How long does it take to charge a 150 AH inverter battery?

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Most of us use a 12 Volt and 150 AH inverter battery in the home to continue electricity even if there is an outage. Have you ever thought about how long it takes to charge a 150 AH inverter battery?

In this article, I’ll explain the same and show you the formula to calculate it.

TLDR; it takes around 13~14 hours to charge a 150 AH battery.

How? Here is the explanation, read carefully…

First, understand the C rating of a battery. The battery C rating is the measurement of the current at which a battery can be charged and discharged. Usually we get C5, C10, and C20 ratings.

In the inverter, most of us use 12 Volts β€” 150 Ah C10 battery.

Check out β€”

Time = AH Γ· I

Battery’s Ah rating is 150 AH. Now we just need current for further calculations.

The Current (denoted by I) needed to charge the battery is AH Γ· C# (in hours).

I = 150AH Γ· 10H = 15A.

So, applying the time formula:

Time = Ah Γ· I
     = 150AH Γ· 15A
     = 10 Hours (theoretical, without battery's efficiency).

A battery requires a little more current, like 1+ or 2+ Amps more, to charge the battery.

So I added 1 more Ampere to the rated value.

Time = Ah rating / I
     = 150 Ah / 16 A
     = 9.375 Hours (without battery's efficiency).

If you want to calculate exact hours, just add more than 40% loss because lead-acid batteries are only 60% efficient.

So here I am adding 40% more time to the formula:

= 9.375 Hours + (9.375 Hours * 40%)
= 9.375 Hours + 3.75 Hours
= 13.125 Hours ~ 13.5 Hours.

So, to charge a 150 Ah battery, will take around 13.5 hours of charging. If you have a different configuration of battery, do calculate the values using the above formula.


Q: What if I am of using 2 batteries of 150 Ah.

A: If batteries are connected in parallel, the Amps will double. If connected in series, then Ah and Volts will double.

Q: I am using a solar setup and I only get 6-7 hours of clear sun. Still, the time will be the same.

A: Yes, just make sure the whole time it is generating enough charging current. The formula is using DC current, not the AC current. So make sure the solar system generates more than 15-16 Amps of current all the time.

Do you have any other queries? Do let me know in the comment section below.

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