Battery always flat... ...alternator?

P

Psy

Member
 Putney, London
Hi all,

Oct/Nov last year, battery was constantly going flat, fitted a new one (Bosche Silver from Halfords).

All fine so far, until over the last fortnight has been flat 4 times - not even turning over, lights just flash and nothing happens. :headbang:

A friend of a friend (works for the AA), suggests without seeing the car that if it's a new battery, then it's the altenator or a trickle drain from something. Nothing is draining the battery (no lights stuck on/iPod charging etc), so could the altenator be causing a problem?

I only drive the car 3ish times a week, mostly the weekend to GF's/parents and rarely more than 100 miles a week at most.
Could the low mileage really be causing this? :?

Appreciate your thoughts,
Si
 
I doubt it's the battery, could be the alternator not giving enough output, or something else that's draining the battery. Even though you only do 100 miles a week, it should be more than enough to keep the battery charged. No doubt other members will be able to offer you some ideas. Hope you get it sorted soon.
 
na its not the short journeys i had a z3 that did the same there was a drain on the battery found out it was the alarm. so i did not activate the :) arlarm while it was in the garage then all was fine no flat batt again.
 
you can check the alternater put a volt meter across battery check volts then start the car and moniture the voltage .be around 12 to 13 volts mine was 13.6 volts :D
 
I had a similar problem. Transpired there is a junction box under the bonnet on the bulkhead, The heavy red wires from starter, alternator and battery are all connected here. Long story short it was getting very hot (loose connection). £11 part + 1/2 hour labour.
I think I posted before in more detail.

Good luck, let us know how you get on.
 
I had a similar thing in the past with another car - as I had also bought the battery from Halfords they were happy to check it out for me. It might help in your diagnosis to eliminate the battery by getting it checked out.
 
Thanks to all above.

Dropping car into dealer's on Saturday for them to take a look - all under warranty.
Will mention the junction box to them.

Si
 
Sorry I should elaborate a bit.

Only just got the Z4 and from the start sounded like it was struggling to start. Well, the other day after driving 35miles or so I stopped at a shop and when I came out DEAD! So much so the time had reset.
Bump started from my friends car and all seemed well. I went to work that night and it did start afterwards but still sounded some what half-hearted in doing so.

Took the battery off and put on a conditioner, but that didn't seem to work either. The guy at the local motor factors put a tester on the battery and said the battery would be fine just needed a good charge. It had 12.4V but 0A!! This makes no sense to me at all, so bought a new battery anyway. What the battery tester also said was that 'something' was taking power with ignition off, boot light disconnected & interior light off.

So I was wondering if you got to the bottom of what was causing your battery to die?
I have spoken to a family friend who is a retired auto electrician, and he seems to think it could be the 'hedgehog' the thing that blows off the positive side of the battery in the event of an accident. Apparently they can fail an cause this type of thing.

He has just phoned me and asked me to take it over to have a look so I better go......... :cry:
 
Just had it all checked out, appears that it was just the battery. The new battery indicates 0.8A draw which is a little high but not massive and it is my daily car so shouldn't be an issue.

Got shown how to reset the auto windows as well.

So if anyone is interested, you push the button to lower the window and hold for 3 seconds then raise the window and keep the button held for 3 seconds. It will now auto open and auto close.

I also got it wrong about the hedgehog that's something to do with the heater???? :D :D
 
Hedgehog = blower motor resistor pack

blower-motor_resistor9.jpg


Also, the battery disconnect is monitored and should trigger a warning light if there's a problem.
 
I had this with my 320d so I replaced the hedgehog and it seems to have cured the problem
 
Hi guys, old thread bump...

...car stopped doing it, but the last couple of months have been just annoying. Culminated in dead every day for a week.

Dropped it off at the garage (under warranty) on Thursday, they are taking a look for me, but confirmed in a couple of hours that it is definitely a drain, the alternator is fine.

They gave me a loaner Astra, which was acceptable but...
...went to the actual dealer I bought the Zed from(and my previous 330, family friend), he has leant me an Audi S5.

Oh wow... ...have a horrible feeling I might be telling the guys to keep the Zed and a few grand and I keep this monster.


Will suggest to the garage about the hedgehog. :thumbsup:

Thanks,
S
 
Just spoke to them - pretty knowledgeable guys.

He was familiar with the hedgehog and had tested the control box - the battery in the Zed is controlled by a computer in a box that sits just next to the battery. It is in turn controlled by other computers connected to the ECU proper.

After chatting to some guys at BMW, he currently thinks its that one computer, somewhere, is not going into 'sleep' mode when the car is switched off, thus draining the battery.

I'll keep you updated...

Si
 
OK, an update.

They think it is my iPod connection box... ...can't remember the name (ICE?) but it the audio system isn't shutting down properly because it detects the iPod connected to it and tries to charge the iPod.
Long and short, the computer doesn't shut down and the battery is slowly drained.

Going to pick up car on Saturday and hear the full story.

Will be very sad to return the S5... :(

...will wait to see what they proposose as partX value for the Zed... :?
 
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