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Alternator "voltage booster" for AGM battery retrofit
Not a diag question, just something I'm curious about and wanted to know if anybody has an answer.
I just started hearing about people installing these in vehicles that have had an AGM battery retrofitted. Specifically I was reading about a guy that replaced the lead acid battery in his 2016 4Runner with an aftermarket AGM battery. The battery requires 14.6 volts to charge properly and the stock Toyota ECM limits charge voltage to 13.6 volts. Apparently guys are installing the GM charging circuit diode
HERE
. I am curious if this is actually sending any more voltage to the battery? If alternator output voltage is going up due to higher resistance, what is the voltage change at the battery? How does this diode affect charging voltage? Does it have a resistor? If so, wouldn't the resistance be dropping the voltage after the diode? I don't believe Toyota is monitoring amperage use of the vehicle at the battery. Maybe I'm overthinking this. If I have this all wrong, can somebody please explain to me what is going on?
They appear to be putting the diode in the PCMs voltage sensing circuit. What the diode is doing is dropping the voltage sensed by the PCM by the diodes forward voltage. Probably about 0.7Vish. That'll trick the PCM into commanding higher charging voltage.
13.6 v seems low I suspect the.ECM is controlling charging voltage by PWM. If it is using PWM I can't see a diode working.
If the charging voltage is pwm controlled by the ecm based on a voltage sense circuit, a diode with its voltage drop would make the ecm see a slightly lower system voltage and in return crank up the pulse width in order to reach the desired charging voltage, wouldn´t it?
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