The location of your battery on a mini quad might not seem like a big deal, but it does make a difference to your quad’s flight performance. The LiPo battery itself is a mass, in fact it’s so heavy it considerably changes the centre of gravity of your aircraft when it’s moved.
Battery top mounted, bottom mounted:
[2 pictures of back of a quad, showing COG and COT with top mounted and bottom mounted]
Top Mounted Battery
The benefit with top mounted: The centre of gravity (COG) is closer to the centre of thrust – the intersection point of all the props where the thrust is generated.
When the overall COG of your quadcopter gets closer to the centre of thrust, the force that rotates the quad becomes more effective and efficient due to the shorter lever and the smaller moment of inertia. This translates into sharper response, better control and stability.
Another benefit of top mounted battery is that the weight can be used to balance out the weight from the HD camera (Gopro) on the front.
Finally, it’s easier to pull of tricks like “touch and go” (aka “wall tapping”) with the battery on the top of the frame.
Top mounted battery requires more top space in a frame, especially if you plan to use an HD camera as well. A longer body means higher drag when flying fast, although the issue with drag might not too much of a problem nowadays with modern powerful motors.
On some “flatter” frames, LiPo is more likely to get cut by props if strap is not properly fastened.
Bottom Mounted Battery
To mount the battery on the bottom, less top space is required which allows a lighter and more compact frame design. The Slimmer mini quad frame also means less drag for high speed flying.
LiPo is better protected from prop strikes when mounted under the frame.
Another benefit is that when you crash, there is a high chance your quad will land right side up and allows you to take off again.
Finally, bottom mounted battery doesn’t cares about battery’s size and shape.
The centre of thrust is usually way below the COG when the battery is bottom mounted, the quadcopter will experience a larger rotational inertia. The symptoms could be a less stable and agile craft, you might even notice the pendulum effect in some extreme cases. But because we have such powerful machines these days, this disadvantage is usually hardly observable
Another downside is that it’s harder to get “Turtle Mode” to work with the battery underneath.
It’s also easier to scratch, puncture and damage your battery when landing on rough surfaces.
This is a controversial topics, and the decision really comes down to personal preference and what you are allowed to do due to frame limitation.