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MASTER THREAD: Powering house or other things with Model 3

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The Tesla 3 battery is thought to be a 365 VDC battery. That is interesting as the Model S and X batteries are thought to be 20 to 30 VDC higher.
I don't think I have heard what the voltage level is on the Model 3 batteries, but I know that the Model S/X batteries have come in two varieties, with the lower capacity ones being 350V and the bigger ones being 400V.

350V battery nominal sizes:
60, 70, 75

400V battery nominal sizes:
85, 90, 100
 
When I changed the pyro fuse I measured the voltage from the pyro fuse to the negative terminal and then to the positive terminal. They were about -170 VDC and +170 VDC. The pyro fuse is then in between the two half of the battery in series. They were not exactly the same. I didn't write it down. I think the battery was about half charged and the total was about 350 VDC. So 365 VDC would then make sense.
 
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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
Very nice writeup Marc!

Questions on the trickle charge of the 12V battery - is that trickle charge ever increased when the car is running or in camp mode or similar? trying to figure out why the DC-DC invertor would support 2000-3000W without more power going to the 12V battery at times.

Also if you were powering a fridge that cycles occasionally, would that work via the 12V battery with the slower charging/top off? or is that pulling the SoC of the 12V down too much?

EDIT - I saw the text about the inverter capacitor drawing enough power to trip the DC-DC "fuse"; could you 'precharge' the capacitor by hooking it to a 12V battery on a gas car (one that is running maybe), and then move it to the Tesla? I'm assuming the capacitor won't instantly lose power.

Thanks..
 
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Very nice writeup Marc!

Questions on the trickle charge of the 12V battery - is that trickle charge ever increased when the car is running or in camp mode or similar? trying to figure out why the DC-DC invertor would support 2000-3000W without more power going to the 12V battery at times.

Also if you were powering a fridge that cycles occasionally, would that work via the 12V battery with the slower charging/top off? or is that pulling the SoC of the 12V down too much?

EDIT - I saw the text about the inverter capacitor drawing enough power to trip the DC-DC "fuse"; could you 'precharge' the capacitor by hooking it to a 12V battery on a gas car (one that is running maybe), and then move it to the Tesla? I'm assuming the capacitor won't instantly lose power.

Thanks..

I guess the 12V system is designed so that most loads take power direct from the DC/DC converter. Very little is pulled from the 12V battery, so there isn't much need to charge it any faster than 6A.

You might be able to use a 12V inverter with a remote start capability to reduce the inrush current. I'd have to check, but I've never seen mine spark when hooking it up to a 12V battery. It has an on-off switch and the capability to wire it up to a remote switch. A simple RC circuit could be added that would automatically turn it on a few seconds after the 12V DC/DC comes on to prevent inrush current, if your inverter has a 12V remote control input. That could eliminate the need for the extra relay.
 
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Marc, that was quite a report. Why did you choose this method rather than hooking up directly to the main battery? With your knowledge you have probably worked with power systems and connecting to the main battery directly should not be a daunting task. That is not for beginners but you are definitaly not a beginner. I would be afraid to work with the DC to DC charger because I wouldn't want to take any chances like the large current draw due to the capacitance, a total surprise! The computer system in a Tesla is so complex that probably only Tesla should mess with it unless you want to make it your life's vocation. I have already screwed up my port module so that I can't charge my main battery by removing the rear tailight ground which also unhooks the ground to the port module, under power. It still has power after the 12 volt battery is disconnected, surprise! A 400 VDC to 120 VAC inverter is inexpensive. However, my Tesla is so expensive and I think a litttle fickle, so a gas powered generator is my choice. A Honda is so quiet and easy to start, that is my choice.
 
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Marc, that was quite a report. Why did you choose this method rather than hooking up directly to the main battery? With your knowledge you have probably worked with power systems and connecting to the main battery directly should not be a daunting task. That is not for beginners but you are definitaly not a beginner. I would be afraid to work with the DC to DC charger because I wouldn't want to take any chances like the large current draw due to the capacitance, a total surprise! The computer system in a Tesla is so complex that probably only Tesla should mess with it unless you want to make it your life's vocation. I have already screwed up my port module so that I can't charge my main battery by removing the rear tailight ground which also unhooks the ground to the port module, under power. It still has power after the 12 volt battery is disconnected, surprise! A 400 VDC to 120 VAC inverter is inexpensive. However, my Tesla is so expensive and I think a litttle fickle so, a gas powered generator is my choice. A Honda is so quiet and easy to start, that is my choice.

I think the reason is that you can only get 6A out of the 12V battery charger, so you can only draw less than 6A continuous. Otherwise, the 12V battery will be discharged.
 
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The DC-DC converter must run the heater, airconditioning, seat heaters and some auto computer mondules that draw high 12 volt current. Then I wonder why Tesla needs the 12 battery at all.

HVAC is run from the high voltage.

