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Comment by czinck | Hacker News Reader

> I actually think what Tesla is doing is in fact illegal.

It's hard to tell because this article is pretty terrible. It depends on what they mean by "voids warranty". If Tesla just won't replace the 12v battery for free because he deep-cycled it out side of the intended use, that seems pretty reasonable to me. If Tesla tries to use this as an argument against replacing any other part of the car (including the main battery), I think that's pretty clearly a violation of the Magnusson-Moss Warranty act. IANAL.

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>> Through the low voltage architecture, you can get the power from the main battery pack and power several devices on the inverter.

He was pulling 12v from the 12v battery, but the car was topping up that battery from the main power pack. So he was effectively drawing power from the main pack. This would impact more than the 12v battery. I doubt tesla ever anticipated the 12v battery being discharged so quickly/continuously. They probably just don't know how this might impact any number of systems. An overheating 12v charging/rectifier system could fry something totally unrelated. This is exactly the sort of situation where a warranty for the entire car could/should be voided.

Being in this field, I can say that it depends on the setup. If it is directly connected to the electrical system of the car while it is inverting the power, this could void the warranty for the entire battery monitoring system and thus the car itself. Lithium batteries are controlled and monitored for safety and messing with this circuit by utilizing the LA battery as an external power supply could cause damage to the system that could result in catastrophic outcomes.

That LA battery is there for a reason. I don’t work with Tesla, but I would assume it is there as a backup for the monitoring and safety systems. There is a reason they are using an LA battery in a lithium powered car.

They switching that to lithium one soon. Chemistry is not the question, question why it's there in first place? Why does it need a backup battery?

The problem is that they can legitimately claim more than that. This massively increases the workload on the DC-DC converter, arguably voiding its warranty as well.

Obviously there are things that should still be covered, but there is more potential for harm here than just to the 12V battery itself.

Depends on where the 12v was drawn from. If it was connected to the 12V cigarette lighter port (that thing has a 15A or 30A fuse in my car) that should be expected load, but maybe not 2+kW drawn constantly for hours directly from the battery's leads.

Anyway the Tesla doesn't generate power during driving like a regular car does, so the 12V power is always topped up from the main Lithium battery and the DC-DC converter needs to be reasonably sized to accommodate eg. 600W supply. If power was taken from the regular port than i would count it as regular use (eg. when camping i would count on my car to charge things, even if it uses fuel and generates 0 km/miles.)

There's another catch:

What if you keep jump starting another car with leads directly attached until the LA battery is depleted? That is a very common scenario and Tesla should size the electronics correctly or make it resilient for that use.

Last I checked, Teslas are not intended to be used for jump starting other cars.

Same with most hybrid cars. Toyota/Lexus strictly forbids this and is have denied warranty claims.

It’s also clearly stated on the owner manuals.

I completely agree. If this were just using a cigarette lighter connector or USB-C, I'd have a hard time seeing the issue. In all the Teslas that I'm familiar with, both are connected behind an electronic fuse to protect the car and the device.

Fair. I don't think it would be much of an article though if they just denyed the claim on the battery though.

Never underestimate the power of spin and selective reporting.

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