Weird ess charging behaviour

DIY
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1

Hi,

I have a MultiPlus-II ESS setup with AC-coupled PV connected on AC-out (for island operation).

I noticed a strange behavior:

  • If grid charging starts BEFORE PV production ramps up, everything works fine and the system keeps importing/charging at high power.

  • But if PV is already producing first, and I then allow grid charging, the charger only starts with a few hundred watts and ramps up very slowly.

This happens even with:

  • low battery SOC

  • high grid setpoint (+8kW)

  • charging allowed

  • no visible charge current limit

I already tested:

  • Keep batteries charged

  • Min SOC 100%

  • DVCC on/off

  • Weak AC input off

The interesting part is that the behavior completely depends on the startup order:

  • charge first → then PV = good

  • PV first → then charge = slow/limited

System:

  • MultiPlus-II 48/15000

  • ESS on Venus OS

  • ~128kWh LiFePO4

  • AC-coupled PV only on AC-out

Is this known ESS / VE.Bus behavior with AC-coupled PV on AC-out?

Thanks :slight_smile:

2

Do you have any custom controls or programming on the system or is it just base programming?

What is triggering this? Time or something else?

3

Hi, Home assistant does the triggering via the victron integration.

When my cheap window starts, home assistant sets the grid setpoint to 8kw (max of my main fuse) and sets minimum soc to 100% (to force charging)

There is also grid limit 32amp active.

Triggering via venus directly does not make any difference.

There is only base programming.

4

It is what scheduled charge is for. So that is interesting.

5

Sorry I mean I did set manually the grid setpoint en soc limit within the Venus OS. The scheduled charging is not tested yet but interesting to try next time.

But today everything worked as it should. So home assistant did set the charge limit and grid setpoint via the Victron integration and I have full grid power while already 5Kw PV was charging.

Bit confused now because nothing has changed since yesterday :s

6

Alignment of starts and planets :man_shrugging:?

Thats software for you. Works user change nothing… Doesn’t work. Cant find reason… Now it’s working again. Lol

7

Today the problem showed up again.

Initially it started good with max grid import when de cheap window started. And after couple minutes it does only around 500watts. Soc is only 70%

Scheduled charging does not make a difference.

When I connect my EV and start using the whole PV generation. So charging with 8kW. There is still almost no grid import.

Not with scheduled charging

Not with grid setpoint 8kw and minimum soc 100%

Or combination of both.

8

Ok.
I just want to make sure i understand correctly.

Ypu are grid connected. It is a cheap tarriff (is this a fixed window?)

You want to

  1. charge the inverter battery from the grid using the cheap tarrif.
  2. At the same time the ev is charging on the inverter output
  3. And your ac pv is producing at the same time to assist?

The chief compaints are…
A. The system is not charging at full power in this window
B. The system is not ramping up the ac pv to full power either in this window

Is the system discharging the battery during this time?
Is your input current limit at 32A?

9

I’m grid connected 35amp fuse single 230v

All is on the AC out of the multiplus (house, PV, EV charging)

During cheap window 12-16hr in summer I want to charge the battery to 80% the rest is reserved for incoming PV

Sometimes the multiplus does not ramp up the the allowed 32Amp, this is mostly when 5Kw of PV is coming in when the cheap window started.

10

Here exactly the same.

Only in the weekend. Nothing out of limits, net voltage 234, freq 50 Hz but charging is all over the place and doesn’t stabilize

11

Your PV seems to be DC coupled, is that correct?

12

No, my solar is AC coupeld (Ac-in)