Mixing Closed-Loop and open loop batteries Sol-Ark

[DIYrich]

I read about parallel batteries, and I am of the belief that it is ok to mix capacity with same voltage/chemistry.

I have a Sol-Ark 15k with 6 new 5.12kWh Endurengery batteries (30.72kWh) in closed loop. I needed an "installed" system for the Energy Storage Solutions (f/k/a Connected Solutions). But, nothing stops me from "enhancing" the system.

I'm thinking of building a DIY battery with 280ah EVE batteries. I can get them for about $2,600 including BMS.

FWIW: the rack batteries are in 2 rack cases holding 3 batteries each, both cases connected to a bus-bar, that is then connected to the 2 battery connections of the sol-ark (DIY battery would also be connected to the bus bar). So, in some respects, it would be two 15kWh racks plus a 14.6kWh DIY. While the "banks" are close to equal, the batteries in parallel are really One 14.6kWh battery and Six 5.1kWh batteries.

The question is: Any thoughts on what would happen if I kept the Six Endurenergy batteries in closed-loop with the Sol-Ark, with the DIY battery also connected?

While the SOC that Sol-Ark receives via closed loop is 50% off with respect to remaining energy (does not take into account the DIY battery), does it really matter? Sol-Ark will keep taking power until SOC reaches the set lower limit.

Which would you do: Use the closed-loop for SOC, or go with Sol-Ark calculation of SOC (use voltage to cutoff)?

 

[sunshine_eggo]

I read about parallel batteries, and I am of the belief that it is ok to mix capacity with same voltage/chemistry.

Agree.

While the SOC that Sol-Ark receives via closed loop is 50% off with respect to remaining energy (does not take into account the DIY battery), does it really matter? Sol-Ark will keep taking power until SOC reaches the set lower limit.

Not sure I agree.

If everything is connected optimally, the BMS should still report approximate bank SoC.

The presence of the DIY battery reduces the drain from the closed loop battery, so the actual SoC will be approximately correct provided your banks share current in the ratio of their capacities. Rounding:

Closed loop = 30kWh
DIY = 15kWh

If the DIY shares 1/3 the load, then the closed loop SoC will represent the true bank capacity.

What I see here is an argument to wire TWO DIY batteries in parallel, so closed loop and open loop components are very nearly the same capacity.

 

[niktak11]

I have 4 batteries in closed loop (seplos mason) and 3 other non-communicating batteries connected to a single 15k. No issues doing that at all.

 

[629658]

Why not go all open loop attach a Victron Shunt to the entire pack and know 100% what the SOC is at all times. Feed the shunt data into a Solar Assistant and you have a winner.

 

[niktak11]

Why not go all open loop attach a Victron Shunt to the entire pack and know 100% what the SOC is at all times. Feed the shunt data into a Solar Assistant and you have a winner.

Can sol-arks read the SoC data from the shunt or solar assistant somehow?

 

[629658]

Can sol-arks read the SoC data from the shunt or solar assistant somehow?

Not as I can tell a few have reported some success. I keep telling Sol Ark they need to figure out how to implement this. I was hung up on closed loop when I started but after 9 months on open loop I really can’t find a compelling reason to spend any time trying to figure it out. That’s why I’ve said that closed loop comms are a gimmick. Open loop works great and in some respects better than closed loop. I think when your starting this journey the sales people put a lot of emphasis on it but in real world not an issue at all.

 

[629658]

If you are mixing brands of batteries installing a shunt is the only accurate way to track SOC.

 

[niktak11]

If you are mixing brands of batteries installing a shunt is the only accurate way to track SOC.

It doesn't do you much good if the sol-ark can't access that SoC though

 

[629658]

It doesn't do you much good if the sol-ark can't access that SoC though

The Sol Ark will keep its own SOC. It’s not as accurate as I’d like but it stays within 5% most of the time which is close enough.

 

[niktak11]

The Sol Ark will keep its own SOC. It’s not as accurate as I’d like but it stays within 5% most of the time which is close enough.

Mine drifted by about 5% per day. So after a week without a full charge it was way off.

 

[629658]

Mine drifted by about 5% per day. So after a week without a full charge it was way off.

I do find if I can’t get to 100% SOC every few days mine drifts too. I told Sol Ark that they have some work to do when a $150 Victron Shunt is 100% more accurate than a $7500 inverter. Now if I could figure out a way to feed my shunt SOC to the Sol Ark all problems are fixed. Once I got my shunt settings correct it’s just as accurate as my BMS. They make a usb cable that plugs into the shunt I haven’t tried it but that would be the best of both worlds. I like setting my charge parameters manually and leaving them alone. If I can just feed the correct SOC from the shunt it’s golden.

 

[629658]

If they can make the Victron work it would make no difference what battery you hooked up everything would immediately be compatible.