?
To calculate how long to charge 50ah battery with a charger you need these steps
- Multiply the battery Ah by the battery depth of discharge
- Multiply the battery capacity in Ah by 1.15 if you have a lead-acid, AGM, or gel battery. Or by 1.02 if you have a lithium-ion (LiFePO4) battery.
- Divide the step 2 value by the charge output Amps.
50 * 50% = 25Ah
25 * 1.15 (lead-acid) = 28.7Ah
Suppose you have a 5A charger
28.7 / 5 = 5.7 hours
Here’s a list of how long to charge a 50ah lead-acid battery with a different amp charger:
- 2 Amp charger: 14 hours
- 4 Amp charger: 7 hours
- 10 Amp charger: 3 hours
- 20 Amp charger: 1.5 hours
- 40 Amp charger: 45 minutes
Maximum charging current for 50ah battery?
in order to maintain the battery health they are recommended be to discharged and charged at a specific percentage of current.
Here’s a list of types of 50ah batteries with their recommended max charging rate
- 50ah lead-acid, AGM, and gel batteries: 12.5A or 150 watts for 12v battery or 300 watts for 24v battery
- 50ah Lithium (LiFePO4) battery: 50A or 600 watts for 12v battery or 1200 watts for 24v battery
How long to charge 50ah battery? – chart
Here’s a chart on how long it takes to charge a 12v 50ah lead-acid battery with different size solar panels using an MPPT charge controller
|Solar Panel Size||How long to charge 50ah battery|
|20 watts||22 peak sun hours|
|50 watts||9 peak sun hours|
|70 watts||6 peak sun hours|
|100 watts||4.4 peak sun hours|
|120 watts||3.5 peak sun hours|
|150 watts||3 peak sun hours|
|200 watts||2 peak sun hours|
12v 50ah lead-acid battery will take anywhere between 22 (using 20 watt solar panel) to 2 peak sun hours (using 200 watt solar panel) to get fully charged from 50% Depth of discharge
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