Overview
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Objective
Design solution to mount battery box (enclosure) to vehicle
Background
Battery Box Design
Based on prior discussion (2017-01-14 Battery Box Size), the current battery box weight and dimensions can be summarized as follows:
- We will be using 2 boxes, each housing 18 of the 36 modules
- Rough Dimensions: 24" x 18" x 5" (L x W x H)
- Approx weight of 40 kg per box, based on 80 kg estimate for both boxes (see Weight Budget)
Battery Placement in Chassis
*Regarding the pontoon hull, the current proposal would be to split the two battery boxes between the hulls as per above.
Previous Discussion
Previous documentation relating to the Battery Box mounting solution can be found here: Battery Box Mount
Design Considerations
| Requirements | Constraints |
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*Regarding the configurability of mounting solutions, having this option would allow for better weight distribution depending on the number of battery modules used (per different regulations for maximum battery capacity) by allowing for the repositioning of the battery/batteries in the vehicle. This would also be the case for adjusting when racing with a driver + passenger vs. driver only.
Sub-Functions
Based on the above requirements and constraints, the function of the battery box mounting system can be broken down into the following sub-functions:
- Guide system (what will actually hold battery box, provide support in "x","y" direction)
- Mounting to chassis
- Locking mechanism (what will secure box in place, support in "z" direction)
- Vibration dampening
Design Selection & Analysis
Solutions to these sub-functions can be analyzed in a morphological chart:
Morphological Chart
| Sub-Function | Option 1 | Option 2 | Option 3 | Option 4 | Option 5 | Option 6 |
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| Guide System | Tracks (low friction) | Tracks (wheels) | Enclosure (box) | Enclosure (skeletonized) | Enclosure (C-channel) | Webbing |
| Mount to Chassis | Weld | Bolt Into | Fasten Around | Adhesive | ||
| Locking Mechanism | Pin | Straps | Arm | Ratchet | ||
| Vibration Dampening | Foam | Springs | Tight fitting guide | Tightening guide |
Design Proposals
| Design | Sub-function Solutions | Sketch |
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| Option A (Datum) |
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| Option B |
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| Option C |
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| Option D |
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Selection Procedure
The above proposed solutions can then be ranked based on the following criteria. The ranking scheme used will compare designs against a datum design (Option A) ranking them with either: +1 (better), -1 (worse), or 0 (equal).
Ranking Criteria:
| Critical | Good to have |
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Design Selection Chart
| Criteria | Option A (Datum) | Option B | Option C | Option D |
|---|---|---|---|---|
Securely hold battery box in place | +0 | -1 | +0 | +1 |
Securely mount to chassis | +0 | +0 | -1 | +0 |
Robustness | +0 | -1 | +0 | +1 |
Easy removal of battery box | +0 | +1 | +1 | +0 |
Manufacturability | +0 | +0 | +0 | -1 |
| Vibrations | +0 | -1 | +0 | +0 |
| Configurability | +0 | +0 | +1 | -1 |
| Total | +0 | -1 | +1 | +0 |
Discussion
Based on the design selection chart, it can be demonstrated that Option C is best design moving forward. The use of c-channels bolted to mounting points on the chassis will provide the best security for the battery while also allowing the battery box placement to be configured within the vehicle. In addition, a "tackle box" style latch or arm to hold the battery in place will allow for easy removal of the battery box while providing adequate security to hold the battery in place and removing vibrations.
Some issues that still need to be addressed are:
- whether to manufacture or purchase the channels and/or arm
- the length of the channel (whether to use multiple segments, or one long channel)
- the design of the arm to provide proper tensioning
Moving Forward
- Go over possible design solutions with Graydon McDonnell (Deactivated) (Monday, January 23)
- Go over proposed solution with Devon Copeland (Monday, January 23)
- Create concept sketches of proposed design