The plan for energy storage in my power station is to use recycled 18650 batteries. I don't have the means to build a normal battery pack with welded metal straps and all that, so I'm building something using these battery holders you can see in the Getting Started log.
I'm aiming for roughly 12V in the setup. With Li-Ion batteries, you cannot really reach that exactly, so I'm going a bit below, with a 3S2P battery setup, meaning 3 batteries in series, and 2 in parallel, which comes out to a nominal voltage of 11.1V (3.7V * 3). Here's a picture of what that looks like electrically:
So that'll be two of the battery holders, connected back to back. In addition, there will be a Battery Management System, to make sure nothing goes up in flames. Let's get soldering (and hot gluing apparently)
The BMS board has plates on the battery connectors, I assume to allow for spot welding of the metal strips you normally see on battery packs. When I tried soldering my wires to them, I found that there were also just soldered on, and came off quite easily when applying a good amount of heat. Without them, there's just regular plated holes to solder to, much nicer if you have wires and not a metal strip.
I plugged in 3 batteries for testing, and the pack shows proper voltages on all pins and on the XT60 connector. So I'll call this a success for now.