How Long Will A 200 Ah Battery Last?

Have you ever calculated how long a 200 Ah battery would last?

If you have, then you might know how tedious the calculation is!

If you haven’t, then you needn’t look further.

Well, the question is a very interesting one, but there’s no simple answer to it. Nevertheless, if you know a few specifications and can do some calculations, you can estimate how long a 200 Ah can last.

Let us begin by answering simple questions.

What Is Ah?

Ah, short for Ampere hour is the amount of energy stored in a battery that it can provide for one hour.

Ah is also a unit that determines the capacity of a battery.

If a battery has a 200Ah rating, it means it can deliver a charge of 200-amps in an hour in ideal conditions.

Ideal conditions can mean optimal temperature, consistent power, and zero vibration. However, such conditions hardly exist.

A battery with greater Ah will deliver more current, which ultimately reflects power in watts.

Can You Predict Accurately How Long A 200Ah Battery Will Last?

The answer to the main question of this article is not going to be 100% accurate.

However, as irritating as it sounds, the answer is going to be the best estimate or a guess. It is as simple as tracking a 200Ah battery and determining its longevity.

This is because of the factors involved in determining the duration of a battery. They are never subject to constant change.

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The factors that determine the duration of a battery are as follows:

Age Of The Battery

New batteries can store energy closer to its rating. The 200Ah battery you buy today will have a 200Ah capacity today.

As time passes, this capacity will decrease even to half.

Type Of Battery

Different batteries have different maintenance conditions that optimise them for performance.

Although the how-to of battery maintenance is not in the scope of this article, all it takes is a little research.

For example, the maintenance of NiCAD batteries is such that one should fully discharge them before the next charging session.

If you do not discharge NiCAD batteries before charging, the battery life will decrease.

On the other hand, one should never fully discharge lithium-ion batteries. Lithium-ion batteries will not operate at their best if you fully discharge them.

Operating Temperature

Extreme temperatures, either hot or cold, affect a battery’s performance. This means that it will operate at a lower capacity.

A Manufacturer’s manual mentions the ideal storage location and temperature for best performance.

A battery under the shade will have a higher capacity as compared to a battery under the sun.

Battery Discharge Time

The quicker a battery exhausts, the lower its capacity.

If one pushes a 200Ah battery to deliver its entire capacity in an hour, the battery may not last for all 60 minutes. However, if the working time increases to 4 hours, there is a good chance it will run the entire duration.

This phenomenon varies across batteries and capacities. But unless you push your battery to the limit, this will not be an issue in the estimation.

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What Type Of Battery Should I Buy?

There are primarily two types of batteries that are used. One is the lead-acid battery, and the other is the lithium battery.

Although lithium phosphate batteries have a higher initial cost, they have many advantages that make them worth the buy.

Simply put, lithium batteries can deliver more power as compared to other batteries of the same rating. This is because one can discharge them to depth more than lead-acid batteries.

One can discharge them as much as 95%. However, experts recommend an 80% discharge to lengthen the life of the battery.

Lithium-ion batteries don’t need maintenance, while the maintenance cost of lead-acid batteries is higher for small batteries.

Lithium-ion batteries have greater efficiency as compared to lead-acid batteries.

Lithium batteries also have a longer warranty period of 8 years, while lead-acid batteries are 4 years.

Lithium-ion batteries deliver a discharge rate of 10,000 cycles as compared to the 1200 cycles provided by lead-acid batteries.

In summarising the above points, lithium-ion batteries prove to be better than lead-acid batteries.

How Long Will A 200Ah Battery Last?

Out of the several ways to determine, let’s use the simplest way to break it down.

200 Ah is 200 amp hours. This is the maximum rate of the current flow of the battery. So it implies that if you draw 200-amps, it would take one hour to drain the battery.

Similarly, if you drew 100-amps, it would take 2 hours to drain the battery. If one draws 50-amps, the battery will last four hours and eight hours for 25-amps.


Let us add the voltage of a battery to the mix.

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If the 200Ah battery has a voltage of 12V, the total capacity or charge in the battery will be 200 times 12 equals 2400 Wh. Similarly, a battery of 24V will have a capacity of 4800Wh.

Depth Of Discharge

But this is not it. Every battery has a depth of discharge and this impacts the total deliverable current rate of the battery.

A 200Ah lithium battery with a 90% DoD will have a current rate of 180Ah. A 200Ah lead-acid battery has a 50% DoD and can deliver only 100Ah.

Average Wattage Of Running Device

Now it is time to consider how energy-intensive the power-operated device is.

A 200 Ah battery with 12V has a capacity of 2400Wh. A 100W device, therefore, will run for 24 hours till the battery is exhausted.

However, a 400W device will run only for 6 hours on the same battery.

Running Time Of Battery Formula

Considering the above factors, we can form an equation:

Running time of battery = Capacity x Voltage x (Depth of Discharge/Device Wattage)

Considering a 200Ah battery of 12V with 90% (0.9) DoD and a 100W device, we get the Running time of battery = 200 x 12 x (0.9/100)= 21.6 hours.


As mentioned earlier, all attempts to answer this question will be, at best, estimates.

However, we have given a strong case for how long a 200Ah battery will last. The examples and formula will be very helpful to you. If you want to calculate the same for a larger battery, you can use the formula to find out how long it will last.

To make the most of your battery, use the right type of battery and maintain it under ideal conditions.



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