Victron ESS - Minimum SOC (unless grid fails)?

Hi all,
I was never in the situation, but with the load shedding being current fashion and trend, I finally need to get this clarified.
I’ll try and explain the question as best as I can.

I have pylontech lithium battery bank, and set this option to 20% (older version of batteries).
Say for an example that during the night I reach down to 22% of battery, and then eskom comes to play and turns the grid off.

What would happen?
Would ESS disconnect all the loads once batteries drop to 20%, or will it keep draining them till pylontechs turn off them selves (for protection) I guess at around 10%?

I know how it behaves when grid is on, but never had a situation to check what happens when the grid is not available.

Please can someone shed light? :nerd_face:

Well, that’s why it has “unless grid fails” in brackets… because people ask that a lot.

It’s going to discharge until the battery is empty. In practice, with Pylontech, what happens is you’re going to get to around 10% SOC. At that point the battery is going to send DCL=0 to the GX device (DCL = discharge current limit) and this will switch the Multi off.

The Multi will be turned back on when the battery has recharged to 12%, of when the grid comes back on.

When the grid comes back on, the Multi will skip the relay test, and charge the battery instead. When the battery reaches 20% SOC, the Multi will disconnect the grid, do the relay test, and reconnect to the grid.

The Multi will not feed energy into the grid (from the battery or solar) until the relay test has been done.

If you didn’t have the CAN-bus cable plugged in (so the battery could not instruct a switch-off), then it would discharge to 0%, and then the BMS would switch off. At this point the battery is not completely empty, it has enough energy left to power the electronics of the battery itself, so that it might start charging later, but for all practical purposes it is OFF at that point. But with the CAN-bus connected, you should never reach this point.

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Yet, here is me asking exactly that :man_facepalming: :joy:

Sorry, I suspect that the question was answered, but upon googling I never found as straight forward answer like the one you just provided :slight_smile:
Thank you, I was suspecting something like this, but you just re-assured me and it makes perfect sense now :slight_smile:

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