200Ah Battery Backup Time Calculator
A 200 Ah, 12 V tubular battery gives about 3 h 24 min of backup for a 300 W load (a fan, lights and a TV) through a home UPS, using the safe 50% of its capacity. Backup hours = Ah × volts × usable depth of discharge × inverter efficiency ÷ load watts; the chart below shows common loads.
How this result was calculated
200 Ah × 12 V × 50% usable × 85% inverter efficiency = 1,020 Wh usable. 1,020 Wh ÷ 300 W = 3.4 hours, about 3 h 24 min.
Key facts
- A 200 Ah, 12 V tubular battery stores about 1,020 Wh of usable energy for a UPS when used to the recommended 50% of its rating.
- That 1,020 Wh runs one ceiling fan (80 W) for about 12 h 45 min, two fans with lights (200 W) for about 5 h 6 min, and a 1,000 W load for only about 1 h 1 min.
- A 200 Ah lithium (LiFePO4) battery at 12.8 V gives about 6 h 32 min at 300 W, almost twice the tubular figure, because it can use about 90% of its capacity.
- A 150 Ah tubular battery gives three quarters of the backup of a 200 Ah battery at the same load: about 3 h 50 min at 200 W.
Formula
t = (Ah × V × DoD × η) ÷ P
- t = backup time in hours
- Ah = battery capacity in amp hours
- V = battery bank voltage
- DoD = usable depth of discharge
- η = inverter efficiency
- P = load in watts
How to read the 200 Ah battery backup chart
The chart below uses the loads most Pakistani homes put on a UPS. One ceiling fan is about 80 W; two fans with LED lights about 200 W; a fan, lights and a TV about 300 W; a fridge with fans a few hundred watts more; and 1,000 W is the kind of load an iron, a microwave or a water motor adds. Each row is a 12 V tubular battery through a UPS at about 85% efficiency, using 50% of the battery.
Every doubling of the load halves the backup. To stretch a 200 Ah battery through a long outage, keep the TV and fridge off the UPS and run only fans and lights; the backup climbs from about 3 h 24 min to about 5 h 6 min.
150 Ah battery backup time
A 150 Ah tubular battery at 12 V holds about 765 Wh of usable energy through a UPS. That is about 3 h 50 min at 200 W (two fans and lights); at 300 W with a TV added it drops to about three quarters of the 200 Ah figure of 3 h 24 min. The 150 Ah rows in the chart give the exact hours for each load.
If a 150 Ah battery is not enough, a second battery in series on a 24 V UPS doubles the energy, but you must change the bank voltage to 24 V in the calculator rather than entering the Ah twice.
Worked examples
200 Ah battery backup time for one fan
One ceiling fan at 80 W: 200 Ah × 12 V × 50% × 85% = 1,020 Wh, ÷ 80 W = about 12 h 45 min, a whole night.
200 Ah battery for two fans and lights
Two fans with a few LED bulbs are about 200 W. 1,020 Wh ÷ 200 W = about 5 h 6 min on a 12 V tubular battery.
200 Ah battery for a 1,000 W load
1,020 Wh ÷ 1,000 W = about 1 h 1 min. The UPS draws about a hundred amps from the battery at this load, and a tubular battery drained this fast gives less than its label Ah, so the real figure is shorter.
200 Ah lithium battery backup
200 Ah × 12.8 V × 90% × 85% = 1,958 Wh usable. At 300 W that is about 6 h 32 min, roughly double the tubular figure for the same load in the chart.
150 Ah battery for two fans and lights
150 Ah × 12 V × 50% × 85% = 765 Wh, ÷ 200 W = about 3 h 50 min.
200 Ah and 150 Ah tubular battery backup chart (12 V, through a UPS)
| Battery | Load | Usable energy | Backup time |
|---|---|---|---|
| 200 Ah | 80 W | 1,020 Wh | 12 h 45 min |
| 200 Ah | 200 W | 1,020 Wh | 5 h 6 min |
| 200 Ah | 300 W | 1,020 Wh | 3 h 24 min |
| 200 Ah | 500 W | 1,020 Wh | 2 h 2 min |
| 200 Ah | 1,000 W | 1,020 Wh | 1 h 1 min |
| 150 Ah | 80 W | 765 Wh | 9 h 34 min |
| 150 Ah | 200 W | 765 Wh | 3 h 50 min |
| 150 Ah | 500 W | 765 Wh | 1 h 32 min |
Common mistakes
- Counting the full 200 Ah. A tubular battery should only be taken to about 50%; going deeper every day cuts its life to a year or two.
- Entering the Ah of two batteries added together. Two batteries in series on a 24 V UPS keep the same Ah and double the volts; set the bank voltage instead.
- Forgetting the inverter loss. The UPS turns only about 85% of the battery energy into AC power.
- Expecting the chart figure at a 1,000 W load. The label Ah is rated over about twenty hours; drained in an hour a tubular battery gives noticeably less.
Safety: Keep tubular batteries in a ventilated place away from sparks, use cables and fuses rated for the UPS current, and have a licensed electrician connect the UPS to house wiring.
Frequently asked questions
What is the 200 Ah battery backup time for one fan?
About 12 h 45 min for one ceiling fan of about 80 W on a 12 V tubular battery through a UPS. An inverter fan or a DC fan draws less and runs longer.
A 200 Ah battery gives how many hours?
About 3 h 24 min at 300 W, about 5 h 6 min at 200 W and about 12 h 45 min at 80 W. The usable energy is fixed at about 1,020 Wh; the hours depend on the load.
How much backup does a 200 Ah tubular battery give?
The calculator uses 50% of the rating and a UPS at about 85% efficiency, giving about 1,020 Wh and 3 h 24 min at 300 W. Many UPS units run the battery lower than that, which gives more hours but a shorter battery life.
What is the backup of a 200 Ah lithium battery?
About 6 h 32 min at 300 W for a 12.8 V LiFePO4 battery, nearly double the tubular figure, because lithium can use about 90% of its capacity. Switch the battery type to lithium above to see other loads.
Can a 200 Ah battery run a 1,000 W load?
Only for about 1 h 1 min, and less in practice because of the fast-discharge drop. The UPS must also be rated for 1,000 W or more; a typical home UPS of about a kVA cannot deliver it.
Is there an inverter battery 200 Ah backup chart?
Yes, the chart above lists one fan, two fans with lights, fan with lights and TV, fridge with fans and a 1,000 W load for 200 Ah and 150 Ah tubular batteries. Change the inputs for any other combination.
How long does a 200 Ah battery run two fans and lights?
About 5 h 6 min for a 200 W load on a 12 V tubular battery, which covers an evening of loadshedding with margin to spare.
What is the backup time of a 150 Ah battery?
About 3 h 50 min for two fans and lights (200 W), from about 765 Wh usable. For a fan, lights and TV expect three quarters of the 3 h 24 min that a 200 Ah battery gives.
Sources
Last reviewed: