It’s not finished, but once several rounds of design iteration have gone by it will be further refined. My strategy is to populate, assess, and compress. It is designed around the V7.2 battery parameters, which had 33 Ah of power per side. V7.3 and V8 will have 22 Ah per side.
I’m once again glad I committed to the size reduction. Even with 36” in total length, this barely fits the slots needed for 8 batteries. I might find a new battery unit to act as the principle unit (I’ve been using combinations of 11 Ah LiPo batteries) so that the width of each slot can be reduced.
Additionally, I left out the connecting mechanics between the battery and the charging unit. This critical component is also Absent from the V7.2 drone design currently up on this site. I hope to devote some significant research to this topic before continuing with the Charge Unit design. The battery/drone/charger connection must handle roughly 1500 - 3000 insertions and disconnections in order to ensure the lifespan of the drone, so it will need to be a robust connection. In addition, it must also handle the already existing requirements of being vibration resistant and high-current.
Positioning of this connection on the Charging Unit and Drone will be critical and need to be stress tested for thousands of cycles, likely with a pneumatic rig. Additionally, thoughtless placement of the connection in the Charging Unit risks voiding the IP22 rating if dripped water accumulates and bridges the contact.
The battery swap on the drone is meant to be splash proof - the battery rig is compressed into a soft, silicone sealing strip. However, the sliding latch for this compression hasn’t left my sketchbook yet. These latches will be present in V8. This means the critical battery/drone/charger connection doesn’t need to be fully waterproof, as it is already protected from the elements inside the environmentally controlled electronics bay.
Once I have designed this connection I can focus on how it is implemented in both the Drone (V8) and Charging Unit (V8). My current thoughts are two banana-style compressing copper inserts which contact inside two corresponding copper tubes. In addition to that, spring pins will contact a simple exposed pad for the cell balancing during charging. At minimum, this will create a starting point for me to begin the design of this small assembly. Updates in the weeks to come.