Yamaha xt 350 charging without battery only 8v

    Hi, recently replaced my regulator with oem one, and after starting it only charged 8v, however my battery is dead and when i jumped the battery it charged 14.5.

    My question is why is it only charging 8 v without battery?

    What´s worse is that the engine operated without a battery (even an otherwise dead one does the trick!) will quickly result in a fried regulator/rectifier unit. The rectifier diodes can´t withstand the voltage peaks produced by the alternator when being operated without a battery (or capacitor).

    It quickly stops rectifying due to the diodes going dead and subsequently and actually having AC when the meter is set to DC will give you incorrect readings.

    Hence the option of using a capacitor instead a battery for weight savings when bike not being equipped with an electric start (which is for pussies anyway 8o )

    If you´ve only operated the engine at or near idle revs nothing bad probably happened but revving the engine up towards redline without a battery installed would prompt me to check the function of the recifier first.

    Be advised that the headlights (and the rear light but NOT the braking light!) are being powered by AC from a seperate coil behind the flywheel which are neither recified nor regulated! One of the lovable quirks of Eighties dual sport bikes....

    1985 XT350 55V
    Simply change the gravitational constant of the universe!

    I think it's because it needs a voltage signal to know at what charge state is the battery. When the battery is dead or there is no battery it doesn't charge i.e. because no battery status to know how much voltage to regulate, running it without a battery won't damage it because the DC is only used for charging the battery. AC for the lights goes from different coil to lights and returns to regulator to be rectified to DC. Even if you revv it to red line it doesn't matter if you have battery or not it won't damage the diodes because it will disapate as heat on the regulator body.Now I have installed a LED headlight and I converted the AC light system to DC. And even if I turn the lights now it won't fry anything because the coils produce more than 10 amps and the LED headlights draws less than 10.

    Thanks for the answers I found the cause.

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