Thursday, August 19, 2010

Trunk Modifications Part I

I've been working on modifications to the car over the past couple weeks. In order to get the AC back into the car some of the cells needed be shifted from the front of the car to back. Additionally, I want to add a more cells. The only solution was to make better use of the trunk. The number of new cells I'll add is still not firm but I'm looking to add as many as possible for multiple reasons.
  1. Greater range. More cells means I have more energy and can travel further before recharging.
  2. Distributed load. The more cells I have, the less they have to work for my daily commute which will increase the life of the cells.
  3. Performance. Currently the 144v system allows the motor to hit about 4k RPM before the controller switches to VMax. Any additional increase in RPM greatly reduces torque requiring you to shift to a higher gear. Increasing the voltage will allow the torque to remain steady for higher RPM meaning the motor will want to rev out higher.

Here is a shot of the original trunk space. You can see there isn't much usable space currently above the fuel tank, about 3" and it opens up to only about 8-10" on the far right.

The old spot I use to have the charger has a curve to it and greatly reduces the usable space.
A couple of minutes with my plasma cutter and the rear most area is opened up and ready for a new battery rack.
This area now allows for storage of all 15 cells that used to take up the remaining trunk space (including charger). The rack is lined with a thin plastic and sealed to keep out water, etc. I used an expanding foam on the outside underneath the car to also fill in any open areas. The sides use a 1/4" thick steel for strength since the rack is also binding the cells together. If you use a thin metal it will bend as the cells begin to swell which is very bad on the cell life. It's amazing how much pressure is needed to contain them properly. The top (black) metal is much more light weight and designed to simply keep the cells from being able to shift upwards on bumpy roads or a rollover.

Next I will be working on the area where the gas tank use to sit. It looks like I can fit another 18 cells here if it all works out. I will need to make some suspension modifications for the extra weight I'm adding with these additional batteries.

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