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12 volt madness


mom

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Hello all! I am hoping someone can offer me some advice on a leisure battery problem. (and please excuse my lack of knowledge here!) I have a VW T4 which was never orginally wired with a leisure battery. The previous owner had a 110 AH leisure battery installed and, due to some false assumptions on my part about that "extra switch in the wall", it happens that in 3 years we have "never" drained current from the leisure battery! This explains several confusing flat starter batteries!!!! Anyway, it came to a head on the weekend and after many hours tracing wires behind the zig panel and keen use of the voltmeter, I have determined the following... 1. The vehicle starter battery still runs through the normal zig 12 volt switch. The positive wire runs to this switch, and then to the "positive voltage" backbone of the zig. 2. The leisure battery negative wire joins the zig panel "with" the starter battery negative wire. 3. The leisure battery positive wire runs through the "extra switch in the wall", and runs from there straight to the positive voltage backbone of the zig. So, using one or the other switch should run the van 12 volt electrics from the corresponding battery. So far so good. Now to the voltmeter readings... 1. The vehicle starter battery reads 13.6 volts and everything is fine. 2. The leisure battery reads 2.8 volts. This explains why the zig doesn't even shine the test light for this battery. Now to my problem. It sounds as though the leisure battery has run down over quite a while, and simply needs a charge. However, I was told by the previous owner that in order to charge the leisure battery, I should drive the van with both switches down. This effectively places the two batteries in parallel and the alternator should charge both. This I have done an many occasions, including twice this week, but clearly the leisure battery is not being charged. I don't know enough about electrics to know better, but I have become suspicious from other forum threads that things aren't this simple. I am concerned about charging the battery conventionally as one possible answer to this is a fault with the leisure battery. And one last piece of info before I handed this over in the hope of someone enlightening me!, the other day I left both switches down overnight by mistake, and the next morning that starter battery was dead. Probably drained by the leisure battery? When both switches are down the zig cigarette lighter reads 10.5 volts, and dropping. Do I simply charge the leisure battery and all will be sorted? Is the concept of parallel batteries charging directly from the alternator flawed, even dangerous? How do I tell the health of the leisure battery? Help?! Regards, mom
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Hi mom if your leisure battery is reading 2.8 volts I would suggest that it's absolutly knackered. And no amount of charging will have any effect apon it. Sorry but I would buy a new one, and try again, as I would imagine this with the right switches down would solve your problems. Olley
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Hi mom I have a couple of suggestions; 1) After charging your battery test it with a hydrometer. This is simple enough and would identify if individual cells are down, which they probably are. Could not quite visualise the wiring but if they are being charged in parallel, then the likelihood is the starter battery is a lower Amp Hour and therefore the leisure battery can never be fully charged, because when the starter battery is full then the alternator stops charging. We fully explain 12v batteries and charging in Go Motorhoming Europe but for your problem you would be well advised to look at The Motor Caravan Manual by John Wickersham, published by Haynes. This book really is worth the £17.99 list price, although it is cheaper on Amazon and is available from the library. Go Motorhoming Powering your Dreams
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Sounds like you have a strange wiring system! My understanding of zig is that it is like ours i.e. with engine off leasure electrics and vehicle electrics are seperate when it gets 12v from alternator then they are connected. It appears that someone has tried to wire yours so leasure battery can be isolated when engine is running and also vehicle battery can be connected to leasure electrics when engine is off. If this is so I would rewire it as 'standard' it is then vertualy automatic, i.e. no remembering to switch over and little chance of a flat vehicle battery. If battery is down to 2.8v its proboly 'had it'.
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I agree that at 2.8 volts your leisure battery almost certainlu=y wants replacing. How to wire it in? The basic Split Charging system would be a good start!. Have a look at http://www.motts.dsl.pipex.com/SPLIT%20CHARGING%20SYSTEM.htm Good luck If you have any detailed questions feel free to PM me. C.
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