Based on the specifications of the 8807 Foldable UAV, an suitable modification to the drone is the replacement of the battery with a battery of higher capacity. Indeed, the battery provided with the 8807 has a 900mA capacity but the large dimensions of battery slot on the 8807 foldable drone does allow inserting a Li-Ion battery of much higher capacity.

Instinctively, the urge is to pick a battery with a huge capacity as advertised on E-Bay, however most of these high capacity Li-Ion batteries simply do not deliver the advertised specifications - that's right, they're a total fugazzi.

Things to mind when purchasing a battery:

• the voltage required by the 8807 foldable UAV is 3.7V,
• the capacity (measured in Amperes) should be as high as you want to go - however, capacity usually dictates the size of the battery such that it may not be able to be fitted inside the enclosure,
• the brand,
• the discharge rate,
• whether the battery has a protection circuit

A good video to watch is a benchmark between the LG 3500mAh, Panasonic 3400mAh, Panasonic 2200mA and the (whooping) 6000mAh batteries by David Sunshine and mirrored here for preservation purposes:

Most Li-Ion 18650 batteries are shipped with a protection circuit that connects the anode to the cathode of the battery and, amongst others, regulates the discharge rate of the battery. Compared to home appliances, drones require a very high discharge current in order to quickly swerve or provide enough lift - in other words, drones expect, if necessary, that the battery provides as much of its capacity instantaneously. You can allegorically compare this required behaviour to a regular car battery that needs to be able to provide as much capacity as needed on a single key turn in order to get the engine running.

For a drone, the protection circuit should be removed and a trickle LiPo charger with protection should be used instead to provide the necessary safety to charge the battery.

To identify whether the battery has a protection circuit, you will notice that a Li-Ion 18650 battery with a protection circuit will be slightly larger than a Li-Ion 18650 battery without a protection circuit. Furthermore, on feeling the contour of the battery, there will be a metal connector leading from the anode to the cathode of the battery. Using a knife, gently peel off the battery wrapping and remove the protection circuit.

For this mod, the Panasonic NCR18650B rated at 3400mAh and without a protection circuit was used.

Regrettably, the 8807 battery slot cover contains plastic resistance struts that must be sawed off for the cylindrical Li-Ion battery to fit. This is best done with a Dremel saw and gently slicing off the extra plastic.

A nice finish could be applied with some transparent varnish, as well as using a polishing kit to make the black plastic appear flawless.

The only other concern with replacing the stock battery with the high capacity battery would be moving the center of mass towards the aft of the drone - however, during testing, that issue has not had any observable consequences and the drone has not tilted.

The Panasonic NCR18650B is not shipped with leads; obviously, because the battery is meant to be used with a device that hosts 18650 Li-Ion type batteries such that this step will require some soldering skills.

With a Dremel sandpaper bit, the top and bottom caps can be lightly scratched after which flux can be applied and solder will be able to grip onto the metal without a hassle.

The stock battery is fitted with a JST connector that can be recycled by carefully peeling off the sticky tape off the stock battery and then desoldering the leads.

Once the leads are attached, the battery should fit into the 8807 foldable UAV battery slot, the plastic cover will perfectly fit on top and thereby the flight time will be increased to approximatively 20 minutes - which is gargantuan even for high end and expensive UAVs!