Two banks in one rack?

[SparkyGage]

I don't think so.

I would hope so.

I disagree. Assuming wiring to the bus bar is equal length and resistance is the same (no bad connections) I really don't see any issues.

It shouldn't matter if the PowerPro goes empty first, the 6 server rack shouldn't see more than 0.5C rates if everything is wired correctly.

My current setup is two 230Ah and one 305Ah pack in parallel, I don't have any issues. My next expansion will consist of of two 460Ah, one 230Ah and one 305Ah in parallel, I don't expect any issues.

@Stotts47 I can't help you with communications, I only run open loop. I would absolutely use 4/0 between the server rack stack, Powerpro, bus bar and inverter; I didn't specify that earlier.

So... you are saying if the 6-pack (as a whole) and the PowerPro are correctly connected to the small buss with the same length/resistance of wire, they will CHARGE correctly even though the PowerPro is likely to be flat when the 6-pack is still likely over 50% capacity?

• Does that mean you can safely add a matching battery (full LiFePo factory pack with BMS) that is at 50-20% SOC to a system at 80%+ SOC and they will all charge to 100% without interfering with each other? Example: (3) 24v 100Ah batteries in parallel, one is removed and returned later at a lower state of charge, they will all charge correctly back to 100% without any special balancing procedure?

 

[Brucey]

So... you are saying if the 6-pack (as a whole) and the PowerPro are correctly connected to the small buss with the same length/resistance of wire, they will CHARGE correctly even though the PowerPro is likely to be flat when the 6-pack is still likely over 50% capacity?

• Does that mean you can safely add a matching battery (full LiFePo factory pack with BMS) that is at 50-20% SOC to a system at 80%+ SOC and they will all charge to 100% without interfering with each other? Example: (3) 24v 100Ah batteries in parallel, one is removed and returned later at a lower state of charge, they will all charge correctly back to 100% without any special balancing procedure?

The power pro won't be flat while the 6 pack is at 50% because it's connected to the same bus. they will discharge proportionally.

 

[Steve_S]

Properly configured battery bank with Varied Capacity Packs with LFP is fine as this is one of the few chemistries that works PROPORTIONATELY relative the the AH ratings of the packs within the bank. I've explained this far too many times to repeat it again. I really wish some "folks" would actually do tests in the shops that show how this works and what to do to make it happen but very very few ever bother and leap to Conclusions based on their incorrect assumptions. Assumptions are only goor for ONE THING, - making an ass out of oneself.

But then What do I know... years of working at it, spending criminal cash amounts on testing & burning stuff up to find the edge cases and deploying systems...

Interconnecting Battery Packs using CANbus/RS485 can allow them to regulate & control each other while also ensuring your not overworking any packs. If connecting to an Supported Inverter/AIO can further tweak things down so it is all seamless but it takes time, observations, testing & tinkering which does take some time... NONE of this is "Instant Rice".

 

[Brett V]

What Steve_S said. Because the voltage curve (or lack thereof) is so flat relative to SOC, putting different capacity batteries in parallel magically works very well with LFP

 

[Steve_S]

Proportionate Discharge A-Typically looks like this when observed.
A Bank with 100AH - discharging at 10A, 200AH at 20A and 304AH @ 30A if an Inverter is pulling a total of 60A. Using simplified numbers, this will happen though as shown with a bit of float 1 or 2 Amps between packs as it progresses, You can actually watch it Realtime while it is going. This also works similarly when Charging, the higher capacity packs will take more while the smaller ones will take less but all proprotionately.

 

[42OhmsPA]

So... you are saying if the 6-pack (as a whole) and the PowerPro are correctly connected to the small buss with the same length/resistance of wire, they will CHARGE correctly even though the PowerPro is likely to be flat when the 6-pack is still likely over 50% capacity?

• Does that mean you can safely add a matching battery (full LiFePo factory pack with BMS) that is at 50-20% SOC to a system at 80%+ SOC and they will all charge to 100% without interfering with each other? Example: (3) 24v 100Ah batteries in parallel, one is removed and returned later at a lower state of charge, they will all charge correctly back to 100% without any special balancing procedure?

See the replies from the members above. I've learned lots from them since becoming a member here.

I would not parallel them until SOC is within a few %.

 

[SparkyGage]

Proportional

Thanks @42OhmsPA @Steve_S @Brett V and @Brucey - the fog is lifting and this clears up the gap in my understanding that was giving me trouble in planning my own configuration for my shop. (I hope this discussion is helping @Stotts47 as its helping me.)

 

[Brett V]

Proportional

Thanks @42OhmsPA @Steve_S @Brett V and @Brucey - the fog is lifting and this clears up the gap in my understanding that was giving me trouble in planning my own configuration for my shop. (I hope this discussion is helping @Stotts47 as its helping me.)

If you have prior experience with lead batteries, the behavior of LFP requires an unlearning step that's hard to wrap your head around at first.

 

[SparkyGage]

If you have prior experience with lead batteries, the behavior of LFP requires an unlearning step that's hard to wrap your head around at first.

About 30 years of unlearning to be precise. The biggest hurtle has been remembering that the batteries themselves are "smart" (unless you are talking about raw cells) and having to pay close attention to what the *battery* is expecting to see in terms of load and charge current.

 

[Steve_S]

About 30 years of unlearning to be precise. The biggest hurtle has been remembering that the batteries themselves are "smart" (unless you are talking about raw cells) and having to pay close attention to what the *battery* is expecting to see in terms of load and charge current.

I went from FLA to LFP - yup lots to unlearn, shit loads more to learn too. Ohhh the "Subtleties" are enough to make one cuckoo during the relearn process.