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Help Please - Batteries discharging


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I am in a bit of a panic as we are preparing for a trip next week and I have discovered my batteries are discharging - if anyone can help, I'll be eternally grateful.


I have 2 * 110 leisure batteries which have been installed just short of 12 months.

The voltage looked low yesterday - which was a bit worrying as I had been driving the 'van about 50 miles per week and not been using it for camping in the last month.

I confirmed that the engine was charging o.k with a voltmeter.

I therfore plugged into mains for 24 hours and checked, after disconnecting the voltage was 13+. I then waited a couple of hours and checked again - and the voltage was way down. (I can't say excactly as my voltmeter is one of these that gives a good, low or flat reading. )


I have taken one battery off and put it on a bench charger - it seems to be holding the charge.


I intend to do the same with the other one.


I have a Van Bitz battery master fitted - so it is possible this is sucking some juice to the engine battery (that seems fine by the way). I'm not sure if I can disconnect that to see if it makes any difference.


There is something called a 'Spannungregler' next to the charged on the 'van - that seems to be a bit warm.


Has anyone got any ideas -


:-( please

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We had a similar problem a few weeks ago. In our case it was an additional battery charger that I fitted to help "boost" the vans own charger. The extra battery charger "boiled" the batteries dry in a matter of weeks! I topped them up with distilled water but the damage was done. Eventually I had to replace 1 of the 110 amp batteries as the cells had broken down.


An expensive lesson in battry management!


Is there an extra charger on your van? If so this could be it.


Good luck.

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Hi Robin,


You can't do much without a multimeter, there's a cheap one at Maplins on link http://tinyurl.com/22rrvt , which will allow you to pinpoint your problem.


The 'Spannungregler' is most likely a voltage controller and will always be a little warm when the charger is on.


Place the batteries on charge using the MH charger, check the battery voltage with the charger on, the voltage should be 13.8 volts. If you have 13.8 volts your charger is working ok.


Leave on charge for 24 hrs and then switch the charger off and disconnect the negative lead from each battery, let the batteries rest for at least 8 hours, then check the battery voltage, it should read 12.7 to 12.8 volts. A reading of 11 or 12 volts suggests the battery is u/s, 12.5 volts suggests the battery is only 50% charged.


If all above is good, the next test will determine if there is a load across the battery when all electrical items have been switched off, a leak if you will.


Place the multimeter on the 10 amp range and hold one probe on the negative terminal of the battery and the other probe on the disconnected negative lead. The reading should zero, if you have any reading at all, you will need to isolate some devices to check which ones are causing the load and thereore the discharge.


Things to check and disconnect ;-


The charger when switched off, can discharge the battery because of a bad component in the charger electronics.


Also - try removing each fuse from the distribution panel to endeavour to locate where the battery drain is sourced, checking each time with the multimeter on the 10 amps range, connected as above, looking for the source of the discharge.


To check if your alternator is charging the leisure battery, with the batteries reconnected, start the motorhome engine, using the multimeter on 20 volt range, check you have at least 14.4 volts across the leisure battery, with the engine at around 1000 rpm.


Let us know how you are getting on - Regards Terry



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I don't have an additional charger and the levels in the batteries look ok.k.


Just to let you know, I am following your recommended course of action - I took them off charge about 3 hours ago and so far they seem to be holding the voltage (I haven't got the multimeter yet - I am just off to Maplins)

I have disconnected the battery master and not set the alarm.

Thanks for your help....


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Terry's course of action is the one to take, but as a long shot, have you got a 'mains' LCD tv coupled up to 12v, many of these cannot be switched off without unpluging, they normaly go into standby and can consume just as much power.
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I have to thank you more for your comprehensive instructions - I have followed them and found the problem!


I had a reading of 0.2 amps with everything switched off. After removing each fuse on the distribution panel, I have isolated the problem to one of the circuits. This circuit includes the lighting down the right hand side of the 'van and also the Remis roof light. This now begins to make sense as I have had a previous problem with this circuit - basically, whever a light was switched on, the built in 12volt LCD TV would switch off. This was resolved by the supplying dealer - I think they wired the TV into this same circuit. It seems like they have not resolved the problem.... It will be back to them after my hols.


I now know that the batteries themselves are in good condition, and that the alternator and on board charger are working correctly, so will be able to survive the three week tour without worrying about hook ups.


Thanks again


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Hi Robin,


Pleased you found the fault. Connecting the LCD TV into a lighting circuit is not a good thing to do, the TV will take the best part of 4 amps and this coupled with lighting on the same circuit, will cause some significant voltage drop.


Some TV's used in the leisure market, support a feature that will automatically switch off the TV when the TV senses the voltage going low, typically 10.5 - 11.5 volts, the Panasonic G10 for example will sometimes switch off when the water pump is operated, the extra load of the pump sending the battery voltage to maybe 11.0 volts momentarily.


I have wired another 12 volt socket directly to the battery to drive the TV, I have of course included an in line 10amp fuse close to the battery.


Your CEC Plug in System Manuals are on their way by email.


Regards Terry

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