120 Ah battery backup time
How long a 12 V 120 Ah tubular inverter battery runs at different loads, alone and as a 24 V pair.
- About 5 h 10 min at 200 W
- About 2 h at 400 W
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One 120 Ah battery (12 V inverter)
A fully charged, healthy battery. At 400 W it discharges at about 0.35C, against the C20 (0.05C) its Ah is rated at, so it gives less than the label.
| Load | Backup | Example |
|---|---|---|
| 50 W | 23 h | Wi-Fi and two lights |
| 100 W | 11 h 30 min | A fan and three lights |
| 150 W | 7 h 20 min | |
| 200 W | 5 h 10 min | Two fans, four lights, TV |
| 250 W | 3 h 55 min | |
| 300 W | 3 h | Three fans, lights, TV, Wi-Fi |
| 400 W | 2 h | Three fans, six lights, TV, Wi-Fi |
| 500 W | 1 h 20 min | Add the fridge |
| 600 W | 1 h 05 min | Four fans, lights, TV, fridge |
| 800 W | 50 min | A big house, or a cooler |
Two 120 Ah batteries (24 V inverter)
The usual set-up for 1.5 kVA and 2 kVA inverters.
| Load | Backup (2 batteries, 24 V) |
|---|---|
| 300 W | 7 h 20 min |
| 400 W | 5 h 10 min |
| 500 W | 3 h 55 min |
| 600 W | 3 h |
| 800 W | 2 h |
| 1000 W | 1 h 20 min |
| 1200 W | 1 h 05 min |
| 1500 W | 55 min |
120 Ah models we list
Specs as stated on each manufacturer’s page. Sorted by brand; we don’t rank them.
| Model | Type | Warranty | Maker’s backup at 400 W |
|---|---|---|---|
| Exide FEM0-IMTT1200 | tall tubular | Not stated | — |
Method: watt-hours at 12 V × the share lead-acid delivers at that current, fitted to V-Guard’s published 400 W backup table, ÷ load. Checked against Exide’s Inva Zen tables, which it matches within about 10% from 200 to 400 W and undershoots at 100 W. Real backup falls as the battery ages.