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Thread: 851 Battery Light staying on

  1. #1
    Join Date
    Apr 2017
    New Zealand

    Default 851 Battery Light staying on

    Over the last couple of days the battery light on my 851 has come on and stayed on. It's solidly lit, doesn't flicker or go out regardless of revs. Bike has done 10,000km and battery is only 6-8 months old.

    I've had a Ctek MXS 5.0 charger for a couple of years now to help maintain the battery on a number of vehicles I have. I have plugs on my cars, bike and boat and just swap the charger over for time to time. What I completely forgot about when I got the Ducati is that the charger has a Car/Bike mode to account for the small charging rate needs.
    My typical practice has just been to unplug and swap over and plug into the next vehicle etc and as a result I've been charging the Ducati on Car mode at 5A instead of 0.8A! 😬

    From Ctek...
    The MXS 5.0 has got 4 modes, this is for you to choose between.
    MC: this mode will charge with 14.4V and 0.8A the low Amp will assure that smaller batteries (from 1.2Ah) will be fully charged but not overcharged.

    CAR: this mode will charge with 14.4V and 5A the higher Amp will shorten the time to fully charge batteries from 14Ah.

    AGM: this mode will increase the voltage to 14.7 in order to fill AGM batteries to the top. Should be used together with MC mode for smaller batteries and with CAR mode for batteries from 14Ah.

    RECOND: should be used with wet batteries together with MC or CAR in order to prevent and repair batteries with stratified acid.

    What made me discover this is that my battery light came on the other night (and stayed on). Reading across the forums this could be due to the alternator wiring/plug going crispy or the alternator or the regulator or the battery. So I thought I'd try putting the battery on the Ctek to give it a freshen up and when it hadn't reached the last light that's when I had a closer look and realised I hadn't put it on bike mode 😣

    So it's possible I've killed the battery... I've changed it over to "Bike" on the charger and its been on charge for 24hrs now and is on the 7th light but cant seem to get to the 8th light?

    I've checked the wires from the alternator to the regulator and they showed the common signs of being melted so I replaced them and the light remains on.

    So at this stage I'm thinking its the battery but before I rush out and replace it does anyone have the process for checking the current from the alternator to the regulator? Also what volts should I be experiencing at the battery under revs? 13v? 14v? It's showing 12.65v at the battery with the key off and drops to 12.3v running.

    I have a volt meter etc so can test just need to know what I'm testing for and where.

    Thanks in advance. KCG.

  2. #2
    Join Date
    Jul 2014


    The battery should have at least 12.50v when unloaded, when running the volts should be 13.5- 14.5 max with lights/drain off,
    Your battery can still read 12-13 volts but have a dead cell and not have the cold cranking power to run the bike properly,try it with a known good battery/jump leads and see what the results tell you

  3. #3
    Join Date
    May 2008

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