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Overcharging leisure battery?


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I bought a 2005 Elddis Sunseeker 300 in July this year, on 1st using it with the leisure battery connected to mains hook-up it overheated and failed. I took the motorhome back to the dealer, they told me it was a faulty battery and replaced it for me. Since then I've connected the motorhome to a mains connection at home via the correct power inlet, and after only 4-5 hours on charge we noticed a strong smell of sulphur. When I checked, the new battery was very hot and I was concerned about the possibility of fire! I've again taken the motorhome back to the dealer, and after checking it over they tell me there's no problem with the charging system and they've again replaced the leisure battery! I can't believe that this is a correct diagnosis, as it seems improbable that 3 leisure batteries could develop the same fault so quickly! I feel this must be a charger issue rather than a battery problem, as my manual states that the mains connection can be left running indefinitely and the charger should cut out when the leisure battery is fully charged. This is both frustrating, and concerning and I'd like to hear if anyone else has had this problem and if there's a practical solution???

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Either the dealer stocks duff batteries, or its a series of unfortunate circumstances.


The only way to tell is to see to use an ammeter and voltmeter to measure what is going on over a period of time.


On our battery the charge peaks at about 3 amps at 14.4 volts, then drops down as the battery is charged to 13.2 volts at 0.01 amps. Maybe 15 mins if the battery is already charged to a couple or hours after a days average use . (Whatever that is ?)



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Hi Ralph, and welcome to the madhouse where there is plenty of advice - mostly conflicting!


With a digital multimeter you can check the battery voltage both when on charge and when at rest and these will give you a fair idea of what is happening.


There should be absolutely no smell from the battery or any of the wiring whatsoever and any aromas are an indication, as you suspect, of a fault, or faults.


A good 12 volt battery should show about 12.8 volts when fully charged and, when not connected to anything, should be able to hold that for several weeks without significant voltage drop. Unless you know exactly what you are doing do not attempt to measure current amperage as a lot of damage can come from connecting it up incorrectly.


I don't know what voltage your on board charger should be charging at - the handbook might tell you - but I hazard a guess that it will almost certainly be significantly less than the 14.4 or so volts your alternator charges the engine battery at, and possibly as low as 13.8 volts. However that is a guesstimate as I am no expert other than having a lot of vans with a lot of batteries and a lot of aggravation over many years! We never use EHU as we are more nomadic campers so I am not overly familiar with their foibles and voltages.


My inclination would be to visit an independent auto electrician who should be familiar with taking the various voltage and amperage readings that will tell you what you need to know.


If your on board unit is made by Sargant they are very helpful and knowledgeable as long as you can give them solid information to base any diagnosis on and they can be found online by a Google search, as can much info on batteries in general.


Leisure batteries are notoriously crappy and it is not unknown to need several before you get a good 'un - what make are they supplying you with?


Does that help as a starter - if not ask again and an expert will be along later!

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My thanks to those that responded! I've now taken the m'home back to the dealer, and after 4 days he's told me there's no problem with the charger or charging system, and has replaced the battery (again!). I queried why this is happening and have been told that the charger is not a smart charger and therefore doesn't cut out when fully charged - it's up to me to disconnect it. I've double checked in the handbook supplied with the m'home and it clearly states in the instructions that the charger cannot overcharge the battery - which conflicts totally with what the dealer is telling me.........so helpful (not).

I have now written to the manufacturers to find out who's giving me duff information! let's wait and see what happens next!


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