Adventureboy
Well-known member
If your truck is plugged in for more than a few days without turning it on for any substantial period, your 12V system will still shut down many components to conserve energy. This may have affected your initial SOC reading since it may not have tracked it when things shut down. On a couple of occasions, I've seen it happen where the SOC meter climbs or drops shortly after starting to drive as it readjusts itself. It seems to be very specific to letting the truck sit for more than a couple of days. I expect the true SOC is what you set it to when you plugged in.
If you are leaving the truck for more than a day, you should put a trickle charger on the 12v battery behind the Frunk. This is an annoyance but because of the way the charge cycle is designed, 30-40 hours after your truck is charged, the 12v battery will need to shut down many systems to save the 12v battery. More than likely the module that tracks your SOC is among those that get shut down). I expect when you start up the truck after a few days, it reads the HVB voltage and takes a best guess until it fully initializes (that can read a bit higher or a bit lower than the actual HVB SOC). I say the 12v charge design is flawed - I've tracked it to many glitches like this one and I'm willing to bet lunch that if you connect the 12V trickle charger, the problem will disappear.
See my post here for the details: https://www.f150lightningforum.com/forum/threads/update-failed-12v-battery.16533/post-337593
If you are leaving the truck for more than a day, you should put a trickle charger on the 12v battery behind the Frunk. This is an annoyance but because of the way the charge cycle is designed, 30-40 hours after your truck is charged, the 12v battery will need to shut down many systems to save the 12v battery. More than likely the module that tracks your SOC is among those that get shut down). I expect when you start up the truck after a few days, it reads the HVB voltage and takes a best guess until it fully initializes (that can read a bit higher or a bit lower than the actual HVB SOC). I say the 12v charge design is flawed - I've tracked it to many glitches like this one and I'm willing to bet lunch that if you connect the 12V trickle charger, the problem will disappear.
See my post here for the details: https://www.f150lightningforum.com/forum/threads/update-failed-12v-battery.16533/post-337593
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