New battery for E86 ?
- Thread starter roblightbody
- Start date
Greenhithe, Kent
raymond.harper
Senior member
It should have lasted longer than that! I fitted an Exide 70Ah AGM battery to my Z4 in April 2021 and it quite often doesn't get used for a couple of weeks, but always turns over fine when I use it.
I'd be checking the static voltage and the voltage with the engine running. It sounds like it isn't charging properly which may be a bad earth as raymond said, a dying alternator or you've got a parasitic drain.
I'd be checking the static voltage and the voltage with the engine running. It sounds like it isn't charging properly which may be a bad earth as raymond said, a dying alternator or you've got a parasitic drain.
OK so I just checked, and it was showing 12.00v until I started it, when it went to 14.61v.
raymond.harper
Senior member
The battery should be at least 12.4. Alternator is fine. Either a duff battery or parasitic drain.
So I drove the car 40 minutes to work yesterday, and about 45 minutes home again. All seemed fine. 5 minutes after parking up in the evening, battery was at 12.40 volts.
Car has sat for 24 hours, and is now showing 12.14 volts.
My hunch is that its just a crap battery
Car has sat for 24 hours, and is now showing 12.14 volts.
My hunch is that its just a crap battery
raymond.harper
Senior member
12.40 is low for a fully charged battery; it may not have had sufficient time to get a charge. The voltage loss for 24 hours is acceptable. If possible, give the battery a trickle charge overnight to rule out a duff battery.
Hi Again.
I decided to fit a new battery. As you mention, it might not be the battery, but I think its the most likely culprit. I got a 115-sized battery as per other topics on here, and it fits perfectly - the battery is bolted down solidly and can't budge at all. Much more satisfactory than the previous 096-sized one. I opted for a very good Bosch AGM one too - https://www.tayna.co.uk/car-batteries/bosch/s5a11/ This forum has been a big help, because all of the online battery checkers for this car were showing the wrong sized battery.
I decided to fit a new battery. As you mention, it might not be the battery, but I think its the most likely culprit. I got a 115-sized battery as per other topics on here, and it fits perfectly - the battery is bolted down solidly and can't budge at all. Much more satisfactory than the previous 096-sized one. I opted for a very good Bosch AGM one too - https://www.tayna.co.uk/car-batteries/bosch/s5a11/ This forum has been a big help, because all of the online battery checkers for this car were showing the wrong sized battery.
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raymond.harper
Senior member
Keep an eye on the voltage readings over the next few days, not that I'm paranoid!
I will, thanks! At least this way, I've eliminated the battery if there's still an issue.
raymond.harper
Senior member
We had a similar problem with my son's BMW Mini. In the end, we got an autoelectrician to find out what was wrong. After an hour spent pulling fuses, it turned out to be the diode in the alternator. I disconnect the negative terminal if he is not using the car for more than a day while I build up the courage to change the alternator.
Tncdrew
Member
You should've bought an AGM battery. What you have is essentially an improved flooded battery (old technology). Not ideal for your car. You don't need a battery designed specifically for Start/Stop systems. This from the Varta website...
I picked this battery up from Halfords after reading about someone else doing the same. Bigger than the 096 battery I had in before and has a bit more oomph. Car starts like a dream now and importantly, the battery fits properly! I can now get rid of the wooden spacer I’d had to put it previously. Don’t really get that the advice seems to be get the 096 battery when it’s the 110 that actually fits in the designed space!!!