Battery Box Mount - Design Selection

Overview

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

*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:

1. Guide system (what will actually hold battery box, provide support in "x","y" direction)
2. Mounting to chassis
3. Locking mechanism (what will secure box in place, support in "z" direction)
4. Vibration dampening

Design Selection & Analysis

Solutions to these sub-functions can be analyzed in a morphological chart:

Morphological Chart

Design Proposals

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:

Design Selection Chart

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

Design Concept

Several refinements have been made to Option C to better improve costs, weight, and reliability:

• Guide rails - 2 aluminum or steel L-beams instead of a single c-channel to reduce weight and costs
• Mounting - aluminum brackets with buttresses to mount the L-beams to the chassis
• Fine tuning - slot milled into brackets to allow for bolting to chassis. Slots allow for slight adjustment of guide rail position to improve fit against battery box
• Friction - adhesive backed plastic shim attached to either battery box or guide rail to reduce friction/ eliminate interference
• Rollers - (possibility) spring loaded rollers along rails and detent in box to guide battery box into place and/or for user confirmation that box is correctly installed

Quick concept sketch of above proposed design:

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