Another Split Charging Thread...

[PoloSi]

First post!

Been researching on here and the brickyard forums about installing a split charge system in a T25 and I think I've got my head around it:

Starter Battery
Leisure Battery

Starter battery +12v connected to relay then relay connected to leisure battery +12v, this provides the charging current when the relay is switcehd on.

+12v from leisure battery via 6 core wire to my new fusebox where I can run power sources to my various appliances.

Correct yes?

Now the only thing I am unsure of is what I can take a feed off for the trigger wire for the relay? In a camper mag I got it states that you should use the 'Alternator Warning Lamp Wire' as this only becomes live when charging is occuring, after starting essentially. This is all fine and dandy but this guide is for a bay not a T25 and being relatively new to the camper side of VW's (my first T25) I don't know if this even exists on a T25 never mind where to find it, lol.

Any help is appreciated.

Simon

[jaymo]

Hi Simon,

I don't know if this will be of any help to you, I know it was to me.

I bought an intelligent split charge system for my T25 from ebay which has been fitted since last november and have not had a sinlge problem. This is the item number for a similar kit to the one I bought: 280340843308

The kit is really simple to fit and comes with perfectly clear instructions. One of the best features about this kit is, you don't have to touch the alternator or the fuse board. It's wired straight from the main battery via an intelligent split relay and two fuses to make it nice and safe. You basically 'fit it and forget it' as the seller says.
When the engine is started, and providing the main battery is pushing out around 13.5v the split relay switches over to charge the leisure battery. When the engine is turned off, the relay switches back to prevent any charge being lost from your main starting battery. The kit always favours the main starting battery ensuring you can always start your van.

If you email the seller with what you plan on connecting to your leisure battery, he will make up a custom kit to suit. This guy is extremely helpful and really knows his stuff.

Hope you get sorted.

Mark

[PoloSi]

That seller is the same as this website http://www.rawcomponents.co.uk" onclick="window.open(this.href);return false; which is where I was going to order from anyway lol. They seem really clued up. I am looking into the voltage sensing kit but waiting on my mate to find out the ratings on the leisure battery first. Cheers for input though mate was going to ask if anyone had bought from them before so i am reassured:).

Simon

[Oldiebut goodie]

If you use a voltage sensing relay you just run it from the vehicle battery - the relay will then only charge the leisure battery once the vehicle battery is recharged. Go for a minimum of a 70 amp setup - the standard 30 amp is too puny.

[PoloSi]

It does sound like a viable option but i'm atight git and would rather save the pennies and go for a normal one. Can anyone shed anylight on a suitable trigger feed for a standard split charge relay?

Simon

[VWCamperfan]

I use the charging indicator option. Take a feed from the blue wire going to the dashboard connector and run this to the relay.
The relay will now only switch to the closed position when the alternator is charging.

[neil3965]

Hi Simon

On my van (1982 2.0L Aircooled Devon) the split charge relay sensor wire is spliced into the battery charging lamp wire in the engine bay. This is the blue wire that comes from the alternator and disappears into the wiring loom that runs along the rear inside edge of the engine bay.

The relay wire is fed up the offside air intake and through a grommet to the space behind the trim card and on along the side of the van to the relay which is behind the drivers seat.

[Red Westie]

Dito...look at the back of the alternator, there should be a single blue wire with a standard female spade connector attached (shielded) this is the switched feed you want to control the switching side (low current side) of the relay. This wire can be relatively thin (1.5mm) as it isn't carrying much current.
The relay it'self needs to be a minimum rated 40amp and the bridging wire: starter to leisure with relay needs to be suitably heavy guage with a fuse holder close to the starter battery end (probably rated around 30amps). I wouldn't go as far as Oldie but goodie with 70amps plus (although this wouldn't be a bad thing), I would be looking at relay/wire/terminals to handle 45-55amps which is plenty enough for a simple single leisure battery setup. This considering Westfalia's setup in California's/Atlantics was built around a 30/40amp 5 pin relay but if you are doing this for yourself i would rate components a little higher for reliability. Personally I solder all my joints to avoid high resistances which generate heat and to minimize any volt drop unless you posess a pair of professional crimping pliers (the ones with the ratchet action)
Martin

PS....why do some owners report that they blow 25amp fuses, well poor connections due to terminal joints not being made correctly, old wiring/fuses, charging a very flat leisure battery....is this a reason for upping the fuse rating....well that is considered bad practice, fuses are there to prevent current overloading a circuit....fix the cicuit don't just put a bigger fuse in there. I admit that there might be circumstances where a 25amp fuse may be too low ie: very large or multiple leisure batteries perhaps where you should uprate everything (relay/wiring/fuse) etc perhaps by 50%.
I am no auto electrian but I do have a reasonable understanding....I say that loosely....the way an alternator controls it's output is by increasing/decreasing the strength of the magnetic field within the rotor, basically sensing battery voltage and increasing/decreasing output when needed/not needed. When you have two batteries, starter and leisure, one say at 75% and the other only at 10% charge state, the signal back to control output kind of splits the difference (because the batteries are connected physically in a parellel circuit) so the alternator isn't sensing a near flat battery and as a consequence you never get the alternators FULL output capability being rammed down that bridging (Leisure charging) wire. This is why the split charge circuit only needs to be capable of handling a proportion of the alternators rated output.
Now I'm sure you will have some smart arses cutting and pasting some wicky at this point and I may not be explaining this as technically as it could be but basically, that is why you don't need to have a 90amp relay and associated 7mm wiring for leisure charging when you have a 90amp/hr alternator. Yes you occasionally hear of a 25/30 amp fuse blowing but this is likely just an initial surge with constant charging current flow even on a flattish battery of probably less than 20amps. If we have any AA patrol techies out there with their amp clamp equipment? this could be an interesting test to carry out on a flat in car leisure battery. Please post the results here.........

Martin

[AngeloEvs]

have to say I would opt for the intelligent relay, simple to wire and does what it says on the package, also prioritises charge to the starter battery before charging the leisure......have a link for an alternative source if you can't find on ebay and want to consider that alternative.

[bigherb]

Essentially what redwestie says is right it is the surge that blows the fuse. The probem is solved by fitting the right type of fuse, normal fuses are designed to blow insantaniously. Blade type maxi fuses and the older strip fuses are capable of withstanding surges for short periods which is why vehicle manufactures use them in the battery power circuits.

[cornishpete]

As in my earlier thread, my 30amp fuse between the split charge relay and the battery blew and I didnt know it had gone, so my leisure battery was very very flat after a weeks wild camping. When I found out about the fuse and replaced it, I drove home about 20 miles with that very flat battery now charging and the fuse stayed good! the alternator put enought charge into the battery to start and run the 12volt only fridg. My friendly auto electricion blamed the fuse (blade type) blowing on a surge of current.

[Red Westie]

The fuse wire can deteriorate over years of carrying current, it can also corrode. It is not unusual to have an old fuse blow for no apparent reason and then be fine after a new replacement is fitted.
Martin