Easysolar and BMS "fighting" each other?

DIY
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1

Dear forum users,

Since this month I am the owner of an ESS system consisting of:

  • Victron EasySolar GX 5kW

  • Yixiang Vertical 16.1kWh battery with JK BMS

  • 3* 420W solar panels connected in series

  • ABB/Fimer 4kW AC inverter (coupled via modbus/sunspec)

  • 6* Enphase 7+ micro inverters 290W (stand alone, not possible to couple with Victron)

After setting everything up, I noticed a problem with the battery voltage behavior.

The JK BMS seems to push the DC voltage up to 55.2V–55.4V.
In Victron DVCC, I have set the maximum charge voltage to 55.2V, so I assume the MPPT should not exceed this value.

However, once the battery is considered “full” by Victron (showing “1h @ 55.2V”), the system randomly starts discharging to a lower voltage again (possibly towards the 54.0V float voltage?).

My current JK BMS settings are:

  • Cell RFV: 3.375V

  • Cell RCV: 3.45V

I assume I made a mistake somewhere during the setup, but as a rookie with ESS systems I could really use some help understanding what is happening.

I added screenshots of my settings below.

Thanks in advance!

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2

Hy Rick and welcome :waving_hand:

If you’ve enabled “DC excess feed-in,” the system will increase the charging voltage by 0.4V… Just give it a try; otherwise, your JK BMS will still turn off the charging FETs and display a warning message if your voltage is to high with +0,4V …

With the JK, you’ll have to experiment a bit and check out the videos from “Off Grid Garage” too…
In general, constantly switching between charging and discharging isn’t a problem for your batteries or the system.

3

Yes, i feed back my AC (forgot to mention in my first post, ill edit this) and DC coupled PV energy. In The Netherlands we still reiceive base price + VAT + excise duty back as long as we consume more then we produce, we pay about 10ct to the energy supplier. So until the end of this year this is very lucarative.

Is there any way to get the system a little bit more relaxed, does is help to lower Cell RCV and Cell RFV a little more to match my wanted 55.2V?
I do not want to hurt the battery bank too much because of the low profits until the end of the year.

4

You only set the charging voltage in the DVCC… the MPPT adopts this value when operating in networked mode. This is where you need to set your voltage… the settings in the BMS are irrelevant here… this is only for reporting to the GX… e.g., battery SOC 100%
So be sure to test the voltage in the DVCC… anything else won’t help
Your overvoltage warning at 3.65V is fine, though… I have that too… I have relatively high charging power, and if the balancers are too slow, a cell can sometimes get too high here and trigger a warning… but your setting is okay

I used the setting from Gobel Power …

5

Thanks, I’ll cross reference your file with my settings tomorrow and check if there are any major differences.

This is the location where I’ve set the 55.2V:

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But i was a bit worried about the higher voltage the MPPT is aiming for, its the 0.4V surplus you mentioned:

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Finally what are your thoughts about shared voltage sensor? Some AI advice me to turn it on to be sure the BMS value is used and some other tell me to leave it off..

6

So I turned “on” the SVS… but I don’t notice any difference when I turn it on or off. So it stays on.

0,4V meens 0,025V per Cell … no Problem in a balanced System …