Split Charge Relay

moonshine · Post by **moonshine** » Mon Oct 30, 2006 9:26 am

Hi Grumpo,
It would seem that split-charge relays have got a little more sofisticated since I last fitted one to a road vehicle. The one I last used was a simple high-current relay which connected the batteries together for charging purposes. Once the coil was energised, the contacts closed and the batteries were connected in parallel, so one would discharge into the other if the engine wasn't running to put some charge in. Obviously, with that set-up, if the coil was connected to the accessory (radio) terminal the relay would energise and connect the batteries together without the engine running.

I used the same set-up on my last boat, but the ignition switch on that had no accessory terminal as the auxilliaries were wired on a completely different circuit, directly from the leisure battery. It worked fine, and as far as I know is working still. The latest owner of that boat still belongs to the same club as me, and he hasn't said anything about it no longer working.

I haven't got a leisure battery on my Bongo yet, as so far I haven't needed one, but when I do I will take a closer look at the modern types of split-charge relay.

Veg_Ian · Post by **Veg_Ian** » Mon Oct 30, 2006 9:46 am

Moonshine

not all that more sophisticated except that some have extra output circuits for supplying more than one application but the cheapo stuff from the likes of Towsure aren't really up to the job and only handle low current. In terms of sophistication you could add a diode in the charge relay between the feed and earth to try and prevent feedback once the coil is engaged but I'm not convinced this would overcome the problem with the Bongo alternator's no charge configuration.

As Grumpo suggests, heavier battery connection wires is really the answer .

moonshine · Post by **moonshine** » Mon Oct 30, 2006 12:25 pm

I think my last split-charge relay came from Halfords. It had contacts rated at about 70 amps (I think) and worked very well. It has been on the boat now for at least 10 years as far as I know.

I did mention in my previous post that I would recommend cable of at least 60 amp rating, but the heavier the better really to avoid voltage drop. On a boat I would recommend even higher than that, as cable runs tend to be longer than in a Bongo.

I agree entirely with what Grumpo says, and it makes perfect sense if comparison circuits are included, but in the ones I have used in the past, they were not. The relays were just that, simple high-current relays. With a simple relay system such as I used, the only way to wire it is to energise the coil from an ignition-fed source. This way the relay is energised immediately you turn the key past the accessory position, but as you are about to start the engine anyway, the batteries are only connected together very briefly before you activate the starter. The starter battery would be fully charged, so no starter current would flow through the relay, as the leisure battery would be at a much lower state of charge. When the engine starts, the leisure battery would receive most of the charge, for exactly the same reason.

Hope you manage to get your system sorted out Ian, and that I havn't caused too much confusion.

Veg_Ian · Post by **Veg_Ian** » Mon Oct 30, 2006 12:43 pm

Not at all Moonshine. It's been a rewarding learning experience (

), thanks for your input. I'm thinking of using old jump start cables for the connections between the batteries. I've just got to devise a way of connecting fuses in there somehow.

Yamaha · Post by **Yamaha** » Mon Oct 30, 2006 1:46 pm

Hi Veg_Ian

The other alternatives you, and I, could consider, is the voltage-triggered relay device from Towsure - I guess this could sense the charge voltage going to the main battery, then switch on the SC relay when it reaches, say, 14volts. I guess that then, when you stop the engine, the main battery voltage will fall below the threshold of the Towsure relay, which will drop out, disconnecting the SC circuit.

Mike

ChrisEm · Post by **ChrisEm** » Mon Oct 30, 2006 2:08 pm

This is the sort of fuses you want for cable most decent auto factors not halfrauds but the independents who supply to trade will get them for Order a Durite catalogue off the web as they make similar items to these, most auto factors sell durite stuff http://cgi.ebay.co.uk/Mega-Fuse-Holder- ... dZViewItem

Veg_Ian · Post by **Veg_Ian** » Mon Oct 30, 2006 2:39 pm

Ouch!! You don't want to be blowing many of them at that price.

grumpo · Post by **grumpo** » Mon Oct 30, 2006 3:09 pm

Hi Ian,

The complete fuse unit suggested above looks a good piece of kit, and
I would use it if the fuse links were cheap enough and available. Most
converters use a simple in line fuse holder and I suspect that the links
for these would be about the same price.

