Older BMW CANBUS Charger - funny issue

[andysdad]

I have the older (grey) CANBUS charger (71607688864). Has worked fine for years on my K1300GT via the Hella socket near the gear lever.

I have just used the Accessory Socket by the headstock to wire-in a relay to a cigarette lighter socket, to power my satnav, using pins 1 and 3. All works fine.

The charger won't have it! I get the Red error light on the charger.

What happens - turn bike on, then off, wait c.60 seconds. I hear the relay drop-out when the Accessory socket shuts-down, then the charger shows "Error".

If I disconnect the plug (that feeds the relay switch) from the accessory socket, all is well.

I know the simple solution is to connect the charger to the battery, but I like the existing set-up.

Any ideas?

 

[landmarkjohn]

Whenever something comes up on these older chargers I post the instructions below. They took me a bit of digging to find. I had bought a used charger and was having trouble getting it to work on my 2008 GS. Bods usually come along and say that's not how it works on my XWZ model so your experience may differ. Anyway I think it is worth a try:

ATTENTION!!!! You must first turn the key on to the bike, then you plug the charger into the accessory socket, then you plug the charger into the wall for power, then you turn the key off.
Failure to do it this way will result in the charger not charging the battery and overheating.

 

[andysdad]

LMJ thanks for that - but it has worked fine for years.

Without the charger connected, power-down works fine - satnav remains live for c.60 seconds then goes off when the Acc Socket powers-down.

I can get the charger to work fine if I unplug the Accessory plug; which negates the whole point of having a switched-live feed.

BTW - if anyone can find a PDF of the factory instructions please send it to me. The only link I could find is dead (I think this model was sold until c.2010!). I have a text copy without pictures.

 

[andysdad]

I think I have solved this - someone on Eurokclub's forum suggested the relay might be the problem.

It is the relay - if I directly power the satnav off the factory acc plug (bypass the relay), it switches off and the charger starts up OK (there seems to be a "but" - see below!).

I put the relay in because the satnav is via a cigarette socket, so something else might get connected that draws more than the Acc Socket provides.

Perhaps the relay coil remains as a load even when the acc socket has turned-off. Anyway, the over-clever charger goes "Error" then.


* - if I leave the satnav in the cradle, after c.75 seconds from shut-down, the charger goes into "Error" again. BUT if I remove the satnav from the cradle before then, all is well.

The power to the satnav switches off c.45 seconds after shut-down, but after a few seconds the power light on the satnav lead starts to flash for about 30 seconds - I think this is the Charger signalling the Canbus. If a load is present at the end of this (if the satnav is in the cradle), it errors. But if there is no load (satnav out of cradle), it charges OK.

 

[knutk]

The described issue is caused by the relay installed.
The thing is, the AUX-port share the input to the ZFE with the hidden GPS-socket.

The CANbus compatible charger sends an 'open the port' signal by adding +12V to it's pin prior to checking voltage and polarity, which is the norm for the none-CAN-bus compatible chargers.

ZFE opens the port, but this will also power the installed relay. This drain from the GPS-socket is registered by the ZFE as a faulty drain, as it has no knowledge of such a drain, hence ZFE close the AUX port again.

I had the exact same setup on my bike, and I resolved it by unpluging the relay when it was time for the winter storage and connecting the charger.

 

[timeandtide]

There are some very clever people on here!

 

[RadioFlyer]

I wrote the following for another pupose on another forum but it has relevance to some of the previous info posted her.

How often have you seen or heard the term “CAN-bus” in the context of a compatible charger for the accessory socket? Way too often and almost always dead wrong.

“CAN-bus” is probably the most misused term in all of BMW-related forum electrical discussions. For an understanding of what the CAN-bus actually is and does I suggest reading the article on Wikipedia.

The ZFE (Zentrale Fahrzeugelektronik or Central Chassis Electrics) is one of several controllers on modern BMW motorcycles. Its job is to manage chassis electrics. It senses logical inputs from switches and responds by turning things (lights, horns, grip heaters…) on and off. It also monitors current draw. If the current draw exceeds a threshold then the circuit is shut down so the ZFE replaces fuses. If the current draw is below a threshold on a light circuit the ZFE assumes that there is a burned out bulb or a wiring fault and tells the Kombi (the instrument cluster) to display a warning. The ZFE manages the accessory port and shuts it down if too much current is drawn (> 5A). The ZFE also monitors the accessory port for the presence of a compatible charger and connects it to the battery for charging.

Compatible chargers are often referred to as “CAN-bus” chargers or some other term using “CAN-bus”. This is nonsense and has led to a great deal of confusion. This misuse of the term “CAN-bus” probably originates with charger vendors. Early on the vendors would characterize chargers as being suitable for “CAN-bus equipped” motorcycles as a way of saying that the motorcycle had a ZFE. Later the terminology morphed into terms like “CAN-bus compatible”, “CAN-bus charger” and “CAN-bus mode”.

The CAN-bus itself does not play a role in charging via the accessory port. That many say it does is part of the mythology.

The ZFE “listens” for a specific electrical handshake from a charger and if the handshake is present the ZFE connects the charger through to the battery. No CAN-bus messaging is required to accomplish this.

A ZFE compatible charger sends and repeats a pulse train to the accessory port. The pulse train starts with the charger presenting 12V to the port for 1 second. Then it waits for 150 milliseconds. Next it sends a series of ten 12V pulses each having a duration of 10 microseconds and spaced 100 milliseconds apart. It repeats this pulse train until it senses that the ZFE has connected it to the battery and then it starts its charging procedure.

Of course you can always attach a charger directly to the battery but BMW instructs you to not do so while the battery is installed in the bike. Why? The reason is that many modern chargers are “smart” and will try to recondition (desulphate) a battery if it decides that the battery needs reconditioning. The desulphation process involves the application of high voltage pulses to the battery and if the battery is connected in the bike then all the bike’s expensive electronics also get exposed to the high voltage pulses as well. So there is some risk of damage involved. BMW isn’t going to try to explain how to determine whether your particular charger has a desulphation capability or not so it just tells you not to charge the battery directly in the bike to mitigate the risk.

If you have a smart charger and intend to connect direct to the battery while the battery is in the bike you should read the charger’s manual to see if the desulphation mode can be disabled. I use the Optimate 4 charger in its “CAN-bus mode” (sic) direct to the battery because in that mode high voltage desulphation is deactivated. I can’t be bothered with charging via the accessory port.

 

[izi0]

hi All, thanks a lot for the info so far... I have a question:
I used this charger on my R1150gs for years and I've never had any issues.
But now I'm trying to use it on my RnineT Urban GS 2020 with the original AGM battery but I can't make it working.
I've tried all the combinations starting from the one suggested by @landmarkjohn (ignition on or off, plug it before or after the ignition on and/or before to plug the charger to the wall socket) Nothing

Does anybody know if this charger can be used on this type of bikes and if yes, how?

thanks a lot in advance and enjoy the ride