BMW R1200RT/R1250RT Forum

I changed my R1200RT after 6 years for an ex-demo R1250RT a couple of months ago. I use the BMW charger to charge the bike but have twice had the battery drain on me in spite of being left on trickle charge. Initially I thought it was because I was using the rear charging port but the fairing one yielded a similar problem. The bike was recovered and there’s apparently no fix.


It seems the canbus system shuts down the charging ports and the trickle charger cannot access the circuit to charge.  With the tracker fitted, after a week I’m down to 35% charge. BMW have said a software update will be issued but not before February 2022.


I find it incredulous that the advice is to charge the battery directly. This entails removing and refitting the lower fairing to attach crocodile clips to the jump start points, or attaching a lead to the battery terminals, contrary to the advice in the manual.  It means I will need to buy another charger too as the BMW one doesn’t have the connector to allow either of these.


A £20k bike with a basic issue and a 3-4 month fix time at best. Anyone else had this?

Oldnickers wrote:I find it incredulous that the advice is to charge the battery directly. This entails attaching a lead to the battery terminals. It means I will need to buy another charger too as the BMW one doesn’t have the connector to allow either of these.

How about something like this Optimate lead, O8 Panel-Mount DIN Socket — OptiMate UK

I have seen this spoken about somewhere before and I am led to believe that its a software issue


I would always prefer to charge straight to the battery as it removes the risk of anything between the charger and the battery going wrong


It would be hard or expensive to make an adaptor of some sort to charge the battery directly and be able to leave it attached I know its not ideal but its a solution for now

Motorworks sell this Auxiliary power socket kit universal, Motorworks BMW Motorcycle Specialists - Shop - Spares and Accessories could be used to replace the rear charging port/aux. socket.

As fitted to a 2011 Camhead, BMW R1200RT / R1250RT forum - The BMW R1200RT/R1250RT forum and used for battery charging.

I have a 2019 1250RT & use the BMW charger via the fairing accessory socket. It has never failed to operate as you would expect charging the battery & going into standby mode once it completed charging.

Is this a software issue with RT’s with the new tft as I haven’t had a problem with my current 2019 bike or with its 2017 predecessor.

I always understood that the BMW charger & the canbus talked to each other so they could ‘interact’ even after the bike had shut down.


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This is a known problem. There is a issue with the aux socket charging. Although I have been charging and checking batteries on my own 2019 bike and a 21 1250 and have had no issues with battery drain charging via the aux socket with an Optimate 4. But both bikes do not have the BMW tracker activated, therefore as in the OP, I think the issue is with the aux socket charging waking up the tracker and making it active, so the tracker seems to be taking more out of the battery than is going in. That is my theory only All I know is I don't have an issue with the two bikes I have on charge

From what I have read elsewhere, the tracker fitted is likely to be a Datatool Stealth S5, 1 new message (datatool.co.uk)

"As soon as the ignition is switched off, Stealth S5 creates an invisible geofence around your bike and starts monitoring for signs of unauthorised movement."

Will Datatool units drain my battery?

Datatool trackers have their own internal battery, so it only draws power from your bike’s battery when it needs it. Datatool units have industry-leading battery management software built into the unit. However, the Datatool platform also notifies you if your battery voltage drops via text message, so you should never be left with a flat battery.

Well done David, your browsing skills are unto scratch as always. The facts are, the battery draining whilst charging only seems to happen with bikes that have the BMW tracker fitted not those who haven't got one. Or of course there must be something different between individual bikes. The issue (according to our dealer) is only on 1250 bikes and not exclusive to the 21 model. In our fleet, which consists of 5 1250s we have been charging via the socket and with an Optimate 4 and monitoring the battery drain. When not on charge, the batteries have something like 35mamps parasitic drain, which is well within limits. When on charge, the batteries are showing no discharge and are accepting the charge fine, none of our bikes have the BMW trackers fitted or active. So like I said earlier, it might not be the tracker, it might be a BMW charger fault only or it might be only on some bikes (least likely), so the only difference is (1) we use Optimates (2) we don't have the trackers fitted.

