A 12v 100ah lead-acid battery with a 50% DoD limit will run an appliance that requires 800W for about 40 minutes. But, it’s not recommended to discharge your 100ah lead-acid battery at this much higher rate, it can permanently damage your battery
Keep reading I’ll explain how you can calculate how long will your 100ah battery run on an 800-watt appliance
100ah Battery runtime Calculator
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.
- 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%.
How To Use The Calculator
- Enter the battery capacity in amp-hours (Ah): in this case, it’ll be 100
- Enter the battery voltage: is this a 12, 24, or 48-volt battery?
- Select the battery type: Select “Lead-acid” if you’re using a flooded or sealed (AGM or gel) lead acid battery. Select “Lithium (LiFePO4)” if you use a lithium-iron-phosphate battery.
- load Connected with inverter?: Are you using an inverter to run the load or is the load connected directly through the battery?
- Enter total load in watts: Enter the total load in watts (e.g 800 for 800 watts of output load)
After entering the information, click “Calculate” button to find out how long the battery last running a load.
Video – Solar battery 101
Steps To Calculate 100ah Battery Runtime On 800-Watt Appliance
Follow these steps to calculate the 100ah battery life/runtime while running an 800w load.
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 100ah battery
100ah battery in watts = 100 * 12 = 1200 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 = 1200 * 50% = 600wh
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 = 600 * 90% = 540 AC watt-hours
4- Divide the battery AC watt-hours by the total load connected. Let’s say 800-watt appliance is connected to your 100ah battery
100ah battery runtime on 800w appliance = 540 / 800 = 0.67 hours
How Long Will A 100ah Battery Run An Appliance That Requires 800W
here’s a chart on how long will a 12v, 24, and 48v 100ah lead-acid or Lithium battery will last on 800-watt load.
|Battery Capacity||Battery Type||100ah Battery Runtime on 800w|
|12v 100ah||Lead-acid||0.68 hours|
|24v 100ah||Lead-acid||1.36 hours|
|48v 100ah||Lead-acid||2.7 hours|
|12v 100ah||Lithium (LiFePO4)||1.3 hours|
|24v 100ah||Lithium (LiFePO4)||2.7 hours|
|48v 100ah||Lithium (LiFePO4)||5.4 hours|
- A 12v 100ah lithium battery will run an appliance that requires 800W for about one hour and 15 minutes
3 Steps To Extend Your Battery Lifetime
Assumptions & Shortcomings of All These Methods
Here are some extra yet essential points to keep in mind when figuring out how long your 100ah battery will last running a load
Battery life cycle count:
- The battery’s storage capacity 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 )
100ah lead-acid Batteries are rated for 5 amps over 20 hours of time:
- Especially lead-acid type batteries are designed to be discharged at 20 hours. ( means 100ah lead-acid batteries are recommended to be discharged @ 5 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 100 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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