Cameron Motor Works Electric Vehicle Conversion

Battery Box Construction

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March 2005

Battery Box Sizes

From the design of the battery boxes, we have:

Engine Battery Boxes Layout:

Note: The batteries shown here are the new Deka Dominator 8G34 Gel Cells (appropriate only for a high voltage system). These batteries are placed on end to be able to fit into the New Beetle. Two boxes will be used, the front box will contain 8 batteries, the rear engine battery box will contain 4 batteries.

Rear Seat Battery Box Layout:

Hatchback Battery Box Layout:

Battery Box Material

The battery boxes will be constructed from gauge steel (same gauge as the VW body). They will then be sprayed with an acid proof coating then lined with a watertight rigid PVC liner.

The insulation will be 1/2" PE Ethafoam.

Battery heaters will line the case and be driven from AC power while connected to the mains power.

Cut out the Car

Form up the steel boxes

Undercoat and topcoat spray the boxes

Weld in the boxes

Spray (touch up) the boxes

Spray inside with corrosion resistant paint

Build and install the PVC liner

Build battery hold downs

Install venting

Install insulation

Install heating

Install access for wiring

Build and install lids

Get new rear springs

Battery Box Reinforcement

The battery boxes are light gauge material and so need to be reinforced. Here are the initial designs:

Cutting out the car

The important thing when cutting a uni-body car is to ensure that frame members are not cut. Other things to consider:

No wires cut
Free movement for parking brake cables
Brake lines intact

The tools for this job include a sawzall, jigsaw and the "last resort", an air chisel:

The first step is to cut out the floor where the battery boxes will be placed.

Building the Battery Boxes

A sheet metal shop cut and folded the material. The rest was to weld the boxes, weld on the reinforcement and paint:

The finished result...

Installing the Battery Boxes

Installing the battery boxes was as simple as clamping in place and welding in the skirts and extra reinforcement:

The finished result...

Insulating the Battery Boxes

1/2" of PE Ethafoam was cut and contact cemented to the insides and floor of each battery box.

The finished result...

The Front Battery Boxes

The front battery boxes needed to be build to very specific tolerences as there was not much room in the front compartment.

The firewall battery box, which holds 4 batteries is installed behind the drive, directly on the firewall:

The front battery box, which holds six batteries is installed between the frame rails in front of the drive:

References

Mig Brazing cooler welding technique which works well for galvanized material.

Successfully welding sheet metal

Making a sound mig weld

Welding Galvanized Steel

Kits for soldering and brazing aluminum

Using 3M Tape for bonding Aluminum plates