Series 3 Split Charge System

Bump said:

Not sure what you expect a £100 relay to do differently to a £12.50 + £1.50 one, but, my £12.50 + £1.50 one (which cost me £10 a few years ago) allows me to flick a switch on the dash and for my second battery to be charged from the alternator as i drive. I can't quite see what more i'd want it to do tbh.
(I prefer to have it on a switch than the ignition as i like to have control over the split charge system)

I'm about to upgrade to a 3 battery system so will be purchasing another cheap relay.

I'll buy quality stuff where it matters, e.g. tools but something as simple as a relay it doesn't seem worth it.

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cheap relays may last years but will be less robust than more expensive versions of the same thing. you can bet your bottom doller they will burn out when you most need them not to. but your right, i would rather climb out of the cab, in the snow, and roll around naked than pay £100 for a relay (if it happens pics will be uploaded........you have been warned)

a 200amp ralay + fuse holder and fuse is about £28 and £2 every time the fuse blows. my method £7 and 6p every time a fuse blows (not that a 200 ish amp fuse operating a 34 amp split charge system will ever blow)

my method is cheaper and easy to repair if the worst happens. it uses standard easy to obtain, pluggable components.

yep more time consuming to set up initially, but cheaper.

both methods work, both methods are "a proper job" just another option i was giving the op, just in case he was short of £20 and didnt mind tying up electric string for a couple of hours.

for the record i have seen a number of split charge systems fail using your system and every one of them was down to s**t solder joints failing, my method involves a lot more soldering.

btw why do you want 3 batts? not critical just interested.

Fair enough, i can see your point, i think if my relay died in the field i'd just by-pass it and have both batteries parralled together.

I'll be honest there is no need for 3 batteries at all, other than i have 3 lying around. I have a normal car battery for all the normal car stuff then i have 2 x 100Ah batteries (well will have, just have 1 in at present) which will be used for the winch, lights, external 12v for tools, etc.

I'm in two minds over the 'jump start' option, i either want one of the batteries easily removable to take to vehicles which need a jump - which means you dont have the hassle of trying to get the landy close enough to a dead vehicle for the jump leads to reach, or, have one of those jump start points and making some descent length high quality jump leads.