RedFlow ZCell Flow Battery Image

RedFlow ZCell Flow Battery

consumption is showing proportional to PV inverter production


Hi a customer has the following system

multiplus-II 48/3000/35-32


zcell battery

fronius primo connected on grid side of multi

dc coupled mppt connected with

meter is ET112 connected to ccgx via usb rs485 cable.

all connected on VRM with remote access available

since the start of the year the calculations and energy flow have been wrong, at first I went to site expecting the customer to be using more electricity, but when I turned off all the circuit breakers apart from the energy system the ac load value should have been zero but instead showed around the same value as the solar production.

The multiplus was also making some strange sounds.

i have tried updating firmwares on ccgx, fronius, multiplus

see attached screen shots

any help would be greatly appreciated

Thanks Tom

Thomas johnston asked
Alan edited ·

1 Answer

Charge rate limited by Victron charge algorithm on flow / high impedance batteries?

Hi folks,

Does anyone out there know the voodoo behind the charging algorithm or what, other than temperature, could be causing Quattros and MultiPlus's to not reach their maximum charging currents?


The inverter/chargers are not reaching their maximum charge rate. A cluster of 6 x Quattro 15000 can theoretically push 1200A. There are 45 flow batteries which can each accept up to 50A during charge.

However, test results on this system showed a maximum of 1050A reached which after 5 minutes reduces to 900A which is then sustained. This is only 150A per Quattro. This results in 9 hours to charge rather than 6 hours which should be possible. This impacts the business case for some clients. This was the same on both a 35 degree day and an 18 degree day (Celcius).

The system is running the ESS module. The tester commented that charging fewer batteries and/or with ESS not running he has observed the 200A charging on other systems, but for some reason, it has not been able to be reached in this system.


The comparatively high internal impedance of the flow battery being 80 to 100 milliohms (all connected in parallel) may be causing the algorithm to not adjust the voltage high enough to push enough current into the batteries.

What does the "lithium batteries" checkbox in the charger page actually do/change? Again, I imagine this would change some characteristics of the charging algorithm, even if lithium battery is not chosen from the list of battery defaults. Li


How does the charging algorithm work for the charger in Multiplus II and Quattros?

Is it possible that the charging algorithm would not raise voltage enough either due to high impedance?

or the ESS module somehow altering behaviour?

Lothar Ledgerd asked
mrt answered ·

2 Answers

ESS,ZCell and draining batteries

Hi Guys,

I have reported this previously but this time I have the same issue with a site with solar - it's Quattro's running with ZCell (5 batteries) and ESS - ESS is saying recharge while the Quattro is discharging the battery - what is going on ?



dewitpj asked
Redflow ZCell Service commented ·

2 Answers

Quattro not lifting DC voltage to pre-charge

Hi Guys,

As you know by now, we have Quattros connected to ZCell. The batteries has run flat now and they are awaiting pre-charge. The pre-charge voltage of 55v is being set by the BMS but the Quattro seems to ignore this. Can anyone please advise how we can get this fixed ?



dewitpj asked
Redflow ZCell Service answered ·

2 Answers

Quattro and ZCell running batteries flat ?

Hi Guys,

We have 1 x Quattro 48/10000 with 5 x Redflow Batteries. The site is on Grid only (no solar) with generator backup. ESS is enabled (ZCell and Venus talking via Can Bus)

The Grid is limited to 35 Amps and the generator to 120 Amps. I have instructed the Victron to "keep batteries charged" and set the min. SoC to 50%.

The Victron seems to never want to charge at any rate and prefers to suck energy from the battery.

Also, our grid has a set point of 50W - not sure if this is relevant :)

How can I this "fixed" - I want to limit Grid to 35 Amps, keep the batteries at 50% and if needed, use PowerAssist to get the rest from the batteries.

or - How can I debug this - something must be saying not to charge ?

Thanks ! :)

dewitpj asked
Guy Stewart (Victron Community Manager) commented ·

1 Answer

Updating SoC from ZCell over Modbus TCP (I know it's deprecated but... :) )


I am trying to update the SoC via Modbus TCP. It's enabled on the CCGX (running 2.22). The CCGX has a Quadro connected and it's reporting the following error:

ERROR 2018-12-18T00:59:15.773 "Error processing function code 16, unit id 246, src, start address 30, quantity 1, byte count 2 :" "Requested device (service) does not exists"

I followed the instructions from:

I know it's deprecated but this is my only option for now. I have checked the registers and it appears that I have the right unit/registers ?



dewitpj asked
dewitpj commented ·

4 Answers


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