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.
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.
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.
Obviously there are things that should still be covered, but there is more potential for harm here than just to the 12V battery itself.
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.)
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.
It’s also clearly stated on the owner manuals.
From linked article:
> Through the low voltage architecture, you can get the power from the main battery pack and power several devices on the inverter.
I don't know how Tesla is wired but this article suggests that 12V lead acid battery is constantly charged from primary lithium battery. It sounds like hooking up electrical load to main battery but with extra steps.
My 17 Volt has a 175 amp DC-DC converter that charges the 12v battery from the traction battery. It's interesting that this converter is cooled via the same liquid cooling loop that cools the traction battery.
I have a 4kw inverter connected to it and have used it several times to power large loads for several days in my home during power outages, including refrigerators, lights, TV/Computers, vacuum cleaners, and also the furnace(as the guy in the article has).
I have been doing this since I bought the car in 2018 and the only ill effects are when I forget to turn it off(when the vehicle is off) and it drains the 12v battery. I've done this (drained the 12v battery accidentally) about 20 times so far and it has not noticeably impacted the 12v battery.
I also would not expect any warranty support for this charging system and battery as I am clearly using it outside its intended purpose.
Why do Teslas still have these wet batteries, do you know?
Also, does the Tesla not have a standard wall socket in it? Why would you need to use an inverter?
Tesla has decided to not provide a 120v inverter from the factory. It's not the underlying tech, because other manufacturers do ship inverters and they're a straightforward thing to integrate (as the manufacturer) with the HV battery pack.
This is probably about (besides the normal Tesla-being-the-Apple-of-car-companies) battery pack degradation. Tesla currently warranties their battery packs based on mileage, and frequent use as a stationary power bank will put more cycles on the batteries.
There is precedent for this - ICE vehicle warranties can be voided for excessive stationary operation. Generally they don't bother for light duty, but medium and heavy duty trucks with PTO have maintenance requirements and warranty terms based on engine running hours as well as mileage.
It helps conserve your actual battery and works well.
They have a separate 12v system from their 400v+ system that they use to run the motor.
the batteries wouldn't like it. where-as alkaline & lead acid batteries are efficient at low-discharge, lithium ion batteries generally don't enjoy low-discharge . buck converters are also probably going to be more efficient when they have some modest load to deliver- otherwise the drive circuitry & mosfets are consuming some (little) juice, just to produce a trickle of power.
in general this is an automotive vehicle using automotive rated electronic parts. having a conventional 12v battery-powered architecture for most systems makes loads of sense, is is hella convenient, and based off my above reasoning i'd guess more efficient. yes with that low-drain the inefficiency feels like it probably won't matter but I rest easier thinking that the li-ions can truly rest when the car is off. it's better for them.
I have dealt with these shenanigans with my ICE car and a dealer (they did not want to honor the warrenty for the car battery), this why I knew about bringing the battery to an Auto Parts store.
If you are curious about my situation, essentially my fiancee went and got the battery replaced at the dealer (we brought in the car for a different issue, and the dealer wanted to replace the battery).
About 6 months later, the new battery failed, and this battery also had a very clear sticker saying "3 year warrenty" right on the battery (it was certainly not an OEM part).
An auto parts store which helped me confirm that the battery was dead (they were actually very helpful, they offered to charge the battery and diagnosed the issue free of charge).
After working with the auto parts store, I called the dealer asking about this. They wanted us to bring the car to them, charge us a $100 diagnostic fee (essentially, doing the same thing the auto parts store did for free), then they would decide if it needed replacing, and not commenting on whether they would honor a free replacement. The battery at the auto parts store was $100! I just decided to buy the battery and install it myself. That battery does have a five year warrenty.
I strongly suspect that the original battery was never replaced, based on how they treated my fiancee in both interactions.
https://pbs.twimg.com/media/EuodaE6WQAA3tKN?format=jpg
It looks like they just didn't honor replacing the 12v battery under warrenty, which makes this article pretty much a nonstarter.
Warranties are for intended use. If I drop a boat out of a helicopter on onto concrete from 1,000 feet and it breaks, I can't make a warranty claim. This is SPECIFICALLY covered in the warrenty for TESLA's as well.
Now we are getting legal advice on HN that this violates the magnuson act! This is an only on HN comment.
This is not how these batteries are intended to be used.
Lawsuits like this are why we have crazy warning labels in Americas on things.
It's a totally reasonable use-case and is done all the time for a variety of reasons. It works just fine using an inverter like this one:
https://gpelectric.com/products/3000-watt-industrial-pure-si...
... and although we use a different emergency power solution now[1], we used an inverter like this with the plain old car battery in my Chevy Silverado for 5-6 years.
