Conundrum

[Chris63]

I’ve posted a few questions on here recently
Another conundrum, I’ve always suspected that my leisure batteries are original and I’m not sure about the vehicle battery also
The van is a 2011 Autotrail Dakota.
On Wednesday I traveled from Kings Lynn to north oh Lincoln. , I was parked for around an hour and a half when the alarm sounded on the control panel , I assumed that it was the leisure batteries even though nothing was switched on
It was the vehicle alarm , it had gone from 13.1 volts to 10 . 4 in no time and again nothing drawing on it
Both batteries were flat ??
Next day a fellow traveller gave me a bump start and now I’m in Pateley Bridge and the batteries haven’t moved from 12.9 leisure and 13.1 vehicle
I seriously thought I would be buying a vehicle battery and possibly leisure batteries also
Why should both have died and now they appear to be good
Your thoughts on this will be appreciated
Regards
Chris

 

[Richard n Ann]

Sounds like the fridge relay could have stuck on but it's a total guess. You'll have to be there quickly with a multimeter when it does it again.
I'd fit a BM1 battery monitor if you haven't got one already, you know exactly what's going in and out of your battery with that. Even shows starter battery voltage.

 

[cmcardle75]

You don't know they're good. When a lead acid dies, it often just gets less capacity, but still shows good voltages when charged. However, it might only have 5Ah instead of 100Ah available. Simply looking at the voltage after a charge won't tell you much about the health of the battery.

 

[Odd-no-more]

I had a relay stick once, it drained both batteries, it also took out the charger when I plugged the EHU. When the relay stuck it kept the heater on and the split charge relay on as well. I got it to an auto electrician it was with them for a week and they couldn't find the fault. I had it for years after and just checked the heater control had gone off every time I switched the engine off, if it was still live (very occasionally) I switched it on/off and it was fine.