Fitting diodes into the comparison circuit is really not a good idea because
the volt drop across the diode - between 0.3 and 0.6 volts - would interfere
with the comparitor switching point.

As I believe the Bongo alternator current output is around 60 amps, It
would appear that you have the perfect split charge relay for the job.
Why not make a proper job of it and uprate the cables and fuses ?.

Come on, you know it makes sense.

Grumpo.

PS.......

I have noticed on several occasions that Towsure relays were being used
for split charging. As you say, these relays are not up to the job, and the
reason is that they are specifically designed for fitting to Towsure
towbars where the additional socket is fitted to supply a caravan 3 way
fridge, allowing the fridge to have a small topup while on the move.

The maximum current for these is 30 amps and the 3 way fridge draws
about 20 amps, more than adequate for the intended purpose.

ChrisEm · Post by **ChrisEm** » Mon Oct 30, 2006 3:14 pm

The fuses are actually about a quid, the link was the holder et al.

Veg_Ian · Post by **Veg_Ian** » Tue Oct 31, 2006 8:21 am

Now this is getting silly.

Last night I started to overhaul the SC Relay system in readiness for fitting heavier cable etc. I removed the wire tap from the alternator no charge wire and moved it to the radio as before. Relay is still disconnected.

When I switched the ignition on all was well except that the glowplug light is flashing both before and after starting the engine. Charge and sediment lights go out. Now what's that all about? I meticulously disconnected the starter battery before messing around near the alternator.

By now it was getting late and I was beginning to lose my rag so thought I had best give up before I start to get rough and throw spanners around. I tried to come on here to gain a clue and couldn't connect to my ISP aaargh!!!

Anyway accessed from here at work, I searched the archives and found that it may be a blown fuse. Not sure how that could have happened but that has to be my next step.

All this hassle just so that I don't run the battery down on the odd occassion I go away for a weekend........

Yamaha · Post by **Yamaha** » Tue Oct 31, 2006 9:39 am

Hi Ian

Doesn't the flashing glow plug lamp read the ECU faults? I would be tempted to just disconnect the main battery for 5 mins - that should clear anything.

You're on the downhill straight now, man - don't jump under a bus just yet!!

Mike

Veg_Ian · Post by **Veg_Ian** » Tue Oct 31, 2006 12:01 pm

ECU faults? It's a diesel. I thought that the only supplied control codes were basic and for the transmission and displayed via the HOLD light? Disconnecting the battery for 5 minutes or more is exactly what I was doing while restoring the wiring to the alternator ..... ?

Veg_Ian · Post by **Veg_Ian** » Tue Oct 31, 2006 5:58 pm

I owe you an apology Yamaha there is an ECU diagnostic routine (I was getting mixed up with engine management systems in petrol cars).

So I've disconnected the battery and pressed the brake pedal as it says in the manual, checked all fuses and the glow plug light continues to flash. I think all systems work (I'll check that next) but I don't seem to be able to cancel the diagnostic light. Oh well at least it isn't raining (yet)

Yamaha · Post by **Yamaha** » Tue Oct 31, 2006 6:30 pm

No apology needed, Ian - it was only a stab in the dark!!

I'm a new convert to Bongo'ing, so I'm still on a steep learning curve!
Managed to win a towbar on eBay - it arrived at 10am - along with the rain!

Luckily, it cleared after dinner, enabling some progress to be made - the towbar is fitted and bolted up - just the wiring to do tomorrow!!

Hope you sort your problem out - can't think what would have caused that fault. I'm sure someone more knowledgable will provide an answer.

Mike

Veg_Ian · Post by **Veg_Ian** » Tue Oct 31, 2006 8:27 pm

Hahahaha!! I definitely get dafter as I get older. When checking the fuses I omitted No1 Interior because I've done the Pippin mod. and connected the interior lights to the leisure battery. As I had disconnected the relay and stuff it didn't occur to me it could be my 'new' No1 fuse. It was! So all cables and fuses uprated and connected up, glowplug light is no longer flashing and all is go. Moral of the story - don't be too quick to overlook the obvious.

Thanks guys. Time to close this thread I think.