Leisure battery overheating

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BarumMike

Joined
May 30, 2021
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Devon, UK
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81,606
MH
C class motorhome
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I'm a newbie
Our leisure battery is getting very hot. We have a 2021 Zefiro 696 and are on a trip currently in the western highlands of Scotland. The battery was replaced with a Yuasa AGM(sp?) about a year ago because it was over discharged during the winter. On electric hookup the voltage was 13.83v using a multimeter. I have disconnected the MH from the EHU and will check voltage later tonight.
Am I right that likely possibilities are an internal short or a problem with overcharging?
We are nowhere near a MH dealership (Gairloch for 48hrs). We could swing by Inverness on Thursday. What can I do with modest technical expertise and a multimeter to diagnose the cause? If I knew it was a battery problem replacement would be simple in Inverness.
And any other advice welcome?
 
Are you at home or away?
 
Do you know what type of mains charging system is fitted in your motorhome?

Some systems are really too basic that they will just keep trying to pump out a fixed voltage (my van was 13.8V) continuously which would be trying to overcharge. It should at least be "smart" so that it goes through bulk, absorption, and finally float stages - the latter reduces voltage once the battery is full which won't cook it, unless the battery is faulty.
 
RM_Marine said:
Are you at home or away?
Click to expand...
He said he's on a trip in the Highlands and from his avatar he seems to be from Devon so a long way from home..........

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If it's 13.8v on charge and smells of rotten eggs I would say the battery is faulty.
The battery voltage may be lower off charge as 13.8v will be the charge voltage, not the true battery voltage.
Should be rechecked an hour after disconnecting charge and not used in that time.
Standing voltage should be around 12.6v

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At 13.8v the gassing is minimal, almost all of that will re combine back if the valve holds. So I would rule out to high voltage. A daily cycled battery can be kept at 13.8v float 24/7 without damage.
Heat is energy loss, very likely a internal fault causing the battery to heat up. Stop using it to avoid thermal runway. Thats what I would do. Try to replace with a sealed flooded VRLA.
 
One possibility is a shorted cell inside the battery. That means only 5 of the 6 cells are working. If the battery is not being charged, the voltage will drop to about 10.5V instead of 12.6V after a few minutes. If it is being charged by a standard battery charger at 13.8V then that will be overcharging what is now a 5-cell 10.5V battery. So it will probably overheat and produce gases and it's best to avoid charging it. If you have meter it should be easy to see if the voltage is down to 10.5 or so.
 
Be very careful that you vent it well before doing anything that might cause a spark. A Marquis engineer hurt his face very badly when our battery exploded while he was testing it. Made an awful mess in the old van, and we were finding bits of battery for a long time after.
 
Ours did the same in 2019. Shorted battery cell and reading 10.5 volts

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Thanks everyone for the prompt replies. Absolutely brilliant to be in touch with expertise so quickly from a remote campsite!
Answers to questions and current state of play.
We are indeed Devon based and are presently in the Highlands.
I haven’t worked out what mains charging system we have but will post on RollerTeam Facebook page if need be to find out.
So, I haven’t worked out how to turn off mains charger to allow reconnection to electric hookup.
Overnight (off EHU) the leisure battery has cooled down. I have not disconnected it so it is still providing low drain 12v power. The lowest battery voltage I measured was 12.3v this morning. Does this rule out the battery being the cause? BTW it is a Varta battery not Yuasa.
The solar panel is still connected, and we have a Vechline PWM Solar Charge Controller. The solar panel indicator is flashing indicating the panel is providing voltage and the battery indicator light is continuous red which I think is the normal functioning state. The voltage across the leisure battery is 12.93v at 10.45 in brightish daylight.
Thanks for safety warnings.
So, I will find out about the MH’s mains charging system, and advice on next steps please?
 
I have found the battery charger under the passenger seat. Does anyone know what I have to do to disable the charger so I can reconnect MH to mains power without powering up the leisure battery? I am assuming the solar panel is successfully ( and safely) charging the leisure battery.



IMG_7985.jpeg
 
The charger in your picture isn't the 230v mains charger, it's a DC to DC charger....only works when the engine is running and takes power from the alternator.
You will have a 230v charger somewhere.

