ESS mode ignores BMS BMZ ESS-X control

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ondra asked Mar 10, '21

ESS mode ignores BMS BMZ ESS-X control

I would like to ask if it is normal that ESS mode ignores BMS control from BMZ ESS X battery. Configuration 3 x MPII, 3 x BMZ ESS-X, MPPT 250/85, Fronius Symo and AC OUT1, Cebo. All devices have the latest version of FW. Unfortunately even if the BMS battery sends a parameter - CCL = 0A:

so the batteries are still charging. The charger is set according to the manual for BMZ = Absobrtion time = 1. Unfortunately = Absobrtion time is never one hour, even 7 hours at a time.

Status code # 3 should appear in ESS mode: BMS disabled charging, I've never seen it with BMZ ESS X in ESS mode. I run another 4 similar systems with BMZ ESS X and I have also never seen status code # 3: BMS disabled charging.

I'm worried about the batteries, about the safety of operation. I think I overcharge them this way and they could be damaged. Please tell me if this behavior is normal (the battery is not overcharging) or if it is an error. Thanks Ondra

Multiplus-II ESS BMS

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Answer 1 · 2021-03-15T12:01:06Z

Daniël Boekel (Victron Energy Staff) answered · Mar 15, 2021 at 12:01 PM

Hi @Ondra

first: absorbtion time, etc. is not used when using a CANbus controlled battery, the battery controls charging.

in this case 'absorbtion' means that the charge voltage is reached, and Bulk that it is below target voltage.

second: because ESS is continuously charging / discharging the battery, the system will just keep the target voltage of 61,5 volt, otherwise the battery would stop charging, and a little later charge again.

So as long as CVL is respected, there is no problem and your battery is not overcharged.

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ondra commented · Mar 15, 2021 at 12:59 PM

Hi @Daniël Boekel (Victron Energy Staff)

Thank you for the explanation. I'll be calmer right away :-) Maybe this explanation could be part of the ESS manual or the VE Configure setup manual for BMZ batteries (https://www.victronenergy.com/live/battery_compatibility:bmz_ess). There would be fewer similar questions.

Ondra

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ondra commented · Apr 03, 2021 at 08:17 AM

Hi @Daniël Boekel (Victron Energy Staff)

Unfortunately, it has now happened several times that the battery has been overcharged - see the picture below - CAN-bus BMS battery warning High voltage.

Data from MPPT, here you can see the maximum battery voltage of 61.98 V, while the maximum is 61.5

So I don't think battery charge control is working properly. I have found that this only happens when DC-coupled PV - feed in excess is enabled and the battery is 100% charged.

I use MPPT 250/85 connected via VE.Can. The battery is connected via BMS Can. See settings:

Thank you for your reaction, or for recommending something else to try to avoid overcharging. Ondra

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Daniël Boekel (Victron Energy Staff) ♦♦ ondra commented · Apr 03, 2021 at 08:59 AM

Hi @Ondra

I've learned that the BMZ batteries are kind of special: between CVL and high voltage warnings there is very little room.

When 'feed in excess DC solar' is enabled, the MPPT's get a 0,4V higher setpoint, and the inverters pull this down to CVL (this is how it feeds in), when inverter power is not enough to pull down to CVL, this effect you experience happens. normally no problem for a 48v battery.

In the latest Venus-OS release candidate (and the soon to be an official release) 2.65 there is a setting in the DVCC menu to set a lower maximum charge voltage. for your system this would be ideal.

https://community.victronenergy.com/questions/83451/venus-os-v2658-available-for-testing-1.html

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ondra Daniël Boekel (Victron Energy Staff) ♦♦ commented · Apr 03, 2021 at 09:16 AM

Hi @Daniël Boekel (Victron Energy Staff)

Thank you for your quick response and explanation. I'm using FW in Cerbo-gx release candidate 2.65 - 8, now it's version 2.65 - 9, so I just installed it and adjusted the CVL setting to 61.5 V. If that makes problems, I'll reduce the CVL voltage to 61V. Have a nice Saturday. Ondra

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ondra Daniël Boekel (Victron Energy Staff) ♦♦ commented · Apr 06, 2021 at 12:53 PM

Hi @Daniël Boekel (Victron Energy Staff)

So, we have several days with testing new function with DVCC, manual setting CVL.

