If it is protecting that end users can plug arbitrary loads into, that is one thing - but this doesn’t sound like that?
Why did that fuse blow? Because if that is not addressed, it’s likely to just blow again.
"While Tesla’s pyrofuse costs €11 and the BMS reset is around 50€, allowing the car to be safely restored, BMW’s approach borders on illogical engineering, with no benefit to safety, no benefit to anti-theft protection — the only outcome is the generation of billable labour hours and massive amounts of needless electronic/lithium waste."
It's not a choice between 'ridiculously inaccessible with the potential to create more damage than your car is worth' and 'push to reset'. There are many options in between, some of which would be a happy medium between the two that protect both safety, the environment and the customers' wallet. Which BMW's solution clearly isn't.
This is BMW we're talking about. Their guarantees are worth absolutely nothing if my experience is anything to go by and them accepting liability is not something you should have to pay 4K for if other brands can do the same thing under $100.
I had a doozy of a trip issue on one project, a motor would occasionally (not always, no real pattern, hot/cold/etc. didn’t matter) trip the breaker, requiring a sparky to come out and open up the panel to reset it. We tried a bunch of things, megger-ing the motor, testing peak startup current on each phase with a fancy meter, checking phase-to-neutral current (Larger than you’d think! But this was normal, apparently.)
Everything was normal. In the end all we could think something was weird about the contactor. They took it out (I was off site at the time) and took it down to the substation to test it out.
With three phases connected to the contactor (and nothing connected on the other side) they energised the coil, and with an almighty bang it tripped the main incomer and took the entire sub offline.
Turns out there was a manufacturing defect in the contactor and sometimes for a millisecond, if the phase of the moon was right, it dead shorted two phases.
So there, even when you know everything, you don’t know everything.
$1000 for the module with the fuse seems ok to me. Another $3000 to link the module to the vehicle is the outrageous part.
I’ve never had a fuse blow on a car less than 20 years old, and then it was due to shorts due to damaged insulation and bad grounds due to corrosion, which are legit problems that need to be corrected.
Also, unlike breakers, fuses are generally immune to issues with HF interference and the like - they work through basic thermoelectric effects which iron out all but the most extreme issues. If you’re moving multiple amps in a situation described as ‘RF’, or ‘high frequency’ in a DC system that’s not just noise!
That’s a real problem that needs fixing!
Not fixing the underlying problem behind a blown fuse (or constantly tripping breaker) is how your car (or house or whatever) burns to the ground.
Or you have a Lucas, in which case my condolences.
If that was the issue you wouldn't be allowed to change your wheels on the side of the road. They'd be locked down to the car and require a complex software procedure to guarantee they were swapped correctly and won't endanger lives.
This is a professional shop raising the issues. They are liable for how the repair is done. BMW is just liable to lose money if people can easily fix their car at some other, cheaper, professional garage.
If you would see how EV Clinic "repairs" Tesla batteries, you would not say they have any concern for liability.
Even the basic mechanical disconnect and lowering of the battery is far from simple (and requires A LOT more expensive tools than changing a wet belt - not because they are greedy, but because a lift that can lower such hevy battery costs a lot of money, mostly in materials), and that's not even opening it, making sure you don't get electrocuted when you work on it ect.
The only real issue in reality is thermal runaway
I think you are intentionally misrepresenting this and moving the goalposts to make your point. GP blamed safety and liability for the way the process looks like, not the complexity of the task. When it comes to safety you bet that an improperly installed or inspected wheel or tire can be dangerous.
A short internet search tells me [1][2] that some sort of tire malfunction causes tens of thousands of accidents and kills hundreds of people every year in the US alone. That doesn't include wheel malfunctions (e.g. wheel coming off). Yet this isn't locked behind some manufacturer approval and proprietary tools.
How BMW chose to approach this is profit driven. The old money printing machine from ICE maintenance, repairs, and spare parts is slowing down so they come up with new ways of extracting money. Like making the lives harder and more expensive for any non-BMW shop to do repairs. They're not alone in this, other brands do the same.
> If you would see how EV Clinic "repairs" Tesla batteries, you would not say they have any concern for liability.
More moving of goalposts mixed with not understanding what liability is, and where it belongs. So you tell me what's Tesla's liability when EV Clinic "repairs" a battery.
[1] https://www.smithlawcenter.com/practice-areas/defective-tire...
[2] https://www.safetyresearch.net/nhtsa-gets-real-on-tire-fatal...
It started out with (nominally, voltage can rise and fall based on charge levels) (30S) 144V packs, (96S) 352V is very common and there are (192S) packs that do 704V (but that are marketed as 400V and 800V respectively).
You don't want to get zapped by any of these, it's middle voltage DC which is quite dangerous, so the fuses definitely have a safety aspect in case of a crash, they are to protect emergency personnel from touching the frame and exposed wiring. But that's in case of a very serious crash, your average encounter with a rabbit might set off the crash detector (which can't really know ahead of time how bad a crash will be) but has extremely little chance of resulting in exposed wiring. In the case of BMW that rabbit could end up being pretty expensive.
I'd personally prefer e.g. 48V even if that meant some more losses and/or thicker cables.
