Using a Tesla to power your freezer in a power outage.

[PhysicsGuy]

I know there are other posts related to this and I have read quite a few of them. This idea of this post is to focus on how one can set up to actually use a model 3 to power a freezer for a few days, or even a week, during a power outage. There are two possible ways to approach this that I know of and I would love to hear discussion of which way is best and why, as well as the drawbacks or risks associated with either way. To be clear, this is not V2G; the goal is simply to have an extension cord running from your parked model 3 to your freezer (and/or refrigerator). I am thinking some of the key questions are where to do it (in the frunk or the back seat, for example), how to do it (what inverter to use...?) and also: is it a good idea at all? What are the drawbacks, pitfalls and risks.

As I understand it, and I am a fairly new model 3 owner without a long history of Tesla experience, in the model 3 there are two places where one can tap into power. (I am leaving out the 12 V adapter in the console since it is fused way too low). One is in the frunk by connecting directly to the 12 volt battery. The other, I believe, (hoping someone can confirm or dispel this) is under the back seat where there are some power taps? Is this true?

Once a location is chosen, I believe one could connect an inverter that converts 12 volt dc to 110 AC. I don’t think that puts too much load on the traction battery, but it could make the dc to dc converter work pretty hard, and I wonder if that could lead to a failure of the dc-dc converter at some point. I don’t know if the car would have to be “on” for this to work. I am thinking not, since the traction battery will charge the 12 volt battery as needed even when the car is parked and locked. Does this seem like a reasonable choice for the inverter*? Would one need fuses in the install? Would love to hear the ideas of people here with thoughts and maybe experience with this endeavor.

Regarding the energetics, I think a typical modest freezer draws about 5 amps at 110 volts and runs about half the time. The total energy per day would be about 500 watts x 12 hours, that is, 6 kWh, which is about 10% of the capacity of a long range model 3 battery. So it seems like one could do this for 5 days with a parked car and in that time go from 90% state of charge (SoC) on the traction battery to about 40% SoC. That seems reasonable to me. The current draw on the traction battery is more than an order of magnitude less than freeway driving, so even if it technically voids the warranty, that is not a warranty I expect to use since I keep my battery mostly between 20 and 80% (and I imagine it will outlast the warranty.)) This use would not harm the traction battery in any way I can see. On the other hand, the dc to dc converter (which takes the roughly 360 volts of the traction battery and drops in down to 12 volts) would be working pretty hard. Would the dc-to-dc converter overheat? I have seen some discussion of issues associated with the circuitry around the dc-dc converter and would love to understand that better. Is it designed to or able to handle that sort of semi-continous use? Is there something that limits the current?

So just to summarize: a few questions:
1.Would you do it?
2. How would you do it?
3. Can the dc-to-dc converter and its circuitry handle this?
4. Is the 1500 watt Cantonape a reasonable choice? Is that an appropriate size? Any reason to go bigger? Any reason to go smaller? Any reason to choose pure sine wave or a different type of inverter?
5. Should there be external fuses? How would you install those?
...
…

*Cantonape 1500W/3000W(Surge) Car Power Inverter 12V to 110V AC with LCD Display

 

[smatthew]

Oh no. Stay away from the modified sine wave inverters.
Your assumption about power usage is wayyyy high. A typical freezer uses 35 watts on average, and about 350watts when running. But you really need to find out the details on the freezer or fridge you plan on powering. Buy a Kill-A-Watt and see how much power yours uses when running.

 

[PhysicsGuy]

Oh no. Stay away from the modified sine wave inverters.
Your assumption about power usage is wayyyy high. A typical freezer uses 35 watts on average, and about 350watts when running. But you really need to find out the details on the freezer or fridge you plan on powering. Buy a Kill-A-Watt and see how much power yours uses when running.

350 watts is about 3 amps, so I think we are in about the same range and reaching the same conclusion (that is will work from an energy point of view). More importantly, why stay away from a modified sine wave inverter? I thought that only mattered for sensitive electronics and wouldn't really make a difference for the capacitor/compressor components of a freezer?

 

[jjrandorin]

I know you say "I have read a lot of threads", but have you read this one?

Powerwall 2.0 Backup Runtime Extender

To answer the thread question "would you do it?" my answer was "no" which is why I bought Tesla powerwalls to accomplish a proper backup.

