So I just had an interesting experience in my 2015 Model S. I was on my way to a supercharger and I knew I was cutting it a little close… it showed that I would reach the supercharger with 1% remaining. I have pulled up at superchargers with only a couple of percent remaining before, and even 0% remaining once, so I wasn’t too worried. However, this time, a little less than a mile from the supercharger while the car still showed 1% remaining, it started beeping and telling me that it was out of power and going to shut down. As I was pulling over the instrument cluster screen shut off. Shortly after that the MCU shut off and at that point the car was completely dead. I know that the remaining battery power is just an estimate and given that it was at 1% I figured that while it was inconvenient it was likely that the BMS system had just miscalculated by a bit and I wasn’t even going to post about it.
However, what really confused me was that $130 later, after a short ride on a flatbed and a 12V jump the car came back to life and still reported 1% remaining. And surprisingly (to me, at least), it also allowed me to put it into gear and I was able to back into the supercharger stall under the car’s own power. I‘ve seen other posts that suggest that the car stops charging the 12V battery when the main battery is very low and I‘m wondering that if it’s possible that it wasn’t the main battery pack that ran out of power and shut off the car, but the 12V battery instead.
This is a March 2015 model S that I got used from a private party in March of 2017. I know that I have never changed the 12V battery and I don’t know for sure if the original owner ever did, but at best the 12V battery is 4+ years old and at worst it’s the original 6+ year old battery. On a possibly related note, I have also noticed that lately vampire power drain seems to be increasing with the car losing as much as 7 or 8% a day. I’m wondering if this could be a symptom of the 12V battery not holding a charge and the car needing to use the main battery pack to charge it much more than normal.
I haven’t seen any alerts or warnings about the 12V battery, so maybe I‘m just reading too much into this, but do you think it’s possible that the 12V battery is on it‘s way out?
However, what really confused me was that $130 later, after a short ride on a flatbed and a 12V jump the car came back to life and still reported 1% remaining. And surprisingly (to me, at least), it also allowed me to put it into gear and I was able to back into the supercharger stall under the car’s own power. I‘ve seen other posts that suggest that the car stops charging the 12V battery when the main battery is very low and I‘m wondering that if it’s possible that it wasn’t the main battery pack that ran out of power and shut off the car, but the 12V battery instead.
This is a March 2015 model S that I got used from a private party in March of 2017. I know that I have never changed the 12V battery and I don’t know for sure if the original owner ever did, but at best the 12V battery is 4+ years old and at worst it’s the original 6+ year old battery. On a possibly related note, I have also noticed that lately vampire power drain seems to be increasing with the car losing as much as 7 or 8% a day. I’m wondering if this could be a symptom of the 12V battery not holding a charge and the car needing to use the main battery pack to charge it much more than normal.
I haven’t seen any alerts or warnings about the 12V battery, so maybe I‘m just reading too much into this, but do you think it’s possible that the 12V battery is on it‘s way out?