Why no start if I disconnect leisure battery?

[paulandchez]

The other day I was fitting a propex, so before I forgot, I disconnected the leisure battery neg. As it was, I never got up to completing the wiring, but I left the lead off anyway.
However, when I came to put the van away, it wouldn't start. I just had normal lights on dash but turning key did nothing. Refitting leisure negative resulted in starting first time.

I have one of those intelligent split chargers fitted, so I'm assuming it's something to do with that, but my simple mind thought that if the engine was off, the batteries were two totally separate units. Mine is the type where it needs to see a high voltage (engine running) from starter battery before charging the leisure.

If this is right, ie no start if taking neg lead off leisure, what do I need to do to continue to use van if I take leisure battery out? Remove the split charge fuse nearest the starter battery?

Thanks

Paul

[California Dreamin]

All I can think of is that you are confused about which is the leisure battery.
The starter battery on a left hand drive Westy is behind the passengers seat....leisure behind the drivers.

Martin

[paulandchez]

I'm not great with electrics...but I'm not that bad!

[ghost123uk]

It won't be owt to do with the voltage sensing split charge relay.

Has it got an alarm / immobiliser fitted (even one you don't know is there). That might be being fed from the leisure battery and thus cause this behaviour.

[Ruralman]

Is it not just because you broke the circuit, both starter battery and leisure battery usually have the negative poles of each battery joined.


Regards
Keith

[ghost123uk]

Ah, but Keith, Paul's dash lights were lighting up

[Oldiebut goodie]

I think that every owner should be forced to keep a written record of all wiring modifications made/found as after 30 years who knows what's what!
Maybe someone has modded it to run the radio off the leisure and somehow included the dash lights at the same time.
Is there a helper relay for the starter solenoid that is powered by the leisure?
Good luck tracking it all!

[royt28]

i think your starter battery needs testing. The auto split charge relay is working in reverse
keeping the relay open. will only disconect when shut off voltage is reached on the l/battery.

[ghost123uk]

i think your starter battery needs testing. The auto split charge relay is working in reverse
keeping the relay open. will only disconnect when shut off voltage is reached on the l/battery.

With the greatest of respect, that isn't how it works. A voltage sensing relay remains off (ie batteries not connected) until the voltage on it's input reaches around 13.6 Volts. With no engine running neither of the batteries can be at that voltage, so it remains off.

[royt28]

He might have a cheap relay.or solar panel which will open the relay. only a thought.

My setup is 4x90amp batteries on the leasure side a 140amp Durite voltage split charge relay, 88amp starter & 100w solar panel. during the day the relay is open because of the solar input or i start using the ham equipment in the back or ebber startup it will dissconect until solar replacement or alternator charge from engine. The only problem i can see having the relay open like this if the main starter battery was quite smaller in amps .

[paulandchez]

It won't be owt to do with the voltage sensing split charge relay.

Has it got an alarm / immobiliser fitted (even one you don't know is there). That might be being fed from the leisure battery and thus cause this behaviour.

Ooooo you might just have hit the nail on the head. I'm sure I fitted the alarm to the leisure battery when I first installed it, just to make sure everything was sound and I didn't drain my starter due to mis wiring. Bet I never remembered to swap it over!!

I'll check tomorrow