Do I (Does anyone?) Need A Second Battery Isolator?

Submitted: Monday, Feb 04, 2008 at 18:42
ThreadID: 54234 Views:3501 Replies:4 FollowUps:6
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I have just finished setting up my Prado with an auxiliary battery and heavy cabling via an Anderson plug to the van battery, as per this link.

I have used an electronic battery isolator between the car battery and the auxiliary battery (in the car), which, I understand, ensures that charge from the alternator goes first to the cranking battery until it is charged, then to the auxiliary battery.

Following that logic, shouldn't there then be another battery isolator between the auxiliary battery in the vehicle and the caravan battery? This would ensure that the charge would go to the cranking battery until it was full, then to the auxiliary battery until it was full and finally to the van battery.

It seems to me you might need this if the auxiliary battery was flat and the van battery nearly full, or vice versa because without an isolator the two batteries are just connected in parallel and the flat battery will just drag the fuller one down, requiring BOTH batteries to be re-charged and having to share the charge from the alternator. That seems to me to be pretty inefficient.

Wouldn't it be better to have a second electronic isolator to direct the charge between the vehicle auxiliary battery and the van battery, just as the first isolator directs it between the cranking battery and the auxiliary?

But I haven't seen or heard of this, so is there a reason it's not done?

Cheers

FrankP

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