5pcs 3.7V 500mAh Rechargeable Li-Po Batteries with 6in1 Charger Compatible with UDI U818A, U818A-1 U817 U817A RC Drone NOT Compatible with U818A WiFi FPV Discover Model (500mah)

The batteries are charging up from 4.13v to 4.19v measured by a calibrated Fluke multimeter. That seems to be close enough to the advertised 4.2v. The only issue seems to be that plugs get stuck and are very hard to remove from the charger. I use these as an upgrade for mini quadrocopters and did make a mod to improve flight. The adapter was making the wires too long and the extra weight to the aft end was causing erratic flights. Removing the adapter and soldering then heat shrinking the wires solved the problem.

Used in a drone & recharged fewer than 20 times before batteries will not recharge either with this usb charger or a wall plug for same type. gives less than 10 sec. flight vs. 5-6 min. with a different brand battery.

Fit my drone perfect according to specs. Was expecting 5+ minutes bases off the original batteries. Couldn't get more than literly 30-45 seconds out of each battery. Very highly dissatisfied with these.

Batteries dont hold charge and charger doesn't work waste of money

We bought a drone at a yard sale and it requires these batteries. We’ve had fun flying it in the yard. The batteries don’t last long but with a few beers it’s a barrel of laughs. They charge fairly quick.

These batteries do not hold a charge. They are junk.

Glad i purchased using rewards points. These batteries hold absolutely no charge (all 5). As soon as i plug them into my UDI RC drone, which they say they're designed for, the battery low level warning chimes and the drone dies. I read other reviews where some batteries were bad, I at least figured 1 out of 5 would hold a minimal charge for my $20. POS...Stay far away...

Batteries would not hold a charge. Only lasted about 30 seconds. Very weak.