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Restarting PW during power grid outage

wjgjr

Active Member
May 11, 2020
1,218
952
Silver Spring, MD
I was having this discussion in a different thread. @wjgjr mentioned that the PW shutdown at 10% when power grid was out. I was surprised, because when I did the Self Powered test with 0% reserve in app (5% GW), the batteries were drained all the way down to 0% in app (5% GW). That's troubling, because in that thread, I was only able to get 11.1kWh per Powerwall when it went all the way down to 0% app (5% GW). So this means I would only have 10.5kWh per Powerwall if there was an actual outage. How come Tesla advertises that PW has 13.5kWh usable energy? The inverter efficiency is 10% round trip, so it can't be due to inverter loss.

Tesla definitely should be more clear on this. As you say, Tesla advertises 13.5 kWh of usable energy (and also 14 kWh total energy, implying they have accounted for reserves and/or losses,) so as a consumer looking at PWs for the first time, I would expect a full discharge to be 13.5 kWh of power to the home, after accounting for any reserves/losses. And, they should advise consumers on what to expect in low battery situations - particularly, if it really will shut off at 5% on the app, they should be clear on that (and this could even be an optional alert notification in the app when you hit 10% plus a warning, similar to when a car hits a low fuel state.) It was certainly a surprise for us in testing.
 

woferry

Member
Mar 4, 2019
403
474
San Jose, CA
I was having this discussion in a different thread. @wjgjr mentioned that the PW shutdown at 10% when power grid was out. I was surprised, because when I did the Self Powered test with 0% reserve in app (5% GW), the batteries were drained all the way down to 0% in app (5% GW). That's troubling, because in that thread, I was only able to get 11.1kWh per Powerwall when it went all the way down to 0% app (5% GW). So this means I would only have 10.5kWh per Powerwall if there was an actual outage. How come Tesla advertises that PW has 13.5kWh usable energy? The inverter efficiency is 10% round trip, so it can't be due to inverter loss.

My Reserve is currently set to 4% in the App (GW = 8.8%), so with the grid out the PW stopped supplying energy at a higher battery percentage then it does when the grid is working. I'd been playing with my Reserve level (I've typically left it at 0) since I'd added the owner-API's total_pack_energy figure to my list of monitored/logged data, and noticed that it takes a significant dip every time I actually hit the Reserve level, so I was trying to determine whether it happened every time the Reserve was reached, or only when the battery dips below some charge level. At 0, 1 or 2% Reserves when the Reserve was reached total_pack_energy would take a dip, at 4% Reserve it did not. As time goes on I'll need to watch the overall trend more closely, it seems the actual linear trend of this figure may not really be affected by these events (it takes a larger dip, but recovers afterwards).

Screen Shot 2020-08-17 at 7.56.45 AM.png

But as you can see from my total_pack_energy reading after ~17 months of operation I'm already at 11.33 kWh, and that matches the Owner API % level (i.e. energy_left = 1861.3, total_pack_energy = 11335, 1861.3/11335 = 16.4208% = percentage_charged, GW API = 20.75%, app shows 16%). So I agree that 13.5kWh 'usable energy' seems like a stretch based on what I've seen, and I'm being kind when I say that. Unfortunately I only learned of the total_pack_energy reading a month or two back and took some time to get logging up and running, so I do not have history beyond what's in the above graph.

After I turned Powerwall back on, I could see the light in the Gateway panel. I also noticed that there was a reset button, and pushed it for a few seconds. How long did you push it for? I read later that I needed to push it for 10 seconds? And where did you get the 12V from the Powerwall to jump start the gateway? Or did you get it from a 12V battery?

I pushed the button for less than a second. But the reboot takes a minute or so (I didn't actually time it, felt line an eternity :) ) to actually complete. The Gateway plays some notes when it's finished rebooting, and that's the moment the PW's turned on and started providing a microgrid to the house again. As I said for my second attempt above (once I removed the JUMP connection) that I was not doing anything special to the GW (I'd already put the inner cover plate back in place), so the Gateway was running purely off the 12V supplied by the PW on the 4-pin PW connector.
 
Last edited:
  • Informative
Reactions: m3-pw2

zƬesla

Member
Apr 16, 2020
366
111
US-NH
With 2 PWs installed in Spring, the total_pack_energy is currently 27608. It seems to be steadily decreasing over the last 10 days when I started logging. Started around 27680.
 

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