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Discussion Starter #1
I've posted a couple of times before about battery issues, most recently in this thread, but I thought it'd be worth it to start a new one.

A quick summary: once I had trouble starting the bike after it stalled in traffic on a hot day. Engine just wouldn't turn over. I waited a few seconds and tried again and it started up, but it was annoying. In replies a few people suggested the OEM battery was too weak and I should get a new one.

And on my last trip I got fed up with the accessory circuit cutting out every time I started my bike. My alternator is great, the battery voltage seemed good (12.4-ish), and the dealer did a load test and found it fine. Yet unless I've just pulled it off the charger, every time I start the bike I get a red <!> and a battery icon in the display, and the GPS and Autocom lose power and reboot.

After pressing the dealer, they agreed to replace the battery under warranty. So, over the weekend I got a new OEM battery for my '07 K1200GT. The accessory fault problem reproduced at the dealer the 2nd time we started the bike. I took it home and put it on the charger, and it was fine for the first start the next day, but after that every time I started it I lost accessory power and got the battery warning again.

Do you have the same experience with your GT when starting it?

For those of you with accessories, is it just the canbus accessory circuit that cuts out? Could I solve the problem by powering everything from the battery and switch them all off the front parking light?

What's the brand and, if available, part number for the aftermarket battery for the K1200GT? Anyone know if the (too damn expensive) canbus-compatible BWM battery charger will work with the aftermarket battery?
 

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In the 2.5 years I've owned my GT, the low battery warning has always appeared on the display immediately after starting, but it goes out after about 10-15 seconds. I'm not sure what you mean by the "accessory circuit cutting out," and I haven't experienced any problems with my GPS or Autocom, both of which get power from a Centech fuse box.

As a preventive measure, I just replaced the OEM battery with an Odyssey PC680MJ battery, and the low battery warning is still there after startup, which leads me to believe the low battery indication is "normal." I've used Odyssey batteries in the past and have found them to be much better than OEM.

I also have the BMW battery charger for CanBus, and it seems to work fine with the Odyssey.
 

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Discussion Starter #3
gc916 said:
I haven't experienced any problems with my GPS or Autocom, both of which get power from a Centech fuse box.
How is the power to the fuse box switched? Is it always on, or is there a relay? If a relay, what line did you use to switch the relay?

The accessory circuit I mean is the plug that's available under the battery cover and/or the power outlet on the side -- they both appear to be controlled by the same circuit. This is the circuit that stays on for a few minutes when you turn off the bike. I used that line to switch the relay for my other accessories.
 

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I have a digital voltmeter installed on my '07 GT. When the vehicle starts, there's a delay that occurs before the alternator starts to generate output. This is not unlike typical vehicle alternator where there's a load response delay at startup so the starter isn't cranking the additional load of an excited alternator. In other words, alternator slowly ramps up after about 3 to 5 seconds AFTER the vehicle is running. I don't use the CANBUS hookups, but my guess is that either the voltage on the battery drops below minumum input voltage for your accessories, which causes them to reboot, or the computer shuts off all unnecessary loads, including CANBUS circuit, during the cranking process, which then causes the toys to reboot. Third possibility is the voltage drop between the battery and CANBUS output is such that when the battery voltage drops during cranking, the resistance goes low enough out the CANBUS output that the toys reboot. For testing purposes, move the power wires for the toys directly to the battery positive, start it up and see if they reboot.
 

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bonafidebob said:
How is the power to the fuse box switched? Is it always on, or is there a relay? If a relay, what line did you use to switch the relay?
There is a relay for the Centech, and it gets power from the front parking light.

This might be a stupid question, but regarding the accessory circuit, is it possible that your accessories are drawing too much amperage? I don't profess to know a lot about these things, but I think I remember reading that the accessory outlet is limited to a draw of 5 amps, and that things like heated clothing will exceed that limit and CanBus will shut down the circuit.
 

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Discussion Starter #6
gc916 said:
There is a relay for the Centech, and it gets power from the front parking light.
...is it possible that your accessories are drawing too much amperage?
OK, I've been thinking of adding a centech fuse box anyway, maybe I'll move the relay line around when I do. I'll try watching the parking lights when I start the bike, I bet they don't turn off. (So then the only drawback will be that the circuit won't stay on for a few minutes after I shut off the bike... hmm, I guess I could power the relay from BOTH circuits, so it'll stay on during start and stay on after shutting off the bike.)

I seriously doubt the accessory load is a problem. I had the GPS reboot issue even when it was only the GPS on the circuit. It's a Nav III installed by BMW. I don't have the Nav III specs, but the Garmin 2820 (which is more or less identical) is listed as 12w max. @ 13.8v DC, or less than 1amp.

The accessories added on the relay are an Autocom and PS+ lights, but these are powered directly from the battery. The only additional load on the accessory circuit is the relay itself, which draws only 160mA.

So maybe I'll hold off on getting a new battery until I mess with the accessory wiring.
 

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Just fyi, I have a first generation Centech which means that all devices that get power from it are "controlled" by the relay. It is my understanding that the new Centech panels feature the ability to connect some accessories directly to the battery for "always on" power.
 

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I have a 2006. I have never experienced the low battery light at any time and my ABS draws power wheneverr I touch the brake. I am powering my Gerbings,GPS, motolights and kissan license plate frame from the AP-1 fuse box relayed to the battery from the gps socket near the battery. Next year I will be replacing the battery with a new Odyssey as it will be the 3rd winter season.
I replace all my car batteries after 3 full years so I have plenty of cranking power in the winter, as most batteries lose a great deal of capacity from natural ageing.
 

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gc916 said:
Just fyi, I have a first generation Centech which means that all devices that get power from it are "controlled" by the relay. It is my understanding that the new Centech panels feature the ability to connect some accessories directly to the battery for "always on" power.
Actually, there are 2 different Centech models and both are still available. The one you have is the AP-1, the "always on" model you speak of is the AP-2.
 

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Discussion Starter #10
Another data point - I left the bike on the charger overnight again, and this morning the accessory circuit did NOT switch off when I started the bike, but I still saw the battery icon and red <!> on the display. That would make sense if it takes a bit for the alternator to kick in. ...and so the accessory cutout does not appear to be directly tied to the low voltage warning on the dash.
 
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