So not only will the MH-CD42 charge your lithium-ion cells when given a nominal USB input voltage (4.5 – 5 VDC), it will also provide essential protections for the battery. That means looking ...

Many chargers double as maintainers, but you don't need many amps just to keep a battery topped up. Photo credit: David Traver Adolphus / AutoGuide.com. A charged battery is a happy battery.

But if these batteries are rechargeable, you need a charger. That’s where [Jon]’s entry for the Hackaday Prize comes in handy. It’s a small, cheap charger for LIR2032 and other rechargeable ...