R1250 RT: Charging Battery Direct

[Tiedend]

I live in the UK & I’ve had 1 episode of the bike failing to start. The bike is 3 at the end of Feb 2022 so possibly the battery needs to be replaced. Currently bike is with dealer for that just now.

I have a BMW charger which I use via the accessory socket. I’ve become aware of the issue with the bikes software not shutting down the accessory socket when the charger goes into standby & the resultant slow discharge by leaving the charger connected. The technician at the dealer said the software fault (due to be fixed next year) does not allow the charger to sense when it needs to start recharging after going into standby.

My dealer has suggested charging direct to the battery but the riders manual cautions against it unless you disconnect the battery from the bike. So going forward what’s best? Is there a danger of damage to the bikes electrical systems by charging without disconnecting as suggested in the manual.

My dealer says no it’s ok to charge without disconnecting. So who is right.

Clearly BMW say this in the manual for a reason. But why? 

What is everyone’s experience.


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[David.]

Some similar problems are highlighted and discussed within this thread, BMW R1200RT / R1250RT forum - The BMW R1200RT/R1250RT forum

Reply #13 is the theory I came up with, other owners may have different thoughts.

[exportman]

Hi


I have the 2017 model and a Canbus aware charger, but I have placed a din socket on the left side plastic cover and wired it direct to the battery. Not had a problem with it thorough the lockdown.  Bike has been used a great deal less than normal and starts first time every time  8)

[Casbar]

I have charged my 2019 1250 by the can bus since purchase, I charge 3 other 1250s by the can bus charger no problem. Had the same discussion with the dealer, but came to the conclusion, it was either because of the factory fitted tracker becoming active (none of the bikes have this enabled) or the BMW charger. On all the bikes we use the Optimate 4 Canbus charger. Eitherway you should have no issues using a direct battery connection.

[Tiedend]

Thanks all.

Had read that thread. But was just concerned at the contradiction between the handbook & the dealer.

Thanks for the advice.


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[Stu]

The handbook wants you to buy the BMW charger and use the socket


Its perfectly fine to charge direct to the battery

[David.]

Was just concerned at the contradiction between the handbook & the dealer.

If in doubt, get the dealer to put it in writing, especially as a BMW charger is being used.

The BMW Motorrad battery charger manual also states that the battery should be removed from the bike if charging directly to the battery poles and not via the on-board socket.

If the battery is not maintained correctly with a BMW approved battery charger, this may invalidate the battery 2 year warranty.

BMW Battery Information | BMW MOTORCYCLES OF SAN FRANCISCO SAN FRANCISCO, CA (415) 503-9988

[Casbar]

You do not need to use a BMW approved battery charger to maintain a battery. In fact you don't have to use anything to maintain a battery. My BMW dealer sells Optimates, does that make it BMW approved

[David.]

My BMW dealer sells Optimates.

Could be because some folks are experiencing problems with the BMW one not working properly via the on-board socket and the battery going flat.

[simbo]

The handbook wants you to buy the BMW charger and use the socket


Its perfectly fine to charge direct to the battery

I agree, I've never had a problem charging a battery whilst connected on any vehicle, car or bike.

[beemerboy9]

I've been charging the battery directly since 2005.


Probably time I disconnected it.

[David.]

My dealer has suggested charging direct to the battery but the riders manual cautions against it unless you disconnect the battery from the bike. Is there a danger of damage to the bikes electrical systems by charging without disconnecting as suggested in the manual.

Clearly BMW say this in the manual for a reason. But why?

Found this thread on BMWSportTouring, CAN-bus Charging, CAN-bus Charging - Hexheads - BMWSportTouring

Seems to back up the theory of a desulfation type charger having the potential to deliver more than 15 volts.

[Old Foxy]

I have my Optimate charge tails connected to the battery - fitted (and recommended) by the dealer.  I had the same (from the same dealer) on my K1600 and have never had any issues in keeping the battery charged.  I just plug in the Optimate, if I'm not going to use the bike for a couple of weeks and leave it at that. 


Interestingly, my BMW dealer does not recommend the BMW charger.......


Old Foxy

[emlevy]

I’ve been charging direct to the battery since 1994, on a number of bikes, including about a dozen BMW’s (some with CAN-Bus, some without). Absolutely no issues, and I tend to get 7-8 years life out of my batteries, if that provides any comfort.

[David.]

My BMW dealer does not recommend the BMW charger.

Why not?