Words and images by Kevin Trollope
Camping in the bush while having vehicle electrics drawing up to 4A, is not sustainable. Trying to solve the problem with back-ups like solar-powered DC-to-DC chargers, or installing a second battery, won’t work either. The excessive current draw has to be eliminated or reduced, and that’s that. This is a challenging problem (raised in the March issue by Alan Moseley, a Ford Ranger owner), and one that many of us 4x4ers have, especially when a vehicle is left standing and unused.
When I tested my (diesel engine) Land Cruiser 70 Series Troopie, for example, it drew 1.29A with the ignition on, and dropped to 750mA in the accessory position. With the keys removed from the ignition (everything off and courtesy lights switched off) the current draw was about 300mA when a door was open and then closed. After a longish two minutes with all the doors closed, the current draw dropped to about 50-70mA sleep mode.
The make of vehicle under test should be irrelevant to this discussion, as most modern vehicles with central-locking systems probably have similar current draws. If yours is higher, as in the case of Alan’s Ranger, then a battery isolator switch (a proper 300A unit with a solid ‘cluck’ when switched over) should be considered. I looked at many Aussie and American blogs on the matter, and was surprised to see that the installation of such an isolator switch is almost standard practice as an aftermarket modification, where the isolator switch is installed in the cable that connects to the negative terminal.
When the vehicle electrics are disconnected from the battery, there’s no chance of running the battery flat. The reality is that, if a courtesy light is left on by accident or a door is not closed properly, this may prevent the car’s electronic ‘brain’ from going into its low-power sleep mode. However, if the battery is isolated from these systems, then, when the vehicle is left standing, it would be only the selfdischarge of the battery one had to contend with − which becomes more of an issue as the battery ages; but that’s a topic for another discussion! As an interim measure, the negative terminal can simply be disconnected. However, this becomes a pain in the long-term.
By installing a secondary 100Ah battery, many things are possible, particularly if one installs a split-charging system in addition to a battery isolator. National Luna offer just such a DIY split-charging kit, which disconnects the main or starting battery from the vehicle electrics via the isolator switch, and allows the auxiliary battery to power the camp fridge and lighting. When driving, it works like this: on start-up, the split charger allows the alternator to charge up the main battery; and then, when the system detects that the first battery is fully charged, it closes the contacts and allows the alternator to charge both batteries, in parallel, to full charge.