This wire guide under the PCB serves to guide the wires and avoid any potential short-circuits that could be caused with the pins that go through the PCB.
Where is it located?
What wires are going underneath?
The wires that go to the battery modules are:
Thermistors
There are 4 thermistors on the module, each have 2 wires
Voltage measurement
3 wires for each of the voltage points in the pack
Balance Wires
3 wires to draw current from each of the battery cells
<100mA during regular operation
Also used to manually re-balance cells at higher currents (~10A)
How much room do we need for the wires?
Wire Use | Wire Gauge | Reasoning | Diameter (Nominal) | Datasheet Image | Datasheet Link |
|---|---|---|---|---|---|
Thermistor | 22AWG |
| 1.6mm |  | |
Voltage Monitor | 22AWG |
| 1.6mm | Same as above | Same as above |
Balance Wires | 18AWG |
| 1.96mm |  | https://www.iewc.com/assets/specsheets/Champlain%20EXAR%20150%20UL3266-3398.pdf |
With the number of wires required, and the already determined 12mm width of the opening, I wanted to check how tall of an opening we need, so I created a quick sketch in Solidworks:
We figured that a 4.5mm tall hole works pretty well with a bit of extra space. So we started with 4.5mm then went to 6mm tall based on the sizes of standoffs readily available.
Standoff locations to mount the PCB:
In the hexagonal holes, there will be standoffs that go through to mount the PCB module to - this is an off-the-shelf part.
Requirements of the design:
Protect the wires from shorts to the underside of the PCB module (the pins for the connectors poke through the board). The pins can be sharp and can rip through the insulation material.
Connector pins are highlighted in blue here (this is a view of the underside of the PCB.
Provide strain relief - I need to make a confluence page on why this is important
Images of the design:
Where is it located - on top of the module acetal isolation cover, below the PCB
View of the underside of the piece that shows the cover to the PCB
Section view showing the cable crimps that it connects to:
What wires need to go through here and where do they go?
The area with all 14 wires going through it at the top will be filled with a rubbery glue - to provide some strain relief to the cables.
Features relevant to Isolation Cover
When the isolation cover, a few features are needed.
How will we get it on - the chamfer (red) allows a lead-in so that it is easier to push the isolation cover on top - otherwise, it would need to be aligned perfectly prior to pressing it in.
The holes (blue) allow the pins on the isolation cover to lock in and keep the isolation cover on the module.
