Battery Drain

Is it normal for a current still to be present in a bike with the ignition
switched off?



I have a battery that goes flat overnight on my R100RS BMW (1978) I checked
the current flow with the bike switched off and it was 0.37 mA, now I am
guessing that that is so close to bugger all that it really does not make
any difference. With the onboard analogue clock connected the current drain
is about 6.0 mA. The alternator is charging OK, so now I suspect a dud (near
new BMW) battery. I will buy a hydrometer and test the cells tomorrow.



Any other suggestions?



Boxer

 

it will be if you have a clock or alarm fitted , do you ?
have you placed an decent amp meter in line to determine the drain ?

funny you mention this , bloke over the road is precious and drives a
318i , was going to pay $400 for a bmw battery and had to return it and
reverse the cc after a week , I bought a 2 year warranty no name for
$118.00 on his behalf...

 

Depends on any equipment that draws current while otherwise off, such as
clocks, alarms, (as suggested by the other poster) whatever.

No, 370mA is very high, and certainly not normal. My guess is, it would
flatten your battery (we are talking bike batteries here) in about 24 hours or
so, depending.
Certainly flat enough overnight for all intended purposes as far as you're
concerned anyway...

That sounds very high too. Sure 6mA is a far cry from 370mA, but it's still
abnormally high. Any clock, (during standby in case of LED types) take only
microamps. This goes for digital and analogue mechanical clocks.

I don't buy that anyone would design a clock that takes 6mA, and still have
a job at the end of the day. First thing I'd be asking is why those damned
engineers aren't shot yet.

There is a slim chance that figure is 'normal' for that clock, in that case,
I stand corrected. But I'll still want the idiot engineers shot just in case.

Be wary, it's almost an art diagnosing a dud battery without the right
equipment.

Good call. My guess is it's not the battery anyway. Mainly because you've
measured that abnormally high off current.

That current is going somewhere, that's for sure. Might be an idea to pull
fuses and see where it goes. Only one should cut it of course, but that's
barring any abnormal faulty switch action that's on, where is should actually
be off.

What kind of bike is it? Others here may be intimately familiar with it,
and can suggest what is hooked up to power when ignition is otherwise off.
It'll give you an idea of what to look at, and perhaps find something that
takes more than it's fair share of juice.

 

The drain is not 370 mA it is 0.37 mA, the clock in the BMW is a analogue
quartz unit and 6mA really does not sound a lot to me.

I will pull the battery and have it load tested after putting it on a
trickle charger for 10 hours.

Boxer

 

He said .37mA not 1000 times more!

 

Reading and comprehension isn't really your longsuit is it John?

 

My fault Clem, I forgot to mention it was a Gold colour!

Boxer

 

Yes, just re-read that. You should have said 370uA. I would have picked
that right away. (In other words, it's your fault. Ahem).

Either way, in that case, that drain is quite reasonable.

Unless I'm miss-reading that one too, it's absolutely obscene. Any analogue
quartz clock made this side of the cold war doesn't take that much. We have
many around the house that run on a single AA battery for several years or so.
I have at least one watch that does the same with so many years between
battery changes, I forget.
Don't forget to shoot the engineer. Or the project manager that let them
put that clock in. Better get them both just to be on the safe side.

Now that my brain has found a gear that isn't completely stripped, it does
sound like excessive self-discharge.
Another poster mentioned the perfect reliability record BMW batteries have.
They're clearly not designed by the same morons who designed the clocks...

 

I'm surprised you can measure .37mA but that is truly tragic. I
predict that will run your battery dead flat in around a million
hours, which is probably more than the expected life of the battery.
6Ma is a different story. This could possibly run your battery flat in
a couple of months. I can give you a possible explanation for the 6Ma
but john T wont like it. Clocks of some quality that run from a
battery source (not the one in your kitchen wit the AA battery) have a
built in power storage capacity which is charged constantly. This
could account for the clock taking that much power when being
reconnected. I suspect if you measure it the next day, it will be far
less.

If it's going flat over-night, it's fucked mate.

Theo
Beer?

 

6 MA? I'd expect less than 1 kA at a dead short!
6 mA would be more like it ...

6 mA out of a nominal 20 Ah or so battery should give you a couple of
thousand hours to discharge, so I don't think that's the problem, even
though your nights up there are a bit longer than down here at the
moment, what with daylight savings.

Boxer, are you measuring the amps at the actual battery terminal rather
than the fuses? There's a path back through the diode board which
doesn't go through the fuses ...

-----sharks

 

I have taken the positive lead off the battery and used the meter in between
the battery positive terminal and the positive lead.



My guess is that the battery has a dead cell. I have a few bike batteries in
the garage so I will swap one out and see how it goes.



I have been using genuine BMW batteries in this bike as it is a Concourse
winner and having the incorrect battery would cost points.



The clock draw pulses in time with the second hand from 3-9 mA, I suppose I
am lucky that the extra current draw from daylight savings is not affecting
the battery life.



Boxer

 

OK, it's not that then! I'd probably try charging the battery up, then
leaving it standing on top of the beer fridge with just a voltmeter on
it, see if it's self-discharging. If so, return to the Bavarians!

Amazing, that whole Concourse thing. There's a couple of people working
on finding the parts to make an absolutely stock XLV. Never understood
it myself, but!

-----sharks

 

I am not really into it, but as the bike was 95% concourse when I purchased
it, whay not keep it that way (worth more in the long run).

Boxer

 

Bunch of crap really unless you're at Pebble Beach. Original should be
untouched....and that's a real challenge.

justAL

 

Late mid-late 90's Triumphs (eg Daytona T595) seemed to have this
issue occasionally. I believe the consensus was a dud relay was
draining current..in the absence of any other issues such as faulty
alarm or beer fridge/hair curler left running overnight.

So..if the flat battery overnight syndrome is repeatable..try pulling
relays and see if flat battery syndrome disappears.

The 0.37mA (ie zero point 37) too be too low to be an issue, unless
you can observe whether this figure remains constant or jumps
significantly.

 

omg that reply was grammatically appalling.. muscat and keyboards are
not fully compatible technologies.

 

The battery has been replaced by BMW under warranty, it had a dead cell.

Boxer