Will Battery Charge at idle? - Honda Shadow Forums : Shadow Motorcycle Forum
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post #1 of 5 (permalink) Old 05-19-2008, 11:26 AM Thread Starter
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Will Battery Charge at idle?

88 Honda Shadow 600.

I have another thread about how to test the rectifier:


... but I'm wondering if I actually have a problem or not. I read a thread that said the battery will not charge while the bike is idling.

The other day I started the bike up for the first time of the season and it idled for 20 minutes or so. Before starting it up the battery had a fresh (overnight) charge. After idling for that period of time I turned the bike off and then tried restarting it and the battery wasn't strong enough to start it up.

Is it possible that the 20 minutes of idling drained the battery?

I don't get over 13.5 V on the battery while revving but I have also seen threads that say this is OK (though my manual says I should be getting closer to 14V).


88 VLX 600
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post #2 of 5 (permalink) Old 05-19-2008, 12:42 PM
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Most Shadows start charging at 1,500 RPM. Your bike idles between 1,000 and 1,100. My Nighthawk doesn't start charging until 2,200 RPM!

So, no your bike isn't charging while it's idling, and even worse, it's running down the battery!


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post #3 of 5 (permalink) Old 05-19-2008, 03:53 PM
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Some of the bigger bikes do not charge much at low rpm's.

The VLX will most definitely charge at idle, if it's working properly and
your idle speed is within spec (1200 +/- 100 RPM).

The VLX has a very good and healthy charging system compared to bkes
that are bigger than it.

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post #4 of 5 (permalink) Old 05-19-2008, 05:10 PM
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I would not think that 20 minutes of idling would "drain your battery" and if you had a full charge on it overnight it should not run down in such a short time as you stated. Regarding the 13.5 volts vs 14.0 volts that could very easy be attributed to the accuracy of the volt meter. (I prefer a fluke meter) The fact that you are reading 13.5 volts probably indicates there is some current charging. Do several voltage checks, one with just the battery charged, engine not running. Depending on the volt meter accuracy it should be somewhere around 12.3 - 12.8. Now start the bike, for a second you will see the meter drop down on voltage as the starter pulls some current then it should rise, at idle it might show a little more then what the battery only was. As you rev the engine should see the voltage raise a little (under a volt) keep revving it higher and you will notice the voltage increasing to a point where the regulator steps in and does its work, at that point the voltage will flat top, not increase or decrease but saty level.
I think the exact voltage isn't as important as seeing these changes, which is about a volt from battery only, to bike revved up.
Another test would be to temporarily installing a car type amp meter between the negative battery post and ground and watch the charging current. A center reading amp meter is handy (shows neg or postive swing).

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post #5 of 5 (permalink) Old 05-19-2008, 10:22 PM Thread Starter
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Thanks for the replies. I have a Fluke and a Wavetek multimeter. They both read the same values.

I know I was read around 12.6V before starting the bike. When idling it went up a little. Revving it up brought it to a max of 13.5V.

I will have see if I can duplicate the problem - its too late now and don't wanna wake everyone up

88 VLX 600
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