Discharging Battery

[pawel]

The one year old Westco battery in my R1150RT goes dead in a couple of days. The current draw is about 4.5 milliamps with the bike not running. My Chilton manual say the maximum should be 2.0 milliamps. Does 2.0 ma sound right for a maximum?

[Joe Frickin' Friday]

Even with .0045 amps continuous draw, the battery should last for at least a week before being completely flattened (19 amp-hours divided by 0.0045 amps = 11.56 days). Something is wrong with your battery. If it's only one year old, then there's some sort of defect. Is it still under warranty?

 

The definitive test would be to charge it to capacity, and then leave it disconnected (open-circuit). That will tell you for certain that there's an internal short.

[Peter Parts]

If you monitor the current that goes into and out of your battery using the ground strap as the shunt and any voltmeter, you will learn just about everything you need to know about your battery's flow in (charging) and out.

 

Going from ammeters to voltmeters was one giant step backwards.

 

See write-up at URL below.

 

Ben

[Pat Buzzard]

I have the same problem. I just replaced my battery this spring and it doesn't stay charged well at all! I will try the above trick and report my findings

[dirtrider]

Morning pawel

 

According to the BMW service bulletin I have – (on key-off battery drain) your 1150Rt should have a max parasitic draw of 2.6 mA. Even the 1200 hexhead with all the onboard electronics is only 2.5 mA (key off after ZFE shutdown).

 

So your 4.5mA is on the high side.

 

You have some options and the first would probably be as Mitch suggested to disconnect the battery and see if your dead battery problem goes away.

 

If your dead battery issue goes away then hook your ammeter back up and remove fuses (or disconnect added wiring) until the parasitic draw goes to below 2.5mA. Then let it sit for a few days again.

 

The next option is to remove the battery, then fully charge it, then have it load tested. One of the down sides of the GlassMat batteries like the Westco is reduced storage capacity if overcharged or fully discharged. Personally I quit using the Westco battery’s for the very reason you are seeing. They seem to suddenly lose capacity and have very little reserve with even a little patristic drain. I have an old Westco battery on my test bench here that sits there forever at 12.86 static volts and can power up small devices and stay above 12.4 volts but will fall totally flat if I try to use it to start a motorcycle or test a starter.

 

[Peter Parts]

I have the same problem. I just replaced my battery this spring and it doesn't stay charged well at all! I will try the above trick and report my findings

 

If using a mechanical meter, disconnect when cranking.

 

You can calibrate the set-up by changing any known current draw (headlight, brake light, Gerbing's gloves...) and seeing how the voltage drop across the ground strap changes.

 

Sure beats the rigamarole of the previous post.