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2 Powerwalls 0% to 99% during storm watch with 7.7kwh

I had a recent solar panel install with 2 powerwalls, inspection passed but I’m still waiting for PTO. On the app it looked like the powerwalls were charged to ~25% during the install and then bled down to 0% over the past 3 weeks. I had storm watch turned on and it activated tonight, recharging the powerwalls from the grid. The thing is, the app says they took in only 7.7 kWh and now show 99% charged. I was under the impression that they should have taken closer to 27kwh? Could they be damaged from sitting at 0% or defective? Any ideas? Thanks.

Comments

  • Could the PWs have taken some of their energy from the PV array?
  • No, it’s not turned on as I haven’t gotten PTO from the utility yet
  • Maybe you're looking at the peak charging rate rather than the amount of energy they took? Also if you looked at a daily number, it could have been charged over two days.

    A few others have reported screwy numbers when first installed/used, although I didn't notice it myself on my system. Once you have the PTO and solar on, wait a couple of days for everything to stabilize out. I very much doubt it's defective.

    There is a hidden reserve in the PW to prevent battery damage at 0% SOC - something like 5% of the capacity that is below the reported 0% SOC. This means from 0 to 100%, it should take about 25 kWh. Now conversion from AC to DC is not 100%, so you are likely to lose about 5% there. I don't know if the displayed energy is actually battery power or the power going into the PW. I suspect the latter, so it may all wash out.
  • According to the app it charged for only 3 hours drawing about 7.7kwh from the grid to from 0-99%.
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