I was not interested in the slightest in using my car battery that way, but understand others feel differently

 

[PhysicsGuy]

I know you say "I have read a lot of threads", but have you read this one?

Powerwall 2.0 Backup Runtime Extender

To answer the thread question "would you do it?" my answer was "no" which is why I bought Tesla powerwalls to accomplish a proper backup.

I was not interested in the slightest in using my car battery that way, but understand others feel differently

Yes, I have seen that thread. Thanks. That looks different and much more difficult than what I am suggesting for discussion here.

 

[Tam]

...
1.Would you do it?..

No. That's because I am not handy and my knowledge is limited.

...One is in the frunk by connecting directly to the 12 volt battery...

Tapping directly to 12V battery (such as very low power usage dash cam or higher woofer amplifier usage...) used to be fine for Roadster, S and X... until Model 3 came out, then your 12V battery will be dead prematurely with all the S, X, 3, Y (I guess the Roadster is too old to upgrade its characteristics to Model 3's) ...

...under the back seat where there are some power taps? Is this true?...

Yes.

There's High power access there as well as 12V DC to DC converter there.

Don't ask me how because I don't want to mess around that stuff.

I would suggest accessing through your cigarette lighter outlet and use low power usage appliances for the rating (there are 12V freezers too).

Or if you can wait for CyberTruck that will have 240V outlets for construction tools.

 

[Watts_Up]

Yes, I have seen that thread. Thanks. That looks different and much more difficult than what I am suggesting for discussion here.

You could also review the following postings #125 1nd #127 Is it safe to connect a large inverter to the 12V battery?

Do you have an idea of how much current the freezer needs when starting?
You might consider adding some capacitor to absorb the peak current.

A safer approach would be to connect the freezer to a portable battery generator,
And to use the Tesla 12 V battery to charge this specially designed generator.
See the following video:

 

[Sophias_dad]

Perhaps the very first sticky thread under batteries and charging would help, since its describing how to do it in detail.

MASTER THREAD: Powering house or other things with Model 3 12V battery

 

[smatthew]

350 watts is about 3 amps, so I think we are in about the same range and reaching the same conclusion (that is will work from an energy point of view). More importantly, why stay away from a modified sine wave inverter? I thought that only mattered for sensitive electronics and wouldn't really make a difference for the capacitor/compressor components of a freezer?

Modified sine wave will cause the freezer compressor to work less efficiently, create more heat, and potentially shorten the lifespan. A good inverter is a one-time purchase. Why purchase an inverter that won't work well with everything? For instance - what happens when someone wants to charge their laptop while the power is out? Don't try that with a modified sine wave.
There are freezers out there that will work on the Morningstar SureSine 300. Very efficient little inverter.

 

[jerry33]

1. Would you do it? No. It will void the warranty on your Tesla. Potentially much less expensive to purchase a Powerwall.

 

[Ritz]

1. Would you do it? No. It will void the warranty on your Tesla. Potentially much less expensive to purchase a Powerwall.

Indeed...or just invest in one of the lower-end whole home generators and automatic transfer switch. After a couple of multiple-day power outages (I live out in the country), I ended up doing that. So I've got juice for up to about 2 weeks in a pinch (when my propane supply would run out). Seems silly to risk damaging an expensive car when there are better alternatives available. I find this akin to jury rigging a gas car up on blocks with a belt attached to an alternator. Can it be done? Sure. Does it make sense when you can just buy a generator? No.

Best,

 

[electrongeek]

While this could work fine, and I would do it myself in a pinch, it makes a hell of a lot more sense to buy something like a Honda Eu2200i portable generator for about $1100 to run your freezer, refrigerators, and a few other minor loads like LED lighting. Obviously you could go a lot cheaper and get more power if you don't want an inverter generator, but that little Honda is a sweet solution with a very clean sine wave output. I actually run two refrigerator/freezers off a little Eu1000i which I bought to keep on my sailboat for emergency battery charging. It can just handle the startup load of each appliance, but once running it gets about 8 hours on 1/2 gallon of gas. The Eu2000i costs little more, but is twice as heavy at 53 lbs.

