Battery flat. .. risks and tips?

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HighSharpe
Joined: Sun 28 Jul, 2013 00:01
Posts: 42

  Z3 roadster 2.0

Battery flat. .. risks and tips?

Post by HighSharpe » Mon 11 Aug, 2014 08:45

Hello All



Had a successful MOT the weekend before last, but for him commenting on rust on brake discs; a topic I would have separately discussed, but for something new that came up.
This weekend, tried starting up the car but battery was completely flat. Not sure why - can't swear no light was left on. In any case, i pulled out the battery, a Bosch S4 72Ah which was showing a voltage of c 0.65 volts. I bought a battery charger :


http://www.argos.co.uk/static/Product/p ... :c|adp:1o4


Left this on for some time but the charger seemed to stop charging after some time (c 15-20min) almost as if no battery is charged (high internal resistance?). The voltage on the battery is c 10V but surely it must be unusable.

1/ So clearly is it new battery time?
2/ Any way to easily check if there's some electrical fault that caused the battery flat ?
3/ Havent gotten a friend to help jumpstart, since I had the charger, but surely now its a pointless exercise? Plus not worth stranding another good car if electrical fault ?
4/ Most important ... Are there any ill effects of the car having a flat/no battery in it for a few days? Anything to worry about in terms of memory / indicators when i fit in a new battery ?

Many thanks for any advice !

-HS

Del
Joined: Sat 19 Nov, 2011 18:35
Posts: 2115

  Z3 roadster 1.9

Re: Battery flat. .. risks and tips?

Post by Del » Mon 11 Aug, 2014 09:56

Battery voltage readings are a bit strange in that a reading of 12.2 v shows a battery in a state of approx. 50% charge whilst 12 v equates to just around 25%. From 0 v to 11.9 V the battery is more or less completely discharged. If after charging, you cannot attain more than 10.5 v then a battery cell is completely dead. Your situation therefore sounds like a simple case of a "dead battery".

Others may like to comment, but in the context of Z3s, the only likely problem I can think of is the possibility of having to re-enter the security code on a audio unit.

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Southernboy
Joined: Thu 07 Oct, 2010 13:39
Posts: 6312

  Z3 roadster 3.0i
Location: Johannesburg

Re: Battery flat. .. risks and tips?

Post by Southernboy » Mon 11 Aug, 2014 10:35

Not having the battery connected is not an issue... except perhaps the audio as stated.
"Normal is overrated"
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Robert T
Site Admin
Joined: Mon 12 Jun, 2006 11:35
Posts: 9984

  Z3 roadster 1.9
Location: Cheshire

Re: Battery flat. .. risks and tips?

Post by Robert T » Mon 11 Aug, 2014 10:39

There are occasionally problems with the alarm system after removing the battery for a prolonged period, but the later alarm system (which you have on the 2.0) doesn't seem to have as much of an issue with this. As mentioned the only other problem is with the original BMW stereo which requires a code to be entered after losing power - which is only a problem if you don't have the code!

It does indeed sound like a cell has gone down in the battery, which can happen at any time, but it is also possible that something has taken the last of the charge out of it, and the one thing that comes to mind is the seat motor being stuck on - this has happened to one or two people on here and draws a current of several amps over a prolonged period. If someone else has recently driven it (i.e. MOT) then I'd have a close look at the driver's seat and make sure that it is not at the end of its travel and moves in all directions on command.

One other thing, which I'm sure you weren't going to try anyway, but do NOT attempt to bump start the car - they don't like it. Jump start using the terminals under the bonnet instead.

Cheers R.
Arctic Silver '99 Z3 1.9 & Black '59 Frogeye 1275cc
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HighSharpe
Joined: Sun 28 Jul, 2013 00:01
Posts: 42

  Z3 roadster 2.0

Re: Battery flat. .. risks and tips?

Post by HighSharpe » Mon 11 Aug, 2014 12:34

Thank you all. I seem to have a non-OEM head unit, so not concerned about audio. I will order a new battery soon and report back once fitted. I guess I will go for the same battery model, unless any one has any thoughts about that , especially higher / lower Ah than the existing 72 Ah ?

regards
HS

Del
Joined: Sat 19 Nov, 2011 18:35
Posts: 2115

  Z3 roadster 1.9

Re: Battery flat. .. risks and tips?

