How Long To Charge 50ah Battery? + Calculator

How long to charge a 50ah battery with solar power will depend on these factors

  1. Battery depth of discharge
  2. The size of the solar panel
  3. 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:

Battery charge time calculator

Solar Panel Size
Watts
Battery Capacity (Ah)
Ah
Battery Volts (V)
Volts
Battery Type
Battery Depth of Discharge (DoD)
%
Charge Controller Type

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.

how long to charge 50ah lithium battery
how long to charge 50ah lithium battery

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.

Method #1

⚠️ 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

Method #2

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

There will be 20% less power output in real-world from your solar panels

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

  1. Multiply the battery Ah by the battery depth of discharge
  2. 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.
  3. Divide the step 2 value by the charge output Amps.

For example

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 SizeHow long to charge 50ah battery
20 watts22 peak sun hours
50 watts9 peak sun hours
70 watts6 peak sun hours
100 watts4.4 peak sun hours
120 watts3.5 peak sun hours
150 watts3 peak sun hours
200 watts2 peak sun hours
Table: How long to charge 50ah battery

Summary

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

Keep reading…

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I'm an experienced Sales Consultant with a demonstrated history of working in the renewables and environment industry. Skilled in Photography, Customer Service, and Sales.

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