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Smart charging alternators

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  • Smart charging alternators

    Well today I decided it was a good day to scope out the alternator, capture some screen shots for those that are interested or can interpret scope patterns.
    I have added some notes to help with what it all means.

    As of main interest one of the pics shows a maxed out voltage of 13.95v, this is even after I forced the voltage as high as it will go on a scantool. Scantool was asking for 14.6v but it got no where near it.

    The pics show the blue line as Alternator voltage.

    red line is the alternator internal AC ripple and this you can see power up and down in a wave. Also each little bump is one magnetic field from the rotor cutting through a coil of stator winding.

    The green line shows the pulse width modulation of the output control, I am presuming like most engine management controls its pulled to ground by ECU which means when signal is down the bottom its ON and when up the top on full voltage its OFF.

    Cheers, Spook

  • #2
    Good to see you are investigating electrical systems now Luke. There is a lot of discussion on the Prado forum about fitting an auxiliary battery and the ways to ensure that both the original and the extra one get a full charge. DC-DC converters seem a way to get the second battery up to a high enough voltage as the Prado at least seems to float around 13.6 volts according to techstream on my car. Obviously diode splitters reduce the voltage from an already low starting point.
    Or is it low? presumably Toyota know what they are doing and set it to this for a reason. Being such an old codger all my experience is with older alternators which the standard regulated range was 13.6-14.4 volts. Perhaps holding the voltage over 14 is detrimental to batteries especially in warm climates? no worries about that in the UK at present.


    • Spook1205
      Senior Member
      Spook1205 commented
      Editing a comment
      My opinion is 1 to 1.3v over battery rating of a lead acid battery is enough to full charge over time. It’s a fuel saving measure. When an alternator is loaded up it takes a lot to turn it. I once saw an exercise bike being pulled apart in a gym and it had a car alternator to crank up load on resistance. Just put more power into rotor and it’s harder to go around.

      As far as second batteries and types plus what works there is so many opinions and science behind it I don’t fully understand enough.
      Personally I would put a waterproof DC-DC charger behind grill and most likely run seperate earths for the only reason being I know the power actually flows out of the Neg side of the battery to the positive side. Electrons are negatively charged and are amassed on neg plates. Although it really makes no difference I would just get enjoyment out of doing this.

  • #3
    Thanks for doing the research on this Luke , it confirms my suspicions that the alternator is not able to put out any more than 14v using ECU control. So im still toying with the idea of either an external regulator setup or an alternator from a Euro 4 model 1GD.
    2016 GX , in White