Optimate and auxiliary socket

[Roymondo]

It's in the manual. Sounds like bollocks to me too.

Suggest you read it again. It doesn't tell you not to connect the charger direct to the battery (in fact it specifically tells you that the battery can *only* be charged this way if it has gone completely flat - Canbus needs some battery voltage to "wake up" the auxiliary power socket). What it does advise is that you shouldn't charge the battery directly while it is connected to the bike's electrics. The reason for this is that the unregulated, unsmoothed output of *some* types of charger *might* damage sensitive electronic components. Optimates and similar are regulated and will not cause such damage (same is true of the vast majority of modern chargers - but as BMW have no control at all over the internal workings of 3rd party chargers, you can hardly blame them for advising against direct connection).

 

[Bendy toy]

Suggest you read it again. It doesn't tell you not to connect the charger direct to the battery (in fact it specifically tells you that the battery can *only* be charged this way if it has gone completely flat - Canbus needs some battery voltage to "wake up" the auxiliary power socket). What it does advise is that you shouldn't charge the battery directly while it is connected to the bike's electrics. The reason for this is that the unregulated, unsmoothed output of *some* types of charger *might* damage sensitive electronic components. Optimates and similar are regulated and will not cause such damage (same is true of the vast majority of modern chargers - but as BMW have no control at all over the internal workings of 3rd party chargers, you can hardly blame them for advising against direct connection).

Cheap or faulty chargers can also damage the electronics on non canbus bikes but as @Roymondo said, Opimates are fully regulated. The easiest fitment is presumably to connect the connector block and lead supplied with the Optimate directly to the battery with eyelet terminals.