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Tesla home battery should theoretically be able to supercharge?

m6bigdog

Member
Mar 29, 2015
150
33
San Ramon, CA
No!
The Home battery is limited to 2 kW and 5.8 amps continuous. Peak watts/amps is higher but I assume that is not adequate for the time period for charging.
So 1 is a pretty wimpy charger and it would take (correction) 10 to exceed the HPWC's 20kW charge rate.

The next question, is the PowerWall's battery voltage sufficient to charge the MS battery, i.e. the PowerWall's discharged battery voltage must be higher than the charged MS battery voltage plus some additional voltage for the charge regulator control elements to drive the current transfer.
 
Last edited:

yobigd20

Well-Known Member
Oct 28, 2012
5,926
528
Skaneateles, NY
No!
The Home battery is limited to 2 kW and 5.8 amps continuous. Peak watts/amps is higher but I assume that is not adequate for the time period for charging.
So 1 is a pretty wimpy charger and it would take a 20 to exceed the HPWC's 40kW charge rate.

The next question, is the PowerWall's battery voltage sufficient to charge the MS battery, i.e. the PowerWall's discharged battery voltage must be higher than the charged MS battery voltage plus some additional voltage for the charge regulator control elements to drive the current transfer.

actually they updated the output to be 5kW. if you string 9 of them together you could charge at 45kW theoretically I guess...
 

m6bigdog

Member
Mar 29, 2015
150
33
San Ramon, CA
HPWC is 20kW maximum, but usually less due to low line voltage. (240V * 80A = 19.2kW, 235V = 18.8kW, etc.)

I stand corrected. The HPWC is 20kW max, with 10kW per charger in the MS. I don't know how I came up with 40? bad brain...

However it would take a lot of PowerWall units at 6-9 amps @ 350-450 volts each to get to the HPWC rating and to get to supercharger capacity, well not very realistic with max capacity ratings of only 63 & 90 kWh with 9 in parallel. Mainly current limited.

Also the PowerWall has its inefficiency rating so you could throw away a lot of kWh's charging one battery with utility AC to charge another battery.
I would say it is cost prohibitive @ $3-3.5K per unit plus the cost of the DC-DC current regulating EV service equipment and I don't know where you would get that equipment off the shelf.
IMHO, I anticipate that would cost more than a 8-9kW Solar PV system that is capable of generating enough power to Net-Meter 100% of the electricity for a large home plus charging the MS @ 40-50 miles a day.
 

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