Stay In Charge Of Your Battery Life

Our Diamond Dave repairs motorhomes for a living, which makes him the technical guru to consult when things go wrong.

Diamond Dave

First, you need to bear in mind the 50% rule – a 100Ah battery is only reliably good for 50Ah. You also need to consider that the battery’s actual capacity will vary according to how much current is being drawn – the higher the current, the less the actual capacity will be. That 100Ah battery is looking pretty puny now.

One recent case in point was a bit of a head scratcher. The customers were new motorhome owners, who complained that their twin leisure batteries wouldn’t last more than a couple of hours when they were watching TV.The batteries were new and had been tested and deemed good, and the charging systems were all functioning well, including the solar panel; so it was time for some testing.

The setup was two 100Ah leisure batteries, and a 1000W inverter whose output is fed into the ’van’s 230V sockets via a selector switch in the wardrobe (enabling the entire 230V system to be powered from the mains hook-up, or just the sockets from the inverter).

The TV system was a roof-mounted auto satellite dish and a 12V monitor connected to a Sky receiver powered from the inverter. With it set up and running, and all the internal lighting switched on, the battery voltage was monitored, as well as the total current draw (around 11A).