BMW canbus charger on 07 GSA

[oldenoughtoknowbetter]

....runs through its pre-check sequence ok then starts on red then through the two yellows until green. But it doesn't stay on the green (full charge) led for long before jumping back to red and starting over again! Sometimes it doesn't even reach green before going back to red. I can often see two or three of these cycles within say, 15 mins of turning on. Can't remember it doing this last year. Am charging via the standard socket.
Is this normal or indication of a weakening battery?
(Tried a volt meter accross the posts whilst charging and that's showing around 12.5v. Doesn't seem much. I'll leave the battery off charge for a while and see if it drops below 12v).

 

[wilbjr21]

....runs through its pre-check sequence ok then starts on red then through the two yellows until green. But it doesn't stay on the green (full charge) led for long before jumping back to red and starting over again! Sometimes it doesn't even reach green before going back to red. I can often see two or three of these cycles within say, 15 mins of turning on. Can't remember it doing this last year. Am charging via the standard socket.
Is this normal or indication of a weakening battery?
(Tried a volt meter accross the posts whilst charging and that's showing around 12.5v. Doesn't seem much. I'll leave the battery off charge for a while and see if it drops below 12v).

This is seems like normal behaviour.

It's more than just a charger and reacts to the battery voltage. A voltage of 12.5 V from the battery would start the charger off through it's charging cycle. I don't have the booklet with me, as I'm at work at the moment, so I can't tell you at what voltage the charger goes to green and just lets the battery voltage fall (through the residual current drain) until the value is such that it starts again.

 

[cookie]

sounds like it's telling you it doesn't need charging.

 

[wilbjr21]

sounds like it's telling you it doesn't need charging.

It's not like that Cookie - it can stay on all the time the bike is laid up. This is the way it works; by charging at different rates - or not at all, according to the state of the battery.

 

[Jon P]

Mine behaves exactly the same way. Very different from my old Optimates.

 

[TyreMark]

Yes mine also and its a nearly new battery (replaced under warranty). Seems to be no rhyme or reason to the light sequence but battery always appears fully charged.

 

[oldenoughtoknowbetter]

Many thanks for all that. I'll assume it's normal. Same charger and battery 12 months ago though but no rapidly changing sequences like those seen now. Odd.