3 Powerwalls only charging to 87% from grid on time base control

[Bobster]

Hi! All,
I had 2 Powerwalls for a year and they charged to 100% on 'time base control' setting without issue. As this was not quite enough capacity to get through between the off peak periods of Octopus Intelligent Go tariff I had a 3rd Powerwall installed a couple of weeks ago. When the 3rd Powerwall was commissioned the system charged to 100% on the first night. On the second night they only charged to 88%. I assumed this was because the Powerwalls need to sync with each other. The following day they charged to 92% and the next to 100%. Then the days as follows: 92%, 100%, 100%, 93%, 87%. As it is all Time Based Charging from the grid, I would expect the Powerwalls to charge to 100% every night as there is 6hrs of off peak available. I have checked all the settings in the app and there does not appear to be anything amiss.
Any advice/thoughts on this?

 

[buckets0fun]

Posssssssibly could maybe almost, be that they’re(powerwalls) balancing the entire system to each other and wanted to take their time.

If this continues being odd, look to filing a request with support to look into the behaviour you’re reporting.

 

[JohnRatsey]

If you've also got solar panels then the system will be looking at the solar generation forecast and, when a sunny day is forecast, may be leaving some battery capacity available for the solar generation. That's what my system does.

 

[xWren]

If you've also got solar panels then the system will be looking at the solar generation forecast and, when a sunny day is forecast, may be leaving some battery capacity available for the solar generation. That's what my system does.

I'm yet to be convinced that Powerwalls in the UK use any kind of weather forecast, but yes time based control does apply some algorithm that estimates both solar generation and use based on your historic data (e.g. what happened yesterday, or this day last week) and will decide not to charge 100%. This guess was wrong so often, and cost me money by drawing from the grid at full price, that I stopped using time based mode and control the off peak charging behaviour from self consumption mode by adjusting the backup reserve percentage via a script and my own more reliable estimate of what tomorrow will bring.

 

[miimura]

log into the Powerwall Gateway and get the system information.

For example: https://192.168.0.xx where xx is the IP of the Gateway on your local network. You can use the Customer login option with your own e-mail and the last 5 digits of the Gateway serial number as the password. After you log in on that web interface, go to this URL in another tab in your browser and look at the data there.

https://192.168.0.xx/api/system_status

You should be able to see the "nominal_energy_remaining" and "nominal_full_pack_energy" for each Powerwall. If they are not close to the same percentage (remain/full pack), then you may have a problem with the installation.

I don't suspect that you have a problem with the hardware, it's probably just the wonky grid charging algorithm.

Do you have solar as well, or is this a pure grid interactive system? If there is no solar, then there is no reason to charge less than 100%.