One of the most practical gadgets I’ve tried is the IMAX B6 multi-function charger. A product that can serve you to feed many projects with Raspberry Pi, Arduino, since it allows you to charge different types of batteries that are used in projects of many makers.
All these DIY projects need power, and it’s not always possible to leave the Arduino board connected to the PC’s USB for power or you may need a special type of ‘string’ power supply. It is also sometimes not possible to have a specific type of charger for each battery. With the IMAX B6 charger you can get what you need from everything it has to offer.