# How Long Will 200Ah Battery Run 400W Appliance? + Calculator

A 12v 200ah battery will run an appliance that requires 400W for between 2.7 hours (with lead-acid battery type, 50% DoD limit) to 5.4 hours (with lithium battery type, 100% DoD limit)

Keep reading I’ll explain how you can calculate how long will your 200ah battery run on a 400-watt appliance and also some shortcomings of all these methods

## Battery Runtime Calculator

Battery Capacity
Ah
Battery Volts
V
Select Battery Type
Wh

Note! use my solar panel size calculator to find out what size solar panel you need to recharge your battery in desired hours with solar panels.

### Assumptions:

• Inverter Efficiency: 90%
• Lead-acid battery: 50% depth of discharge limit
• Lithium (LiFePO4): 100% depth of discharge limit

Battery Depth of discharge DoD: is the percentage of the battery that has been discharged relative to the total battery capacity. The recommended depth of discharge limit for lead-acid, AGM, and gel batteries is about 50%. Only lithium (LiFePO4) batteries can be fully discharged to 100%.

After entering the information, click “Calculate” button to find out how long the battery last running a load.

## Steps to calculate 200ah battery runtime on 400-watt appliance

Follow these steps to calculate the battery life/runtime while running a load.

### Steps

1- Converter battery ah into watt-hours (Wh). to calculate the battery capacity in watt-hours use this formula

``Battery capacity in watt-hours = Battery amp-hours (Ah) * Battery Volts ``

let’s say you have a 12v 200ah battery

``200ah battery in watts = 200 * 12 = 2400 watt-hours ``

2- Multiply the battery watt-hours by the battery depth of discharge limit. ( Default battery depth of discharge limit, Lead-acid battery: 50% DoD limit; Lithium: 100% DoD limit ). Let’s say you have a lead-acid type battery

``Battery capacity in wh after DoD limit = 2400 * 50% = 1200wh``

3- Multiply the battery capacity after the DoD limit with the inverter efficiency rate to calculate the AC watt-hours ( Most of the inverters are about 90% efficient)

``Battery AC watts = 1200 * 90% = 1080 AC watt-hours ``

4- Divide the battery AC watt-hours by the total load connected. Let’s say 400-watt appliance is connected to your 200ah battery

``200ah battery runtime on 400w appliance = 1080 / 400 = 2.7 hours``

## How long will a 200Ah battery run an appliance that requires 400W

here’s a chart on how long will a 12v, 24, and 48v 200ah lead-acid or Lithium battery will last on 400-watt load.

## Assumptions & Shortcomings of All These Methods

Here are some extra yet important points to keep in mind when figuring out how long your 200ah battery will last running a load

### Battery life cycle count:

• The storage capacity of the battery will decrease with every cycle ( a cycle is when you charge and discharge the battery to its DoD limit ).
• if you have used your battery for a few hundred cycles then the result will be different. ( this factor isn’t included in my above-given methods )

### 200ah lead-acid Batteries are rated for 10 amps over 20 hours of time:

• Especially lead-acid type batteries are designed to be discharged at 20 hours. ( means 200ah lead-acid batteries are recommended to be discharged @ 10 amps in order to maintain the battery health and reduce the discharge efficiency ).
• on the other hand, AGM and lithium (LiFePO4) can be discharged at 50% of their capacity.
• Discharging your battery at a higher rate will increase heat in the battery’s internal cells which will cause power loss. (this factor isn’t included in my above-given methods).
• For example, if you discharge your lead-acid battery with 200 amps then it’s will not last 30 minutes ( keep in mind the 50% DoD limit ). but it may last about 15-20 minutes.
• Check the battery discharge rate on the specs sheet of your battery or it’ll be mentioned on the battery (1h → 1C, 2h → 0.5C, 5h → 0.2C, etc.)

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