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If you have solar, then that will confuse things if you are looking at the battery voltage. The battery 'resting voltage', when it's not being charged and with no load on it, should be between 12.0V and 12.7V. You may have to wait until dark to check that, if you can't disconnect the solar. It may take some time (a couple of hours maybe) for the battery to settle to its resting voltage after being charged. If the battery voltage stays over 12.0V when there's nothing charging it, then at least you know it's not a shorted cell.
 
Last edited:
pappajohn said:
The charger in your picture isn't the 230v mains charger, it's a DC to DC charger....only works when the engine is running and takes power from the alternator.
You will have a 230v charger somewhere.
Click to expand...
The battery charger is lurking under that DC-DC converter, not very visible, the model number isn't very visible either, probably an NE287, as rb62 suggested.
 
pappajohn said:
The charger in your picture isn't the 230v mains charger, it's a DC to DC charger....only works when the engine is running and takes power from the alternator.
You will have a 230v charger somewhere.
Click to expand...
The mains charger is what the DC to DC charger s sitting on.
 
It is indeed a Nordelettronica NE287, not sure if 17 or 21 versions. Thanks rb62 for link to manual. The unit does seem to be a modern unit with appropriate charging profile for the battery.
I have disconnected the 230v feed kettle plug, and reconnected the mains EHU. I will keep an eye on battery temperature.
I will recheck battery voltage after dark but did this last night and expect voltage will be in 12 to 12.6v range. Is there anything else I can do diagnostically? We may be able to limp along without EHU charging of the leisure battery as long as solar panel and alternator charging are working, until we get back to North Devon or the main dealer in Weston.
 
autorouter said:
The battery charger is lurking under that DC-DC converter, not very visible, the model number isn't very visible either, probably an NE287, as rb62 suggested.
Click to expand...

eurajohn said:
The mains charger is what the DC to DC charger s sitting on.
Click to expand...
Strange, I didn't even see that. :doh:

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Keep a eye on the solar as well, the PWM controllers can go south. Personally I would change that battery ASAP, as it heated up, no longer has adequate electrolyte left in it. Plus the plates are buckled from heat rest assured.
 
Make sure all the battery connections are clean and tight. Loose connections can create heat but usually to thd terminal tops only. (y)
 
I had a similar issue with a Rollerteam MH and found that the charger set to AGM (same charger as mentioned) however at some point a sealed lead acid not AGM battery was fitted
Not saying this is the problem but my battery cooked and if I read it right a Varta type battery is a sealed lead acid and not AGM
There are tiny dip switches on the charger that set the charging profiles, maybe worth just eliminating that one.
Ps once a battery gets really hot I would replace it any way specially if the sides are swollen
Good luck

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The battery is cooked. 11.8v last evening. Next step is to find a leisure battery in the Highlands. Any local knowledge? We are on our way to Aviemore passing by Inverness.
Why did a one year old battery cook? I will check charger jumper settings. Clearly I don’t want to fit a new battery to see it go down the same road. Is there anything I should be keeping an eye on to make sure it was not the charging system that was the battery killer.
 
If it's over heating change it , it's on its way out whatever you else you might find wrong, during a Battery Course I went on (not , Lithium) it was stated if a battery goes flat 3 times , it will start deteriorating IE. It's damaged
 
BarumMike said:
The battery is cooked. 11.8v last evening. Next step is to find a leisure battery in the Highlands. Any local knowledge? We are on our way to Aviemore passing by Inverness.
Why did a one year old battery cook? I will check charger jumper settings. Clearly I don’t want to fit a new battery to see it go down the same road. Is there anything I should be keeping an eye on to make sure it was not the charging system that was the battery killer.
Click to expand...
Suggest you get the exact battery model number and capacity off the label on it.
Check the type against the settings on the charger to confirm LA or AGM and set it up appropriately.
Guess it wont be cheap buying a quality leisure battery in Inverness. Could you order from, say Tayna, etc, and get it delivered to somewhere you could collect from?
If you're really stuck we're in Glasgow if any use.
 
There is a Go Outdoors in Inverness. They are competitively priced and I don't think as a company they do 'regional pricing'.
 
meanders said:
There is a Go Outdoors in Inverness. They are competitively priced and I don't think as a company they do 'regional pricing'.
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There is but the last time we were in there (couple of years ago and not for a battery, right enough) didn't see any in stock so worth a phone call first.
03443 876834

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