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Yeah, I couldn't find good info on that. However my main concern is you'd be constantly discharging the battery while the car is running and it'd be constantly trying to charge it. As long as the charging system stays on all the time, current should pass through and you should be fine. But there...

My guess is that you should be fine. I'm pretty sure there is some circuit between the DC-DC bar and the standby battery and therefore you can't just pull a bunch of amps, but 8A should be fine while the car is awake. The car will tell you if the standby 12V battery is dipping too low (although...

Fair point. I made sure the inverter ground was not connected to the negative. I was worried about the DC-DC positive shorting to the chassis anywhere, so I connected it directly to the inverter and taped it carefully :)

There is indeed no right answer on the resistor. You want it as big as possible to slow down the current, but not too big that the relay won't close. This is totally specific to your inverter in your relay, That said, 100 ohms is probably a good place to start (I initially had 1 Ohm and it...

err, isn't it exactly what I'm doing? :)

Inverters have a big capacitor on the 12V side. Capacitors can take mostly infinite current (1000A or more, whatever your wire will allow). This will cause a massive spark every time you connect to a battery. The battery does not care, but the DC-DC in the car does, and it will shut down. So...

Ok, since I can't edit the first message, and my solution is now hidden in the middle of the thread, I'll post it here again: Marc's Blog: electronics - Using a Tesla Model 3 as Emergency Power Source In Case of Grid Failure

I feel ignored :) First, 10 messages to tell me that the DC system cannot be bidirectional when it's the AC system that isn't, and then I wrote twice already that you'd need a battery-less powerwall at home. Powerwalls use 400V-ish, so clearly those inverters exist and are as common as...

Please don't get things mixed up. I am not talking about AC charging, please re-read what I wrote. I am talking about DC charging which can now be done at 250KW, which at 400V is 625Amps peak (it used to be 400A peak, but that was raised recently). I'm surprised that they have enough diodes to...

Ok, fair enough, thanks.

Just to be super clear, are you sure the diodes are on the 400A DC bar? You need some big ass diodes for 400A, and doesn't the video say that the DC current can flow backwards for pre-heating the system when you are driving to a supercharger? Actually, sorry, 250kW for the new superchargers is...

I understand the car cannot generate and output AC, but the DC can be run backwards, can it not? If so, as I wrote earlier, you could get DC from the charge port, and plug that into a battery less powerwall that would convert that DC back into AC and sync up with the AC from your house. Or am I...

you don't need a two way inverter, as long as you can get DC out of it from the charge port, that's enough to plug into some battery-less powerwall and do V2G

Are you sure? Tesla poised to unlock vehicle-to-grid abilities with 'bi-directional' charging systems says "There's logic to allow DC to flow out the battery pack. So you can supply an external grid-tie invertor with that and let it do the rest of the magic. Making it part of the HPWC would make...

You can easily run a 120/240V extension cord out of the door with the door closed. My car is in my garage though, so I don't care either way :)

You summarized correctly, you can only get 200A from under the seat, the frunk battery is definitely behind a low amp charge controller and should not be used for anything more than a few (<5) amps for any extended amount of time. As for wiring, I put the inverter in front of the right...

do you know what fuse it's connected to? how many amps? by connecting to the DC-DC under the rear seats, you get 200A :) Marc's Blog: electronics - Using a Tesla Model 3 as Emergency Power Source In Case of Grid Failure

Nice build, you don't screw around :) Given that I may very well never actually use my build (i.e. a real half or multi day power outage), I didn't work too hard on mine past what I posted, but about the resistor, I found out that my inverter, would sometimes charge too quickly even with the...

Correct, that's why my system is overbuilt, but the question was about overheating over time. Transient load over a few seconds won't cause significant heating as you know :)

The tesla DC-DC does not have a fuse that blows, it's a self resetable circuit. I'm not sure how many times it will self reset, but I'm assuming a fair amount. Putting a fuse in front is fine, as long as you have a stack. Given that the system is rated for 200A, you can put 4 of those fuses in...

To answer your questions: 1) I imrproved the wiring to reduce the voltage drop 2) yes, there is a loss of efficiency 3) no, I didn't calculate it end to end, nor do I care :) This is not a design for long term use, but emergency use 4) I ran my fridge and a 100W light bulb for multiple hours to...

You should be fine as long as you have a fast blow fuse and the car is a slow blow fuse (which is likely true).

It shuts down at the same time than the 200A DC-DC system, so you have to keep the car awake with sentry mode or camper mode or something like htat.

I'm not sure you can even pull 6A full time from the model 3 battery, I didn't measure carefully, but I believe the battery recharging system isn't even meant to provide that much power. You'll get more power (10A+) from the cigarette lighter adapter. Unkel, ok, model S, sure. It's totally...

OMG, no you cannot. Please read the thread, this has already been answered.

That's what I've read, and I've gotten 120A from it in a test, so I'm willing to believe it'll do around 200A

which fuse are you referring to? The DC-DC converter is supposed to output 200A (not sure if that's continuous) and definitely does not have a 50A fuse, I've drawn 120A from it already. I'm talking about a model 3. I'm not sure which car you're talking about and where the nose cone connector...

