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Discussion Starter · #1 ·
Hi folks! I can't suggest enough the importance of cleaning connections to troubleshoot charging system. Learned this on the side of the road a few weeks ago.

That said, connections are very clean and I'm now am getting a healthy reading of 12.7 when I just turn bike off, 13.5-14 at 2000rpms, and then over 15V when I run engine up to almost red-line. I am curious about this latter reading, as I am also discovering battery acid is leaking a little out the overflow hose. The Honda Shop Manual does list 15.5V at 10,000 rpm as acceptable, but I wonder if this is too high and causing battery to bubble over? I'd like to eventually get a sealed LiFePO4 one (and powdercoat the acid drips on frame), but not until I determine if my regulator is not working. Is 15.5V too high?

-I have a custom lower seat pan, and no starter motor, so am using a smaller battery. A Yuasa 12-N9 (pretty sure). It breathes out towards frame, instead of towards wheel, but was what I could find in the right size, so I've modified the battery case a bit.
-I tested the stator, and have acceptable readings. Same for rectifier, although this test was a bit harder to figure out.. followed Rick's diode test video, as well as a diagram posted on this site for troubleshooting charging system.
-Haven't found a way to test regulator.

Thanks in advance for any help!

27,171 Posts
You are thinking of the re-charging current in terms of voltage alone, NOT in terms of both volts and amps....
The factory regulator was chosen to keep a 12V 12 Amp battery fully charged....
Since your battery is both physically smaller (less fluid to disperse the heat) and of less amperage (so it can only accept a smaller "flow" rate) you are "cooking" it.....
Any lead/acid battery should be charged (at the max) at 10% of its amperage rating.....
So, (for example), the 1.2 amp "push" that would be acceptable with a 12 amp battery is 33% too strong for a 9 amp battery, and will cook it....
IF you eventually intend to use an exotic metals battery as you mentioned, you will need an even MORE precisely controlled re-charging rate in terms of both Volts and Amps, or instead of just boiling out acid, you could have a fire or explosion.....
NOW is the time to get a modern Rectifier/Regulator unit that is correct for the exotic metal battery and install them both....
Your current battery is likely damaged anyway......
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