Different LiFePO batteries connected in parallel

[Dave Z]

I currently have 4 Fortress eFlex 5.4 kW batteries connected to my 12kW Sol-Ark inverter.
I asked Sol-Ark if I can install another 4 batteries of another manufacturer in parallel with these and initially they said yes and now no.
I already purchased 4 SOK 48vdc 100 A/hr batteries for this and am wondering if I should return them.
Currently the Fortress batteries are connected closed loop to Sol-Ark, they say that the SOK batteries will not work. Any good advice there, much appreciated.

 

[timselectric]

It depends on what type and cell count the Fortress batteries have. If they are the same, it will work fine.
Monitoring may be a little off, due to only having communication with the Fortress batteries. (If using comms)

 

[Dave Z]

It depends on what type and cell count the Fortress batteries have. If they are the same, it will work fine.
Monitoring may be a little off, due to only having communication with the Fortress batteries. (If using comms)

Fortress Power does not seem to want to tell me what cell count and type they use
Any thoughts?

 

[Rocketman]

What are the settings you use to charge - bulk, absorb & float. And what is the low voltage cutoff.

Do these match the new SOK batteries?

 

[The Good Package]

I have a |48v|100ah|15s| battery in parallel with several |48v|100ah|16s| batteries and it's working fine. It's not ideal, but I keep the charge voltage capped at 55.2v to prevent overcharging the 15s battery. I have a single Victron SmartShunt monitoring the array as a whole and I've subtracted 5% from the available amp hour setting to factor in the "loss" of the 16th cell across the board, so this provides a more realistic SOC. I also don't let the array drop below 30% SOC to prevent over discharging the 16s units. For me, the extra 80ah gained from the 15s battery is worth it.

 

[Dave Z]

What are the settings you use to charge - bulk, absorb & float. And what is the low voltage cutoff.

Do these match the new SOK batteries?

My Sol-Ark settings are as follows, mostly default settings
Float - 56v
Absorb - 56v
Equal - 56v
Shutdown - 52 v - 20%
Low batt - 51.8v - 35%
Restart - 52v - 50%
Empty - 48v

The SOK info I have is as follows
- Absorption - 57.6v, recommended up to 58.v max.
- Float - 55.2v
- Charge target - 100% SOC
- Low batt - 48v

Also, if I were to connect 4 eFlex and 4 SOK in parallel would you recommend putting all 8 in parallel with cables or have each set of 4 going to positive and negative terminal blocks, from there going into my Sol-Ark?

Much appreciated

 

[timselectric]

Fortress Power does not seem to want to tell me what cell count and type they use
Any thoughts?

The manufacturer charge parameters will tell us what the cell count is.

 

[timselectric]

Actually the tag on the battery should display nominal voltage.
48v = 15s
51.2v = 16s
Assuming 3.2v LFP cells

 

[Dave Z]

Actually the tag on the battery should display nominal voltage.
48v = 15s
51.2v = 16s
Assuming 3.2v LFP cells

Attached is a pic of both batteries, Does this help?

 

[timselectric]

Attached is a pic of both batteries, Does this help?

Both are 16s.
No issues with putting them in parallel.

 

[Dave Z]

Thanks, do you recommend taking both groups of 4 batteries + and - to distribution block and then to inverter?

 

[Vigo]

Not sure what alternatives you were considering but that is a good way to do it. Certainly better than stacking cable lugs at the inverter connections!

 

[Dave Z]

Thanks for your help!!

 

[timselectric]

Thanks, do you recommend taking both groups of 4 batteries + and - to distribution block and then to inverter?

Absolutely