Re:Question about charging system and batteries - - Excellence in Motion
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post #1 of 8 (permalink) Old Jun 19th, 2007, 8:24 pm Thread Starter
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Re:Question about charging system and batteries

I hope I can avail my self of the brain trust here on this forum as this question popped up in my head today. For what ever reason I've just excepted the fact that motorcycles have finicky electrical systems and you need to do things for them like keep battery tenders on them so that the batteries don't die prematurely and that seems to be all bikes not just our K bikes, it is true of my Honda and has been true of the various Yamaha's and Kawasaki's that I've dealt with over my years of bike ownership. I've always noticed that even after a nice long ride that when you hook the battery tender up to the bike that it goes into a charging mode for some times 20 or 30 minutes and I could never figure out why that was when it's been charging the entire time I was riding? I also used to have a 12 cylinder BMW 850 that had almost 2 of everything including battery's! I always jokingly refereed to it as my electric car as I had to keep it plugged in anytime I wasn't using it and AGAIN I just excepted this as a quirk of that model of car, but lately I've been doing maintenance charges on my GMC Yukon with a fresh battery and very good condition alternator and even IT requires a fairly long charge time after I put a battery charger on it even though it gets driven every day. So what's up with that? It looks like it's inherent of all charging systems of every kind of vehicle. What am I missing and why does this seem to be? Looking forward to the answer. :-)
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post #2 of 8 (permalink) Old Jun 19th, 2007, 10:18 pm
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Charging sytems

Most chargers charge to a slightly higher than operating voltage, at least 14 volts vs 13.9 or so . My truck sits 6 days a week without attention. None of my many motorcyles batteries get charged unless they will sit for more than a couple of weeks.

K12s really have a smaller battery than they should, but BMW has a history of doing that. The alternator on these bikes are certainly more than adequate at 50 amps.
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post #3 of 8 (permalink) Old Jun 20th, 2007, 1:45 am
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Batteries aren't a precise science because they are both chemical and electrical. All chargers have difficulty knowing whether a battery is fully charged or not. The voltage you get at the terminals isn't precise. For example, a battery left standing will eventually settle to 12 volt perhaps needing 1/2 hour. If you measure the terminal voltage after a ride it could be up to 14 volts then start slowly dropping.

Most chargers will put current into a battery to lift it up from the 12 volt level. A fully charged battery will move to around 14 volts very quickly and the charger then backs off. A part charged battery will not do this and stays on charge for longer.

What we're saying is a half and full charged battery left standing will have about the same terminal voltage and it's only by putting current into it that you find its true state of charge. Temperature is an important variable as well.

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post #4 of 8 (permalink) Old Jun 20th, 2007, 4:32 pm Thread Starter
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I really appreciate your explanation about that, it makes more sense than anything I've yet heard, and it does put me a little more at easy about my charging system's. I guess that I thought with modern electronics that things were a little more precise than they actually are. Thanks again. :-)
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post #5 of 8 (permalink) Old Jun 21st, 2007, 5:34 pm
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I keep both bikes (R1100RT, K1200RS) on Yuasa float chargers. I ride the RT most days to work and back (only 3 miles!). And when I plug it in once back home, the "charging" light stays on for 3-5 minutes before going to "maintenance" mode. The charger on the RS (which generally gets out for 50+ miles at a time) usually goes right to maintenance mode. I am using 2 identical chargers.

I have never had a bike not start. Even the day I left the RS parking lights on all day while at work. I replace the batteries every 2-3 years, need it or not. And I also carry a small set of 8 gauge jumper cables from Yuasa in my tool kit (which I have used a few times to help other bikers).

Temperature was mentioned as a factor.
Also trip distance.
Also farkles. I run a radar detector, and in winter an electric vest and heated grips. That's it. The radar/radio/GPS/ham/CB stuff you may use shouldn't draw much. The electric clothing I believe does.
How often do you check the battery level (if it's not a gel/sealed battery)?
Are you on an ABS Beemer? I understand the ABS system requires quite a bit of juice to do it's thing and to not give you an ABS fault.

I have few answers. Just wanted to throw out my 2 cents worth.
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post #6 of 8 (permalink) Old Jun 21st, 2007, 7:39 pm
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For those that use a battery tender do you connect it directly to the battery or plug it into the augzilery power outlet ?
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post #7 of 8 (permalink) Old Jun 22nd, 2007, 6:35 am
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Originally Posted by aus1200gt
For those that use a battery tender do you connect it directly to the battery or plug it into the augzilery power outlet ?
I plug into the outlet.
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post #8 of 8 (permalink) Old Jun 22nd, 2007, 9:22 am
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I do not use the standard BMW plug for this application. I have a seperate wire under the seat that goes directly to the battery, with a plug on the other end that works with my girlfriend's electric vest, my air compressor, and the charger.
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