Choosing an inverter battery
Two decisions: how much backup, and which type of plate. Everything else follows.
How much backup — the Ah
Start with the Ah in your inverter's manual, then adjust for how long your cuts actually last. As a rough guide, a 150Ah battery on a 900VA inverter running two fans, four LED lights and a TV lasts around 4 to 5 hours. Double the Ah and you roughly double the hours. Going below the manual's figure is the one thing not to do.
Flat plate
Cheapest to buy, 3 to 4 years of life, recharges quickly. The right answer where cuts are short and occasional, and where the inverter sits somewhere a slim trolley has to fit.
Tubular and short tubular
40 to 70% dearer, 5 to 8 years of life, and far better at holding charge through long or daily cuts. Cheapest per year of use. Short tubular is the same technology in a squatter case — the answer when height is the constraint.
Gel and lithium
Gel is sealed: no topping up, no fumes, safe indoors. Lithium is a fraction of the weight with many times the cycle life and no maintenance at all — highest upfront, lowest over its life.
Three things people forget
- Trolley height. A tall tubular battery does not fit a slim trolley. Measure before you order.
- Ventilation. Anything that needs topping up needs air. If it has to live in a cupboard, buy gel or lithium.
- Voltage. A 24V inverter needs two batteries, not one. The listing says how many.