Thread: Multiple batteries

I'm no auto electrician (where is Relay?) but I would think it would depend on the type of batteries where you could connect them. The accessory battery is usually a deep-cycle type and the dual battery system will cope with that on its own. But if you put a normal car battery in parallel with it then the dual battery controller will not be able to manage them properly.

If the batteries are wired up correctly - then the system that looks after the 2nd circuit will measure volts and amps - and it will average out between the 2 or three.

I don't see an issue here, as long as all the batteries are usable - if you have 2 good and one naff one it will upset the apple cart.

ladas

On the Simpson Trip we wired the Traxide SC80 to a 200Tdi defender with dual batteries in the battery box and a couple of very large deep cycle batteries on the tray.

The tray mounted batteries powered two fridges, lighting, 2000W 240V invertor (used to boil kettel etc) and a water pump for the 400 litre tank. The rear batteries had an independent monitoring / alarm system attached.

We found that the rear batteries never got to a fully charged state, although they were on battery chargers before the trip. The 200Tdi had a 50amp alternator, which may have been a bit weak...

..... (continued - sorry, got called out at work). The Defender had the Italian alternator rated at 50amp output. It bench tested okay, but the volt meter never showed more than 13V with all the batteries attached (we carried a spare alt - just in case). Once the excess batteries were removed after the trip, the volt meter again showed 13.8 Volts. One of the batteries may have been suspect, and have been drawing down the whole system. I suppose with more batteries you need to be more aware of each battery's health, and the health of your charging system. Toward the end of 2 weeks, once food supplies were getting lower, we disconnected one of the fridges to conserve power / battery charge. And although we used the 2000W invertor to boil the kettle, we always kept the motor idling during (alternator charging) during such peak power consumption periods.

In summary, the extra batteries were a bit more complicated to manage and diagnose than we anticipated.

Thanks guys. Both of these batteries will hold a charge but can't manage to work as cranking batteries. This means they are a little dodgy. I was hoping to use them to power a fridge and a compressor.