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marv2097 avatar image
marv2097 asked

ESS Discharging and Exporting to grid when Battery Full.

I am seeing some strange behaviour with my ESS system:


TL;DR: When the battery reaches 100% full and with ample solar to cover the AC loads I start seeing the battery discharge. This causes excessive export to the grid until the battery reduces to 97% SOC. I would expect this to be idle until the solar cant cover the AC loads then it would start to discharge.

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Background: I have been running a Victron ESS for a couple of years now with no major issues. I recently made some upgrades which I suspect are the cause of the new behaviour but wouldn't expect this behaviour.

I have recently upgraded from a unmanaged nissan leaf pack to a Seplos Mason batteries that support DVCC over CAN, this is now working well and I see the correct CCL and CVL being sent.

I have also swapped out my single MP/5000 for a pair of MP/5000 and these appear to be working well also. Firmware on the Multi's and Cerbo is all latest at time of writing.

Here you can see the discharge/export behaviour, once full i would expect it to sit idle but instead it starts discharging at approx 2kw which causes the increase in export.This then stops at 97% and it charges back up to 100 and repeats.

My grid setpoint is set to -20w so I would not think ESS should be commanding the 2kw export during these times. I also don't see the Charge Voltage Limit drop below the system voltage.

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Any help would be appreciated, more detail can be provided if needed. Thanks!




ESS
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Jason - UK avatar image
Jason - UK answered ·

@marv2097 , A few qurstions?
Do you have anything connected to AUX1, if so what?

Do you have a CT sensor, and if so, is the CT sensor fitted the correct way round?

When you updated the units, did you disable 'Use Aux1 as disable feedin signal'?

None of these maybe the cause of your problem but I had a weird charge then discharge issue and it was because I had my CT sensor connected to AUX1 without unticking the 'Use Aux1 as disable feedin signal

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marv2097 avatar image marv2097 commented ·
Hi @Jason - UK thanks for the comments, no i dont have anything connected to AUX1, the multi's are set to use the internal sensors. When there is no solar, or the AC loads exceed the solar then the multi's discharge as expected to keep the grid import export near 0.
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