Skip to content
wattmaths

How long will a 200Ah lithium battery last?

By Last reviewed

A 12.8 V 200Ah LiFePO4 battery holds 2,560 Wh, about 2,048 Wh usable. With a 500 W load through a 1,000 W inverter it lasts about 3.7 hours.

Your battery and load

LiFePO4 is 12.8 V a block.

Between 1 and 2,000

From the appliance's rating plate.

Between 1 and 20,000

A 230 V appliance needs an inverter.

Inverter

Maker figures. Continuous watts at 25 °C in brackets.

No model for this voltage. Pick another, or type both figures.

Maker's peak figure.

Between 50 and 100

What it uses switched on with no load.

Between 0 and 200

Advanced settings
Advanced

If the maker gives Wh. Replaces Ah × volts.

Between 10 and 100,000

Depth of discharge you allow.

Between 10 and 100

Lead-acid loses Ah at high current. 1 turns it off.

Between 1 and 1.5

Continuous discharge from your battery's spec.

Between 1 and 2,000

See result ↓

Your result

Runtime

3.7 hours

2,048 Wh usable ÷ 559.5 W at the battery = 3.7 h

Usable energy
2,048Wh
At the battery
559.5W
Battery current
43.7A
C-rate
0.22C
Without idle draw
3.7h
Common shortcut
4.8h

The shortcut: volts × Ah ÷ watts, all of the battery, no inverter. It is what many tools show.

Choosing an inverter? Check its size and the current it pulls.

Fix the highlighted field to update.

Link copiedShared

How we calculated this

  • Usable energy is the battery volts times its amp hours, times the share you can safely use.
  • A mains load runs through an inverter, so its losses and idle draw are added.
  • Runtime is the usable energy divided by the power drawn at the battery. Lead-acid loses capacity at high current.

Full method, tables and sources: Battery runtime calculator

  1. Usable energy

    12.8 V × 200 Ah × 80% = 2,048 Wh

  2. Power at the battery

    500 W ÷ 91% + 10 W idle = 559.5 W

  3. Runtime

    2,048 Wh ÷ 559.5 W = 3.7 h

  4. Current and rate effect

    43.7 A, 0.22C, 100% of rated capacity

Your load on each battery type
BatteryUsable WhHours
LiFePO4 (lithium)2,0483.7
Lead-acid (AGM, gel or flooded)8171.5
Shortcut: volts × Ah, all of it, no inverter2,4004.8

Each type at its default usable share and rate effect, same capacity, load and inverter. The shortcut row is what you get from volts × Ah ÷ watts.

This version starts with a 200 Ah LiFePO4 battery running a 500 W load through a Victron Phoenix 1200 VA inverter (1,000 W). Type your own load, or pick a bigger inverter.

200Ah lithium battery: what the sources say

Estimate

  • The same load on 200 Ah of lead-acid lasts about 1.5 hours. Half the capacity is usable, and at 43.7 A it gives less than its rated Ah (Peukert exponent 1.25).

Official source

  • Victron rates its Phoenix 1200 VA inverter at 1,000 W continuous at 25 °C and 850 W at 40 °C. It draws 10 W on 12 V with no load at all.
  • Victron allows 400 A continuous on its 12,8/200 LiFePO4 battery, but recommends 1C (200 A) or less because of heat.

New to battery maths? Read how runtime is worked out on the main battery runtime calculator.

Questions

How long will a 200Ah battery run a 1,000 W load?

About 1.8 hours on 200 Ah of LiFePO4 at 80% usable, through a Phoenix 1200 VA at 91% plus 10 W idle. Type 1000 in the load to check.

What size inverter suits a 200Ah lithium battery?

Check the battery current, not only the Ah. At 12.8 V, a 2,000 W load pulls about 169 A, under a 200 A (1C) limit. A 3,000 W load pulls about 248 A.

Is two 100Ah batteries the same as one 200Ah?

For energy, yes, if they are the same model wired in parallel: 200 Ah at 12.8 V. Each battery still has its own current limit. Follow the maker’s wiring instructions.