The task stop with exceeding CVL / overcharging is OK. Perhapas, there is one dissadvantage, which we can see in partly cloudy days (changing cloud with full sunshine). I would like to explain:

The battery is full charge (97% - 100%). CVL is manualy set up to 61V. Allowed grid feed in from MPPT. And we have sunshine and CVL is automatically increased from 61V to 61,4V. The battery is charging with increased voltage. And now, there is cloud (stop sunshine) and power from MPTT is low, incresing about 0,4V is deactivate and battery has for example 61,2V. Now, there is setting CVL 61V and with this start discharging to 61V. When we have voltage 61V, discharging stopped. This cycling we have all day and this is issue for battery timelife. Should be better by manually setting CVL to deactivate discharging from value CVL +0,4V to set up value CVL.

Many thank´s for your support. Ondra

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Daniël Boekel (Victron Energy Staff) ♦♦ ondra commented · Apr 06, 2021 at 01:20 PM

Hi @Ondra

This little bit of cycling is really no issue for batteries.

Also LFP batteries have very little capacity in the fully charged region, so very little energy is actually transferred.

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ondra Daniël Boekel (Victron Energy Staff) ♦♦ commented · Apr 04, 2023 at 06:41 PM

Hi @Daniël Boekel (Victron Energy Staff) ,

It's been 2 years since I last addressed here that ESS ignores CVL, CCL when DC-coupled PV feed in excess is switched on. If I don't set the limit in DVCC – Limit managed battery charge voltage, I get Hign Voltage alarms

the voltage is up to 61.9V (61.5V + 0.4V due to switched on DC-coupled PV – feed in excess). If I set the Limit managed battery charge voltage in the DVCC, when the voltage is exceeded, or when the irradiance is suddenly reduced (MPPT power reduction, canceling the supply via DC coupled PV), to a sharp short discharge of the battery to bring the voltage to/below the set limit - without the 0.4V increment.

Furthermore, at SOC 100%, the battery is overcharged with currents of 20-50A for several hours, when the battery voltage slowly increases. If I turn off the DC-coupled PV - feed in excess, charging stops immediately.

A lot of other users here in the forum are solving the same problem. Someone solves it by dismantling MPPT regulators and installing AC inverters, someone "plays" with Node red, etc. It would not be possible to add the function that if I turn on DC-coupled PV - feed in excess, there will be another option - the second parameter " ignore BMS-CCL Yes/No", as stefan1967 writes here https://community.victronenergy.com/questions/106290/bug-in-ess-dc-feed-in-enabled-charge-current-limit.html If I chose No - then CVL would not increase by 0.4V and CCL = 0 A would be observed, exactly as sent by the BMS from the battery, or it would not even increase by 0.4V DVCC Limit managed battery charge voltage, if it were set .

I think it would help a lot of users. If the solution is not found, I will probably have to remove and sell my MPPTs and replace them with AC inverters, which of course I do not want, it is an expensive matter and I would like to have both AC and DC coupling.

Thank you Ondra

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Alexandra ♦ ondra commented · Apr 04, 2023 at 08:07 PM

You will face the same problem with ac coupled inverters. Unless you have them on the grid side of the victron.

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tranzorb Alexandra ♦ commented · May 04, 2023 at 08:12 PM

Hi,

Actually no, it is operating perfectly fine with inverters on the ac out side. That's what Ondra does, and I have exactly the same problem he has.... And no answer from Victron, yet it seems to be a real issue.

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Answer 2 · 2023-04-04T20:15:00Z

vicens answered · Apr 04, 2023 at 08:15 PM

Quita la compensacion de temperatura del mppt. A 0.

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