URGENEX 3.7V Lipo Battery 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

Nice upgrade. More mAh than stock battery.

Works great for my electronic projects. Charges quickly.

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!

Ordered these for my eflight umx twin otter they all charge up and work good.

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.

Purchased based on description being suitable as extra batteries for a SkyViper stunt drone. OEM battery is 650 mAh and lasts 5-6 minutes of flight time. These are listed as 850. First they are about 2mm thicker than OEM, and they BARELY fit the battery compartment. The latch cannot be closed. No danger of it falling out though because it has to be forced into place. The capacity of these is just awful. On a full complete charge they last a maximum of 30 seconds flight time before the drone signals low battery and goes into auto land mode. I've cycled them a few times hoping for a temporary increase in performance with no results. Quality control is nonexistent. These are total garbage. Too much trouble to try to return.

I bought these for a Sky Viper 2450gps, I didn't have the highest expectations for these given how cheap they are but I was a bit surprised that the drone would only fly for about 30 seconds with these batteries. After some testing it would seem it is because there is a significant voltage drop with these batteries and the drone I have in particular (that is listed as compatible in the title) has a high cutoff by default.When tested with a capacitance tester, with it drawing around 350ma from the battery, id drops from the fully charged voltage of 4.2 volts to 3.7 volts INSTANTLY. This is insane given known good cells i have will only typically drop around 0.1 volts with the same current draw. Once the voltage drops it does start to stabilize and creeps down from there.The capacitance tester showed that being drained from fully charged to 3.3volts they average around 350mah, and down to 3.0v they average around 525mah. I'm unsure what the manufacturers specified cutoff for these cells are, it could be under 3.0v giving it it's missing capacity, but keep in mind most drones cutoff will be 3.0v or higher and many people recommend not draining lithium cells below 3.0v's especially cheaper cells, so you will at most get 525maH out of these cells draining them to 3.0v.These may still work for you if you have a drone that allows you to adjust the voltage cutoff and you don't mind the 500ish mah actual capacity, but keep those things in mind.

Seem to have lots of power. They seem to be a little wider than indicated