split charge dual voltage charger

[dubslug]

hi all.
my fridge stopped running the other day, problem was low voltage on my leisure battery. It was down to 11.7.
when i bought it i was lead to believe the alternator would charge which ever battery needed it. my main battery was reading 12.4 volts so i would have assumed that leisure battery should have been getting charged??? but it wasnt. i hooked up to mains and instantly it started charging leisure battery.
so my question is....
will leisure battery only charge at 240v?? once it was full it flicked over to main battery for a bit
or does the alternator first charge main battery then move onto leisure battery???
had van 6 months and not had this before
thanks

[bigherb]

It depends on how it is wired up. If it has Zig unit you normally have to switch it to touring to charge the auxiliary battery when the engine is running.

[dubslug]

hi thanks for reply... most wiring is hidden... i have no zig unit....
so far i have found the relay, black box looks about cigarette packet size, looks to have a one + wire to main battery, one + wire to leisure battery and earth.
also under rock and roll bed is a plug socket, if this is off it wont charge from mains.
im sure it used to charge when driving before, i have redone all connections so i know there good... is it feesable that the dual charger will charge main battery first with engine then leisure battery after and vice versa when on mains???

[AdrianC]

is it feesable that the dual charger will charge main battery first with engine then leisure battery after and vice versa when on mains???

Kinda... The alternator puts ~14v to both batteries (via the splitcharge relay). The battery that's lower voltage will "take" more charge, until they're both about the same level of charge, at which point both will charge together. It's most unlikely there's anything intelligent enough to actively direct the charge to one or the other.

Very few mains chargers charge both batteries. I s'pose it's possible that one's been fitted to act like the alternator, and trip the splitcharge relay, but usually it'd only be the leisure that gets charged on mains. If the wiring's been done sensibly, then it's only the leisure that's going to need it, anyway.

As Herb says - depends on how it's all wired up. Gawd knows what some genius might've thought a good idea... <grin>

[bigherb]

Put a picture up of the relay we will be able to work it out.

As Herb says - depends on how it's all wired up. Gawd knows what some genius might've thought a good idea... <grin>

Yeah someone thought this was a good idea.

[AdrianC]

Yeah someone thought this was a good idea.

<shudder>

[dubslug]

just a bit of an update, went away this weekend....
aux battery died again... no matter how much driving was done the voltage sensing relay wouldnt charge the aux battery...
plug into hook up and it charges aux battery, does this sound like faulty relay??
the voltage regulating relay is wired from main battery into relay, then out of relay into aux battery, the relay is also earthed...
help urgently needed
regards

[bigherb]

Put a picture up of the relay so we know which type you are talking about.

[dubslug]

hi thanks for reply, i cant get picture due to after market seats, using mirrors to get info... can see

bsr 12v 60 amp
out in 13.
out in 12.8

[bigherb]

BSR are quite well known relays.
It should switch the relay on charging the auxiliary battery when the starting battery charging voltage reaches 13.3V.
First check the starter battery is being charged above this voltage, there should be two fuses in the circuit, one near the starter battery for the relay and one in the cable next to the auxiliary battery check they have not blown, also check the BSR relay still has its earth cable attached.

[dubslug]

Just at van now, would seem that it's either loosing charge when not in use or not charging correct. Battery was about 12v. When I came out,started it up and have it running and it's not charging above 13.18 V. Am I right in thinking that's reason that aux battery isn't being charged as my main can't get to 13.3 V. Is it new alternator time?

[Oldiebut goodie]

Possibly solved by new regulator/brush pack for the alternator, if that is a voltage sensing relay.

[bigherb]

Am I right in thinking that's reason that aux battery isn't being charged as my main can't get to 13.3 V. Is it new alternator time?

Yes. First check the alternator belt is tensioned correctly and not slipping, check wiring the connections to the alternator and the starter motor are not corroded or loose. If they are ok then you just need to replace the regulator in the back of the alternator get one that is set at 14.2V or 14.4V

This is the part you need to replace

[AdrianC]

I'm getting confused here. What problem are we talking about...?

Failing to charge the batteries with engine running? That's the alternator.
Failing to charge the batteries with engine off and mains hook-up plugged in? That's the mains charger.

Either way - 14.5v(ish) is the "right" charging voltage for nominal 12v batteries. You should be seeing that at both/all batteries that you think are being charged.

The split charge relay disconnects the starter from the leisure, unless "charging voltage" is seen by it, at the alternator output. I guess the actual switch-over rating is going to depend on the relay, but I'd guess at about 13.5v or so. As we said earlier, but it depends on how the mains charger's been wired in, I'd not expect the split-charge to be involved in a mains charger setup - if it's a single-charge-output charger (like most), then it'd go straight to the leisure battery and ignore the starter, usually. If it's a dual-output charger (Westy BBB, probably others, but a bit "specialist"), then it'd probably go straight to each battery.

Just to add to BigHerb's suggestion of checking alternator belt - if the Aircooled alternator mount's like the WBX setup, check that the main alternator mount is still bolted to the block!

[Oldiebut goodie]

On my new alternator and regulator although supposedly 14v I only see 13.7v which p***ed me off. When I get round to it I will uprate it.