# testing a leisure battery charger



## 108717 (Dec 12, 2007)

Hi All,
While returning from France we managed to drain our leisure battery running a coolbox whilst driving. I've had an issue with the fridge not running on 12v whilst moving (posted elsewhere) but on return I discovered that my LB isn't charging whilst on EHU outside the house either. Sockets are powered but no 12V and LB flat as a pancake.

Vehicle is 1988 Hymer B544. I have removed the Leisure Battery charger from under the seat. It looks like the original factory fit and is an Elektromatic LA 110. There are no external or internal fuses. I have metered across the + and - but get no readings even down to milliamps but as this is a charger not a PSU I'm a little unsure what I should be getting. 

How do I use a multimeter to see if it's dead and what readings should I be getting if not loaded by connection to the battery?

As I'm having a few issues with 12V on the move even when it was working, I want to be sure it's dead before replacing it.

Cheers in advance,

J


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## AberdeenAngus (Jul 26, 2008)

You should be getting around 14 VOLTS on the output of the charger disconnected.
Don't put your meter on Milliamps range across any power source - you'll fry the meter, or pop the fuse if its got one.

Voltage is measured in parallel (i.e. across something +ve to +ve and -ve to -ve)
Current is measured in series (i.e. through the meter, through a load and back to the source.

So, simple answer around 14volts (ish) with no load.
But that doesn't really tell you if its working properly, for that you need to hook it up to a load.

I would suggest a 12v headlamp bulb. They will pull about 4-5 amps, a pretty good test for a charger.

You could use the battery as a load, but if the battery is pretty flat then you can expect charging currents of around 20 amps - not many diy multimeters can handle that so I suggest you take the charger and the battery to your local friendly garage and get then check it out for you.
They have high current kit for checking such things.


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## 108717 (Dec 12, 2007)

Thanks Angus. Good info and a refresher on a few issues. Can you belive I have an Electrical and Electronic engineering HND! It was achieved around the time that the earth's crust was still molten and I've forgotten more than I know. I will try the above but in light of what you've told me I think it is fried.

I'm actually wondering if this is a knock on effect from a split charge relay. I've been having some 12Volt fridge issues so I'm wary. If I'm not mistaken, whilst moving a Hymer will normally feed 12V system from the vehicle battery. (the socket used is in the cupboard and definately on the Habitation side as I fitted it myself). I'm wondering if the coolbox and other bits and bobs in use were drawing from the leisure battery instead and all faster than the charger could keep up with Then the drain of a couple of days driving placed on the struggling charger killed it. Is that unrealsistic? THe charger is rated at 7A which seems low by modern standards. 

Other info on the unit I don't understand in case it helps:
T 40/E
30Ah Biel-Akku

James


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