question

Rasmus Mikkelsen avatar image
Rasmus Mikkelsen asked

ESS - discharging battery to grid at 100% SoC?

Hi all

Just recently got my system approved for grid feed (this week)

I'm running a multiplus II 48/5000, with an 250/100 mppt via ve. direct, cerbo GX, 13kwh of usable storage 14S lithium with Batrium BMS, 6.2kwp PV

My problem seem to be when at 100% SoC the system starts discharging the battery (3700w) into grid (3700w allowed in grid feed-in) and shutting down the MPPT until it reaches 97% SoC then MPPT kicks back in and we are charging batteries to 100% again. This cycle repeats as you see in the screen dumps.

I've managed to stop this behavior by disabling DVCC, then it all acts as "Intended" I would assume. Not discharging the batteries anymore at least. But it is my understanding that I want DVCC to be enabled? BMS is running via CAN to GX.

In ESS menu I've set it to Battery life not optimized.

I find this very strange, also I noticed when it's doing it, if I go into the BMS menu on gx and into parameters it has a Charge Voltage Limit (CVL) set to 37.1v, the max CVL is normally 56.0v, but changes to 37.1v when discharging to grid. If I then go into my BMS settings, there are no settings in there that is set to 37.1v, also it wont drain the batteries down to 37.1v but only 97% SoC.

Are there any settings in the ESS setup i've missed? Only have ESS as assistant.

I hope some of you can help me out

Thank you

From Rasmus


voltage-and-current.jpgpv-charger.jpg


ESS
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2 Answers
Paul B avatar image
Paul B answered ·

I suspect the reason its discharging, is that the Batrium BMS is reporting to the system that the max charge should be 37.1 , so the system then starts to discharge the batteries to try to get to that voltage.

so look in the batrium bms as to WHY its changing the CVL to 37.1v maybe one cell is going high when the bank its full and further balancing of the cells maybe required. then when the cell voltage drops it then returns the cvl back to 56 and the discharge stops,

I dont think you can change these settings all you can do is stop the cause, ie one or more cells going high.


maybe contact batrium bms and see what they suggest


under the Parameters area this is ALL CONTROLLED BY THE BMS sending the figures

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Rasmus Mikkelsen avatar image
Rasmus Mikkelsen answered ·

To update this with answer. Batrium provided a new software .40 preview release i believe, that fixed the problem.

From Batrium

We are reaching out to inform you of these updates:


For Victron users, we advise staying at the most recent stable release, Build 2.17.27 for now as we did not anticipate any issues when we created the new build. Updating to preview release 2.17.40 is optional as Build 40 restores the Victron logic, however, the issue with the reported voltage spiking is something we are still currently investigating and working on.

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