gazza avatar image
gazza asked

Feature request:ESS Grid Feed enable when SOC 100%?

There have been many posts regarding CCL limit not being respected when grid feed in is Enabled.

So, if DVCC is set up with grid feed disabled the BMS throttles the MPPT charge current to suit, which respects the battery charge requirement in the latter state of charging (90-100%), as is desirable. Enable Grid feed in and then this allows the MPPT’s to free run to the max, potentially exposing the batteries to high charge current when they would want to throttle back.

  • I would like to request a feature in the ESS allowing Grid feed in to be automated when batteries reach 100% SOC? It is possible to limit the grid feed with a slider switch already of course, but from my experience once the BMS has completed the charge to 100% the batteries only charge and discharge small amounts (based on load and PV available). I don’t believe it would be an issue if the grid feed enable was switched multiple times as long as DVCC was in charge of current limit while batteries less than 100%?
Multiplus-IIVenus GX - VGX
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1 Answer
elvis avatar image
elvis answered ·

What you are requesting is the default ESS behavior when feed-in is enabled.

Batteries charge first and extra is fed into the grid.

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gazza avatar image gazza commented ·
Hi. @Elvis . I know! I think the point is lost in the detail. The main issue is that with ESS Grid feed-in "enabled" the battery CCL is not adhered to. So, you can program DVCC with the battery limits but if grid feed-in is enabled you will get high current spikes into the battery as the MPPTs are not being throttled back, they are just free running to their maximum current output potential. This behaviour has been reported many times.

If you "disable" grid feed in then the battery BMS throttles back the MPPTs as they approach the last 10% of charge, gradually reducing to "almost" zero at 100% SOC. Which is what the BMS is meant to be doing to look after the batteries.

I have found in practise trying to manage this that once the batteries reach 100% SOC, if you then enable grid feed-in, the system is more stable in terms of current spikes. Obviously if you have a larger battery bank (than minimum Victron spec) or a large load "always" on the installation, then the problem is not noticeable since the potential PV is split between loads and battery charging.
One can of course deliberately fix the outputs of the MPPTs (in the charge controller settings) at a lower limit so the max CCL of the batteries should not be exceeded. But, this is effectively de-rating your system when you do want to feed in?

My suggestion was only that... a suggestion to try and alleviate the overcurrent charge surges that seem to be apparent with grid feed in enabled. Actually I would rather Victron come up with a software fix that allows both CCL to be adhered to and grid feed-in allowed to max potential when appropriate.

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