Quadcopters have been my new focus in the R/C area. Rather than spending time and effort building a frame, I ordered the one from hobbyking http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=16583
This quadcopter frame is surprisingly well built for its price. One of the problems i found was the battery placement. It is not the problem with this quadcopter frame, but in general. Placing a traditional battery where cells are stacked one over other creates a non symmetrical center of gravity for the quadcopter. I was looking for a battery structure which distributes the CG evenly. Also, i wanted the ability to place a camera under the frame. If a standard battery is used, then placing a camera platform would crowd the bottom. I was looking for a more cleaner approach. So here’s my mod. Hopefully the pictures are self-explanatory.
So i took a regular 11.v LIPO cell (Turnigy), took out the wrapper, desoldered the individual cells, placed them side by side and taped them up. These are 2600mah cells. Luckly i got almost square profile of roughly 5″x5″. The black stuff you see at the cell tabs is a messy application of ‘liquid tape’ to insulate the intermediate tabs.
So here is the new cage. The 2 gray pieces are hobby plywood (3/16″ thick) that are cut 6″x6″ square. I glued in some wood pieces at the edges of the bottom piece so that it could hold the battery snug. Then i drilled four holes at the center to match locations of the holes of the bottom piece of the quadcopter frame. Then four more holes at the edges with standoffs to accept the top plate. Now the top plate has some double sided tape applied with pieces of sponge. This is so when the top plate is secured, it will secure the battery by the pressure of the sponge pieces. I also soldered the main battery terminals and the balanced charger cable. They are re-used from the original pack.
Battery placed on the lower plate. The small wooden pieces snugly fitting around the battery.
Top plate placed over the battery. Then secure the 4 screws over the standoffs. You now have a low profile 3S battery pack!! Now to place this whole assembly on the quadcopter.
The quadcopter frame with the bottom plate. I used 4 standoffs (roughly 3/8″ tall) rather than mounting the assembly flush.
The lower battery plate mounted on the standoffs and secured with #8-32 flathead screws. So the screw heads are flush.
Battery placed on the plate.
Top plate (with the double sided tape and sponge pieces) securing over the battery.
So there it is. The quadcopter standing on its landing gear with the bottom plate. I now about 3~4″ space below the battery which should be sufficient for a camera mount.
Another view of the whole assembly.