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Discussion Starter · #1 ·
Hi,
Have got a 1995 Hymer 544 which we purchased a couple of months ago.
Been on several overnight trips both with and without 240v hook up and seemingly no electrical problems. This last weekend drove up to the Lakes and arrived to find leisure batteries extremely low even though the van had been hooked up at home for about 3 weeks and engine had been running for over 3 hours.
I have only recently learnt that the fridge can operate on 12v whilst driving since it should be powered from the engine battery and will not operate when the ignition is off. For the last two trips this is what I have done and I have not turned off the 12v switch to the fridge when stopped. The previous owner had installed 2 gel leisure batteries and (I think) a new charger/transformer. When hooked up now the charger whirrs on regularly and the batteries are getting quite hot and seemingly not holding charge.
I 'm pretty certain that the batteries are now damaged which is a bit of a sickener but even more frustrating is not knowing how they got so low in the first place!
Should 12v be switched on at the control panel when travelling and using the fridge? Is it possible to cook the batteries by leaving them on charge for too long? Should I be looking for a blown fuse somewhere in the system or have I just made a glaringly obvious mistake. Any advice would be greatly appreciated since we go away for a couple of weeks soon and this one needs to be sorted first. Thanks
 

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Hi sdsplus

I cant give you an answer but just to tell you to hang on in there, very soon you will find that one or two of the technical wizards on this site will give you the answer.

Your question poses a thought for me too, I'm relatively new to motorhoming with all the electrical gadgetry, and when on hookup, I always put the charge switch on, as I was told that the electrics are then running directly off the charger and not using the leisure battery, the question being then, am I too "cooking" the battery.
 

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SDS, If you dont get a reply for a while, dont worry, a lot of folk are still away.
Every so often, reply to your own post by sayin something like "I am still waiting"
That brings your question to the top again....Like this time.
 

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I'm not familiar with the Hymer electrics, and I'm sure that someone that is will be tempted to reply shortly.

It's difficult to diagnose problems at a distance, since wiring and components vary tremendously from 'van to 'van, and things get more difficult if modifications have been made.

First of all - Don't Panic - there is a distinct possibility it will be something simple. A bit of reassurance and a bit of diagnostic work may help.

Whilst Hymer just might differ, on all my 'vans to date you would leave both the 12V master panel switch and the 12V setting on the fridge on whilst travelling, as you seem to be doing. Not turning off at the panel should cause no problems, and on-site you would no doubt turn the fridge to mains or gas anyway.

The fridge is usually wired across the leisure battery(ies) but with a relay switch in the circuit which senses output from the alternator, ensuring that the fridge only draws current whilst the engine is running (and producing a charging current).

Hence, if everything is OK, any current drain from the leisure batteries is compensated by them simultaneously being on charge. Stop the engine, and the relay takes the fridge out of circuit.

Two potential problems here -

1. The charging circuit from the alternator is protected by a fuse in-line to the leisure batteries somewhere. If this has blown, the fridge still goes into circuit when the engine is started and then depletes the leisure batteries (since they are not being charged due to the blown fuse). Been there, done that, completely dead batteries after long drive to Lakes. Remedy, check and replace the fuse.

2. The output from the alternator is insufficient to both drive the fridge and charge (all the) batteries. Can only really be checked by a multimeter, but might show up if switching all vehicle lights on with engine running. Remedy, auto electrician.

It occurs to me that the above could also result from a bad connection in the alternator charging circuit.

On most standard-fit motorhome charging systems, leaving the charger on won't 'fry' the batteries. Ultimately the charger will step back to a 'float' charge. Haven't had my batteries get really hot though.

I should:

1. Check for the blown fuse as above (easy option)

2. Turn everything electrical off (esp. fridge) and run the engine and see if the batteries recharge (if they don't suspect the alternator charging circuit or batteries). If they do, you should re-check at intervals to see if they hold it.

3.Turn engine and everything electrical off except the mains charger and see if the batteries recharge (if not - batteries or mains charger are suspect). If they do, you should re-check at intervals to see if they hold it.

For quickest conclusion, you really need a voltmeter or multimeter to measure the voltage at the battery when either charging method is being used. It should be well above 12.7V (maybe 13.8V to 14.2V) and you should see it go up immediately the battery goes 'on charge. With this you can rapidly diagnose or eliminate any charging circuit issues. If this reading is OK, but battery won't hold charge, you either have a constant drain on the battery from somwhere, or it is dead.

Hope this helps!
 

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Hi

I have a 96 644, so i would think the setup is the same as mine.

In mine the charger is at the front in one of the side cupboards next to the passengers seat. It doubles up as the fuse panel for the caravan side of the vehicle.

You can turn the charger on and off, and there is also a reset button on the charger which resets it, if it turns of due to being too hot or whatever.

I have only recently learnt that the fridge can operate on 12v whilst driving since it should be powered from the engine battery and will not operate when the ignition is off. For the last two trips this is what I have done and I have not turned off the 12v switch to the fridge when stopped. The previous owner had installed 2 gel leisure batteries and (I think) a new charger/transformer. When hooked up now the charger whirrs on regularly and the batteries are getting quite hot and seemingly not holding charge.
The fridge will only operate from 12v when the engine is running, regardless of 12v switch or ignition switch, so that wouldn't be the problem.

The way a hymer system of this age works is that everything 12v comes directly from the batteries, and the charger is like a simple 13.8 power supply capable of about 10 amps. It would be harmless to gel batteries, as it peaks at 13.8 volts and just trickle charges from then on, which is ideal for gel batteries.

So the first question is - is the standard hymer charger still in operation or is there definately a different charger fitted ?

Are the gel batteries physically big, (12- 18" long by 5-6" wide - ish) or has the previous owner put 2 smaller ones in, as if they are the smaller type intended for golf buggies or mobility scooters, they won't handle the alternator charge.

The alternators the one thing that i think might not be to kind to gel batteries as the charge from the alternator when travelling, can get get quite high. The other possibility is that if another charger has been put in, it may be a simple vehicle battery charger which again, are not good for gel batteries.

If the batteries are getting hot, then it sounds like they have had quite a charge, assuming they are biggish batteries, i don't think the hymer charger is capable of warming batteries up unless they are damaged in some way.

Let us know if you can see the make and spec or model number of the batteries, and of any aftermarket charger if one is fitted.

Cheers

Dave
 

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Discussion Starter · #8 ·
Many thanks for all the helpful advice so far - very informative. I really do need to establish what the previous owner did regarding replacement & original chargers. I will also find out the exact spec. of the gel batteries installed - and pray that it's just the blown fuse remedy!
It's all very complicated for someone who can only just figure out domestic electrics and any additional help very much appreciated.

Cheers
 
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