The location of the battery affects the performance and handling of your FPV drone. The LiPo itself is a mass, in fact it’s so heavy it can change the centre of gravity quite noticeably between top mount or bottom mount LiPo. We will discuss the benefits and downsides of where to mount the LiPo.
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 above 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
The centre of thrust is usually way ABOVE the COG when the battery is bottom mounted,
(Fixed it for you.)
Thank you for your expertise
Many racing pilots use a non symmetrical turtle mode floss on the top of the frame. It’s a great protection for the antenna and makes turtle mode great again :D
One reason against top mounted battery for racing is the fact, that everything on the top is destroyed over time by the gates.
Well soon its 8s with 4s pack on top and 4s pack on bottom so…next article…
Then you are going to destroy your batter in every crash for sure LOL
I agree. Im mostly a freestyle pilot, but when I trie to freestyle with my bottom mountedbattery frame I always end up racing around.
A con that I have also found with the top mount battery is that the high mass of the battery is supported by the standoffs. You bend a lot more of the standoffs as the base plate hits first and the batteries inertia keeps going.
Ah, but that means the cheap standoffs are absorbing energy that otherwise would have gone into the battery.
Question is will that come at the expense of damaging an expensive flight controller or vtx?