Good Evening all members

I am looking for some advice on ESS setup for a Victron Multiplus ii 5KVA 48-50/70. 
 

I have 12 x CS 360 watt panels 

250/70 Smart solar MPPT

BVM712

Batteries are DC Rebel Gen2 LiFePo4 210Ah batteries  4 in series for 48V  and 10KWh.

These batteries have an internal BMS that protects against over and under current as I understand. 
 

I know the charge and discharge specs, but does anyone have experience with such batteries coupled to a Victron Inverter?

 

Any advice will be appreciated. Thank you  

 

12 hours ago, Konrad said:

DC Rebel Gen2 LiFePo4 210Ah batteries

Those batteries does not have any communications from the specs I see on the website. If the battery does have comms that can talk the the Multiplus it does improve some aspects of the overall system, but that is not required.

I don't have these batteries, but my batteries currently does not talk to the rest of the system.
I also use the Multiplus in the ESS mode and it works perfectly.

As your battery does not have communications, you will have to set the parameters for charge/discharge when you install the system. In an ESS these settings will come from the SmartSolar MPPT. Just connect to the MPPT using your phone and the VictronConnect App and make the changes in Settings -> Battery 
Max charge current = 70A (batteries can do 80, but your MPPT only 70)
Battery preset = User defined (the Lithium battery options might be close, so you can try them as long as they are not larger than what your battery can do)
Absorption = 56.8V
Float = 54V
Keep Equilization Disabled

Here is my battery settings:

 

And the specs for your batteries. You are doing 4S.
Also when you set up the inverter settings in the Multiplus for ESS limit your inverter to 80A max.

Thank you @Louisvdw. I just needed some reassurance before I commission. Those batteries seem to be good value for money. Only time will tell. I will just set BMS to “other” during the setup. 
Thank you for your input. 

Oohhhoooo @Konrad get your self ready for some headaches. I know of 4 setups with this batteries where it was a massive #$&@*#. And have seen with my own eyes. Local installer in capetown is using them in his installs. One of my friend friends, well 3 of them used this installer. The ine setup was 4s2p setup. Month later he pick up that something isn't lekker, so my friend pop in to go check. One was already charging over 18v , 2 bms units already blown and one under volts. The installes, same stories. This batteries act the same like lead acid batteries where need a ballancer unit lile HA02 between them to keep the batteries ballance because the battery next to the other battery don't no what is doing and all that sort of stuff. What can happend to is, the bms charge fits open on the one batterye, then all that charge will run to the other batteries over charging them, or the other don't even charge then. 

There was a massive fight on FB between a buyer and the brand name you posted because he had the same problem. Batteries only lasted a few weeks. 

@Gerlach  which inverters were used at your friends installs? 

1 hour ago, Gerlach said:

I know of 4 setups

Friend of mine was here some months ago, with a similar-looking battery, though I cannot remember the brand name. Dead. He was told the Victron 12V charger would lift it out... but it had no effect at all. I think they junked the battery in the end.

37 minutes ago, Konrad said:

@Gerlach  which inverters were used at your friends installs? 

@Konrad Growatt and Sunsynk. 

I added a pick to show how they look inside  

22 minutes ago, plonkster said:

Friend of mine was here some months ago, with a similar-looking battery, though I cannot remember the brand name. Dead. He was told the Victron 12V charger would lift it out... but it had no effect at all. I think they junked the battery in the end.

@plonkster same storie with this and this installed was on your side of the valley to. Maybe same installer batteries. My vriend try to charge them and see if they can get them up and running. No luck to. 

15 minutes ago, Gerlach said:

My vriend try to charge them and see if they can get them up and running

Could be the same guy even. Happened right around the time our lockdown started. We may be talking of the same friend of a friend. Boeta (probably a nickname) arrived here in his Disco... we had one last look but the battery would not even accept a charge current. Looked very similar to the pictures above.

Edited August 18, 20205 yr by plonkster

What I have heard when these batteries”trip” out the BMS sensed over or under current and the only wat to restart the BMS is to jump start it with another 12V battery. Never done this before. Only heard about it. 

1 hour ago, Gerlach said:

@Konrad, looking at these pictures of the inside, I would advise you to rather get a real battery instead. You can build a DIY battery like Gerlach and myself did (check out https://lithiumbatteriessa.co.za/ ) , or buy something like Pylontech, Dyness, Freedomwon that can talk to the Multiplus inverters.

4 hours ago, Konrad said:

What I have heard when these batteries”trip” out the BMS sensed over or under current and the only wat to restart the BMS is to jump start it with another 12V battery. Never done this before. Only heard about it. 

I heard the same thing. Presumably, the BMS itself loses power, and it needs to get power from somewhere in order to allow power to go to the cells. In that case, using a good battery charger should have been enough to raise the voltage and restart the BMS. When we tested it, the battery charger was applying 14.5V (absorption), but putting an ampere meter in line showed mere milliamps flowing for short periods... almost as if there is some kind of electronics in there that's trying, but not succeeding...

Battery was under warranty, so we decided not to... uhm... investigate any further.

Also, not sure it was the same battery as this one. But it looked identical.

We have these same batteries in 4s2p configuration. The data sheet claims these should be charged to 56.8V but we have never been able to push them that far - the voltage would suddenly shoot up and the inverter would shut down.

I assume that one (or more) of the BMS's stopped accepting charge to protect the battery causing the other batteries to get flooded with charge, leading to the voltage spike. I'm not sure if the BMS/batteries have been damaged by these spikes during the initial setup.

