Battery isolation

Hi, I have a 1996 Transit (smiley) Duetto and am looking for some battery advice. Last week I left the 12V on and the pump on and this caused the batteries to drain to the point that i could not start the van. I charged the engine battery using a seperate battery charger and the van now starts. my question is can the engine battery be isolated so that 12v usage in the motorhome does not use the engine battery? I would still want both batteries to charge while driving. Or failing that currently when plugged into mains the charger only charges the leasure battery. Can this be set somehow to charge both batteries?

.....or just remember to turn off the 12v when you leave the van? 

In our 1996 Duetto we keep everything off when its parked at home, and also if we leave it on site for any length of time. Just got into the habit!

The only time we use the van without EHU for any length of time is for a 4 day stay at a folk festival (sadly not this year...). We are careful then not to use too much 12v and we've never had a problem.

But now I know that we could drain the engine battery as well, we'll be even more careful!

Yes I will make sure the 12v is turned off, not sure how I missed it this time. I want to try and make sure if im away for a few days that there is no chance of me draining the engine battery. That was I can use as much 12v as we have and still start it. I guess I could unplug the terminal while parked but that seems a bit of a rubbish way to do it

I suppose we've never had a problem because, apart from the folk festival weekend, its very unlikely that we wouldn't use the van for more than a day, especially without EHU. 

I think I'm right in saying that the engine battery gets a good charge fairly quickly once the engine is started, so even a short journey, to the pub or the beach from the site will give the battery a decent boost.

Achilles heel wrote:I suppose we've never had a problem because, apart from the folk festival weekend, its very unlikely that we wouldn't use the van for more than a day, especially without EHU. 

I think I'm right in saying that the engine battery gets a good charge fairly quickly once the engine is started, so even a short journey, to the pub or the beach from the site will give the battery a decent boost.

Are you batteries under the bonnet? Both of mine are and both appear to be the same type and Im not sure thats correct. What type are yours?

There are a couple of different ways in which the batteries on a Transit were joined together - from the factory - on a Transit of that age. You need to work out which setup you have, because then you'll know if the behaviour that you're seeing is correct, or due to a fault in the split charging system.

In simple terms, one setup has the batteries electrically separate when the engine is off, but linked together by the split charge circuit when the engine is running, and the other has the two batteries "twinned", so that they are connected together at all times. Any modifications that you make will need to account for this, because in the first setup the second battery is never used during engine start, while in the second it is always used to help start the engine.

Both batteries are under the bonnet. No idea which charging setup we've got; the engine battery is 72Ah and the leisure battery is 60Ah. 

We replaced the engine battery over the winter; we have been assured that the leisure battery is the correct type.

Apart from the fact that one is grey and the other is black, I'm afraid I can't give any more detail!

Hi

Roopert wrote:In simple terms, one setup has the batteries electrically separate when the engine is off, but linked together by the split charge circuit when the engine is running, and the other has the two batteries "twinned", so that they are connected together at all times.

I may well be corrected but my understanding is that only the automatic version had linked batteries.

gordonbl wrote:Or failing that currently when plugged into mains the charger only charges the leasure battery. Can this be set somehow to charge both batteries?

First thing's first, let's not worry about that yet. If only the one battery charges the batteries cannot be linked or both would charge. Equally if the starter battery is discharged the leisure battery would be as well.

If the batteries are not linked, it should not be possible for the pump to drain the starter battery. Are you sure that it was the pump.  If you are did it drain the leisure battery as well?

From the information provided so far there are many possibilities. A  problem like this needs logical fault finding otherwise you can waste a lot of time chasing all the possibilities.

I suggest the following as the next test:

With the engine off (no EHU), disconnect the earth wire from the leisure battery and then check the voltage on the leisure battery positive with the meter negative lead connected to the bodywork.

Switch something in the habitation area on , a light will do. You should read almost nothing. If you read the same voltage as the starter battery the split charge circuit is either not fitted or not working.

