Interesting... that answers my question about a 'whole house' UPS application, if so!
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Tesla Energy/Solar City idiots
- Thread starter brucet999
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I would still be okay with using Powerwalls as a whole house UPS solution. I would just keep the UPS's that are already on the crucial stuff (i.e., computers). I wouldn't think that the TV, fridge, etc. would have difficulty with a 500 ms response time.
nwdiver
Well-Known Member
It should be compatible with any UL1741 inverter via AC coupling; I dunno why Tesla has gone with a 48v architecture (cheaper probably). Kind of a step backward from the DC coupled 350v versions they offered initially...
nwdiver
Well-Known Member
. I believe the LG chem battery is DC coupled at ~350v...That's right - a UPS is designed to switch over (if it needs to switch) in less than one cycle, which is 16ms for 60Hz, and 20ms for 50Hz. Typically they do this by always converting the incoming AC to DC and then inverting back to AC, so if the AC drops, the inverter is already running and synced and just continues to use the DC (battery) source.
They don't actually have to disconnect the incoming AC supply - the equipment running on an UPS is not connected to both the grid and the UPS at the same time.
The tesla gateway needs to physically disconnect the grid.
Since I wrote this a few months back, I've had an outage where the switchover time wasn't quick enough and a PC rebooted. I think it may depend partly on whether the powerwall is already discharging to offset grid usage - then it doesn't need to do anything other than disconnect quickly, or if it is charging or on standby, in which case it needs to start and synchronise its inverter and disconnect the grid.
I second this. I have two powerwalls and they don't flip over fast enough to keep my switches, computers or WAPs online. So that is still on a small UPS.
The frig and appliance clocks don't notice it though!
nwdiver
Well-Known Member
TECHNICALLY if it's 'interruptible' it's not an 'Uninterruptible' Power Supply. A true UPS is AC => DC => AC... wasteful but uninterruptible.
- Capt Pedantic
As far as Powerwall 2 interruptions go, if you have no grid draw, like you're in Self Consumption Mode, you won't miss the grid going down and you won't be interrupted. Backup Mode will always be interrupted because almost by definition, you're in Standby all the time. I kept the APC Smart-UPS on my important equipment.
I wonder why Tesla went with 48v. It would seem that higher DC voltage would be more efficient inverting to 240v AC. Most of the off grid inverters are in that range because they trace there heritage back to Lead Acid packs.
I wasn't aware of that 60v "ceiling". That makes more sense than my bootstrap argument about lead acid heritage.
I found out that it definitely is the 48V battery. The 400V battery is coming out the end of next year and will include newer cell technology.
In the meantime I am on the September or October wait-list for the 10kWh battery.
End of next year, as in last quarter 2019? Last quarter 2019 seems like that won't beat Tesla .. :-/
I was hoping to jump over to a couple RESU13, and give up on the PW2 if my SGIP is going to expire waiting on Tesla. The TBC on the LG Chems do sound much more mature and capable than anything Tesla has put out to date (eg 1.20.x)
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