[TeaAndBiscuits]

Hey folks,

About 3 weeks ago, I had parked up and was idling when all of a sudden the iDrive display said something along the lines of 'battery voltage low', now with my car being a 2008 (320d) e90 I thought maybe the original battery is knackered, so I called out a local mechanic who tested it and said it was fine, and just needed a charge, he measured voltages whilst the car was idling and said it was charging normal etc.

I bought one of those chargers, plugged it in overnight (they say to leave the car 2 days trickle charging but how do you do that when you need to use it every day?!) and it seemed to be ok, until last week, when I got in the car, the clock was reset and there was another battery message (and a picture of a car on ramp), it did the same yesterday evening, and then again this morning when I got in the car.

It starts fine, and the batteries are pretty expensive I noticed (£200!) so I would rather not replace for nothing, if I take it to a garage I am at their mercy of probably changing it regardless, but just wondered if there were any other culprits at play here, alternator needs changing or something like that?

[Thermobaric]

I've had a similar thing.

Earlier this year I had a few low battery warnings, no angel eye illumination on unlock so I bought a Ctek charger and did a full charge. Seemed to sort it for a while. Then low battery warning light again and one day, clock e.t.c. reset and the warning symbol of the car on the ramp flashed up for half a second or so just once. I figured it got a bit screwy due to low battery.

I did another charge but this time put it on the recondition cycle despite the battery being as old as yours is and it's back to being OK again. I'll keep and eye on the voltages and maybe charge it once a month and see how that goes.

[TeaAndBiscuits]

Hello mate, yeah, I might try and do it so I can leave the car overnight and then all day/overnight the following day whilst connected, I have one of those AA Battery chargers, will check with the other half if I can borrow her car in the meantime!
I am doing a lot of short journeys of late, with the heated seats on etc, no doubt it's hammering the battery.
I don't mind having to change it if the worst comes to the worst but would not want to do all that only to find it's the IBS cable instead, will get it charged asap!

[un1eash]

Will be the battery, my 2008 320d did exactly the same, you'll find stop start and your rear window heater wont work either. Mine would last 2 weeks after a full charge before the clock reset again. New AGM battery fitted and all was fine.

[TeaAndBiscuits]

Ahh you just reminded me! Start stop has never worked since I bought the car last march ... actually it worked once when I drove to Cornwall (4 hours drive!) so must have had a good charge then! But if all signs point to it, will get another battery, seen an AGM battery on eBay for £118

https://www.ebay.co.uk/itm/252647374965

but read somewhere they need to be programmed in??

[Thermobaric]

Batteries need coding unless the battery is replaced with an identical battery, as in down to the amp/hour rating.

If you go from Lion to AGM, you definitely need coding so the car knows how to deal with it.

[TeaAndBiscuits]

Yeah it's an agm in there now but I think it's 900 and that eBay one is 850, bugger may have to take it to a garage to do in that case.

[TeaAndBiscuits]

Charged it over Christmas , lasted until today now the battery light back on again , so as said above , looks like battery