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I‘ve got no idea how the electronics are different for charging on a CANbus system - but always led to believe that they were. You need a charger capable of keeping the CANbus open and therefore live to the battery. All witchcraft to me.

But it clearly states its not compatible with CANbus models - which was the OPs question.
 

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It doesn’t state either way in the advert above which is why I was slightly suspicious - they usually over advertise if its CANbus compatible. So looked the part number up - there is a link to what I believe is the same model of charger in my earlier post, with the warning regarding CANbus compatibility.
 

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You should note that BMW's manual typically tell you to avoid using non-BMW chargers, supposedly because they can damage the electronics!
Every company promotes their own products - not just good sales tactics but it’s the only way they can guarantee it will work. The point of all this is that in order to charge via the front DIN socket on a 21/22 RT requires a CANBus compatible charger. Like many others, I use an Optimate 4 CanBus edition without any issues at all.
 
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I said right at the beginning that I have no idea how CANBus works but I thought I understood the principe behind it. What you are telling me now Pad seems to go against everything that anyone has ever explained about the system and I’m trying to get my head around what makes a charger CANBus compatible. Why have we all been led down the path that we need a CANBus compatible charger in order to charge through the DIN socket ?

When I read the specifications of your charger on the link you provided - it does state that the lighter socket must be ‘hot’ when the key is out of the ignition. To me, this means either the lighter socket (or DIN socket) is direct wired to the battery or the CANBus is live to effectively ‘switch on’ the socket. We know on the 21/22 RT that the DIN socket remains live for a period of time (up to 15 minutes according to the manual if sufficient current is being drawn) after the ignition is turned off. Therefore, I assume during this time, your charger will charge the battery as the socket is still ‘live’.

What happens after that period of up to 15 minutes ? Does the charger disconnect when the bike shuts down the socket or does your charger keep the socket ‘live’ ? If you plug your charger into the socket after the 15 minutes (when the bike has already switched the socket off), will your charger activate the CANBus to turn the socket back ‘live’ again and therefore start charging ? Is this what makes a charger CANBus compatible - that it can talk to the CANBus to open and keep the socket live ?

It's all depend on how the onboard computer is programmed.
Is this not another way of saying CANBus compatible ?
 
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