Assuming you read nothing run the engine and recheck the leisure battery voltage (earth still disconnected). If you now read the same voltage as the starter battery the split charge circuit is OK. If you still read nothing the spit charge circuit is faulty.

Anyway come back and tell us the result and somebody will suggest the next step.

Brod

I think both of mine are connected all the time.

I was under the impression that the Zig charger only charges 1 of the batteries. My Transit is an auto.

Hi  

gordonbl wrote:I was under the impression that the Zig charger only charges 1 of the batteries. My Transit is an auto.

In the standard configuration, (if I can call it that) it does but if both batteries are linked that cannot happen. The Zig would have to charge either both or none of them. Hence the test I suggest to prove if both batteries are linked or not.

If they are linked you have the choice of leaving it as it is,  loose one of them from the starter circuit and fit a split charge circuit (I can’t see why the auto needs two batteries anyway) or fit an extra battery.

Here's is my split charge relay (fitted under the bonnet on the drivers side). Does your van have anything similar fitted.





Whatever we need to no exactly how it’s connected now and what you want to achieve before making any suggestions

Brod

brodco wrote:
I may well be corrected but my understanding is that only the automatic version had linked batteries.

I believe that's true, though I've never been sure exactly when Ford started to do this. The 1999 Mk.5 Transit with auto transmission that I owned had "twinned" batteries.

The result is of course that - unless a third battery is fitted - there is no split charge relay.

I guess I should count myself as lucky - I owned that van for a long time and never once flattened the batteries. I can imagine it would be very annoying if you do - especially if you were camping wild! Not something you would be likely to do more than once, I would think...

Hi  

Roopert wrote:I believe that's true, though I've never been sure exactly when Ford started to do this. The 1999 Mk.5 Transit with auto transmission that I owned had "twinned" batteries.

Just out of interest do who know why?   I wouldn't think the auto "gubbins" would put that much extra drag on the engine. I've got an automatic car and it has the same battery as the manual version.

Brod

I've never heard an "official" explanation. As you say, I don't think the auto transmission should add a lot of extra load during starting, though I guess the hydraulic pump must run all the time the engine is turning?

My other guess is that they do it because you can't bump-start an auto, so they fit two batteries to make it less likely that you'll drain both and end up not being able to start it. Though it doesn't sound a very convincing reason to be honest!

Hi  

Roopert wrote:My other guess is that they do it because you can't bump-start an auto,

True but I've had a flat battery one or twice in the 12 years I've had the Duetto and even though it's not an auto I've never even considered trying to bump star it!  

I've had dealing with transits ( mostly company vans) since I was little more than a teenager and bump starting a Diesel (even the empty version) was pretty well impossible.

Still I suppose  it must have made sense to somebody somewhere.

Would you agree that there is “probably ” no great downside to replacing the dual battery system with one leisure battery and a slit charge circuit should the owner wish?

I wonder if any forum member has done this and could report on how successful it was.

Brod

brodco wrote:
Would you agree that there is “probably ” no great downside to replacing the dual battery system with one leisure battery and a slit charge circuit should the owner wish?

I suspect that it wouldn't be an issue. It did occur to me that Ford might have made the cabling from each battery +ve to the starter motor slightly thinner on the basis that the peak power during engine start would be shared between the two, but in reality I can't see them having a different loom from the "main" battery than on a standard manual trans van - the saving in copper would not justify having to stock another part. And my recollection of the main battery cable on my van is that it looked typically thick.

However, you might need to pay attention to the current rating of the split charge relay, simply due to the size of the cables, (or you might need to replace the fuse more often than otherwise expected if you stuck with the "typical" A/S fuse rating of 20A). I've long suspected that A/S use relatively thin cables in their split charge circuits partly because it gives a little bit of "priority" to charging the engine battery over the leisure battery... And, of course, because it saves them about 10p on each van...