I welded up a transmitter pack of 8 AA Enloop cells (button top) in early October. The pack now fails to hold a charge. I removed the shrink wrap and found most of the cells to be leaking their contents from the + end of the batteries. The same thing happened to a receiver pack of 4 AAA Enloop batteries after only 2 months. I have used both of these cells in the plastic battery holders (spring loaded) without the cells leaking. I also have a 4 AAA cell receiver pack I made that is wrapped with clear shrink wrap and all of the cells look great and the pack holds a charge. I use 100% nickel strips to spot weld the packs together.
I use an FMA Direct Einstein charger (a charger specifically made for NiCd and NiMH battery packs that allows the user to choose the number of cells and the mAh of the cells) to cycle and charge batteries. I have never had this happen to commercial battery packs I purchased.
Can anyone help me figure out what is happening?