The issue is not that a 12v lead-acid battery can't be used for this - it's a common use-case, actually - it's that the backing store for that 12v battery is usually an ICE with a full gas tank and not a big bank of lithium batteries.
But I don't see why it wouldn't work just fine ...
[1] The excellent DEWALT FLEXVOLT Power Station which is a charging station for four 9AH tool batteries but you can also plug into it and get power out. So you use the batteries you already have for tools, you get a nice quad charger, and you have hours of 15A power out.
9 Amp-hours at 20 volts is .18kWH x 4 batteries is .72 kwh. Not bad (though far below Tesla's battery which may be 100x that).
A good car battery might be 40AH at 12 volts or .5kWH? But if discharge rate is high you get less capacity.
Someone running a 2kW inverter, is going to discharge the battery in 15 minutes. Then you add Peukert constant [1] of 1.2 or so? Maybe half that? Then you realize you need to stay above 80% DoD? Even worse? So a 2kW continuous load is CRUSHING this battery. A light bulb is 100 watts. any type of motor / blower etc is going to be what would be considered a high draw.
When a refrigerator starts you may also be load spiking.
All this could damage the charging circuit to the battery which was almost certainly not designed for this load story (hopefully not)
You may be discharging at a higher rate then the desired charge rate, so just keeping an AGM charged at high draws may wreck it.
Plug in a 20W charger? No problem, the math says that should be pretty easy to handle. A 2,000 watt inverter? Short burst? No problem probably. Continuous - probably going to be a problem as the user found out.
There's a reason everyone refuses to replace these batteries used this way.
[1] https://en.wikipedia.org/w/index.php?title=Peukert%27s_law
Note - I absolutely think Tesla should support this use case, a 100kwh battery pack in your house for when the power goes out would be amazing. The the HV pack could absolutely support house loads for most everyone. You've paid 60K for the battery and vehicle, what a use case that would be! But they'd need to a different path probably through charging cable and the regulatory hassle could be annoying - pushing a lot of power back into household circuits - the liability etc risks go up (but could probably wire as if it were a generator with a transfer switch and islanding etc)
The standard approach here is warranty doesn't cover the part you damaged through misuse. So if you stab the car seats with a big knife, they won't give you new seats, but that doesn't void whole warranty.
Some things do void entire car warranty, those are pretty standard as well. Things like salvage title, submerged in a flood etc.
Others void out powertrain warranty or larger areas, usually pretty logical (flash cars computer with a tune, race car and destroy engine probably one of the more common ones?) Even though just engine may be obviously destroyed, you might lose warranty for entire powertrain (clutch / transmission etc).
I didn't offer legal advice? I said based on my reading, it violates this act. Feel free to show where I am incorrect?
If you want to argue based on the merits of my argument vs saying "This is an only on HN comment", what would your thoughts be if Ford/Dodge/etc. void my warrenty because I idled my car and hooked up an inverter to my lead acid battery?
Let me 100% clear. If you kill your battery because you idled a car and hooked up an inverter then Ford will not cover this claim. That is misuse.
https://www.ford.com/cmslibs/content/dam/brand_ford/en_us/br...
"misuse of the vehicle, such a driving over curbs, overloading, racing or using the vehicle as a stationary power source".
Yes - you can do it. No, they do not have to pay for the damage you cause doing this. I've always known this.
This idea that you can do something that clearly caused damage in the linked article and then TESLA, not the owner of vehicle owes money is backwards.
A warranty covers use of the vehicle for intended purposes, not misuse. The user caused damage by misusing the vehicle, in fact, the very damage one would expect.
So I misread the article at first. This is not a person trying to hook up a power source to the primary Lithium Battery, it is someone hooking up an inverter to a 12v lead acid battery that their Tesla also has.
While I would agree that hooking up an inverter to the primary battery is one thing, voiding the warrenty for hooking up an inverter to the lead acid battery is entirely different, and I would be furious if a dealer tried to void a warrenty on my car based on a $100 car battery. I actually wonder if what they are doing is illegal under the Magnuson–Moss Warranty Act.
What likely happened is that the inverter deeply discharged the lead acid battery, tripping the flag in the car. As an FYI, what you can do if you do this occurs is bring it to an auto parts store, they can inspect your battery to tell you if it is still good, (this is usually a free service), recharge your battery (I have often got it for free, but sometimes it's like a 5$ fee), and if the battery isn't old, that will fix it.
EDIT: if you want to read the act, it is here: https://web.archive.org/web/20130317083941/http://uscode.hou...
But in reading here: https://apb-law.com/understanding-magnuson-moss-act-relates-...
I actually think what Tesla is doing is in fact illegal.