Batteries
Batteries are an area I have a fair bit of experience in (renewable energies). NiCd doesn't get the memory effect because they are being trickle charged, they get the memory effect from repeated 'short cycling'. I.e. only taking a portion of their energy before recharging them. In a camera or other consumer device, the solution is simple - regularly discharge them to dead flat before fully charging them. In a chopper, not so easy unless you could swap them out, discharge them on a workbench, and recharge them externally before being swapped back in.
Lead acids... cheap available heavy. They don't respond well to repeated heavy cycling.
It would surprise me that somebody isn't looking at one of the newer battery technologies Li ion etc. Even a NiMh battery would be a better choice as they do not suffer the memory effect that NiCd's do.