URGENEX 3.7V Lipo 850mah Rechargeable Lipo with JST Plug X5 Charger for MJX Syma Holy Stone Sky Viper RC Quadcopter Drone X56W X400 X400W X300C X400C X800 HS110 HS200 S670 V950hd S1750 V2450

Battery last a long time and I could fly rc planes for a long time. The price is unbeatable and and the quality is great.

I previously stated that these batteries are unable to deliver 3 amps without dropping below 3 volts. I was wrong. The mating cables I was using in the test had excessive resistance. I don't know if they are really 25C, but URGENEX deserves 5 stars for their customer service. They refunded my money when I didn't even request a refund.

Bought these for a drone, they work great, charge quickly and last longer than the originals. I have charged them many times and haven't noticed any loss of fly time. included charger works great.

2 out of the 5 don’t charge. When they are charged, I get about 3-5 minutes with my stock alias quadcopter which they do NOT fit in. They are too wide. Super cheap though. Edit: I received a full refund and got to keep the working batteries after writing this review. Very good service!

This works with a Traxxas Alias Quadcopter. It’s thicker than the Traxxas battery, and is a tight fit. Plug is the mating end for the Alias interface plug, an adapter isn’t necessary. Once it slides into the bracket, it does have a tendency to want to stay at a slight angle. If you gently push from the front and guide it with a slight lift at the back, it falls into place. Removing is the process in reverse. I use a small popsicle stick to help push it out. First flight after charge was 20 minutes. I think this is worth the money.

Size of batteries are misleading

Great Little Package for the price. cool, simple charger. DOES NOT FIT LaTrax Alias Drone without modification to the battery holder.

These are labeled 25C but in actual use, they are nowhere near that. The four year old batteries I have been flying in my Eflite UMX Ultrix give me 4-5 minutes of aggressive flying. Telemetry reports that the voltage is above 3.5V even at full throttle until at least half way through that flight (used to be 6 minutes when new). A six minute flight to 3.5V is a 10C discharge AT BEST. By contrast, these brand new Urgenex "25C" batteries in the same plane at the same average 10C discharge drop below 3.5V and activate my low battery alert IMMEDIATELY on full throttle application for the first take off. A small part of the issue might be the JST connector but since I plan on returning the batteries, I am reluctant to cut a connector off and replace it with a better connector to see if that is a contributing factor.