Post by Del » Mon 11 Aug, 2014 20:38

My 1998 service booklet for my Z3 (a 1.9) recommends a 70 Ah battery which equates to a current day battery model code number of 096. You will find that a 096 battery just fits into the Z3 battery compartment. When I first got my Z3 it had a 075 battery in it which is slightly smaller and slightly less Ah - it worked perfectly well. Many more modern cars, with more sophisticated electrics, operate perfectly well with a 075 battery so I don't know why BMW recommended such a beefy battery.

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pingu
Joined: Fri 30 Apr, 2004 17:01
Posts: 3337

  M roadster S50

Re: Battery flat. .. risks and tips?

Post by pingu » Mon 11 Aug, 2014 23:18

I've got a battery charger like this. It's not cheap, but costs less than two batteries...

Image

I have never not been able to recover a battery.


Empty all the electrolyte.

Fill to correct level with deionised water.

Connect battery and select lowest setting. Note current reading. It will probably be low as the plates will be covered in crud. This has to be dislodged.

Increase the setting and lightly tap the battery with a 1/2lb hammer to remove the crud and start the charging process.

When the current draw starts to rise, reduce the setting.

It can take a couple of days to get the battery back, but I've not been unsuccessful - YET.
Pingu

HighSharpe
Joined: Sun 28 Jul, 2013 00:01
Posts: 42

  Z3 roadster 2.0

Re: Battery flat. .. risks and tips?

Post by HighSharpe » Tue 12 Aug, 2014 07:46

Hey Pingu

Thanks for that. Sadly my battery is the sealed 'maintenance free' type so can't check or top up. The charger I bought was the cheap kind but it did say upto 80AH and 6 rms charging current so chanced it. Haven't bought a battery yet, might just order one off eurocarparts or batterymegastore.co.uk

cheers
-HS

Jonco
Joined: Sat 04 Jun, 2011 08:24
Posts: 382

  Z3 roadster 1.9
Location: Cheshire

Re: Battery flat. .. risks and tips?

Post by Jonco » Tue 12 Aug, 2014 10:07

Del wrote:My 1998 service booklet for my Z3 (a 1.9) recommends a 70 Ah battery which equates to a current day battery model code number of 096. You will find that a 096 battery just fits into the Z3 battery compartment. When I first got my Z3 it had a 075 battery in it which is slightly smaller and slightly less Ah - it worked perfectly well. Many more modern cars, with more sophisticated electrics, operate perfectly well with a 075 battery so I don't know why BMW recommended such a beefy battery.
Agreed in the main - when I got my Zed I inherited a 55 amp/h battery of unknown age. It worked for another 4+ years but was always close to the limit after idle drain periods and without trickle charge.
It was still working when I decided to replace with an Exide O96 - it is a bit overrated but the extra cost equates to a few £/a over battery life and you have the extra when you need it.

Del
Joined: Sat 19 Nov, 2011 18:35
Posts: 2115

  Z3 roadster 1.9

Re: Battery flat. .. risks and tips?

Post by Del » Tue 12 Aug, 2014 10:13

Jonco wrote:with an Exide O96
Great minds think alike Jonco - I put in one of these last year when the existing 075 Halfords one failed. :)

HighSharpe
Joined: Sun 28 Jul, 2013 00:01
Posts: 42

  Z3 roadster 2.0

Re: Battery flat. .. risks and tips?

Post by HighSharpe » Tue 12 Aug, 2014 17:22

Just ordered a Varta off here, just got to wait for it to arrive. Thought I'd go for a higher Ah purely because of the infrequent use I put the car to.

http://www.tayna.co.uk/E44-Varta-Silver ... P7726.html

HighSharpe
Joined: Sun 28 Jul, 2013 00:01
Posts: 42

  Z3 roadster 2.0

Re: Battery flat. .. risks and tips?

Post by HighSharpe » Sun 17 Aug, 2014 22:18

Just back to report, fitted the battery and the zed's back from the dead :) Had a little spark when fitting but guess that's just the boot light and alarm electronics kicking in...
Cheers...will have a new thread for my brake disc queries.

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