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Battery voltage charging change

805 views 6 replies 3 participants last post by  MarlinSpike 
#1 ·
Hi all,
Bit of background a good number of years back I fitted a motogadget speedo(shows battery voltage) and a new regulator (mosfet fh012aa) relocated to under rear mud guard with waterproof connectors, this for all these years was showing 14.1 14.2 volts

Some where around this point fitted flexible led stop and brake light nestled nicely under oem seat, have probably 8months ago fitted slim motone seat which made the flexi strip look as though it was pushed out in free air

Last ride was just before lockdown here in uk, voltage was still reading as above,

To get flexistrip fitting snug again I decided that about an inch of the round frame tube needed to be cut off, to do this I needed to drop the mud guard to do this I unbolted regulator and let it just sit on top of rear tyre, cut said tube with hacksaw not grinder painted end and re assembled mud guard bolt back on regulator fit seat, rear light, started engine and voltage now reads 13.9 and when revving drops a few points 13.6/7 stop revving back to 13.9 only cables disturbed was lowering reg down about a few inches or so, have checked connectors are snug

So question is should I be concerned by this drop or just keep an eye on it, bike is on trickle charger and has been since I've had bike


Thanks for any thoughts
 
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#2 ·
Check that the battery connections are corrosion free and tight. unplug and check the connectors at the R/R for corrosion. Check any splices that might have been stressed while moving things about. check the three wires at the R/R harness to bike alternator connector. Good luck. R.
 
#3 ·
Thanks
I have checked at battery, nice and clean, tight, had already unplugged reg, the connections were spotless, the live and ground where new cables straight to battery, well via fuse of course, have checked fuse blade and all good, the 3 from alternator were routed back from headlight shell to reg so no joints,
Next test at reg, between + & - overrange one way and 980ohms leads other way round

Between negative and 3phase overrange between positive and 3phase around 480 ohms, swapping leads round gives same results just on opposite side, neg and 3phase 480ohms etc, obviously due to biasing

Next step, ordered another reg, (good job mail order is still running in the uk) a used one though due to price, so will give me a comparison on voltage at speedo, if cured leave on, if volts still drop off start pulling loom out
 
#5 ·
Yes a good video , I possibly went over the top with the amount of tests carried out, but what It does show me is that the reg looks okay it also points out when comparing with the mosfet video, that although mine has the pattern and connectors of a mosfet the readings says standard :rolleyes:

Dpd delivery tomorrow of reg should hopefully show something , thanks for the info on vids
 
#6 ·
Follow up: used reg delivered this morning nice and early, tested reg with meter just to make sure

Would certainly recommend Roadstercycle.com video on testing standard and mosfet regs, testing the same just the expected results that change

So fitted on to bike, 14.3v on tick over, 14.4v on revs

In short although my reg tested okay on the bench with multimeter, something was definitely going on for it to start dropping points of volts on revving, glad I got a voltage display on speedo as the first I may have known about this would have been the dreaded click!
 
#7 ·
Good news. Thank you for sharing your experience and information. Certainly help the rest of us when our time comes.
Thanks goes to Mr. rweb also for the video link!
 
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