Battery's dead after 2 days

[silver surfer]

Do I need a new battery?
530i now 5 years old from new and the battery is dead after not driving it for 2 days. Jump starts Ok and starts OK if I run it every day..........?means alternator is charging but there isn't enough battery juice to keep the charge??

SS

[phelix]

Worth putting a volt meter on the car to see what voltage is with engine on and off. You should see 12.5 or slightly more engine off and it should stay there for a couple of weeks unless there's excess current being consumed. Engine on it ought to be 14 to 14.5.

[MitchT]

At a guess I'd say battery or alternator.

Knackered battery = Battery doesn't have the ability to be charged properly.
Knackered alternator = Alternator doesn't have the ability to charge the battery properly.
Symptoms will be the same wither way.

Five years sounds a bit early for the battery to be going. Mine appears to be on its last legs after 8.5 years.

[Autosparx]

Hello mate,
Well... from an auto electricians point of view....
The average car battery under normal conditions has a three year life expectancy.
With-out going to technical ( not knowing your line of expertise ) heres a few obvious pointers.
Your battery warning light should come on with ignition and off with engine run, if it glows slightly whilst driving its a sign that the alt is not covering the full load on the battery, causes could be, poor earth to the alt allthough most alts get there earth connection from being mounted on the block so probably ignore that one, poor main supply input, check the alt terminal marked +30 this should be clean dry and tight, if you use a piece of wire and 'flash' it to the body it should give big blue spark ( mind yr eyes )if you have meters it should sit at battery voltage (12.5v)
If battery w/l comes on with ignition off its a sure sign the diode pack in the alt is nackared, buy a new alt or if yr confident, change the diodes? If w/l is full brightness when driving, the wire marked D+ has chaffed down to earth somewhere between alt and dash.
Do you have any test equipment? dis-connect battery earth lead, use a digital ammeter between the bat neg terminal and the earth lead youve removed, reading should be less than 0.05a ( this is the reading of battery drain, turn yr interior light on to see a rise in the reading... All cars have a very small drain due to all the electronics n stuff.
If your battery is nackered the alternator may be giving a surface charge only, meaning that all the work is giong towards running the fuel/ign etc of the car and NOT charging the battery.

Give us a shout if you need more friendly advice.
All the best.
Mick


Edit to remove phone number

Edited by missdiane on Sunday 13th January 08:23

[carlosvalderrama]

I just had a similar problem. I did as above, disconnected the negative and put an ammeter across it. Then I took out fuses one by one until the current dropped to about 0.04A. Turned out to be the boot light switch which had come adrift. With the boot open it was staring me in the face and I didn't see it...

[steelej]

I had a similar power drain in a 528i, after replacing the battery a couple of times I eventually got one of these

http://www.batterybrain.co.uk/

It's brilliant, it's disconnects the battery if it detects the voltage dropping and it has a remote control to connect it again. I can now leave the car for any length of time without the worry of it not starting when I get to it.

John.