I have two led shed lights bought from Home Depot several years ago. They use a 3 cell AA nicad pack to power 5 leds. The battery pack is identical to the one used in many older cordless phones.
The original plastic rocker on/off switch on both failed after a few weeks. Since I knew it to be a defective design, instead of returning the lights, I went to Radio Shack and bought 2 proper metal toggle switches and fixed both.
The shed lights are solar charged from a small thin-film panel that has a 10 foot cable for remote mounting. Fully charged when new the lights would run for at least 4 hours
The one in my bathroom worked well for a while and then on cell on the outside of the pack went bad. I replaced the bad cell. Today I noticed a second cell was getting weak and decided to try a LiFePO4 cell instead of tearing the pack apart again.
It works. The AA sized 3.2v LiFePO4 cell was put in a AA holder and the original pigtail connector cut and soldered to the new cell holder.
The second pic is a closeup of the circuit that drives the leds. The diffuser was removed so you could see the leds clearly.