Thursday, January 1, 2009

Battery Placement

In the past two weeks it has been hard to keep a good steady pace of work on the EV with the holidays amongst us. It was time to start considering battery placement so I decided to make replicas of lead acid batteries made out of bristol board carton to get an actual visual idea of how the batteries can be laid out. In the basement of our home, I used the kids' arts & craft table to cut out and assemble the battery replicas (dummies). I took the average dimensions of lead acid batteries (13.5" long, 7" wide, 10" high) with a bit of added room, marked the bristol board to maximize coverage, cut it, folded it and applied the kids' school glue along with scotch tape to attach all edges. The replicas where then placed in the trunk of the Mazda Protege in different orientations to see which might be the best or preferred fit.

Eight batteries in the back (trunk):

Four batteries in the front:

I also went back to reading up on those much desirable LiFePo batteries which are selling for about $0.50 per Watt Hour in today's market. This is still a pretty penny especially if you are planning for a capacity of 15,000 watts or more. With the downturn in the economy and the increased competition in the Lithium battery market, one can only hope that prices come down considerably. The question is always when and how much. If the price were ever to come down to around $0.25 per Watt Hour, I would not hesitate to give these batteries a try.

When I looked over the specs of such batteries, I also wanted to make a carton replica of a typical or mid class LiFePo battery and realized that the dimensions of such a battery where almost identical to those of a cereal box. For example, the Thunder Sky LFP160 AH model measures up almost exactly to a box of Bran cereal like the one in the first picture above.

I am now contemplating whether or not I should actually cut the trunk floor or keep it simple for now and hold off. I started making a 3-D drawing of my trunk/rear battery box using Google Sketchup and in a very short period of time, I managed to gain enough knowledge to make some decent drawings. I encourage anyone to play with this wonderful software tool. Here is a sample of one of my battery box drawings.

Happy New Year to all.


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