MakerHawk 4pcs 18650 Charging Board Dual USB 5V 2.4A Mobile Module 18650 Lithium Battery Charger Board with Overcharge Overdischarge Short Circuit Protection DIY USB Board

The premise behind the charging board is simple. Plug into any single 18650 Lithium Ion Battery pack and it will allow you to safely charge and discharge the pack through USB connectionsFirstly, it works. I tried connecting to a single 18650 pack and also to a couple of packs connected in parallel. Both worked perfectly and allowed me to charge the 18650's in a simple holder using a micro USB lead (not supplied but common to most phones and small devices).Charging is slow and steady which is the way it should be with 18650 cells. Overcharging or over current can be dangerous. The unit did not get hot or even warm which is a sign that the charge rate is correct.While charging, capacity can be seen in the backlit screen which is easy to read and is delivered in a simple percentage. That same display is used to denote the amount of power left in the cells as you use the twin USB ports to charge other devices.USB ports are 2.1A which is more than enough to charge most personal devices such as phones or tablets.Also included in the unit is an LED bulb. With a simple reflector this unit can easily be made into a large capacity power bank with additional LED lighting.I now carry my DIY powerbank everywhere as I'm thoroughly impressed with the quality and versatility of these little units.