The location of the battery affects the performance and handling of your mini quad. The LiPo battery itself is a mass, in fact it’s so heavy it can change the centre of gravity. In this article we will discuss the benefits and downsides of mounting the LiPo on top and bottom of the frame.
Top Mounted Battery
By mounting the LiPo battery on top of the mini quad, gets the centre of gravity (COG) 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 battery can be used to balance out the weight from the HD camera (e.g. Gopro) on the front.
Battery on top also makes landing easier, the wide flat base is less likely to tip over when it lands. It seems like every underslung quad I have ends up upside down, even though we should expect it to touch down right side up with the lower battery and CG.
As for handling, I think the differences are pretty subtle given how powerful motors are and how good flight control software is today.
Oh, and 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 more surface area, and higher drag when flying fast.
On some “flatter” frames, LiPo is more likely to get punctured by propellers in a crash if strap is not properly fastened.
Bottom Mounted Battery
To mount the battery on the bottom, less top space is required which allows for a lighter and more compact frame design. The smaller and more weight-centralized mini quad frame also means less drag for high speed flying. Perhaps that’s one of the reasons why it’s preferred for racing.
The LiPo is also better protected from prop strikes when mounted under the frame.
Finally, bottom mounted battery doesn’t cares about battery’s size and shape, and you can slide the battery forth and back to adjust the COG.
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 effects 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, these disadvantages might not be easily noticeable.
“Turtle Mode” is less likely to work with the battery mounted underneath the frame.
It’s also easier to scratch, puncture and damage your battery when landing on rough surfaces.
This is largely a personal preference. But so far from what I have seen, freestylers seem to prefer top mounted battery while racers prefer bottom mounted. Of course this also comes down to frame design and limitations.
I hope this article was helpful, if you have different opinions please let me know in the comment. Happy flying.
- Jan 2018 – Article created
- Sep 2018 – Added pictures