The Battery Pack¶
If the final design includes a curved back rest the battery pack may take a curved form to fit it. Otherwise it may have a large rectangular shape.
If the design is bifurcated by a rail there may be two packs on either side of the rail as that space may be hard to fill with other items. This would be facing the back of the user.
There may be two packs on the backpack at the same time, either for fall over, or efficient use of space and act at one pack.
Requirements¶
- Enough current supply to power some actuators or future one wheel design.
- Large capacity to power onboard compute for automation/ML models.
- Removable
- built in power relay
Nice to haves¶
- Hot swappable
- Battery heater for cold temperatures
- Emergency battery ejection
- Curved to fit back of backpack
- Battery heaters for colder weather may be important and an optional component of the pack. Not required
Battery cells¶
Boston Sonata 5300¶
Currently bought 60 cells for testing.
| Brand | Chemistry | Capacity | Watt Hours (Wh) |
|---|---|---|---|
| Boston | Li-ion | 5.3 Ah | 19.34 Wh |
| Config | Cells | Nominal voltage | Max discharge | Capacity Ah | Capacity Wh | discharge | rate | run time |
|---|---|---|---|---|---|---|---|---|
| 8s2p | 16 | 29.20V | 59.36A | 10.60 Ah | 309.52 Wh | 20W | 0.68A | 15h 29m |
| 8s2p | 16 | 29.20V | 59.36A | 10.60 Ah | 309.52 Wh | 60W | 2.05A | 5h 10m |
Rail pack idea (curved)¶
Battery pack design buss bar along curve or rail and fuses wrapping around from the curved side to the cell tops/bottoms, possibly makes it so it be easily opened and serviced. ( remove individual cells and just re-spot weld fuse wires )
Having the nickel bus bars along the curved edge of the pack, how much longer does it make the fuse wires to the cells?
Does the curved buss-bar become longer? Feels like it simplifies wiring. Solder buss wire to buss bar and then spot weld to cells.
Having the bus bar along the curve of the pack allows you to split the pack to replace any bad cells. How is the the pack held together and encased? Should it be shrink wrapped as well? Could design slots and divets for fuse wire and bus bar strips into the cell retainers.
Curving nature of the pack, how are they wired with a curved buss bar, possibly buss bar segments all wired to small segments of buss bar? Need to do calculations on segments. And groupings, how to wire pack series with buss bar on side or on edges?
May be able to get laser cut buss par parts or nickel strips.
Latching mechanism as part of housing? How to prevent ejection and bending. Venting accommodations.