Tesla Powerwall 3 set up.

JKenH

Since we switched to Octopus Go the PW3 has been working perfectly, or at least until yesterday. Each night it has been charging to 100% in the 00.30 to 05.30 cheap rate time slot. Then last night it only charged to 95% was down to around 75% by mid morning then it charged back up (from the grid as it was a full day to 99%. There was a note on screen saying it was calibrating. Last night it didn’t start charging until3.30 and only got up to 57% by 05.30 when it stopped charging as one would expect. As I write we are sitting at 41% with the prospect of another overcast day and a Sunday roast to cook.

I had read about this sort of behaviour when the battery decides it needs calibrating on the PW3 Facebook group but it is the first time I experienced it first hand.

NedS

When my PW3 underwent a calibration in December, it charged to 100% and then exported everything down to 0% and sat there for around 30 mins calibrating (some users report a lot longer) before starting manually recharge again

You cannot prevent the export process once it starts (even turning off export in the app does not prevent this). However, you can pause the final recharging by turning down the backup reserve and temporarily turning off charge from grid. This is useful if you want to delay recharging until the next off peak window.

I'm not sure if you can pause the initial charge to 100% before the export phase. Mine had already done this before I noticed it was calibrating.

I may be wrong, but it seems like the calibration process is:

1. Charge to 100%
2. Discharge to zero
3. Calibrate

I suspect at this point the calibration is done, leaving you with a calibrated but empty battery, so the battery will then immediately start to recharge from the grid back to it's backup reserve setting (and this would explain why you are able to pause this by reducing the backup reserve and/or temporarily turning off grid charging. IOW I don't think the final recharging is a part of the calibration process, rather a consequence thereof.

JKenH

How often does the PW3 do calibration?

At the moment I have export turned off as a couple of days the PW3 has exported to the grid, not a lot but enough to make us just run out by 00.30. As a consequence the PW3 has not been able to get down to zero by exporting.

There is currently no message saying it is calibrating so it will be interesting to see what happens tonight.

Screwdriva

This is to be expected and the PW3 will soon revert to normal operation. Calibration is usage dependent and typically occurs every 60- 90 days on average.

JKenH

This morning I woke up to find the battery at 9% ahead of another overcast and rainy day. The battery had discharged to 0% just after midnight, charged up to 67% by 3.30 then discharged during the cheap rate period when my immersion heaters were running.

OK, I get that it needs to calibrate but, knowing the tariff, why does it discharge when the rate is cheap. Surely it could be programmed to do so it do at a time when the battery can be replenished with cheap rate power. It is as though it has two different controllers - one that carefully works to keep costs low in normal use and another that does the calibration whenever it suits irrespective of cost. BTW I said yesterday that I had turned off permission to export but when I checked last night it was back on.

Edit: by 8.15 the battery was empty. Fortunately (so far) it hasn’t attempted to recharge.

JKenH

Something unusual is happening today. The sun is shining (which itself is unusual and unexpected) and the Tesla app is showing 6.3kW of PV from my 5kW panels. It did go as high as 6.7kW but I didn’t screenshot that. Previously the Tesla app only showed the generation from the new panels connected to the inverter in the PW3 and the generation from my existing panels showed to be flowing from the “house” icon. (Unfortunately I don’t behave a screenshot from when that was happening.) Today, although I was getting 2kWish from my existing panels, this wasn’t showing in the energy flow diagram so I am presuming that it is being added to the generation going through the PW3 inverter. I had asked my installer when the PW3 and new panels were put in if there was a way of seeing the combined generation from both existing and new panels and was told that was not possible. It looks to me as though this is now happening. If this is the case then the PW3 will, presumably, only be seeing the net generation after the house load has been satisfied.

Edit: if this is the case it is going to be very difficult to establish what the total generation from my combined system is.

NedS

https://forums.moneysavingexpert.com/discussion/comment/81876553#Comment_81876553

I agree, but there does not seem to be any programming logic linking calibration to Time-Based Control so calibrations appear to just happen with no regard to TBC rates.

I believe this issue has been raised with Tesla, so hopefully it is something they may be able to improve.

NedS

https://forums.moneysavingexpert.com/discussion/comment/81876125#Comment_81876125

My system was installed in July and first calibration was in December, 146 days later.

I wonder if regular full cycles reduce the need for frequent calibration. In summer my battery is fully cycled once per day (on IOF), and in winter it is charged / discharged at least twice per day, although not always down below 20-30%

JKenH

Curiouser and curiouser. I took these 2 screen shots of the Tesla app at the same time. One on my phone and one on my iPad. The phone shows the PW3 being charged 1.2kW from the new panels attached to the PW3 and separately 1.9kW from “home”. The iPad image shows 2.9kW of solar from the Tesla set up. Both versions of the app though show the same total amount generated of 6.3 kWh. The Solis app shows 6.1kWh generated from my old panels. My conclusion is that the 6.3kWh shown on the Tesla app is all generated from tne new panels connected to the PW3. Total generation 12.4kWh.

JKenH

https://forums.moneysavingexpert.com/discussion/comment/81877008#Comment_81877008

I have charged to 100% and discharged to 0% several times in the last couple of weeks so was puzzled that calibration was needed. My system was installed 9th December (62 days ago).