The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: marcmiller001 on November 11, 2016, 10:43:30 AM
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Just got done with a couple hours of running errands around town. Mainly 10-12 mile hops here and there, so 4 or 5 on's and off's. I was just getting done with my last errand before home and the bike wouldn't start. All lights on, no issues other than no starter actuation. I rolled it and jump started for the 2 mile ride home and it ran fine. I let it run in the garage a minute and shut it off and went to restart and the starter motor clicked but no start. Obviously - seemed like a drained/draining battery. What is the best way to discern if this is a battery issue or an alternator issue?
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First fully charge the battery.
Then hook up a voltmeter and measure the charging voltage while revving the engine. It should continue rising up to 3 or 4000 RPM and you should measure 14 volts or at least very high 13's. If it sticks down in the 12's then it's a charging system problem.
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How old is the battery ???
You can charge the battery overnight, then start the engine with a voltmeter connected to the battery terminals, rev the engine to 4500 rpm .
Optimal voltage is 14.2 but with these bikes at 30+ years old, you probably won't see that, but you should be close to this .
City driving, multiple stops are pretty much not charging the battery .
When I lived in Chicago, the battery in my '81 R65, would quit after 6 days of taking it to work, if I didn't charge the battery on my days off, or take the bike out for a highway speed ride for a few hours .
I had a 5.5 mile ride to work, max speed 35 mph and 13 stop lights .
Since moving to Phoenix, I have a 13 mile ride to work 1.5 miles of surface streets and 3 stop lights, then 11.5 miles of urban expressway, 70 mph, no problems with battery charging in the 23 years here in a suburb of hell !!!!
With the riding season coming to a close on the western shores of lower Michigan,' lake effect snow ' country!!!!!!! ;D
You may want to go through the electrical system and check for corrosion, loose connections, etc..... in the charging system .
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Hey guys-
Thanks for ALL of this info. I will go through all of the wiring in the winter and also keep my charger out. No telling how old the battery is - I had just gotten done with a 12 mile ride and 65mph and went in the store for only a short time and it wouldn't engage starter. Then a 2 mile ride home - when I tried restarting - it clicked the starter at least - so I think it must be charging a little. I will test it with the volt-meter in the next hour or so and report back.
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First fully charge the battery.
Then hook up a voltmeter and measure the charging voltage while revving the engine. It should continue rising up to 3 or 4000 RPM and you should measure 14 volts or at least very high 13's. If it sticks down in the 12's then it's a charging system problem.
After leaving the battery on a charger overnight
hook the voltmeter up to the battery BE FORE you try to start it
As you are trying to start it see what the battery voltage is during cranking
If it starts then check the charging voltage like Bob and barry said
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Well.. it seems the battery is just giving up. It was on the charger all night and when I hooked up to volt meter...it shows a weak 5 volts. I eventually want to mount battery flat under seat, any recommendations on a good battery to plan on this winter?
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You can mount any AGM or Gel battery flat. The cheap generic AGM's mentioned at the top of this board are good value and they work well.
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Unless you can find something local to you at a better price, Staab has a 22 AH battery that fits in the OEM battery box .
http://www.staabbattery.com/product/UB12220-V.html
They are located in a western suburb of Chicago, so shipping cost should not be outrageous .
If it wasn't for the fact that I have a local source for generic AGM batteries, I would have Staab batteries in my BMW's and Guzzi .
http://www.gruberpower.com/12-volt-18-amp-hour-ah-battery
No matter which battery I get, they only last 2-3 years here in the incessant heat of the low deserts of Aridzona .
I've done some work on the bikes the past few weeks and the label I put on the batteries when I installed them, show that all of them have been in service 30 months, so I probably have 5 batteries that need replacing in the not too distant future !!
There are lithium batteries available, but the cost is over $200 .
There is a thread in the Misc Technical section, ' Anti-Gravity " battery that a member here has had on his R65 for awhile .
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Thanks all..great info!!!