question

bobkersten avatar image
bobkersten asked

Rapid swithing from charging to discharging

Hello everyone. I'm currently investigating if the Victron ESS system will suit my needs, and I believe it will. I was just wondering what impact rapid switches from charging to discharding would have on the MultiPlus II converter and/or the batteries. I want to store my excessive solar energy into the batteries, and I'm looking at setting the Grid Setpoint accordingly. I am monitoring the P1 port of my Utility Meter for that purpose, which updates every second. So the Grid Setpoint can potentially flip between positive and negative every second. Is the system designed to handle that, or do I need to throttle it and accept a little undesired grid in- or export?

Multiplus-II
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2 Answers
beat avatar image
beat answered ·

@bobkersten

For an experimental setup, I have done that with an Victron-unsupported first-gen Smappee as grid-meter. Used ESS assistant on the Multi, and a small flow script on the embedded NodeRED in the Cerbo GX (extended firmware), which is setting grid setpoint 2 times per second to export 10W just to be on the safe side. The Multiplus II reacts quite quickly, within a second or two, but when there is a sudden change, it may take a few seconds to react according to grid code setting.

Actually, I did that because the old first-gen Smappee energy-meter is not supported by Victron, so you would need to do a corresponding interface to your grid meter.

You will need to dimension the system according to your needs (over-dimension Multiplus, get enough batteries to handle the charge power), and to do all the settings. It's a learning curve, but if you have the time for it, worth it.

Also keep in mind that Multiplus II are not very quiet (and can be loud), and generate quite some heat above 50% power. I would not want them in my office or bedroom for sure! but in basement garage starts to be ok.

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nickdb avatar image
nickdb answered ·

ESS always has ebb and flow around the grid set point. You can choose to drop mains to reduce this, but switching the set point quickly is unlikely to help as the inverters have a slower reaction time.

Rather use a conditional AC connection.


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