YamanoteMaui wrote:I checked these forums are read a number of postings regarding the 12v low voltage system. Sure enough, I found the 12v battery to be completely dead. Silly me, thinking an electric car would NOT be vulnerable to a dead ICE car battery. This is certainly a design fault or oversight - there is just no way an electric car should brick because a 12 v battery dies.
Designed that way for several reasons.
The HV battery is normally disconnected for safety. The 12V battery powers the circuits and relay that connects the HV battery, and various events would cause the HV battery to be disconnected, such as a crash. Or failure of the 12V electrical system, including the battery.
The battery is a 12V lead acid due to compatibility and temperature range. Everything electrical for a car (headlights, relays, window motors, switches, head unit, brake controllers, etc) is engineered to work with a 12V lead acid battery. A lead acid battery can operate over a wide range of temperatures, wider than the HV battery.
Yet lead acid isn't ideal technology. The working life isn't long, especially at higher temperatures, capacity is lost rapidly if the cell is discharged below 50%, and reliability isn't great. For various reasons, lead acid batteries can die early deaths. As the car didn't jump start, I suspect your battery developed a dead cell. Lead acid cells can fail open or fail short. A shorted cell would prevent the jump start from increasing the voltage past about 10V, and the HV relay circuit probably requires more.
YamanoteMaui wrote:Perhaps for peace of mind, good idea to carry a lithium jump battery, although I am not sure that would unbrick a Bolt with a fully dead 12v battery.
If the battery was just discharged (because of light left on or other power draw), this would work. If you have a battery that failed, it would not work.
YamanoteMaui wrote:I will probably look at a Model 3 lease next, as 12v problems seem to rare on Teslas.
Tesla uses lead acid batteries for the exact same reasons why GM does. Don't expect anything different in this regards.
A bit of searching found this page.https://syonyk.blogspot.com/2016/10/tes ... lysis.html
Tesla Model S 12V Battery Analysis
It would be great to be able to start this post talking about how the Model S, much to the amazement of many owners, has a 12V lead acid battery. Sadly, I can't do that - because this battery is a failure-prone sore point among many owners, and far too many owners with a >2 year old car are entirely aware of it, as the battery has already failed and been replaced at least once.
#49 on the LEAF 100 mile club.
Most everything around here is wet during the rainy season. And the rainy season is long.
2012 Leaf SL Red
2014 Leaf SL Red
Can't sit in a Bolt seat, hoping for better soon.
Or perhaps a Buick version? Buick Electra 225???