Grid down, cold, and can't charge PWs?

[Ulmo]

Odiemac makes a interesting point with a possibility that the PWs can only heat themselves when the grid is up?
That's the same comments made on the Tesla company forum thread.
The longest power outages we experience here in Kentucky are during cold weather. Ice storms tear the heck out of the infrastructure so power can be out multiple days .......... guess what? It's cold when that happens!
My garage is insulated, and based on this thread, I've ordered a portable propane heater to to use if I need to keep the temperature up in the garage. (45,000 BTU)

Only being able to heat itself when there is not a power outage would be a design failure. I'd like to know more about that. Is it a hardware o0r a software thing? Can anyone ask the engineers? I'd like to know.

If this is a real design flaw, then a shed for the PowerWalls actually makes even more sense.

 

[Ulmo]

I wonder if one could place blankets on the PW late PM and off AM when temps are forecast to be so cold.

They need ventilation to keep cool during hot moments (high use and/or hot days).

I like the general idea, but it would need to have some way to allow ventilation whenever it gets hot. Maybe throw a thermometer in there to open vents when it gets out of spec. Vents would have to be placed properly.

That's why I like the insulating shed idea: the vents could go one at the bottom and one at top, causing hot air to rise from cool ground to hot upward and out. I think a good insulating shed should also have the temperature-controlled vents option. Maybe you could open up the PowerWall and put in a relay sense wire from the PowerWall fan. However, I'm not even sure the PowerWalls use their fan circuits any more. Getting clarification from Tesla would be important before wiring it that way.

 

[Odiemac]

Only being able to heat itself when there is not a power outage would be a design failure. I'd like to know more about that. Is it a hardware o0r a software thing? Can anyone ask the engineers? I'd like to know.

If this is a real design flaw, then a shed for the PowerWalls actually makes even more sense.

If there is such a limitation, it’s surely a software one. Powerwalls can only pull energy from your house, which they can energize as well.
The text on the website seems to indicate the preconditioning also happens on solar, so even the current software implementation would only be a major issue in very cold climates without much sun. But they should update the software so that overnight preconditioning can happen off-grid, as well.

 

[Patrick66]

Only being able to heat itself when there is not a power outage would be a design failure. I'd like to know more about that. Is it a hardware o0r a software thing? Can anyone ask the engineers? I'd like to know.

If this is a real design flaw, then a shed for the PowerWalls actually makes even more sense.

The way the unit is rated I could see 800W charging minimum as being reasonable (relative to inverter). Protection from extreme temperatures seems rational for almost everything.

BUT, I think Tesla needs to figure out how large systems should be used in the winter a little better. The no (IIRC) charge while discharging thing makes it hard to island panels to an off-grid mode while you get stabilization from the battery. Actually seems like a good opportunity for some super capacitors... and a dump-load function.

 

[miimura]

The way the unit is rated I could see 800W charging minimum as being reasonable (relative to inverter). Protection from extreme temperatures seems rational for almost everything.

BUT, I think Tesla needs to figure out how large systems should be used in the winter a little better. The no (IIRC) charge while discharging thing makes it hard to island panels to an off-grid mode while you get stabilization from the battery. Actually seems like a good opportunity for some super capacitors... and a dump-load function.

"Charge while discharge" makes no sense. Energy can only flow in one direction. Either there is a surplus or deficit of power on the micro-grid. Heating is not charging, it's just another load. Now, if you want to talk about how fast the system can respond to changes in load, that's another story.

 

[Patrick66]

"Charge while discharge" makes no sense.

The comment was directed at discharging for the purpose of voltage/power stabilization. Instantaneously you can only charge or discharge, but being in charge “mode” does not preclude switching momentarily to discharge.