[FEATURE REQUEST] mutiplus 2 idle state in ESS,

DIY
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Hi, I recently installed a multiplus 2 48/5000 configured with ESS assistant and a raspberry PI with venus OS connected with the MK3, the BMS is a jbd bms connected to venus OS with dbus-serialbattery from Louisvdw.

Everything runs perfectly, but I noticed that the multiplus has a fairly high standby power consumption, it seems that the power mosfets are always powered up, even if not needed.

To clarify, for not needed I mean the following situations:

  1. battery completely charged and surplus energy coming from the grid tie PV inverter, no power or charging request for the multi.
  2. battery completely discharged and no surplus energy coming from the PV inverter, no power or charging request for the multi.

In this situation the multi absorbs apparently around 30-40 watts (the multiplus also gets warm to the touch), it is difficult to exactly pinpoint the exact consumption because the power flowing between in, out, and DC, is continuously fluctuating.

I tried to set ESS in mode 3 and the multi goes to idle mode, in this mode it absorbs around 10 watts (also gets cold to the touch and you don’t hear the humming sound from the transformer, while in ess mode1 it always stays warm and humming even when doing nothing). In this mode only the led “mains on” is lit.

I wrote some code for controlling the multiplus in mode 3 and it is working fine, as soon as I send a grid setpoint in modbus, the power mosfets kicks in and the transformer starts humming, even if the grid setpoint imply that the multi has nothing to do, when I stop sending updates to the grid setpoint the multiplus goes back to idle mode, power mosfets shut down, humming stops and power draw goes down.

I was thinking that in ESS mode 1 the mosfet stays on in case of a grid failure, but I tried to simulate a grid outage while the multi were in idle state and it instantly turned on the inverter to supply the critical loads.

Is there any particular reason why the idle state was not yet implemented in standard ESS mode 1/2? (or why it is not working in my particular setup, reading around seems to be the same for everyone).

If there isn’t any particular blocker it would be a nice addition, especially during mid summer and mid winter, where the battery always stays full/empty and the multi spends lots of time idling.

As a side note, a part from the power consumption, when the power mosfets are on, there’s a continuous flow of small positive and negative currents between the multiplus and the batteries, (generally around 0,6 and -0,6, but sometimes also as high as +/- 2A) this small currents can possibly slowly make the BMS SOC calculation drifts.

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To overcome the problem I wrote a couple of automations in home assistant, they are running from more then a weeks now.
The basic intention is to retain all the ESS functions, to achieve this I’m switching between ESS external control (where the multiplus goes in passthough) and ESS mode 1 depending on the situation, this way I don’t have to write the complete control loop.

There are four main conditions:

  1. set multiplus to idle: when battery power is between -20 and 20 for more then 30 seconds, set ess external mode: slave 100 address 2902 value 3, and set multiplus address 38 to 0, this enable the multiplus to charge the battery if needed. But remains off otherwise.

  2. set back to ESS m1 for self consuption: when power from the grid is above 100W, and battery SOC is above minimum sock battery life level (if you use battery life otherwise just minimum level) , then put back ESS in mode 1.

  3. set back to ESS m1 for peak shaving: when power from the grid is above your grid limit and battery SOC is above 0%, then put back ESS in mode 1.

  4. set back to ESS m1 for charging: when battery SOC is lower then minimum sock battery life level (if you use battery life otherwise just minimum level) or when grip power lower then -100 and battery lower then 95%, then put back ESS in mode 1.

During this week I didn’t noticed strange behaviours and the multiplus can finally rest when not needed.

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