E30 Battery

Post Sun Nov 17, 2019 8:56 pm

Hi everyone,

As the Winter approaches I'm becoming more conscious of the fact I may not get my E30 out as frequently. As such I'm wondering a couple of things:

1. How long can a standard E30 battery go for, generally speaking (with a good working alternator), between running the car do we think?

2. Is there any manual override for the central locking system if the battery did go flat? Would rather not have to gain access to my car via other means...

Should probably also mention that I have an immobiliser fitted and up to now I have noticed an audible reduction in cranking power with the colder weather (maybe 10% to 20%) if left for a week or so.

Very interested to hear people's thoughts on this as I don't want to get locked out of my car with a flat battery! Thanks in advance

Post Sun Nov 17, 2019 10:26 pm

There is no deadlock on the driver's door. That can always be opened with a key if things are in working order.

Post Sun Nov 17, 2019 11:16 pm

I would not have thought that leaving the car for a week should run down the battery so noticeably, but immobilisers are the Devil's work and may be doing that, or the battery may not be as good as it once was, how old is it? Is it feasible to couple up a maintenance charger, I am a great believer in those?

Post Sun Nov 17, 2019 11:22 pm

Typical parasitic drain current on a parked up E30 is around 30mA, so with a fully charged 65A/hr battery, it should last 65 / 0.03 = 2167 hours = about three months.

Post Mon Nov 18, 2019 7:06 am

Brianmoooore wrote: ↑
Sun Nov 17, 2019 11:22 pm
Typical parasitic drain current on a parked up E30 is around 30mA, so with a fully charged 65A/hr battery, it should last 65 / 0.03 = 2167 hours = about three months.

Thanks for the help there Brian. Central locking system is in full working order as is the key/barrel on the door so that should be fine if worst comes to worst. It should only be going maybe 3 weeks or so at most without being ran so hopefully the battery stays charged enough anyway.

Post Mon Nov 18, 2019 7:08 am

ChrisHC wrote: ↑
Sun Nov 17, 2019 11:16 pm
I would not have thought that leaving the car for a week should run down the battery so noticeably, but immobilisers are the Devil's work and may be doing that, or the battery may not be as good as it once was, how old is it? Is it feasible to couple up a maintenance charger, I am a great believer in those?

Yeah it is an odd one, I think it could be the colder weather more than anything come to think of it. However it wouldn't surprise me if the immobiliser was draining quite a bit of charge. But yeah I will definitely need to have a look at one of those - the battery looks and as far as I'm aware is fairly new, but there's a good chance it's not the greatest anyway. Thanks for the help!