Leisure Battery - Help!!!!

[Gek]

Hi all, I went out to my van this morning and the leisure battery is flat. It was charged on a long drive 2 weeks ago without issue. I've now plugged it into the mains to charge it. Initially it showed an output of 6.2v and has now crept up to 7.8v. The battery is less than 1 year old. Any ideas why when plugged in it's not showing 12v+ output? We are just about to go away for New Year and can't use the fridge etc. etc. Do I just leave it and will it charge up to 12v or has the battery had it. Can't get hold of anyone at Mercedes dealer!!

 

[Grand Tourismo]

Hi Gek, do you know why it went flat, a well cared for 1 year old battery should have maintained some charge even with a 2 week lay up? If there was no service drawing from the battery then I would guess that the battery has conked...most decent garages should be able to perform a "drop" test for you to see how the battery health is but I would really want to get to the cause of the voltage drop before installing a new one and risking trashing it as well.

Lead acid batteries should not be discharged to less than 50% capacity, hopefully you might just get away with it...If you can leave it charging on the mains to 12.6v and plug in on site when you turn up.

 

[Vaughnt]

My older MP use to lose its charge after a week but it would be fine after an hours drive or charge with a plug-in - think the display was around 14v when charged

 

[enano]

Hi all, I went out to my van this morning and the leisure battery is flat. It was charged on a long drive 2 weeks ago without issue. I've now plugged it into the mains to charge it. Initially it showed an output of 6.2v and has now crept up to 7.8v. The battery is less than 1 year old. Any ideas why when plugged in it's not showing 12v+ output? We are just about to go away for New Year and can't use the fridge etc. etc. Do I just leave it and will it charge up to 12v or has the battery had it. Can't get hold of anyone at Mercedes dealer!!

When leisure battery voltage runs too low, the built in charger won't be able to charge it - had it happen a couple of times.
Turn on the engine, turn on the lights and let the alternator charge it. The display should show approx 14V while charging from the alternator. After turning off the engine, the display will show the voltage drop again, but the battery will have absorbed some charge.

My rather worn leisure battery discharges at 0.1V per day when unplugged, with a few gadgets always powered. If your battery is suddenly flat, maybe you forgot your fridge running. Another suspect is the heating - at least I can never remember to turn off scheduled night heating after a trip.