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post #6 of 19 (permalink) Old 28th June 2007
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Hi Lancer - the power supply to the caravan system could be faulty whereby it wants to take all the charge from the alternator and the car gets none. My neighbour had a similar system whereby there is a dual charge relay which directs the charging current to either the car or van was faulty. If it were mine I would drive the car for a few miles without the caravan attached and see if the car starts OK. Additionally it may be worth getting the voltage output of the alternator checked.

P.S. Has your car got a dual charge relay system fitted
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post #7 of 19 (permalink) Old 28th June 2007
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If you don't have the split charge relay, then the caravan will be draining your car battery whenever it's hooked up. Not so much for the leisure battery (this will only charge when the alternator's running) but the fridge is a killer.

But with the engine running, you should still get a decent charge to the car battery. I put an ammeter on the feed to the split-charge relay on my last car but one, and it rarely pulled more than 10 amps, even with the fridge on. To put that in perspective, it's about the same amount of power as your headlights would use on dipped beam. The alternator should still be able to kick out plenty to keep the main battery topped up, and the fact that the alternator is connected to the main battery using a short, very thick cable run means that the main battery will effectively get preferential treatment when charging if both batteries are low.

I got the impression that this was diagnosed by the AA as the battery failing to retain a charge even with the caravan disconnected. If that's the case, then the caravan may be putting additional strain on the system and highlighting the fault, but the underlying problem is still with the car battery.

As for leaving your courtesy light on for a few minutes being enough to kill the battery, that's ridiculous! I've accidentally left mine on overnight before now, and had absolutely no problems starting the car.
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Last edited by Horatio; 28th June 2007 at 06:11 PM.
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post #8 of 19 (permalink) Old 6th October 2007
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Battery Trouble

I have recently had Battery trouble with my Laguna. One day it would not start despite having used the car just an hour before. The RAC were excellent and confirmed the battery charge to be 11.5 volts. He checked the alternator which was charging ok then checked for any leakage of power but found none. He suggested a half hour run to put some charge in. Everything has been fine for about 2 weeks when the same thing happened again.
I thought I would make an enquiry about a new one and have had 3 quotations from leading suppliers.
a) 47
b) 74
c) 97
Can anyone tell me which option to take, all have 2 year guarantee. Is the cheapest one worth going for?
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post #9 of 19 (permalink) Old 6th October 2007
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A fully charged battery should read 12.5 volts at least and with the engine running the terminal voltage should be 13+ volts indicating the alternator is charging the battery and even if you switch on dipped headlights the voltage should not drop below 13v. The alternator should only put out less than 13.4 volts to avoid popping bulbs ( at least that what used to be the case when I was repairing alternators) If even after a period of chaging the battery reads less than 12.5 then it is not holding its charge and should be replaced check what sort is fited to your car as there are varying sorts (i.e. capacities measured in ampere hours like 110 Ah). All these figures can be tested simply with a cheap multimeter connected across the battery terminals. The price you pay is up to you considering such things as guarantee period and capacity.

Last edited by MIKE4369; 6th October 2007 at 10:19 AM.
post #10 of 19 (permalink) Old 6th October 2007
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Hi Norm - diesel engines in particular needs plenty of oomph! when starting especially from cold. I have fitted the 47 variety in the past without any problems but if you wish to spemd more then I would try and fit the best output battery where possoble
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