FYI - Compatibe battery maintenance chargers

[Geo Z Man]

If you want to plug a battery maintenance charger into one of the BMW fitted Power Outlets on a R 18 you must use a charger that supports the BMW CAN-bus electrical system. The Dealer originally sold me a Optimate 2 Pro Duo - great little charge but would not maintain the charge on my TC. I swapped it for a Optimate 4 Quad Program charger with CAN-bus feature and all works well now!

 

[Rufus]

This has already been covered on the forum in detail Geo, if you do a search on the forum you’ll find all the threads. Optimate 4 CAN-bus is a popular choice

 

[AV8OR]

If you want to plug a battery maintenance charger into one of the BMW fitted Power Outlets on a R 18 you must use a charger that supports the BMW CAN-bus electrical system. The Dealer originally sold me a Optimate 2 Pro Duo - great little charge but would not maintain the charge on my TC. I swapped it for a Optimate 4 Quad Program charger with CAN-bus feature and all works well now!

I bought the Optimate 4 as well and it works perfectly all winter long. In spring it starts up in a flash.