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Output of 2 x Powerwall 2?

Discussion in 'Tesla Energy' started by Siggy101, Sep 26, 2017.

  1. Siggy101

    Siggy101 Member

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    I am looking for some info from existing owners who have multiple Powerwall 2s or perhaps an installer.

    I am aware that the max output power of a Powerwall 2 unit is 5kW.
    I intend to have 2 x Powerwall 2s installed, mostly to provide adequate storage capacity for my electrical needs. Can anyone tell me if I daisychain 2 x Powerwall 2s, does that give me a max output of 10kW?
    I am trying to work out if I can run my 6kW electric water heater at the same time as charging my Model S at 4kW without drawing grid power for example.

    I have 240v 3 phase power to my house (I live in Switzerland) as well as 3 phase coming from my solar panels. Will I be able to get 3 phase out of the Powerwall 2s or do they just output single phase 240v?
    I currently charge my car using the UMC plugged into a 3 phase plug. I run that at 5A, 400v (technically 380v I think) 3 phase giving me 4kW on the screen in the car/app. I'd love to maintain 3 phase charging but am not sure if Powerwall 2 supports it.
     
  2. miimura

    miimura Active Member

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    I have only seen specs for single phase PowerWall 2. Your situation would be better served by a 3-phase PowerWall with a different built-in inverter. I would try to contact someone at Tesla in Europe to see if that is on their roadmap. In theory it should be possible to install one Powerwall on each phase, but that's a very big and expensive installation and Tesla may not have the software worked out for that type of installation.
     
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  3. Yinn

    Yinn Member

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    AFAIK, kW is a measure of quantity where as kWh is a measure of usage (quantity over time) So a single power wall has a storage capacity of 5kW, 2 powerwalls will have a total capacity of 10kW. So if your water heater runs for 1 hour, and your car is charging for that same hour, then you will consume 10kW over that hour and use the entire charge stored in the powerwalls (assuming no sun/recharging)
     
  4. miimura

    miimura Active Member

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    A single Powerwall 2 can output Power of 5kW and can store Energy of about 13kWh. So, 2x Powerwall units can output 10kW for 2.6 hours before they will be empty, assuming no other power input like solar generation.
     
  5. Siggy101

    Siggy101 Member

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    Thanks for sharing your thoughts.
    I will likely end up being lead by Tesla here in Switzerland. I was hoping for some real world experience but am aware that not many countries have 3 phase in domestic homes.
     
  6. Siggy101

    Siggy101 Member

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    Yinn. I'm afraid it's the other way around. KWh is the measurement of capacity (of which a powerwall 2 has around 14.6kWh). kW is what my question is about and refers to the speed at which it can empty that stored energy (putting it in crude layman's terms)

    Can anyone offer personal experience about whether combining multiple Powerwall 2s will result in increased output current?
     
  7. Siggy101

    Siggy101 Member

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    Miimura, are you sure that they multiple to 10kW?
     
  8. miimura

    miimura Active Member

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    Yes, they are independent 5kW sustained, 7kW peak inverters, so you can draw from two simultaneously for a total of 10kW.
     
  9. Siggy101

    Siggy101 Member

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    Perfect. That is just what I wanted to confirm.
    So I may not be able to maintain 3 phase charging but if I can get 10kW on a single phase then that will do the job nicely.
    I'll need to plan the installation carefully then. It looks like it's impossible to cover the whole house seeing as it's split over 3 phases but at least I can get the electric water heater and the garage circuit on the phase with the power walls on.

    I'm not sure how I will get all of the solar to charge the powerwalls considering it's outputting on 3 phases but I'll cross that bridge when I come to it.

    Thank you!
     
  10. miimura

    miimura Active Member

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    #10 miimura, Sep 26, 2017
    Last edited: Sep 26, 2017
    If I were in your situation, I would wait for a proper 3-phase solution. It's a big investment and it would be best to get it right the first time.
     
  11. Zythryn

    Zythryn MS 70D, MX 90D

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    This is not the information I have been given.
    Now, it may be because of me using the Power Walls for backup and not daily use.
    In our application, multiple PWs will add capacity, but not output.

    This is in the U.S. though and configured for backup power. So it may not be applicable to the OPs situation at all.
     
  12. miimura

    miimura Active Member

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    I am not going by what salespeople say, but rather experience of owners that actually have a pair of Powerwalls installed.

    [​IMG]

    This image is from a post by @Ulmo in the Powerwall 2 "waiting list" thread.
     
