Advice on a Storage 'On Grid' system

I purchased (and recently received) 16 x 3.2v 320Ah cells. I'm building a 21KW (probably bigger...) solar array and the storage system I am going to go with would be 2 sets of 16 x 3.2v 320Ah cells.

I want 2 x 48v 5Kah banks in parallel. Where I am at now is I need a BMS for both (if possible).

I googled this

The options I have available are:

- Wire Length 8ga 12" or 8ga 24" (Im thinking with the battery pack Im building I should probably get the 24")

- Crimped Copper Lugs - 1/4" or 5/16" or 3/8" (the terminals on the cells is about 1/8")

Is there a 32 cell version or should I just buy 2 of these? After doing some research I'm going to buy 2 of these...

Any suggestions would be VERY appreciated.

The Overkill Solar 16s BMS will get you close to your 5Kwh (but not 5Kah) goal. However, the 21Kw of PV could be an issue. 21000w / 48v = 437 amps. That's too many charge amps for even two of those BMS on separate batteries.

I would get the longer cables without lugs. Cut the cables to fit your situation and put both cables into a single lug for a cleaner install.

Ok, just bought 2 of them (as you described).

My next question is that I saw on another thread ( https://diysolarforum.com/threads/lifepo4-cells-on-48v-system-charging-faster-than-others.19612/ ) that one should "Top Balance" the cells. Soooo what do I need to do that correctly with the 16 x 320ah cells that I have?

Many of the top balance threads or even the how-to doc in the Resources section of the forum have recommendations on what power supply to use. The one I have is limited to 10 amps. I used it to top balance eight cells. It might be a bit undersized for 16 cells, but if you're patient it would work.

This is a good thread on "recommended" power supplies:

You didnt list the Make/Model of the 10a PS you are using - may I ask which one that is?

I have the Longwei 3010DF, similar to the one listed in the recommendation thread.

Looking at another forum ( https://diysolarforum.com/threads/top-balance.22562/ ) I REALLY liked the Riden I saw in a picture Gazoo posted. His looked like a RD6012 ( ? ) - its hard to tell with the picture zoomed in.

Anywho - I just bought this: https://www.amazon.com/dp/B08JPKQD4...omod-us000-pcomp-feature-rscomp&ref=aa_rscomp

It looks like it should fit the bill.

So BMS's are on order (check) and the Power Supply is also on order (check). Anything else I need to get this party started?

Whoa said:

So BMS's are on order (check) and the Power Supply is also on order (check). Anything else I need to get this party started?

Click to expand...

Heat shrink tubing
Heat gun
Crimping tools
Small ring terminals to fit the balance leads
Torque wrench that can measure inch pounds (foot pounds likely will not work)
Compression frame materials

I have Heat Shrink tubing (probably could use more because I see where you are going with this).
I have a Heat Gun.

Crimping Tools - Id love suggestions on what you have/prefer?
Small Ring Terminals to fit the balance leads (I ll get these when I go to Home Depot).

Torque Wrench that can measure inch pounds - Id love suggestions on what you have/prefer?

Compression frame materials (I ll get these when I go to Home Depot).

I'm a buy once, cry once type of tool buyer. I buy stuff that works right, every time. Consequently, I pay more, sometimes a lot more, than many people do.

TEMCo Hydraulic Crimper
Snap-On Digital 1/4" torque wrench

I was rather disappointed with the inventory of small wire supplies at my local Home Depot. Plan accordingly.

I'm switching to uninsulated ring terminals (small ones, 16 gauge and smaller) and then adding my own heat shrink tubing after the crimp is done. I don't like the quality of crimp with the included insulation and it's hard to see if the crimp was done right with the insulation there.

The threaded rod in the electrical department is really long, like 10'. But it's a lot less expensive than the shorter threaded rod you'll find in the hardware aisle.

Add to your list:
Oxidation prevention - I use No-Ox-ID, but there are plenty of alternatives.
Large gauge cable cutters - I bought a set of Klein Cable Cutters at Home Depot. These worked well, but require a good amount of hand strength for 2/0 cable.