Bongo Fury

Been away for the weekend and now the bongo won't start - battery flat

I'm suspecting the split charge relay. When I disconnect the leisure battery, everything carries on working. It certainly didn't do this before and I can't think of any wiring I've changed since.

Does it sound like a change of relay will sort it? Any other tests to do?

Sound like it could be a problem with the Starter Battery terminals/clamps and or the battery earth to body strap. Try giving them all a good clean and tighten.


Good Luck.

Sounds very odd! You need to take voltage measurements with ignition off, on and with engine running of both batteries as a minimum. But first check all the terminal connections, unbolt clean and replace also check the earth strap connections to the chassis for both batteries.

Limited in tools here. Had a jump start and given it a good run.

There were two fuses next to the leisure battery so I've pulled the larger one out which I think has unlinked them. With the fuse in, the lighter socket gadget shows 12.7v with the engine not running. If I pull the fuse out it drops to 12.5v. So I presume the lb is running at the lower voltage.

If I wiggle the relay that I presume is the split charge relay it clicks, so I think it is sticking open (or closed)

All battery terminal connections are perfect, I've undone each and reconnected.

Removing the fuse did the trick for the rest of the trip. I just reinserted it to charge the LB up, but removed it to stop it draining the starter battery.

The only thing I can see that it could be is the relay. If the contacts have welded across then it would stick causing it to stay connected even when the alternator is no longer charging (or at least that is how I understand it!)

The LB is possibly on its way out - it definitely isn't lasting as long with the coolbox so maybe it has been drawing more current through the relay? The relay does feel warm to the touch too.

Now wondering if it is worth putting a switch in to completely break the link when camping to ensure it doesn't happen again.

What sort of split charge system and relay have you got ? Pictures of the relay would help.

sotal wrote:Removing the fuse did the trick for the rest of the trip. I just reinserted it to charge the LB up, but removed it to stop it draining the starter battery.

The only thing I can see that it could be is the relay. If the contacts have welded across then it would stick causing it to stay connected even when the alternator is no longer charging (or at least that is how I understand it!)

The LB is possibly on its way out - it definitely isn't lasting as long with the coolbox so maybe it has been drawing more current through the relay? The relay does feel warm to the touch too.

Now wondering if it is worth putting a switch in to completely break the link when camping to ensure it doesn't happen again.

I've often thought an isolator switch was a good belt and braces idea - not hard to fit or use and might just save the day.

g8dhe wrote:What sort of split charge system and relay have you got ? Pictures of the relay would help.

Not got any pictures but from my quick look the other day it appears to be just a standard size black relay with 4 wires going to it.

I think a wire comes from the alternator to activate it and when it does it connects the two battery positive terminals together.

Would I be better to upgrade to a Voltage sensing one? Like this one:

http://www.12voltplanet.co.uk/voltage-s ... -140a.html

Not necessarily, they are just different switching methods, of more importance is the Ampere rating of the relay contacts if its less then 40Amp then that might be a cause for concern. It should be clearly marked on the cover 20A / 30A / 40A or whatever.

g8dhe wrote:Not necessarily, they are just different switching methods, of more importance is the Ampere rating of the relay contacts if its less then 40Amp then that might be a cause for concern. It should be clearly marked on the cover 20A / 30A / 40A or whatever.

The old relay is a 40A

The info on the top of it says:

NAGARES
RLP / 4-12
12V-40A

Then there is a little circuit diagram with 292 written to the side and it has the following terminals: 30, 86, 85, 87


Should I just replace it with like for like or is it an opportunity to upgrade?

OK well the relay should be OK in terms of current rating, as to if its faulty or not then you need to take measurements to be certain. The symptoms as described at the start don't really pinpoint the problem your having with flat battery.
Just changing the relay for an uprated set of contacts might not be the answer at all. The covers on the relays can normally be removed to inspect the contacts if they aren't welded closed in the operated position then unlikely to be the relay itself, I much prefer to find the problem before randomly changing parts as it may come back and bite again at a later stage!

I'll remove the relay and have a look.

I tried to remove the crimp terminals from it the other day but they were stuck fast! Felt like I would pull the terminals out of the relay before I remove the crimp connectors!

g8dhe wrote:OK well the relay should be OK in terms of current rating, as to if its faulty or not then you need to take measurements to be certain. The symptoms as described at the start don't really pinpoint the problem your having with flat battery.
Just changing the relay for an uprated set of contacts might not be the answer at all. The covers on the relays can normally be removed to inspect the contacts if they aren't welded closed in the operated position then unlikely to be the relay itself, I much prefer to find the problem before randomly changing parts as it may come back and bite again at a later stage!

Relay removed and to be fair I think you are right!

All looks fine and relay appears to operate correctly.

With the ignition all turned off the relay is energised and the batteries effectively linked together. Now just to figure out why!

I managed to remove the crimp connectors from the terminals using some penetrating spray.

Testing the 4 wires that come to the relay - all are constant 12v except for 86.

Any ideas on where to look next!?

Right terminal 30 goes straight to the positive terminal of the starter battery via a fuse so that makes sense to be 12v constant.

Terminal 87 goes straight to the LB positive terminal via a fuse so again that makes sense to be 12v constant.

The other two should be the switch. (One to the alternator, one to GND)

However I would expect both to show 0v and one is currently showing 12v so that will be my first point of investigation.