Re: [bmw] New battery failed?

[ingraham@xxxxxxxxxxxxxxxxxxxxxxx]

A battery can fail when new, and some do.  Battery life is statistical, 
not fixed.  Some fail in one month, some in seven years, and most in
2-5 years.  The warranty period is a marketing feature, not a design one.

A 2-mA drain would not discharge the battery.  But that seems too low.
I'd expect more like 20-40 mA, but even that would take two or more
weeks to discharge the battery.

There might be an intermittent high drain, such as a door lock heater 
or trunk/glove box light; that may not have been on when you took the 
measurement.  

You can check the condition of the battery by fully charging it, then
using a load tester.  Some auto parts stores will do this for free.

Given the 13.5-V charging voltage you measured, your charging system
is working.  It is possible to measure the charging current.  If you
don't have the equipment or know the method, take the car to a tech
for a charging system diagnosis and battery check.

Is this a BMW battery from a BMW dealer?  The LED description doesn't 
fit with that.

What kind of charger are you using?

Curt Ingraham
some 2002s
Oakland, CA

john <j.s.smith@domain.elided> wrote:

> Sorry for this long post...
> 
> My '89 E30 325i failed to start last night - flat battery :-(
> The thing is I bought the battery new from a BMW shop only 6 weeks ago, to replace the existing 
> battery which had been in the car for 7 years! My problem is now that I don't know whether this new 
> battery has actually failed in some way - or is there a fault on the car. btw I only replaced the old 
> battery because that ran flat too.
> 
> What I have done so far:
> 
> 1) Measured the current drain with ignition OFF and everything electrical in sight turned off. The 
> current was about 2mA so I think that's ok
> 
> 2) Measured the battery terminal voltage with engine running at 1000 rpm and most every electrical 
> thing turned ON. The reading was 13.4 volts - so looks good to me.
> 
> 3) The red battery lamp on the dash goes out as normal when I start the car so I *guess* is charging 
> the battery?
> 
> The way the battery went flat is also strange... I used the car the previous evening, no problems. It 
> was standing overnight, weather was warm. Next evening it was completely flat.
> 
> Also, the new battery is a sealed type and has a led indicator built into it. The label says 
> green=ok, black (no light)= needs charging  yellow= replace battery. I've had this thing on charge 
> for 10 hours and led is still off - although the battery voltage is 12.4V and I can take take several 
> amps from it to drive a latge test lamp.
> 
> Is there an easy and reliable way to tell the charging current when engine running?
> 
> I don't want to look a right idiot by taking the battery back and then them telling me it's ok - so 
> would appreciate some help with this.
> 
> Thanks
> 
> ps When I bought this battery from BMW it had a minor scuff mark on the side and wasn't in any kind 
> of box - I just had the feeling maybe it had been lying around a while. Also the labelling on it says 
> it's sell-by date is 4th April 04. Mmm
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