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Tesla Recalls Almost 13,000 EVs over Risk of Battery Power Loss

bloomberg.com

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Re: Tesla Recalls Almost 13,000 EVs over Risk of Battery Power Loss

#21

Post by bryanlarsen »

avianlyric wrote: post #15
ferongr wrote: post #9

Earlier quoted context omitted.

The vacuum reservoir of the brake booster in cars with vacuum servo brakes (whether vacuum is generated by the engine or an electric pump is irrelevant) stores enough energy for 3-4 full applications of the brakes.

EV don’t use vacuum break booster systems anymore. There are much better and more efficient fully electric break booster systems out there which make a lot more sense. Vacuum break boosters only make sense for ICE vehicles where you already have an existing air pump (the actual engine) providing free “vacuum”, they don’t make sense in EVs where you need to an extra dedicated motor to produce vacuum, to power a vacuum…

That's not reassuring. This recall is the exception. The low voltage 12V battery has been far more unreliable in EV's from all brands than the high voltage battery has been.

Is an EV like an ICE in that the 12V bus has power while the car is running even if the 12V battery is dead? In an ICE the alternator puts 13.5 volts onto the 12V bus so a dead battery will prevent a car from starting but it will stay running on a dead battery if boosted to start. I imagine an EV does something similar but I don't know.

Re: Tesla Recalls Almost 13,000 EVs over Risk of Battery Power Loss

#22

Post by briandw »

dncornholio wrote: post #14
arrozconcosas wrote: post #13

Earlier quoted context omitted.

According to the NHTSA, Ford has had 126 recalls this year and the next most is Chrysler with 40. Tesla has 9. https://datahub.transportation.gov/stories/s/NHTSA-Recalls-b...

Is this even a fair comparison when Ford and Chrysler offer a lot more models than Tesla does?

Fords recall numbers have skyrocketed in recent years. So Fords real comparison to its previous self, 2015 they had 68. Why isn’t Fords roughly doubling of recalls news?

Re: Tesla Recalls Almost 13,000 EVs over Risk of Battery Power Loss

#23

Post by diabeetusman »

ferongr wrote: post #9
bob1029 wrote: post #6

What happens in the edge case of losing HV during heavy braking on the freeway? Does the brake booster still function independently of the HV system, or is the driver going to have to push the pedal a lot harder?

The vacuum reservoir of the brake booster in cars with vacuum servo brakes (whether vacuum is generated by the engine or an electric pump is irrelevant) stores enough energy for 3-4 full applications of the brakes.

It's 3 years old, but this video [1] goes over Tesla's electric brake booster (and its lack of vacuum)

[1]: https://www.youtube.com/watch?v=SRZ8XDNz2vU

Re: Tesla Recalls Almost 13,000 EVs over Risk of Battery Power Loss

#24

Post by stetrain »

bryanlarsen wrote: post #21
avianlyric wrote: post #15

Earlier quoted context omitted.

EV don’t use vacuum break booster systems anymore. There are much better and more efficient fully electric break booster systems out there which make a lot more sense. Vacuum break boosters only make sense for ICE vehicles where you already have an existing air pump (the actual engine) providing free “vacuum”, they don’t make sense in EVs where you need to an extra dedicated motor to produce vacuum, to power a vacuum…

That's not reassuring. This recall is the exception. The low voltage 12V battery has been far more unreliable in EV's from all brands than the high voltage battery has been. Is an EV like an ICE in that the 12V bus has power while the car is running even if the 12V battery is dead? In an ICE the alternator puts 13.5 volts onto the 12V bus so a dead battery will prevent a car from starting but it will stay running on…

If the car is on (high voltage battery pack energized) then there is 12V supplied from the high voltage pack through a DC to DC converter.

The 12V battery dying is only an issue if the car is parked and the high voltage battery is disconnected. Then there may not be enough power to 'wake' the car up again.

Re: Tesla Recalls Almost 13,000 EVs over Risk of Battery Power Loss

#25

Post by vel0city »

bryanlarsen wrote: post #21
avianlyric wrote: post #15

Earlier quoted context omitted.

EV don’t use vacuum break booster systems anymore. There are much better and more efficient fully electric break booster systems out there which make a lot more sense. Vacuum break boosters only make sense for ICE vehicles where you already have an existing air pump (the actual engine) providing free “vacuum”, they don’t make sense in EVs where you need to an extra dedicated motor to produce vacuum, to power a vacuum…

That's not reassuring. This recall is the exception. The low voltage 12V battery has been far more unreliable in EV's from all brands than the high voltage battery has been. Is an EV like an ICE in that the 12V bus has power while the car is running even if the 12V battery is dead? In an ICE the alternator puts 13.5 volts onto the 12V bus so a dead battery will prevent a car from starting but it will stay running on…

In a lot of EVs, when the car is "on" there is a DC/DC converter powering the 12V system from the HV battery. So if the car was "on" and experienced a loss of the 12V battery it could continue operating for some period of time.