Next time when the fuse switch in my home I'll buy new home. I shouldn't normally switch on auto-fuse again!
Fuse blows, so you know something went wrong, you check corresponding part, fix it, and enable/change fuse. Nothing special. In home perspective - it could be plugging too many energy needy receivers into one outlet.
In that situation, if you bypassed the fuse, or just kept replacing them without figuring out why it blew (too much load on a specific circuit), you very well might burn your house down by catching the wiring inside your walls on fire.
If it’s something that it is easy to connect loads too, then that is probably not super unusual and easy to fix, because people do that all the time, and you know what is happening and how to fix it. But you do need to fix it.
If it isn’t, then that is very concerning, because something caused that overload, and without that fuse your wires would have caught on fire instead of the fuse blowing. Inside your walls.
Either way, fuses are an emergency measure to stop the wires from destroying themselves from overload. They are destroyed in the process of saving your wires.
And if you are doing this all the time? You’ve got a very big problem brewing.
Or if the tires are not the right size, especially in staggered setups.
If you come from a car that is FWD with AWD capabilities, it doesn't matter as much.
But BMW (at least the ones with the engine mounted longitudinally) which have xDrive are permanent AWD.
Sorry that you feel that way, it was not my intention. But improperly installed or inspected wheel or tire is A LOT less dangerous than crashed EV Battery. And in EU you have a lot of effort going even into this, Police can inspect (and does) the tire from the outside (+ regular mostly yearly MOTs). All new cars have to have pressure sensors in the tire. So I would say EU (where EV Clinic is present) is making a lot of the same strides to make everything around tires safer. And believe it or not, if you go buy any new car in EU, drive it 5 minutes and swap the wheels yourself, it'll flag an error! As the wheels need to have appropriate pressure sensors - that also need to be programmed into the vehicle for a lot of makes.
You think it's profit driven, I don't. Agree to disagree.
> More moving of goalposts mixed with not understanding what liability is, and where it belongs. So you tell me what's Tesla's liability when EV Clinic "repairs" a battery.
I was aiming at EV Clinics liability, not Teslas. And I can guarantee you that both Tesla and BMW take into consideration the bad press if someone, even non official mechanic, repairs their cars and then they kill someone/catch fire. Of course Tesla a lot less than BMW, I even have a feeling that this contributed more to how BMW does things, than profit.
It is.
> I'd personally prefer e.g. 48V even if that meant some more losses and/or thicker cables.
That's unfortunately not an option. The problem with the 600 to 1000 V domain is that it is able to creep where lower voltage would stay constrained and high enough that it can jump small gaps and start arcing spontaneously. The fact that it is DC makes it more dangerous still. But from an economy and practical engineering perspective it makes perfect sense. Keep in mind that these cars are often built using Lithium-Ion packs (though fortunately we are finally seeing a change here towards safer options, even if they are slightly less dense and more expensive), so the electrocution risks are small compared to the thermal runaway risks.
It is unlikely to blow again under normal use.
Are you talking about the charging circuitry?
What are the requirements for the motor(s)?
There is a certain level of risk that is inevitable with moving multi-ton machines at lethal speeds, and deciding that this particular issue is where we are going to draw the line is dubious.
The point that "allowing this fuse to be replaced affordably is too much of a safety issue" is a cop out is valid.
I'm sure BMW would love to not be liable in those cases if they could just decide not to be liable, but inspections and fuses presumably turn out to be cheaper than the settlements they'd otherwise be paying.
Motors, for instantaneous current, can easily exceed 100kW, some much much more than that.
Even assuming limitations to 100kW (which, would be very low for motor current), that's still 2000 amps at 48V. Remember, 100kW is ~134 hp.
I don't think it should be locked away to just the MFG, but it does need to be respected.
Also, the problem is definitely also the cables in your car. Moving to 48V would mean amperage would increase by 10-20x, which would mean cabling thickness would have to increase substantially.
BMW has manufactured engines and cars for over a century and historically they were relatively easy to fix by anyone. Their image in the press never suffered because of bad unofficial repairs.
All of this is trying to find a retroactive explanation that fits the result when the real reason is staring you in the face: they make money by making the owner entirely dependent on BMW as much as possible.
Your explanations are flimsy and disproven by data or history.
You’d need to use silver plated copper buss bar as conductors, 150kW @ 48VDC is 3125 Amps. I’m not familiar with DC ampacity tables, but you’d need (9) 3” conduits each containing (3) #500 MCM conductors for a three-phase 3125A alternating current circuit. One foot of #500MCM copper weighs 1.5 lbs, so each foot would have 27 times 1.5 lbs or 40.5 lbs per foot.
150kW @ 400V is 375A, a single set of #500MCM can carry the current, 4.5 lbs per foot.
The risk of being shocked by 400VDC while using the car is essentially 0, so they use higher voltage to save on conductor material.
There’s no way in hell I’d ever open up an EV battery myself and I know enough to do it safely. DC is incredibly scary, make sure to discharge your start/run caps if you replace them yourself!
Otherwise, they make some very questionable engineering decisions for sure. On their motorbikes, you often have to disassemble half the bodywork just to change the battery; that's just beyond stupid. But like Apple, their products are kind of unique, so people deal with it.