Calling all electrical boffins

[Phil Clarke]

After fitting a new battery to my 1200 it still seems to be loosing charge. There are a few things I need to check but one thing I did was put an ammeter in series with the battery and the earth lead with the ignition off to see if there was any current flow that could explain the battery discharging. I noticed that you'd get about half an amp for about 2 seconds and then nothing. This would be repeated every time you disconnected the battery from the bike wiring and then reconnected. I also noticed that when reconnecting the terminals after removing them there was a very slight spark - presumably caused by this small, brief current flow. Anyone like to suggest why this happens, is it normal or what?? Bike has no alarm and is out of warranty. And don't tell me about alternative batteries to get cos I know that already

 

[JohnnyBoxer]

Dealer fix for a software fault perhaps.............after all it's a Canbus system

 

[Ali-bear]

Sounds pretty normal to me and I should know (I'm a professional electrical/electronic engineer boffin-type person).

Initial current due to your 3 or 4 pooters booting up before going to sleep again.

Do you get any drain current at all with the bike off, a few milli-Amps perhaps?

 

[Phil Clarke]

Nup once the short pulse has died there is naff all current. I think my new battery is a duffer...

 

[Ali-bear]

More likely to be a failure to charge because of some kind of charging system fault.

Regulator / alternator failure perhaps? Sorry that isn't going to be cheap but I would say its best to get whatever fault is there properly and accurately diagnosed before replacing anything.

 

[shugie]

Nup once the short pulse has died there is naff all current. I think my new battery is a duffer...

Have you kept the ammeter connected for a while, just in case the canbus is turning itself on (and off after a few seconds) at intervals?

Does the battery go flat if you leave the bike alone, in the sense of not using it for a few days, or does it go flat if you use the bike?

 

[Phil Clarke]

Alternator is fine - big fat voltage over the battery during running and no battery probs if I use the bike. Original battery croaked last month - loosing charge over night (quicker than the new one) and pronounced fecked. Thought the new one was ok (I posted about this previously - its an exide battery same as oem but without BMW logos and only £53) until I left the bike sitting for a week - result = engine barely able to turn over and only just started. At first I thought it was something to do with the GPS power - I've taken it from the BM socket but I noticed that my quest would power up when attached to the bracket even when the ignition was off (and beyond the normal power down time). It only did it a few times and now seems to be back to normal - ie only powering up when I turn the key

Didn't leave the ammeter for more than a minute during which time there was no current. Too fiddly to rig up something to check current over the long term so I'm going to disconnect the battery and monitor whether it looses charge on its own.

Electronics? you can stuff em!

 

[Deleted account 211025001]

At first I thought it was something to do with the GPS power - I've taken it from the BM socket but I noticed that my quest would power up when attached to the bracket even when the ignition was off (and beyond the normal power down time). It only did it a few times and now seems to be back to normal - ie only powering up when I turn the key

!

Are you aware that there is a software update/fix for the aux. socket - maybe it's connected to that

Andres

 

[Greg Masters]

Alternator is fine - big fat voltage over the battery during running and no battery probs if I use the bike.

With the engine off your battery should read about 12.5-12.7v.

Turn the ignition on (so that a single headlight comes on) but don't start the engine. The voltage should still be higher than 12.0v even after a couple of minutes. If the voltage drops much below that, the battery is shagged. If the voltage holds up, check elsewhere.

When the engine is running, you should see 13.5v-14.5v across the battery.

Greg

 

[Phil Clarke]

Tah for advice
I'll check on the software update when It next gets serviced. And too think I thought my days of fannying around with charging circuits and batteries ended when I sold my Triumph trophy!