Bonneville America Forums Forums Technical Forums General Tech charging system problem?

Hi...3 months ago I replaced the original battery on my '02 Bonneville because it died during cranking and I figured it's time had passed. In the time since then I've had to recharge the battery a few times. Last week I got out the voltmeter and found that the charging system was reading 13.8V at idle (good). Starting right off idle, charging voltage started dropping until it reached a low of 12.8V at 3K RPM and stayed there all the way up the RPM range. I suspect that's not normal. Would anybody with a voltmeter be kind enough to check and post their charging system voltage (across the battery terminals) from low to high RPM's?
Thanks,
Danny

Maybe it's not voltage so much as current that you should read? Just thinkin out loud...

That is true Benny but I don't have an ammeter. I would be more informed if I could get the voltage readings from a bike without a "battery going dead" problem. If those voltage values were similar to mine I'd look elsewhere in order to solve my problem.
Danny

Gocha. Hopefully someone will chime in. I have a multimeter, but my tank isn't even on my bike right now...

I had nothing better to do, its cold, so went and checked mine for ya. About the same as your readings. 13.8 volts up to about 1400rpms. Then dropped to about 12.9 the rest of the way up the rpms. Weird aye. I could even notice the head light dim a bit when you raise the rpms past the 1400 mark.

Thank you Mr. Trash. Although I did think that 12.8 was too low to keep the battery charged I couldn't be certain. A regulator/rectifier is $280 and I was on the verge of ordering one. BTW...I asked for this info on two other NTB forums and nobody could be bothered so I'm grateful to you and this place.
Danny

No problem dan, I'v had so much help from this place I cant begin to say all the thank you's deserved from members here.

If you suspect your charging system, your best bet is to get an ammeter, preferrably a digital one because you can hook it up backwards and it will just have a negative sign before the digits. Analog meters will fry if you hook them up wrong. Even a cheap digital will work, just make sure it's rated for more than 27A which is the highest output of the alternator. Disconnect a battery lead and connect the ammeter between the disconnected lead and the battery terminal. If you read negative, swap the meter cables.

Fire up the bike and see what your current does...

Danny, where on the island are you? My multimeter is out for calibration right now, but I should have it back soon, like tomorrow or the next day. Maybe I could swing by and take a look. I've hooked it up to a wall socket, so I think it can handle the juice

That's real nice of you Benny.. I live in Merrick. I can also swing by you. Why don't you email me off forum. eastk3@aol.com Not to many of us Triumph guys on LI. We should stick together.
Danny

You have mail.