Force battery charging

[Rocktman]

I read somewhere (maybe this forum, maybe somewhere else) that you can force the battery to be charged (w/o TSB installed) by driving with the parking lights on (daytime obviously). Can someone confirm or refute this? If driving with the parking lights on forces the battery to charge, what about nighttime driving with the headlights on?

[ammcinnis]

On 2/4/2023 at 4:12 PM, Rocktman said:

I read somewhere (maybe this forum, maybe somewhere else) that you can force the battery to be charged (w/o TSB installed) by driving with the parking lights on (daytime obviously). Can someone confirm or refute this?

It will cause the regulated alternator voltage to remain at a constant 14.1-14.4 volts, which results in maximum battery charge rates.

For cars that qualify (Legacy and Outback MY 2015-2016, and possibly some early MY 2017), I highly recommend the battery management firmware upgrade per TSB 11-176-17. Since the firmware is in the ECM, a dealer can do this at no charge under the 8-year/80,000 mile emissions warranty.

 

Quote

If driving with the parking lights on forces the battery to charge, what about nighttime driving with the headlights on?

Yes, definitely.

N.B. Why guess, when you can plug a voltmeter into the accessory power outlet in the console (or into the OBD-II diagnostic connector below the dash) and monitor actual system voltage as you drive? If you don't already have a suitable meter, digital voltmeters that plug into the console power outlet are priced as low as $20 or so. Any OBD scan tool should also be able to monitor system voltage in real time.

[Rocktman]

Thanks again for the reply, ammcinnis.