BMW R1200RT/R1250RT Forum

does anyone have a large hammer? 2nd complete strip down because the brand new battery is draining at 0.79 amps. I have a new alternator coming but am not convinced that will fix it. there is no damage to the wiring that I can see, no addons, no alarm. its an 11 plate r1200rt ex police so has loads of spare wiring. I am enjoying getting to know my bike but the sun is out and I'm not. any ideas or anyone near Derby, ? no problem making it worth your time if it fixes the problem.

A new alternator will certainly not fix your problem if i am reading correctly, 0.8A while the thing is switched off is far too high.. usual practice for diagnosing such a problem is to start disconnecting things until the parasitic draw drops to a reasonable level.


I don't have a specification for you, a guess would be 0.01A max.

Is the auxiliary battery still fitted.

I have disconnected and tested but can't find a drop so figured it must be an electrical component? and no the auxiliary battery was taken off as not needed. I am at a loss on this one. I was told that the regulator/rectifier is built into the alternator on my model and figured this is correct as I cannot find one anywhere? 

shane999 wrote:I was told that the regulator/rectifier is built into the alternator on my model and figured this is correct.

Agreed, the regulator/rectifier is integral to the alternator.

Can you give me a brief rundown of the bits that have been disconnected? And also how you are measuring? I feel your pain, these faults can be a nuisance but at least its consistent..


Once an item has been disconnected, if the draw doesnt change do not reconnect the thing, leave it disconnected and move on to the next, the question about the alternator is a moot point, if you have disconnected it and the draw hasnt changed you know 100% it isnt where your problem is at.

hi sorry for the delay but been at away. So, ... I tested by removing all fuses one by one but no change on the drop. I've checked every bit of wiring for damage/grounding but nothing there. I figured if its not the wiring then its a component so started checking them all but nothing. multi meter on the pos. terminal and one to lead shows 0.79 draw. alternator arrived today so Ill put that on and see? watch this space...

shane999 wrote:I tested by removing all fuses one by one but no change on the drop.

Standard Camhead RT's don't have fuses, RTP's must be different, perhaps all the extra equipment fitted.

I'm pretty sure that the special shares most of its wiring with standard, any fuses would be for the special equipment only.


Have you confirmed the alternator is faulty?? If not I can't see much point changing it tbh.

Success!!!!!  new alternator fitted and removed some of the excess police wiring and it starts first time, wish I had Bluetooth on this pc to show some pictures. So... not sure if the new alternator was the remedy or just removing all the excess wiring was the "fix",  but now no battery drain, I'm just so happy to ride it again. thankyou for all the helpful advice.

Out of interest, was the battery drain being measured with or without the engine running.

without engine running

Shane where are you located

derby