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Discussion Starter · #1 ·
We have been having problems with batteries going flat on a couple of our 1250RTs. Apparently BMW have a software issue that they know about, but no fix yet. Basically on some bikes if using the BMW charger through the aux socket, it is actually charging, but won't maintain and is running the batteries down. They are recommending fitting a tail direct to the battery. I do not know if this is happening with Optimate Canbus chargers as well, but my own bike (1250) is on an Optimate and a brand new 21 1250RT is as well and the batteries seem to be fine.

I don't know any further details, but they also mentioned their factory fitted trackers are also running the batteries flat. Although our bikes do not have the trackers fitted
 

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It is always handy to have a fused pigtail direct to the battery. Electric clothing and other items draw too much for the stock sockets. Especially an air pump for flats.
 

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Discussion Starter · #3 ·
Great, but that has nothing to do with the aux socket, that a lot of people use for their battery conditioner, as I do. You should never use the battery conditioner pig tale for heated clothing, wrong amperage. If you want to run heated clothing from the battery, use the supplied fused pig tale
 

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I also have been using Optimate 4 (Can-bus) through the aux socket for years on my '19 RT. I have also used the aux by the passenger seat with no issue. Keep in mind, in order to charge though the aux port on the new bikes, the charger has to be able to communicate over Can-bus. This is the one I have.

 

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Discussion Starter · #6 ·
Guys. This is a new issue that BMW have found with software specific to the 1250s. It’s not clear if this only an issue with the BMW charger or if also with the Optimate 4. So 1200 bikes are not impacted. Like I said, I have a 2019 1250 and have had no issues with my optimate 4. But some 1250s battery flattens. No update to software is available yet. So just be aware
 

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I have a Motobatt CAN bus charger and it is the same issues as the OptiMATE. My old 1200RT charged just fine through the auxiliary plug, but not my '21 RT. It proves to me that it's definitely the bike not the chargers.
 

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Discussion Starter · #8 ·
I’ve got a 21 on an optimate 4 and it has been charging through the aux socket fine. So it looks like it’s not all bikes. The dealer also said it’s not just 21 bikes that are affected but some older 1250#.
 

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Interesting that a software issue would apparently cause different behaviour - I wonder why there would be differences between bikes. My 2021 is fine charging with the BMW charger through the fairing socket, but it won't charge through the rear socket - it was pointed out to me on here that that is by design on the current model, although not why that should be.
 

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I never used the OEM sockets for anything. I find them pretty useless. ( and they put two of them...)
Since their amperage is not enough for heated gear, what are they good for besides putting a battery charger? what about the rear one?
I have a pigtail for my battery charger and a COAX socket for heated gear and never had any issues on my 07 and 19 RTs
 

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I run my Warm & Safe heated jacket and a pair of gloves from the rear socket - plenty of power available (12A total from both sockets on the 2021 - 144W)

Front one is a very handy plug-in charger point (much easier than faffing with SAE connectors in my view), and useful for plugging in a USB charger for devices when on the road.
 

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I never used the OEM sockets for anything. I find them pretty useless. ( and they put two of them...)
Hardly useless... They are very convenient for heated gear, like @Hors Piste mentioned. I don't use them much but my wife on the pillion seat does and it is excellent for the purpose. The '21 RT can do 13 Amps combined so almost 2 sets of heated gear can be accommodated.
 

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Discussion Starter · #13 ·
There seems to be a lot of different views on the socket. I managed to run my heated jacket and my gloves on the front aux socket on my 19 1250RT, that is over 5 amps. I did read somewhere that it was 10amps combined. But others have stated it is 5 amp for each. Both the aux socket cables are spliced together, so how does the can bus know how much amperage is split between two sockets, which kind of indicates it is a combined amperage. But who knows, all I know is my kit works ok :) Interesting to read that on the 21 the amperage is different, especially as the bike is basically the same under the skin as the other 1250s.
 

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On the 21 the two sockets can't be spliced together - you can charge from the front one but not from the rear. Indeed, if I plug the BMW charger into the rear one it complains that the polarity is reversed plus no battery (I don't think the polarity is actually reversed, but something sure upsets the charger. When I get a round tuit I'll go and measure the polarity just to check, but if it is then USB chargers etc would also complain)
 

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Discussion Starter · #15 ·
On the 21 the two sockets can't be spliced together - you can charge from the front one but not from the rear. Indeed, if I plug the BMW charger into the rear one it complains that the polarity is reversed plus no battery (I don't think the polarity is actually reversed, but something sure upsets the charger. When I get a round tuit I'll go and measure the polarity just to check, but if it is then USB chargers etc would also complain)
To be honest I have never tried to charge from the rear socket on my 1250 or the 21 bike, in fact don't think our 21 has a rear socket (basic model). But I will try my 2019, it is good though if they have sorted out the amperage thing, although as I said, my jacket and gloves draw 9amps and they both work off the front socket on my 1250, so I have no idea what is going on :)
 

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I've just checked and as I thought the polarity of both sockets is the same.
 

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Hardly useless... They are very convenient for heated gear, like @Hors Piste mentioned. I don't use them much but my wife on the pillion seat does and it is excellent for the purpose. The '21 RT can do 13 Amps combined so almost 2 sets of heated gear can be accommodated.
What do you consider a set?
A full set for me is : Gloves, Jacket, Pants & Socks. (It can get cold around here. ;) ) 13A is not enough for even one set, which adds up to 13.3A.
Also, the position of the front socket on the right side is very awkward for me since the connectors are on the left side of my jacket
That's why I installed a dedicated socket to the battery on the the left side.

YMMV


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What do you consider a set?
Jacket and pants is a set for us. In our case two pants and a jacket will work off the 13 Amps available load. I know, you guys get proper cold, we only get close to zero here, maybe dips under with wind chill but never below.

Also, the position of the front socket on the right side is very awkward for me since the connectors are on the left side of my jacket
That's why I installed a dedicated socket to the battery on the the left side.
Yeah, it is much more convenient having the socket on the left like the hexheads did.
 

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Discussion Starter · #19 ·
Been charging the 21 1250 on my optimal 4 through the front aux socket for 5 days now, checking the battery every day, no discharge and the battery is fully charged. I still think this has something to do with the BMW trackers that are factory fitted, ours doesn't have a tracker, well not a BMW one. I would bet that opening the aux socket on the Canbus is waking the tracker up and then the tracker is active and taking more current than the charger can put back. But that could of course be rubbish and pure speculation. Its just funny the dealer did say they had had a lot of flat batteries due to their trackers being fitted.
 

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Discussion Starter · #20 ·
Ok, I've been talking rubbish. Just took delivery of a brand new Gerbing Pro Heated Jacked. I also have the Gerbing headed gloves with the controller on the cuff. With the jacket on 5 (full) and the gloves on the hottest setting, the can bus closes down the aux socket on both my 2019 1250 and our brand new 21 1250. Total amperage according to Gerbing is 9 amps, so the aux sockets are not able to provide 10 amps. But if I turn the jacket down it seems to cope. Direct battery connection is the answer then. The socket is fine for just gloves on full, it seemed to cope with jacket on hottest setting for about 2 mins before they both shut down on both bikes :)
 
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