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Charging Issue

Discussion in 'Supersport (1974-2007)' started by Carr01, Jan 5, 2020.

  1. As will all my previous bikes I leave them on an optimate trickle charge when not in use.
    I took out the SS yesterday for a blast and noticed the battery light was on
    After about 15 minutes or so the light dimmed to off.
    I mentioned this when it was in recently for work, It was suggested I change the battery as the wrong one was fitted.
    The alternator was checked and found to be working well.
    I’ve left it off charge to the time being.

    Any clues as to what’s going on?

    Gremlins or something more sinister?
  2. I would guess that the reason the light was on was because you had just drained a significant amount of the batteries power starting your bike, so after 15 mins of riding the generator had now topped up the battery sufficiently so the charge light was now extinguished.
  3. Started up on first turn of the engine.
    Had been on trickle charge for days prior to the last run out.
    Doesn’t add up?
  4. If the light is on, I would say it's not charging, I would be suspecting a reg/rec on its way out, they can be temperamental when faulty.
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  5. It’s been a long time since I owned a 900ss
    the rectifier/ regular failed on that one.
    But I can’t remember, what would be the symptoms?
  6. Overcharging undercharging there’s no balance when they are worn. the battery light you have seen is only a crude device to let you know there is and undercharging situation. Extreme cases an overcharge blows bulbs melts leads and catches fire (like a Honda)
    The alternating current needs to be controlled hence the reg rec.
    I reckon your alternator is either struggling or your reg Rec is buggered. Not sure wether those models have the problem of the nut coming undone on the alternator like on others.
    You need to stick a multimeter across the terminals when it’s running and look for a nice steady 13- 14 charge. Anything over 14.7 stop if under 13 it’s probably alternator, alternator wiring, reg rec.
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  7. Also if the voltage is dropping whilst running you are affectively running a total loss charge system which is no good for the road. you may even experience a misfire if goes low enough as your coils and I’m assuming it’s injection injectors all require a steady voltage to operate.
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  8. It’s a 1997 carburettor model.
    I’ll give it a check with the multi meter
  9. That cool then as it eliminates injectors. thinking about it you may want to find out if these models have the alternator but problem cos you would probably experience misfiring maybe if this was loose cos it may also have the tdc sensor on it.
    I do not know much about those older models but a charging system is pretty simple affair
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  10. The charge circuit on a 900SS appears to be quite simple.
    The red light is connected to a zener diode.
    Once the voltage of the Zener is reached the LED is extinguished.
    I'd suggest that the charge circuit isn't working as effectively as you'd hope or the battery is FUBAR.
    I'd drop test the battery and test the voltage output from the regulator. It may be a loose connection on the gen set?
    Inspect everything and make sure all of your connections are clean and tight.

    Just ideas.
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  11. When you test the charging voltage as suggested, get the revs up to about 3000. Its should be over 14volts across the battery.
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  12. but not more than 14.75 or 15V on a cheap meter.... that's DC range.... less than 0.6V on AC. Lead acid batteries charge best with dirty DC... it helps move the bubbles off the plates.
    Can't find a good diagram... imaging a cross between these lines...
    #13 AirCon, Jan 5, 2020
    Last edited: Jan 5, 2020
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  13. The 97 SS charging system is very simple.

    The usual alternator is a two yellow wire version.....check the joints/connectors where the alternator wires meet the wiring harness up on the left side of the frame.

    Check the warning light bulb, they are only silly little filament bulbs and they can fail completely or mess about until they do.

    Establish which reg/rec is fitted.

    If it is OEM, the bug 30amp fuse by the side of the battery only protects the reg/rec. The contacts can and will get wet and corrode.

    If it is an Electrex RR51, check the wiring from the reg/rec back to the battery and the other connections (see diagram) they get wet too.

    The RR51 doesn't need a fuse.....it has it's own inside. The RR51 is a bit more reliable than the OEM one, but they can still fail.

    As others have said, check the alternator output....but do it at the joints I mentioned earlier above.


    REG WIRING e.jpg
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  14. Thanks Al, that’s a big help.
  15. Lots of items within the system can fail of course but as Al said, the problem often begins with high resistance at the connectors and often the yellow alternator wires primarily, followed by overheating and then escalates to the regulator as it fails to cope with the false demand. The O.E.M. regulators on 90's SS and Monster bikes often came in for a lot of stick reliability-wise, it becoming almost Internet Folklore to just replace them routinely but I couldn't disagree more having seen many original units still going strong after being fitted 25-odd years.


    As Hyper said also, good to establish if over or undercharging first. If it's over then nearly always regulator at fault.
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  16. Forgot to add, possibly been covered already, although obvious, it's worth checking earth lead at regulator (flimsy O.E.M. on SS) and engine-to-frame/battery-to-frame earths for corrosion/conductivity.
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  17. Good point Chris,

    I think many OEM reg/recs got changed, because there was a charging fault somewhere other than the reg/rec, but through not checking other things or just lack of experience, the reg/rec always got changed first.

    One SS owner I knew changed out the OEM reg/rec for an RR51 because he thought it wasn't charging; he nearly bought another RR51....

    ....I traced it to a blown charge light bulb.
  18. And everyone else that chipped in?
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  19. Yeah but, my drawing was better than yours.....;)
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