Boxed In · 14 October 05

Last night I brought home a bunch of scrap cardboard with the one goal in mind of making a cardboard battery mock-up so I can start experimenting with battery placement in the electric car.

Nothing is ever that easy.

“Lessee,” I mumble to myself, “What size of battery am I going to use? I know, let’s check the internet!”

Which led to hours of searching, comparing, hair-pulling, and general lack-of-carboard-making. I’d been sort of leaning towards the Dynasty DCS100L AGM battery but when I went to find information on it, like where to buy it, the results were pretty scarce. Hey, who wants to buy a battery that can’t be found?

This lead to a whole sub-search on batteries, parsing through the various incarnations of the EVList (link below). If you haven’t checked it out yet the EVList is a place that attracts discussion from all levels of EV experience, all over the world. I like to read any post from Lee Hart, but there are a whole bunch of intelligent, honest, and experienced folks posting.

The EVList has been around forever and the archives bounce from server to server like an unpopular step-child. Google seems to only find results from the EVList prior to 2003. Yahoo plays host to a more recent archive of the discussions but seems entirely unable or unwilling to put an effort into searching the list. A great resource that is almost impossible to navigate.

After a few hours of battery obsessing I came away with two choices:

• stick with wet cell lead acid
• use optima yellow tops (AGM lead acid)

Lead acid is tried and true and inexpensive. Optimas are about double the price, sealed (clean!), have a relatively long cycle life, a lower internal resistance, and are built for motive applications. The new Optima D31T looks ideal for Eve.

This means I need to make or buy a battery management system to keep them from overcharging. I’ll justify it as something to be amortized over this and future versions of the EV. Pretty what I’ve done with the motor and controller, which provided over eight years of service in the first EV and should do that much or more with Eve.

At the end of the night I had one piece of a cardboard mocking up the length and height of an Optima with a little breathing room factored in. Being able to lay the batteries on their side means I can make one, contiguous box in the front (and back) sitting above the motor.

Fired up my little battery layout tool to experiment with placement. Looks like I ought to update the tool so batteries can be placed in different configurations (it’s currently lead-centric). Also, a few more battery icons might make things easier.

For this image I input the length and height of the battery (rather than width) and then changed how the batteries look in photoshop after the fact. It works.

The top four would be in the engine compartment, the other eight under the car. The measurements are:

Battery Size: 12.8” x 9.375”
Box 1: 40” x 29”
Box 2: 27” x 20”

Tonight I’ll measure the area under Eve where the gas tank used to be and see if this configuration will work. It would be nice to be able to use the old battery boxes. I don’t have another swimming pool to make more!

Here’s some links for your viewing and dancing pleasure:

• Optima Group 31 series
• The EVList
• EVList Yahoo archive
• Older EVList archive
• The cardboard box graphic is from Australia’s Murfy Recycling Education Program.

Wanna a sure-fire way to find other ev conversion and solar projects? Search for battery box in google images.