Running different sized batteries in a Duel Battery config?

[_Andy]

Hi All,

Is it possible to run different sized batteries in a duel battery setup? So for example have the starter battery as a 60AH but run a larger accessory battery, say 120AH. Will the split charge system deal with this?

[motorman116]

I think that it will cause problems, as basically when the ignition is on both batteries are connected together via a relay. Its much easier to fit 2 batteries the same, just to be on the safe side..

[_Andy]

Thanks, I thought this might be the case, I'll have to give my plans some more thought.

[Altransit]

It's not a split charge system, both batteries are on charge when the engine is running, and will be charged at the same rate.
Personally, I don't think that fitting different batteries would cause a problem, as they're disconnected at power down, but I still think it's a good idea to fit a pair of the highest CCA available, especially if you discharge the aux battery regularly, as the poor old starter battery will possibly need to start the engine on it's own, with not much help from the depleted aux battery

[twin--turbo]

When i got my van the secondary battery kept going flat if left a few days.. they were old and unmatched...

I got two identical batteries based on warnings/advice/etc here.. never got round to fitting them due to other pressures.... as yet 2 months later the old batteries are working fine!


From what I have worked out though... Two identical units is probably the best option.

TT