Re: Tesla Recalls Almost 13,000 EVs over Risk of Battery Power Loss

#26

Post by thesuitonym »

arrozconcosas wrote: post #13
thesuitonym wrote: post #10

Earlier quoted context omitted.

According to cars.com, the cybertruck has had 8 safety recalls, while the 2024 Ford F-150 Lightning has had 2.

According to the NHTSA, Ford has had 126 recalls this year and the next most is Chrysler with 40. Tesla has 9. https://datahub.transportation.gov/stories/s/NHTSA-Recalls-b...

If you want to compare, you need to pick a specific model year, and the same number of models. Ford has 38 current models, Tesla has has 5.

Re: Tesla Recalls Almost 13,000 EVs over Risk of Battery Power Loss

#27

Post by STKFLT »

bryanlarsen wrote: post #21
avianlyric wrote: post #15

Earlier quoted context omitted.

EV don’t use vacuum break booster systems anymore. There are much better and more efficient fully electric break booster systems out there which make a lot more sense. Vacuum break boosters only make sense for ICE vehicles where you already have an existing air pump (the actual engine) providing free “vacuum”, they don’t make sense in EVs where you need to an extra dedicated motor to produce vacuum, to power a vacuum…

That's not reassuring. This recall is the exception. The low voltage 12V battery has been far more unreliable in EV's from all brands than the high voltage battery has been. Is an EV like an ICE in that the 12V bus has power while the car is running even if the 12V battery is dead? In an ICE the alternator puts 13.5 volts onto the 12V bus so a dead battery will prevent a car from starting but it will stay running on…

I can't speak for all EVs but my Ford with a 400v hybrid system (DC-to-DC, no alternator) was able to keep operating perfectly with no 12v battery whatsoever. There was an assembly defect where the positive terminal connecting the battery to the fuse box eventually came partially loose and would disconnect as the engine bay warmed up. It would start up fine and drive with zero issues but then completely black out as soon as the car was turned off.

Re: Tesla Recalls Almost 13,000 EVs over Risk of Battery Power Loss

#28

Post by ajross »

bob1029 wrote: post #6

What happens in the edge case of losing HV during heavy braking on the freeway? Does the brake booster still function independently of the HV system, or is the driver going to have to push the pedal a lot harder?

Tesla brakes are conventional. Yes, the driver has to push harder if the hydraulics fail, same as any car. There's nothing unique to the failure here, normal cars run their boosters off of the power train too (via belts or vacuum usually, also some have 12V pumps and would be subject to exactly this kind failure).

As to whether the booster is run off of the 400V or 12V bus I don't actually know. My guess would be the latter, honestly, since the parts would be more generic. But in any case it probably doesn't matter if the main battery fails as the 12V battery is tiny and would probably not provide enough power to run the hydraulics without the DC/DC converter.

Re: Tesla Recalls Almost 13,000 EVs over Risk of Battery Power Loss

#29

Post by MrBuddyCasino »

bb123 wrote: post #20
bob1029 wrote: post #6

What happens in the edge case of losing HV during heavy braking on the freeway? Does the brake booster still function independently of the HV system, or is the driver going to have to push the pedal a lot harder?

Nothing immediately - Teslas have a both a High Voltage system for the traction battery and a Low Voltage system powered by a separate 12-15V battery. The HV system keeps the LV system charged and most critical safety related functions run on the 12V system. The booster, ABS/ESP, airbags, and steering assist are all designed to remain functional long enough for a controlled stop after an HV disconnection. You obvious…

Didn‘t they switch to 48V?

Re: Tesla Recalls Almost 13,000 EVs over Risk of Battery Power Loss

#30

Post by guywithahat »

MrBuddyCasino wrote: post #29
bb123 wrote: post #20

Earlier quoted context omitted.

Nothing immediately - Teslas have a both a High Voltage system for the traction battery and a Low Voltage system powered by a separate 12-15V battery. The HV system keeps the LV system charged and most critical safety related functions run on the 12V system. The booster, ABS/ESP, airbags, and steering assist are all designed to remain functional long enough for a controlled stop after an HV disconnection. You obvious…

Didn‘t they switch to 48V?

Only on the cybertruck, the Y and 3 are still mostly 12v
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