third battery hookup

[tee3peeo]

I have a `14" T25 syncro. I've attached a leisure battery and linked it in the usual way. I've connected a feed from the alternator to a relay and then the positive and negative from the main battery via the relay. The question is this. Can I link another battery? I've got a spare which I would like to keep charged. How do I connect this one to the system I've described. I would be grateful if anyone coul;d offer tips or a links to a diagram.

cheers
Zeb

[kevtherev]

Yes you can...
just connect the battery in parallel.

It would help if the third battery is of similar Amp hour rating

[tee3peeo]

Hi Kevtherev,
thanks for reply. So - parallel, pos to pos, neg to neg - do I need to add another relay? The amp hour rating is different tho. The second battery is a leisure battery about 115 I think whilst the third would be a starter battery - about 65, is it vital?

cheers
zeb

[kevtherev]

yes it matters to some degree that they are similar, as they discharge at different rates so would be unequal when charging.
Your Alternator would favour the most discharged battery, so the others would loose out.

however if that doesn't matter to you, because you just want to keep it topped up.. then just do it. no relay needed just connect them like you say

[tee3peeo]

thanks kevtherev

zeb

[davidharvey]

would they both not just charge as said to lowest level....ie 65 amp, so therefore not much a gain over the single 115 amp leisure battery? (65x2=130)

[CovKid]

you can also get smarter relays that will charge two leisure batteries.

[kevtherev]

indeed but if he disconnects the smaller of the two once charged they could be recharged in a staggered fashion