I originally bought some of these last year because I was looking at the cost of these vs a kWeld, and the total cost would have been similar. I already had a 3d printer, and had bought 10kg of PETG for $100 a while back, so those were sunk costs. Each roll printed about 11-12 8p cases.
I'm so glad I went with these because they are so adjustable. I currently have a 13s8p primary pack with that I use for my recumbent, and a second 16s8p pack for my cargo bike that'll I'll also split down to 4x4s8p to get a 12v battery for my trolling motor when I get out on the water. My recumbent is also my commuter, and I commute 18 miles each way, so I've run quite a bit of power through the pack over the past year.
The flexibility also lets me easily try different things. I have a heated 12V jacket that is normally plugged into a vehicle 12V system. I took four of my 8p packs, slipped them into a clipboard case, and had a portable power source I could slide into my backpack. I don't need a dedicated battery for something like that, but it's easy to grab a few packs and reconfigure for a weekend project with this system. Afterwards, I could return the packs to my ebike.
The 8p height fits perfectly in the metal 0.50 caliber ammo cans, and you can fit 13s in a single column, or 21s in 3 rows of 7, or whatever you want. I also experimented with the 4x4 vinyl fenceposts, and 4p packs fit into those pretty nicely. 3d print the end caps, and you can make nice compact booster packs that you can slot into your bike if you're going on a longer ride.
My controllers can take up to 21s, so the NESE system let me try different voltages for a while, and easily adjust if it was too much or not enough voltage without having to tear apart the entire battery.
I'm very much a Grin fan, and I think agniusm's battery system is an excellent complement to all the Grin hardware. Both just work, they're not something you have to worry about. However, I think agniusm's system is how Grin should have built their LiGo packs (1s8p instead of 10s1p), because it's just so flexible. Especially when compared to the LiGo system, NESE modules that cost around $10 plus batteries (new would be ~$3/cell, reclaimed ~$1/cell) are an amazing bargain.
I picked up more batteries over the course of this year with the hope the winter sale would return (I'm in the US, so the sale basically gives me free shipping). Time to order more!