A few years later, I repeated Matt's "excellent idea" of tracking a stock non performance model 3 with aero wheels (really it's not, it's stupid, but it was fun to try anyway): 4 laps with my Model 3 at Laguna Seca, 2 1.55 laps with toasted brakes...

Oh, thanks Oh, thanks for that warning. To be honest, I wasn't seriously considering backfeeding my house due to how many sharp edges there are in doing this, but very interesting to know that inverters would do a weird things like putting neutral at a different potential than ground. Is that...

it is not directly connected to the battery in one direction (it can feed it via a trickle charger), but battery cannot feed back to the points I connected to. I have verified voltage drops to 0 when the car shuts down, which is good even that I would not want my inverter to ever be powered by...

If you are connected to the DC-DC system, you aren't connected to the battery (which is good). When the car goes to sleep, the DC-DC feed under the back seat, turns off. My solution works as long as you can keep the DC-DC on, which can be done with camper mode or other ways. I'm just interested...

i ended up doing a writeup of the work I did in case it's useful to others: Marc's Blog: electronics - Using a Tesla Model 3 as Emergency Power Source In Case of Grid Failure

I wrote a summary of my work here: Marc's Blog: electronics - Using a Tesla Model 3 as Emergency Power Source In Case of Grid Failure

So, I have an half unsolved question: what is the most battery efficient way to keep the DC-DC converter running? Camper mode with AC off, a low temperature, and fan on 1, seems to be the best I found so far. Ideally there should be a way to keep the DC-DC on while having the computer screen off...

So, I have an half unsolved question: what is the most battery efficient way to keep the DC-DC converter running? Camper mode with AC off, a low temperature, and fan on 1, seems to be the best I found so far. Ideally there should be a way to keep the DC-DC on while having the computer screen off...

I started this route for my project and I can confirm that on model3, the car only the charges the battery at a low rate. If you are using more than a few amps, the battery will actually discharge more quickly than the car can recharge it. This doesn't work in either direction: 1) the CLA as...

Two other related threads: Aftermarket Sub-woofer Amplifier Installation using DC-DC +12v Power Source MASTER THREAD: Powering house or other things with Model 3 12V battery

Thanks for posting me on yet another thread on the same topic. What I learned while doing my project is that the DC-DC system is a bit finicky in that it doesn't handle spikes like a battery would, and that may be a reason why Tesla doesn't want you to mess with it (although it was pretty well...

Sorry, what I wrote was indeed wrong in the details. They do allow you to store solar and use it at night, but it's stupid to do price-wise (i.e. you're losing money by not sending back solar to the grid), and by "you can't do TOU arbitration", I did mean that you can't charge your powerwall off...

To close off that discussion on this thread too, please go to How many amps can you get from the 12V system for emergency situations? for how I made it work. I now have a 2000W inverter that powers on and off at the same time than the car DC-DC system, without the big current inrush that was...

Here's what I did: I used this 2000W pure sine wave inverter: https://www.amazon.com/SUDOKEJI-Inverter-2000W-Display-Outlets/dp/B07RWHN22W/ref=sr_1_1 200A 12V relay: https://www.amazon.com/gp/product/B01MYPTVJD/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1 100W 1.8Ohm...

Did you disconnect the 12V from both sides? If you only disconnect the battery, the DC-DC will keep the car alive from the other side. If the DC-DC trips, or you disconnect it from under the rear seat, and then you also disconnect the battery, the car's computers have no power and absolutely...

Interesting, I didn't think about those, but I am dealing with 200A, I'm not sure a few of those, even in parallel, are going to do the trick. (3000W inverter at 12V is actually 250A) Other people who worked on this talked about a bypass relay once the inrush is over, and honestly you need a...

Thanks. It's a long document, what part was what actually helped? I'd think that if you disconnect 12V from both sides (battery and DC-DC side), the car should fully lose power and forget the old battery. Are you sure that it's not enough?

How is your battery? Did you keep driving around for months with the "replace battery" prompt? If you didn't replace it, try this: 1) unplug it from the car entirely 2) recharge it with a regular charger 3) plug it back in The car will hopefully detect it as a new battery and should not give you...

You are talking about a Model S, not a Model 3, correct? As stated earlier, I tried an 85W load with a cheap small inverter, and is was just around 7A. Even with that, the battery was discharging faster than it was recharging, even when I removed the buffer battery that you say is the cause of...

Kind of, read on :) Ok, so I hear and understand everything you're saying but it seems that model3 is clearly limiting the charge going to the buffer 12V battery. From what you're saying, I should just be able to drain 10A from it with a small inverter, and it should get topped off quickly...

Hi Jamie, thanks for your post on the 12V DC-DC use. I'm not sure if you get a notification on replies, but if not, could I ask you to look at https://teslamotorsclub.com/tmc/posts/4320260/ ?

Out of curiosity, how does the car decide the battery needs replacing? Is it possible it see this from a low voltage once even though the battery is good? If so, can that condition be reset to let the car verify if the 12V battery is truly going bad, or whether it was a temporary condition...

I'm not going to fork this thread on powerwalls since I specifically said I was not interested in them, and knew why I was not, but in a nutshell, at least in California, PG&E does not allow you to do time of use shifting during a powerwall and storing solar into a powerwall to use it at night...