Saturday, February 24, 2024

DIY battery pack for POTA

I've been playing around with some different sized cells to build some physically smaller battery packs for my QCX-minis. I only use them about an hour or two at a time, so I don't need a massive power source. However, most store-bought (relatively cheap) LiFeP04 batteries start around 6Ah. So I began looking for small cells to build a custom pack or two.

I found some neat little LiFeP04 cells the same size at AA alkaline cells. Since the are 3.2V each but still fit anything that takes a AA, I had to have a talk with the family to make sure no one accidentally used the "purple" batteries! I also bought a universal charger that could charge them. The unit also charges NiMH, Li-Ion and NiCad batteries with the flip of a switch.

I bought a few balancing units and then complexly over engineered a battery pack. It worked, but it not practical. So, I ordered a case with a lid, power switch and power cord and simplified my life. Now I just charge the batteries and drop them in the case and I'm off to the races. The cells are rated for 650Ah so depending on how much I transmit, they can last up to an hour or two on my QCX-mini. Plus, it is SUPER compact!

Next, I ordered some large cells from AliExpress. The orange ones are 26700s (26mm dia. by 700mm long) and are listed to have 4Ah, but we'll see if that it the reality. I'm a little doubtful. Anyway, I printed a few brackets to hold them together and then wired a balancer up. I bought a battery-powered spot-welder to help with the job. So far, it's worked well a seems to charge just fine!