2021 R1250RT Battery Charging thru Accessory Port Issue

[professorb]

In case it matters...

I had paid the big $$$ for the BMW Motorrad "smart" charger, and have used it religiously whenever the bike was not ridden regularly and all through the winter "wheels up" months. The charger looked like it was charging the battery, but I was surprised last summer when the service shop said I needed a new battery -- after only three (3) seasons. I was plugging the charger into the on-fairing accessory receptacle as advised. [photo #1 shows "full charge" notification when connected through CAN-BUS for charging]

Based on discussions in other forums, I just this week connected the charger directly to the battery terminals. For the first time (for me), after the battery became fully charged the display screen on the charger changed to say "Charging Complete/Battery mainten." [photo #2 shows "Battery Maintenance" mode, only when connected directly to the battery]

So, it appears the "smart" chargers will charge a battery through the CAN-BUS connection, but they will NOT perform the designated battery maintenance routines unless connected directly to the battery.

Live and learn...

 

[Omega Man]

Due to endless threads on “charging through the accessory port”, I still like the simple direct connection to the battery for battery charging maintenance.
I wouldn’t be surprised if that fancy battery maintenance charger will work through the port but there is probably a checklist of the relationship between the bike and the charger to make it work.
It’s nice to have the pigtail off the battery for other needs as well.
BTW, three seasons on a battery may be a little short……but not horribly short. Your connection may have been working half the time.
OM

 

[r0ckrat]

I have also heard a lot of complaints when trying to "maintain" via the port - something about who the canbus ECU interrupts the process.

 

[mikegalbicka]

I charge my 07RT with an Optimate 4 in CanBus mode through the powerlet ports with zero problems. It performs all of the maintenance routines including desulphate if necessary automatically just fine. It has to be switched to that mode however to work correctly. Does the BMW charger need manual switching between modes (CanBus vs direct battery)?

 

[rhbike]

I use an Optimate 4 to charge via the Powerlet port via the CanBus, so can't specifically speak to the BMW CanBus charger. But what I've found is that I need to plug the charger into the Powerlet port within a minute or two of powering off the bike, specifically before the bike shuts down the CanBus, in order for the Optimate to negotiate and keep the CanBus open. If plugged in after the CanBus has shut down, the Optimate will NOT charge the battery. If I do have to plug in after the CanBus has shut down, I simply power cycle the Optimate while it is attached to the Powerlet port, and the Optimate will then successfully wake up the CanBus and then start charging. The Optimate indicator lights are a bit cryptic and not overly clearly documented, so its easy to think that its doing its thing just becauseits plugged in and there are lights lit. But it is key to pay attention to what it is saying before leaving the bike.

I would bet the BMW charger works similarly. But the finest German engineers might have dreamed up a way to make it even more convoluted than the Optimate. I have heard of others having challenges with the BMW charger which is why I went with the cheaper and more solidly reviewed Optimate.

Though I choose to charge through the Powerlet port, there is something to be said of KISS - and attaching the charger directly to the battery via DIN plug where you don't have to worry about any CanBus handshaking.

 

[reg26]

I have to agree with Omega Man. It’s just makes sense to go directly to battery. Plug easily hidden when not in use. Get home plug it in and you are sure of good connection that has noticed do with the rest of the bike. Great peace of mind. Have one on all my bikes

 

[strataj]

I have to agree with Omega Man. It’s just makes sense to go directly to battery. Plug easily hidden when not in use. Get home plug it in and you are sure of good connection that has noticed do with the rest of the bike. Great peace of mind. Have one on all my bikes

It also makes for a great connection for an air pump and heated gear.

 

[reg26]

Yes. Absolutely. I use it for other things also. Just put a 15 amp fuse in it for heated gear

 

[globalrider]

In case it matters...

I had paid the big $$$ for the BMW Motorrad "smart" charger...

At what stage in the charging process are you seeing the 14.1V shown in your first photo?

That value is low if it is at the end of the absorption phase and high if it is in maintenance or float mode.

I take it you have an AGM battery.

I used a charger from BMW that was given to me when I bought my 2016 R1200 GSA and my factory YUASA AGM lasted a mere 7 years and 4 months. This is the first time that I used a charger/maintainer continuously. From then on, I spot charge my battery when it needs it and I have a LCD voltage indicator connected to the SAE plug. It reads 12.9V for weeks till it drops another 0.1V.

 

[professorb]

At what stage in the charging process are you seeing the 14.1V shown in your first photo?

The "Not So Smart Charger?" is showing that voltage near the end of the charging process, which of course makes no sense if the battery is fully charged. The battery is the OEM BMW branded "stock" AGM, 12V 16Ah.

 

[globalrider]

The "Not So Smart Charger?" is showing that voltage near the end of the charging process, which of course makes no sense if the battery is fully charged. The battery is the OEM BMW branded "stock" AGM, 12V 16Ah.

The 14.1V is on the very low side for an AGM battery. Depending on battery temperaure, it can go much higher before switching to a float mode.

I can't remember what my BMW panel reads on my GSA, but I think it also charges the battery on the low side. In comparison to my car that has an AGM factory battery, it reads 14.8V to as high as 15.0V at 6C which is in line with the East Penn AGM battery chart. And that car battery is going into its 10th year when it comes out of storage this spring.

And yes, there is no such thing as a Smart Charger. The charge algorithm is programmed by us stupid humans.

 

[pat8635]

I finally just hook directly to battery. Much simpler and no issues making sure bike brain knows that I am trying to charge and or maintain my battery!

 

[globalrider]

I finally just hook directly to battery.

Same here. Nothing like the KISS method.