How Long Will a 200ah Battery Last?

03/04/2022

Many people would choose to use the solar batteries to charge and supply electricity for their home. In this post, i would like to introduce how long will a 200ah battery last. 

In genral, the run time of a 200Ah battery depends on the battery chemistry and the size of the load connected to it. Battery temperature and discharge rate also impacts how long a battery will last, but it’s the load that drives it all.

There are two main kinds of solar batteries in this size range are lead acid and lithium phosphate. Each type has different characteristics, advantages and disadvantages.

A 200Ah lead-acid deep-cycle battery running a 400 watt DC load with 50% recommended Depth of Discharge will last for approximately 3 hours. A 200Ah deep-cycle lead-acid battery will power a 400W rated refrigerator for about 25 hours at a rate of 40 watts per hour.

Are 200Ah lithium Batteries Better Than Lead-acid?

Lithium phosphate batteries are more expensive, but they have several advantages, the biggest being that they are intrinsically deep-cycle.

They can be discharged to a much greater depth than lead-acid deep-cycle. This means that you can get more power out of it for the same rated capacity.

Most LiFeP04 batteries can be discharged 95%, but 80% is recommended to maximize battery life.

A 200Ah lithium phosphate (LiFeP04) batteryconnected to a 400 watt DC load with 80% Depth of Discharge will last for almost 5 hours. A 200Ah lithium phosphate (LiFeP04) will run a 400W rated fridge for about 55 hours at a rate of 40 watts per hour.

How Long Will a 200 Ah Battery Run an Appliance That Requires 400w?

There are two basic types of loads:

DC, such as supplied by solar panels and solar batteries

AC, such as the power supplied by utility companies

In general, a 200Ah battery will run an AC load for less time than a DC load, simply because an inverter is needed to convert DC to AC.

The best quality inverters are about 95% efficient, so you lose 5% running time as extra power is needed to power the inverter electronics.

A 200Ah lead-acid deep-cycle battery should only be discharged 50% in order to maximize battery life, so only 100Ah is available for use. (80% can be used now and again.)

100Ah converts to 1200 watt-hours. Dividing this by 400 watts load gives us the answer:

A 200Ah lead-acid deep-cycle battery with 50% Depth of Discharge will run a 400W AC appliance for about 3 hours.

How Long Will a 200ah Battery Run an Appliance That Requires 200w?

If the load is DC, such as might be found on boats or RVs, then the calculation is pretty straight-forward:

200Ah = 200 x 12 volt = 2400 watt-hours

However, only 1200 watt-hours is available at the recommended 50% discharge so:

Run time for 200Ah battery running 200 watts DC = 1200 watt-hours/200 = 6 hours

For an AC load, it’s a little bit different. Let’s assume it’s a constant load and not a fridge, heat pump or air conditioner with compressor motors on board.

AC appliances use inverters which also need power to run i.e. they have losses. If running at full rated capacity, an inverter may have an efficiency of 95%, if it’s high quality.

The calculation becomes:

Run time for AC load = 1200 watt-hours/200 x 0.95 = 5.7 hours