To avoid this, the MPPT's (2 x Outback FlexMax 60) have been configured to charge rather conservatively (Bulk 55.4V, float 54.8V). And since the MPPT's don't read the same voltage from the battery packs (one reads slightly higher), we've also configured them in a master/slave setup where the MPPT that reads a higher voltage will charge to the bulk setting then go straight into float, while the other continues to charge (at less amps overall) to the bulk setting, allowing the battery balancers (provided with the batteries) to better manage any variances. Well, that's the theory anyway.

If anyone has a better way of managing these batteries, I'd love to hear from you!

PS: We also had to send one of the batteries back to the manufacturer for testing (at our expense and inconvenience). The battery was replaced but that battery pack (3002) has never been stable (before or since) despite many attempts at balancing.

This is the other pack (0098) for comparison:

54 minutes ago, Thurston said:

We have these same batteries in 4s2p configuration. The data sheet claims these should be charged to 56.8V but we have never been able to push them that far - the voltage would suddenly shoot up and the inverter would shut down.

I assume that one (or more) of the BMS's stopped accepting charge to protect the battery causing the other batteries to get flooded with charge, leading to the voltage spike. I'm not sure if the BMS/batteries have been damaged by these spikes during the initial setup.

To avoid this, the MPPT's (2 x Outback FlexMax 60) have been configured to charge rather conservatively (Bulk 55.4V, float 54.8V). And since the MPPT's don't read the same voltage from the battery packs (one reads slightly higher), we've also configured them in a master/slave setup where the MPPT that reads a higher voltage will charge to the bulk setting then go straight into float, while the other continues to charge (at less amps overall) to the bulk setting, allowing the battery balancers (provided with the batteries) to better manage any variances. Well, that's the theory anyway.

If anyone has a better way of managing these batteries, I'd love to hear from you!

PS: We also had to send one of the batteries back to the manufacturer for testing (at our expense and inconvenience). The battery was replaced but that battery pack (3002) has never been stable (before or since) despite many attempts at balancing.

This is the other pack (0098) for comparison:

Good Morning,

I dont have a better way of managing 4 12v series connected batteries, I can just share my setup..

I have a Multi RS inverter with 4 x 200AH Freedom won 12v batteries connected in serries without a balancer (purchase date was 2018) and with a DIY lifepo4 consisting of 15 120ah cells and a single 90ah with them(making it a 90ah 51v battery, managed by a JK bms that is connected in parallel with the 200ah bank via busbars.

this is not a loadshedding backup system, this is 100% of grid.

my charge settings is as follows,

bulk - 54.7v

float - 54.6v

according to my cerbo and smart shunt data, yesterday my max soc was 85.2% 16h30. Yesterday my CBI astute app's timer again malfunctioned and the geyser was switched on at 18h00 and did not switch off at 19h00 and kept on until 23h00. this resulted in my system switching off at 1h06 this morning.

At least the water was hot enough not to start the gas geyser.

anyway keeping in mind that the batteries only achieved 85.2% soc i still managed to pull 284.8Ah from the batteries, the deepest discharge was 331AH

I have never used a balancer on them, when I got them I connected all four in parallel and charged them upto 14.2v (with a bench ps) for a day of two and that was the only balancing ever.

I periodically (probably once a month) I check individual voltages wit a DMM, and they have always been within 0.01v from each other.

Thanks for sharing your setup @stefan44 !

We are on a farm in the KZN midlands and also 100% off-grid so it really matters that we get the best out of the system.

It is quite remarkable that your batteries are within 0.01V of each other despite never being balanced, so you must be doing something right! 🤓

Sadly, I have noticed that the DCRebel Gen2 batteries seem to be fading after only 4 years of service. Directly after installing, the voltage would drop by 0.2V when a load ran on the inverter (eg: borehole pump at 1.6kW). Nowadays, the voltage drops by 0.8V. Also, the battery voltage would be around 52.2V in the morning before they started charging again, whereas recently they are around 51.0.

It doesn't really seem to change much when I fiddle with the charger settings.

Question: is there any value in allowing these batteries to go into absorb?

1 hour ago, Thurston said:

Thanks for sharing your setup @stefan44 !

We are on a farm in the KZN midlands and also 100% off-grid so it really matters that we get the best out of the system.

It is quite remarkable that your batteries are within 0.01V of each other despite never being balanced, so you must be doing something right! 🤓

Sadly, I have noticed that the DCRebel Gen2 batteries seem to be fading after only 4 years of service. Directly after installing, the voltage would drop by 0.2V when a load ran on the inverter (eg: borehole pump at 1.6kW). Nowadays, the voltage drops by 0.8V. Also, the battery voltage would be around 52.2V in the morning before they started charging again, whereas recently they are around 51.0.

It doesn't really seem to change much when I fiddle with the charger settings.

Question: is there any value in allowing these batteries to go into absorb?

I cannot claim that I am doing right, I just use the batteries as I have said, Freedom won deserves the credit for these batteries performance, They were first installed in 2018, I have no idea how many cycles they have done, as I have changed my system a couple of times since then.

afaik absorb charge is the stage after bulk charging with reduced amps and to a higher voltage than bulk(the absorb voltage setpoint) in lifpo4 batteries this is were the internal balancers of every 12v battery starts to work at 14,2v. (BMS dependant)

your batteries might be internally unbalanced from never reaching the internal balancing voltage(14.2)

I would try to charge every 12v battery to 14.2v with a cc/cv powersupply and keep it there for a day or two to allow the internal balancer to work, or connect all four 12v's in parallel and charge them to 14.2 and keep them there for a couple of days/ week.

the internal balancers is usually very weak, they balance at 20 - 100 milli amps so it might take a while to balance a 800ah stack

just checked my volt drops on the system, from 52.57v at 275w dropped to 51.27v at 3582w, and 53.29v at 211w dropped to 52.47v at 2073w it looks almost inline with what you are observing.