3.7v 500mah Lipo Battery with X4 Battery Charger for UDI U818A U817A U817 U818A-1 RC Drone Quadcopter 4PCS with X4 Battery Charger (Not Compatible for UDI U818A FPV)

These are good quality replacement batteries. They hold a charge fine, and based on play time they seem to have the advertised capacity. It's also nice that it comes with a charger that can charge 4 batteries at once. TIP: The connector that fits the charger has to be pushed in VERY firmly, or it will not make a connection and you will get no charge at all. Once inserted firmly the charger works perfectly.

Batteries work great, and nice to have a charger that charges all four simultaneously. Ordered this because I misplaced my one battery that came with the U818a. Given the short flight time of the U818a, it is so much nicer to be able to swap out for the next battery and keep going. We would have enjoyed the drone experience so much more had we had these extra batteries these last couple years. Recommended. Make sure the connectors are pressed in all the way for charging and flying.

Came fast, but I tried charging & using each of all 4 batteries in my RC quad but did not have sufficient juice for flight & got low batt alarm. I put on charger and after 5-10 min batt chrg lite went off. Still couldn’t fly. ? Charging? I started return process, and was contacted by the seller who was very responsive and offered to send replacement batteries right away. 4 stars for seller responsiveness, but still couldn't use/charge the batteries. My drone is udiR/C U28W - which was not listed as an incompatible model, so I'm not sure about the problem.

I have to admit I wasn't expecting much from this purchase but things have gone very well. I am a high school teacher and I keep a few drones around to let my kids learn with. These batteries and the charger work perfectly. The charger charges all 4 batteries at once and gets it done pretty quickly. The flight times with the batteries are the same as you will get with any other battery.

Based on other reviews, it appears that I may have simply gotten a bad batch. That being said, my UDI 818a flies no more than 30 seconds on each of these 4 batteries (fully charged) before the quad's low voltage cut off kicks in causing it to fall from the sky. Checking voltage when I get home, they'd always still be at 4.0 volts. They're simply "sagging" under load. I've now repeatedly tested the 818a quad using the single battery that came with it and other 450 millamp batteries I have around. No issues on the other batteries. Good long flight times. Followed up with one last test on these 4 batteries (fully charged again of course) and no go. Obviously defective.

I used this product to replace a worn out battery and charger for a small RC helicopter. Product worked as advertised and the price made it a great deal.

I read a lot of reviews on this one before buying. Knowing I could get something that was really good or really bad I didn't have a whole lot of expectations. I wasn't delighted but I wasn't disappointed either. The batteries are a little short on life, which is one of the disappointments - but they're not that bad. The charger unit itself - I knew going in what to expect. And yes, like others have said, the plugs that go into the charger are a bit problematic. It's my plan to modify the charger and the cables that plug in. I'm going to remove the plugs and directly solder the cables to the board. That way I only have the battery to plug into each cable. That should improve performance. Performance is not bad. But as I said, it's those tiny little plugs that are problematic. When you get a good connection the charger does what it's supposed to do. At least the one I got does. So if you decide to go forward with this purchase know you are taking the chance you'll receive a good unit. Mine is OK. I'm not unhappy with it and won't seek to return it. But it certainly could have been better engineered.

Great back up batteries for my son’s drone. The batteries don’t last too long (none really do) but having 4 and the charger that can charge multiple batteries at once makes it possible to get some decent flying time.