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Will the battery charge at idle rpms?


I would think it does, but i can watch my voltage drop by about 0.01V every couple of seconds. After gettign on it it ended up puttering out (electrical). So methinks I have to replace the alternator (generator).This all comes after replacing the starter relay.... Damn you mysterious electrical demon!
 

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at idle it should be putting out around 14 volts at the battery
 

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While the alternator may not re-charge the battery at idle, it should certainly put out enough amps to keep the motor running for quite some time.

Now, with the headlight on as required here in the US, it may not exactly keep up with the demand, and so might slowly deplete the battery. It should, however, take quite a while to run the battery out, longer than you would normally idle the bike.

It will takes some time at higher rpm's to put back what was drawn out, whether from starting, and/or from idling for a long time.
 

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Will the battery charge at idle rpms?


I would think it does, but i can watch my voltage drop by about 0.01V every couple of seconds. After gettign on it it ended up puttering out (electrical). So methinks I have to replace the alternator (generator).This all comes after replacing the starter relay.... Damn you mysterious electrical demon!
If this information is correct, it should. 37A at idle is pretty stout output and well above half of the 60A rated max output.


http://www.euromotoelectrics.com/Alternator-K1200-BMW-ALT2888-p/bmw-alt2888.htm
 

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I concur with Jim H's comments. Different bikes, but the BMW tech at my dealer confirmed what I always thought- with regard to a RT- that the battery not only doesn't get charged at idle, but it doesn't when riding "around town" (his wording) either.

A broad statement I know, but a few years back I recall reading that most if not all bikes, in the US with a headlight on all the time, will not put a charge into their battery below 2500rpm.
 

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While many of these statements are true, the bottom line is if you are reading a voltage at the battery terminals that is above 12.67 volts(ball park), then that battery is being charged. Period. If it is below that then the battery is being discharged.
 

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If you're on an LT the output at normal idle (1000 RPM) is sufficient to keep everything going unless you have the power servo brakes and are leaning on them pretty hard. They take a large amount of energy to operate.
 
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