Hi oldnickers, on my 2014 rtlc there is an audible click when you turn on the charger (optimate) and when you turn it off and the port closes (after about 20-30 seconds) so if you are patient and sit next to the bike you should hear it open and close then you will know if the charger is working correctly or if you know someone with optimate charger you could try that, hope this helps cheers. you haven't put your location on the forum profile but if you are near me or fancy a ride you would be welcome to try mine

More discussion on BMWLT, 1250s issue with charging battery through the aux socket | BMW Luxury Touring Community (bmwlt.com)

Thanks everyone for your input on this. I’m awaiting a reply from BMW Customer Services - they have a 48 hr response time which they’ve failed to achieve twice. Will give them a third call next week and ask what the factory solution is in the interim.  Or perhaps have the bike recovered every couple of weeks to make the point that it’s not good enough!  Will keep you posted…

Ok, so first up I have to say I am very comfortable with fiddling with bike electrics.

Way back, my 1993 K75RT killed it's battery every couple of years, so when I replaced it with a new 2001 R1150RT I fitted a pigtail direct to battery and used an Optimate trickle charger.

I did the same with my 2008 R1200RT, 2015 R1200RT. 2018 R1200RT and again with my 2020 R1250RT. What I do, is unplug the connector from the front standard OEM socket and rewire it direct to the battery (with a 10A in-line fuse) then use a standard (i.g. no need for a "CanBus" trickle charger) trickle charger. I used to use an Optimate unit but now use a NoCo one.

So far (since 2001) this has worked very well, modern intelligent trickle charges (Optimate, NoCo, etc) wired direct to the battery with a suitable in-line fuse seems to be the way to go. I have not replace a BMW motorcylcle battery since using this setup.

For me this is a simple set-up that avoids any damage to the bike, is easily reversible, provides a permanent live power socket and offers a simple route to use a trickle charger each day.

PS - Anyone want an Optimate 6 at a good price let me know!

That’s been my approach too, on about a dozen BMW’s and many other bikes as well. Pigtail connected directly to the battery. I use 0.75mA Battery Tender Jr.’s and typically get 7-8 years of battery life. When the bike’s not being ridden, it’s plugged in to the Tender. It’s not complicated.

Oldnickers wrote:I find it incredulous that the advice is to charge the battery directly, attaching a lead to the battery terminals, contrary to the advice in the manual.

Some battery chargers have a high voltage desulphation and recovery mode. An example being the Optimate 4 (CAN-bus) which can deliver a Standard (16V) or Turbo (22V) desulphation voltage. This is above the normal alternator output voltage of around 14.5V +/- 0.3V. However, if used in the CAN-bus mode via an aux. socket, these high voltages are de-activated and a low voltage Pulse desuphation mode remains active.

This might explain the words of warning in the Rider's Manual and Haynes Manual about not connecting a battery charger to the battery terminals while the battery is on the bike.

Further investigation has provided this from the Optimate 4 instructions.

"The charger’s Advanced recovery mode cannot engage if it senses that the battery is still connected to a circuit which effectively offers a lower electrical resistance than the battery on its own. However, if the deep-discharged battery is not removed for recovery, neither battery nor vehicle or equipment electronics will be damaged."

Perhaps the BMW warning is based on the charger not being smart as quoted above. Maybe the danger is using a charger which doesn't have this built in protection.

I've got an old (2004) Datatool charger which does not have a desulphation mode, the max. output voltage is 14.3V, it is connected with a lead to the battery terminals.

It has been confirmed that an Optimate 3 (non-CAN-bus) with de-sulphation modes has the same smart protection as above and can therefore be wired directly to the battery without any risk of damage to the battery, bike or electronics.

It appears that the BMW and Optimate 4 (CAN-bus) chargers are purely for the convenience of using the onboard aux. socket. (That's if the onboard aux.socket actually works). Rather than installing a pigtail or other socket wired directly to the battery.