The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: cobra407 on December 31, 2012, 12:07:59 PM
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I have some occasional electrical issues. Generator light comes on. Battery runs low... etc.
I would like to go through all the electrical system and clean up all the connections -- suggestions where to focus? I will check the ground wire first.
thanks Peter
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If your GEN light stays on above around the 14-1500 rpm range, there is a problem with the charging system .
If you do a lot of stop and go riding, the charging system is barely providing power to run the load on the electrical system, let alone recharge the battery .
How old is the battery ?
Is the bike left for extended periods without being ridden ?
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During the winter not driven at all. During the summer once or twice a week but around town only-- so no significant charging time. The battery is brand new.
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You need to get a battery tender and keep it on the bike when it's parked for the day in your garage .
Batteries don't like to be sitting discharged for any length of time, it will lead to a shortened service life .
If it's a serviceable type battery, you need to check the fluid level in the cells on a regular basis, a low fluid level in just one cell, will damage the battery and again cause a shortened life .
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As Bob said batteries have to be kept fully charged for maximum life and even daily use won't necessarily do that if they are short runs around town. Easy to check with a digital volt meter. Permanent damage due to sulphation begins when the rested standing voltage is allowed to fall below 12.4 volts.
You can also check the charging system with a digital voltmeter by monitoring the voltage at the battery terminals with the engine running. It will be 12 volts or so at idle and should rise to approximately 14 volts when the engine is revved up to 3000+ RPM. 13.8 to 14.2 volts is a good reading that would suggest your charging system is in good order. The battery must be fully charged before this test otherwise you will get a false low reading due to volt drop across the battery. Also to avoid a false low reading the test should be done 2 or 3 minutes after starting the engine. This allows some time for the starting draw on the battery to be replenished but not too much time that engine heat has an effect on the voltage regulator which has a built in temperature coefficient designed to gradually lower the voltage set point as the bike warms up. The regulated voltage would be lower by something like 0.3 to 0.5 volts after the regulator gets hot.
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It may be worth a visual check on the Alternator. Mine checked at 13.87 volts after I had to get hauled home. I thought that it was the battery. (Came with the bike, no idea of age) so after purchasing one, went off for a ride, flat battery again.
New Rotor was required. Previous owner had patched it up.
I might also add that the Gen light didn't work at that time.[smiley=embarassed.gif] But it is a "work in progress."
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I get the idea from the symptoms - intermittent & charge light on - that it might be brushes. That's where I'd look first. If the slip rings are black or anything but shiny copper colored, I'd clean em up!
You can pretty well tell by looking whether the brushes are worn too short by looking at the springs. If they're hung up on the side of the brush holder they won't provide enough pressure for the brush to contact the slip ring. Also, the brush lead may not allow the brush to move any closer to the slip ring - so look for that too. Brushes are 15mm new (as I recall) and worn out at half that length.
I've also heard of brush holders wearing where the brush slides, and the brush hanging up in there.
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The GEN light is a fine diagnostic tool if you know what it's trying to tell you.
Your first order of business would be to charge the battery and then run the DVOM test as Barry has outlined.
A Battery Tender Jr would be a good investment for you, Peter. However, be advised that the instructions with the B'Tender Jr state that the small, 0.75amp unit will not recharge a flat battery. The battery needs to be at least 80% charged for the Tender to do it's job properly.
I have a Tender for every one of my bikes. FLAPS and bike shops usually want $39.95 but I got mine off Amazon for $23.00 each with free shipping. You don't say where you hail from... USA?
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thanks all.
Very cold out but will get the battery tender on tomorrow. Scheduled 13F. After it warms up I will go through testing.