A couple years ago my lovely wife bought me a nice Bosh bit driver. Handy tool, looks and works much like a drill. In fact, there are drill bits designed to fit it. Mostly I use mine to drive a variety of screws.
I told my wife one thing about buying cordless tools: lithium. Repeat after me, I said: lithium. If you buy me a cordless tool, get one that runs on lithium batteries.
She bought a nifty little bit driver powered by lithium battery packs. There are some good advantages over most other common rechargeable battery packs. Lithium has good energy density. That means the batteries can be light, small and long lasting. They also recharge quicker than most other types. All in all, it makes for a compact, light, yet powerful tool.
Only two significant problems with lithium batteries. They can be pricey. Of more concern, they can be temperature sensitive. Just brought in my bit driver from the back of the truck. The temperature out there is in the single digits. The bit driver barely turns. Once it warms up closer to room temperature, it'll be fine.
It's also possible to over heat them. After drilling a whole series of large diameter holes with a paddle bit, the battery eventually wore down. The charger blinked a warning light that the battery was too hot to charge. After letting it cool down for a half hour, the charger accepted the battery and it charged up just fine.
Remember boys and girls. Tell your spouse you want lithium -not for your mental condition, but for your cordless tools.