The 12V battery powers the computers when the car is asleep. The contactors open, disconnecting the HV battery from the car whenever the car is off / asleep.
 
@marc

Nice write-up and project! The overhead to keep the car awake 24 hours a day would be about 5 to 6 KWH that is about half of what our entire house used before we purchased two plug in cars. Since my car seems to be awake for 4 to 5 hours a day when parked, that would be enough to keep a fridge or freezer cold enough and reduce the overhead. If I remember my testing a few months back, a change was made in the firmware that keeps the car from sleeping if the frunk is open.

I installed a quick disconnect on the Negative terminal of the 12V battery on my Model 3 and if you loosen the knob about one revolution the car will be in storage/coma mode after it falls asleep (and will not re-awake up until you tighten the knob) .

A electrical engineering friend of mine interfaced a 34VDC? solar charging system for his 2014 Volt to charge his cars HV battery. He is basically doing a DC-to-DC step up instead of a step down. Not sure how he tackled the HV danger in his design. Be nice if there was a way to use Tesla'a DC-to-DC step down to 12V wherewithal and not have all the overhead associated with a fully awake car but doing so could possibly void the warranty and get you blacklisted for any form of DC fast charging.

Tesla can infer what we do to the car via the logs and could even ask your friends to rat on us. Since I have worked on and modified my cars my entire life, I am not sure how I feel about being monitored.
 
Also, blackouts are going to be the new norm in California - better stock up on Solar and whatever kind of batteries (people use USED Tesla batteries, probably from salvage cars, to power their homes sometimes).

PG&E didn't cause the wildfires, but they got sued and bankrupt anyways. Now they need to either put all their lines near trees underground or turn off the power.

Maybe this will be California's big push towards Solar + Batteries.
PG&E did cause most of the fires due to poor line maintenance. That is why thy are in bankruptcy.
 
I'm still confused as to why you'd need to hook in under the rear seats. Every "power from EV" article or video I've ever seen has a 2k or 2500w inverter wired up to the 12v battery terminals. Prevent the car from going to sleep and you have 2000+w continues available, since the HV battery is constantly recharging the 12v battery.

I see people easily running HVAC system for days with these setups, and multiple articles claim the 3 can handle almost 3000w continuous if tapped in at the 12v terminals. The CLA port is limited to about 150w max as it is in almost every other car.

Where does the rear seat plug come into play, I just don't get it.
 
Note: None or very little of what I am about to discuss has been confirmed by me.

There is a fairly large red cable running directly from the DC-to-DC penthouse port located under the passenger side rear seat to the 12V Power Distribution Center PDC module mounted near the middle of the firewall in the frunk area. There appears to be a somewhat smaller red cable running from the PDC module to the positive 12V battery terminal. From what I have read in other forum posts, it appears the maximum current delivered to the posts of the 12V battery might be limited to around 6 amps. Not sure if the current delivered to the 12V battery is software fused inside the PFC module? There might also be two current paths to/from the 12V battery that could be software fused independently inside the PDC module?

The 12V cigarette lighter outlet is software fused to around 15A but is only powered when the vehicle is awake and the DC-to-DC converter is active; therefore, it appears more continuous power can be provided from the cigarette lighter port than can be attained from the posts of the 12V battery? If you want to pull more current than 15A, then you need to attach directly to the 12V port located under the rear seat. The power from this DC-to-DC connection point is also only available while the vehicle is awake.

I have monitored the voltage and current at the 12V battery post terminals during sleep and awake modes with interesting results. When the car is asleep, the current draw is only about 0.15A of less. When the car initially wakes up, the current draw is around 0.9A but drops down to around 0.7A after only a few minutes. Not sure why the 12V AGM battery charging current is so low? The car appears to wake up when the voltage at the 12V terminals is around 12.7V so the depth of discharge DOD is approx 12.5%. With this DOD. the battery should have enough cycles to last four plus years.
 
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I'm still confused as to why you'd need to hook in under the rear seats. Every "power from EV" article or video I've ever seen has a 2k or 2500w inverter wired up to the 12v battery terminals. Prevent the car from going to sleep and you have 2000+w continues available, since the HV battery is constantly recharging the 12v battery.

I see people easily running HVAC system for days with these setups, and multiple articles claim the 3 can handle almost 3000w continuous if tapped in at the 12v terminals. The CLA port is limited to about 150w max as it is in almost every other car.

Where does the rear seat plug come into play, I just don't get it.

The architecture of the model 3 seems to be different. It seems they have separated all of the large 12V draw items from the 12V battery. Those get powered directly from the DC/DC converter. Only some very small number of things are actually powered from the 12V battery, so therefore they don't need to provide a large charging current to the 12V battery.

It's a better design, in that it minimizes load on the 12V battery and the number of charge / discharge cycles. We should see the Model 3 12V battery last much longer than it does on the Model S/X. But, the downside is that you can't draw much power from the 12V battery. You have to go direct to the DC/DC converter to get high current, 12V power.