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  13. Zythryn

    Zythryn MS 70D, MX 90D

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    Interesting, thanks.
    My information is not from a salesperson, but an installer.
    I am leaning more towards the difference being because of a different configuration.
     
  14. Ulmo

    Ulmo Active Member

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    #14 Ulmo, Sep 26, 2017
    Last edited: Sep 26, 2017
    I'm going to make up answers that sound good and might be halfway right, basically guessing. Basically, this is for entertainment value only. Keeping that in mind, here's what I have to say:
    • 2 PowerWall 2's in Europe output 10kW in 3 phase power (I do not know this; I guessed it).
    • Therefore, you can draw 10kW and not use grid power. (not really guessing)
    • By the way, you'd draw grid power for anything over the 10kW, such as any other loads (guessing).
    • The peak power output is 7kW each, so I think for spikes and such. (guessing)
    Here's what actually happens in USA where everything is one phase with a midway point "neutral" line (i.e., inferior to Europe), and are not guesses:
    • 2 PowerWall 2's in USA output 10kW in 1 phase power (240VAC).
    • Therefore, you can draw 10kW and not use grid power.
    • You'd draw grid power for anything over 10kW, such as any other load. (guessing with respect to spikes below.)
    • The peak power output is 7kW each, so that's basically for spikes and such. (guessing)
    Ok, I'm excited to see what @miimura mentioned me for since I seem so useless.
     
  15. Ulmo

    Ulmo Active Member

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    #15 Ulmo, Sep 26, 2017
    Last edited: Sep 26, 2017
    Correct, if by quantity you mean quantity at an instant.
    Incorrect.
    Correct.
    In USA, PowerWall 2 can do 5kW output (7kW peak) and has ~14,400Wh when new, going down with age. Input is somewhere between 3kW and 5kW. You can see at least around 3kW input at Ulmo.Solar (represented by 3kW * 2 = ~6kW, since you can see some days with almost 6kW solar input). Two PowerWall 2's (USA) have ~28,800Wh when new (spec is around 13.5kWh - 14.3kWh per battery), going down with age. You can charge them at least 6kW and maybe 10kW (I don't know; I think it's closer to 3kW each). Output is up to 10kW (from the pair), no problem. Here's proof:

    Clearly shows 6,000W charging for half a second:
    powerflow.7982.png
    Zoom in:
    powerflow.4563.png
    Experiments I was doing resulted in this, showing max 10kW continuous power draw:
    powerflow.19529.png
     
  16. Ulmo

    Ulmo Active Member

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    #16 Ulmo, Sep 26, 2017
    Last edited: Sep 26, 2017
    This is way more logically accurate than my entertainment-only guesses in my first answers, even though we're both basing our conclusions (of various calibers) on incomplete information.
     
  17. Ulmo

    Ulmo Active Member

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    I am 99.8% certain you were lied to.
     
  18. Ulmo

    Ulmo Active Member

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    Wow, that's cool! I wasn't sure if it could do that. I am so forgetful. That's why we sometimes build flow charts to save information since our brain gets full.
     
  19. Ulmo

    Ulmo Active Member

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    #19 Ulmo, Sep 26, 2017
    Last edited: Sep 26, 2017
    Installation specifics come with infinite variety for the Tesla PowerWalls. What you said is plausible. It would squeak in my 0.2% uncertainty level.

    Let me try to be more useful: the usual capability is that you get x PowerWalls with x * 5kW continuous and x * 13.5kWh storage. If x is 3, that would be 15kW with 40.5kWh. If x is 10, that would be 50kW with 135kWh.

    10 PowerWall 2's would be around $75K to install, with large variations due to building space and electrical work needed. I could foresee it for a large house with 3 long range EV's and enough solar to match all usual use plus surplus, or for an off-grid setup of one third that size usage but about the same solar and battery. Most homes that want a modicum of usual usefulness with grid to fill in gaps would want about 3-4 PowerWall 2's, with smaller homes getting away with about 2 (and only tiny houses that a single person would hardly call normal even for only one person in most of USA would find 1 acceptable). Right now, because of cost and some welfare programs, you can subtract about 1 from that usual estimate (since most people can't shell out $27K for 4 PowerWalls when 3 would be almost as good, and so on down the line, and the welfare programs max is usually 2, but more if jumping hoops).
     
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  20. Zythryn

    Zythryn MS 70D, MX 90D

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    Thanks!
    In my case, it really doesn't matter as 5kW output will handle the power needs of our backup panel.
    In our case, I don't plan to charge the cars while on backup and 5kW will cover our fridge, HVAC and a few lights and outlets.
     

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