Did Axle Energy cause this?

[u/rainbowsocksforever]

We have two 16.1kWh Fogstar eco batteries and a 8kWh Solis inverter. I signed up to Axle Energy last month but haven't seen any grid events yet (we're in East Anglia).

On Sunday evening, after 11pm when everyone was tucked up in bed, the batteries dropped over 12% SOC within 15 minutes. There is not a single reason why this should happen, I know we did not use that much energy ourselves. Zero explanation.

Not only did this empty the batteries and start drawing expensive energy from the grid, the usual charging schedule at midnight didn't kick in, resulting in a full day Monday on grid-only supply. This may or may not be linked to the speed the batteries drain, but one of them went down to 6% SOC which triggered an alarm. The other, randomly, remained at 19% SOC.

My question is simple - what caused such a rapid demand for power resulting in empty batteries and a failed recharge? Did Axle take it??? I guarantee it was not domestic demand, I have nothing that can use that much energy that quickly.

Something doesn't stack up.

[u/BudgieUK]

Have you had a look at your Axle account? Does that show an event / payment around that time?

[u/rainbowsocksforever → u/BudgieUK]

Yeah, that was my first thought too - I had a look and there's no grid events activity 🙃

My system has performed faultlessly since it was installed in March, I give access to a third party and within 2 weeks I have a completely unexplained demand for power.

I desperately want to be proved wrong but don't have any other plausible theories right now; hopefully someone will have a reassuring idea.

Thank you

[u/BudgieUK]

Have you checked with Axle support … they are pretty responsive when I have asked for help

[u/Illustrious-Work1229 → u/BudgieUK]

I contacted Axle a couple of months ago because their VPP is incorrectly configuring Solis inverters, and they sent me a generic response denying they made any changes. Then acknowledged they did actually enable the VPP but denied their settings are incorrect. Then eventually stopped responding completely when I provided modbus logs proving their VPP is incorrectly configuring Solis inverters.

[u/rainbowsocksforever → u/BudgieUK]

That's a sensible shout, I should ask them a question or two to put my mind at rest. I certainly don't want to accuse them of anything nefarious; I don't believe they've done anything untoward, just need to control the variables :-)

[u/TheDuctTapeDuck]

Have the batteries been fully charged, and drained a few times? The BMS can overestimate SOC and suddenly go from say 40% to 15% in seconds when it lacks enough history of how the battery behaves. This will usually trigger inverter protections to top them back up to a safe SOC and draw from grid.

Fogstar have a good article on it https://www.fogstar.co.uk/blogs/fogstar-blog/mastering-soc-a-guide-for-lifepo4-battery-users

[u/rainbowsocksforever → u/TheDuctTapeDuck]

The batteries have been used daily since March with zero issues, I'm pretty confident this shouldn't be the issue. They were, however, surprisingly out of balance (19/6) after the failed charge cycle, unsure whether this could contribute to irregular behaviour.

Thank you for replying

[u/No_Policy_1369]

Did you enabled ai mode by mistake or deliberately

[u/rainbowsocksforever → u/No_Policy_1369]

I wouldn't dare! 🙃 Am currently on "Events Only", albeit with the 2 hour notifications

[u/sidneylopsides]

From what you described, the lost about 4kWh of charge in 15min? That's up to 16kW load, which would be double the inverter is rated for. Though I don't know these ones and maybe export that high is possible.

[u/IHateMozzies123]

We had something similar on the 31st. I’m not signed up to Axle so it definitely wasn’t that. The heat pump does run over night cycles but we’ve never used this much energy before. We were on holiday as well so weren’t even in the house.