 

[Silicon Desert]

350 watts is about 3 amps, so I think we are in about the same range and reaching the same conclusion (that is will work from an energy point of view). More importantly, why stay away from a modified sine wave inverter? I thought that only mattered for sensitive electronics and wouldn't really make a difference for the capacitor/compressor components of a freezer?

I'm thinking something similar regarding Wattage. In fact, our deep freeze (5 cubic feet) only draws 70 Watts average when running, and peaks of 150 Watts. Even our large refrigerator in the garage draws only 90 Watts and peaks at 130 Watts. Maybe older equipment draws more, but newer appliances are much more energy efficient. I also don't get the problem of sine wave inverters on appliances.

Edit: While I'm on the subject, I guess I'll say that clearly different people have different goals. For me, I want to do just the opposite. I want a way to charge my car during an outage as needed, as well as power important parts of the home. I looked at getting a Powerwall, but for less than the price of a Powerwall (with limited amount of power), I was able to get a whole house generator that comes on automatically as needed.

 

[Ritz]

Edit: While I'm on the subject, I guess I'll say that clearly different people have different goals. For me, I want to do just the opposite. I want a way to charge my car during an outage as needed, as well as power important parts of the home. I looked at getting a Powerwall, but for less than the price of a Powerwall (with limited amount of power), I was able to get a whole house generator that comes on automatically as needed.

That's a pretty expensive solution for charging a Tesla car battery. If my 20kw generator was used exclusively to charge a flat Tesla 3 battery, it would use about 12 gallons of propane and cost about $24. Charging from the grid @ 11 cents a kilowatt hour only costs $8.25. So unless I was really in a pinch for juice for the Tesla, I'd probably wait for power to be restored or just charge it enough to get me to a supercharger.

Best,

 

[PhysicsGuy]

Modified sine wave will cause the freezer compressor to work less efficiently, create more heat, and potentially shorten the lifespan. A good inverter is a one-time purchase. Why purchase an inverter that won't work well with everything? For instance - what happens when someone wants to charge their laptop while the power is out? Don't try that with a modified sine wave.
There are freezers out there that will work on the Morningstar SureSine 300. Very efficient little inverter.

Fair enough. I changed to pure sine wave.

 

[PhysicsGuy]

Looks like I had overlooked that MarcMerlin and company kind of solved all this on the master thread...

 

[Silicon Desert]

That's a pretty expensive solution for charging a Tesla car battery. If my 20kw generator was used exclusively to charge a flat Tesla 3 battery, it would use about 12 gallons of propane and cost about $24. Charging from the grid @ 11 cents a kilowatt hour only costs $8.25. So unless I was really in a pinch for juice for the Tesla, I'd probably wait for power to be restored or just charge it enough to get me to a supercharger.

Best,

Good point if your energy for a generator is expensive. For me, it isn't. You might be misunderstanding my reason to have a backup generator. It is not to charge the Tesla. It is for emergency power to the home. BUT, if I needed to charge he Tesla during an outage, I could do it at reasonable cost. Mine generator can use natural gas or propane, and LPG is cheap for me. I could do the same charge you are talking about for $14 if needed. Electricity is even cheaper at under 9 cents KWh. So bottom line, I guess it depends on where you live. Of course, that is just in case of emergency. It costs me about $6.50 to fully charge my X.

 

[Ritz]

Good point if your energy for a generator is expensive. For me, it isn't. You might be misunderstanding my reason to have a backup generator. It is not to charge the Tesla. It is for emergency power to the home. BUT, if I needed to charge he Tesla during an outage, I could do it at reasonable cost. Mine generator can use natural gas or propane, and LPG is cheap for me. I could do the same charge you are talking about for $14 if needed. Electricity is even cheaper at under 9 cents KWh. So bottom line, I guess it depends on where you live. Of course, that is just in case of emergency. It costs me about $6.50 to fully charge my X.

You must be getting a VERY good deal indeed. The average price for residential propane in the US right now is between $1.90 and $2 per gallon. I got my generator for the same reasons. Quite liberating.

Best,

 

[Silicon Desert]

You must be getting a VERY good deal indeed. The average price for residential propane in the US right now is between $1.90 and $2 per gallon. I got my generator for the same reasons. Quite liberating.

Best,

Oh, just to clarify, I don't use propane. I use the natural gas line that comes into the home to power the generator, and yes, it is much cheaper here also. I could use propane as an alternative, but haven't done that.