Sunday, November 15, 2009

Battery layout and rack designs

It's been almost 2 months since I wrote an update. Obviously I'm horrid in finding time to write. Maybe I'm embarrassed too because, although some progress has been made, compared to most other EV converters I am moving at less then a snail's pace.

In the last post I described the transmission and motor mounts, but I hadn't quite finished the torque rod for the upper transmission mount. Well, it's still not done!  The steel pieces for that have been cut but it is still waiting to be welded together.

Yet, since the motor and transmission are in place I can at least figure out how many of my jumbo batteries will fit in the engine compartment.  I had hoped for 4 and planned on 3, but more careful measurements showed that only 2 will fit. Just barely. And I might have to seriously modify the sub-frame to make it happen. Very disappointing. So that means 11 batteries have to fit in the back seat area. That put me in a bind with the back seat battery box design but I was able to cram them in. Here are a couple CAD views of the back seat area.

The "lower tier" (which holds 6 batteries) sits where the back seat bottom was, the "upper tier" will be bolted to the lower tier box and is at the level of the trunk floor. The upper tier box is higher than I'd like, but I really didn't want to cut away any of the floor pan. In addition to the two tiers being bolted together, they will also be bolted to the frame and through the floor pan in 7 places. Should keep them in place in case of an accident.

What is my weight distribution going to be now?
I didn't weigh the car before I started the conversion, but according to the door jamb the car started out with 1470lbs on the front axle and 900lbs on the rear axle. That's a 62%/38% ratio, 2370lbs total. Based on the current battery layout (2 where radiator had been, 11 in the back seat/trunk area) I will have 1570lbs on the front axle and a whopping 1600lbs on the rear axle. That's a 49%/51% ratio. More balanced for handling, you might say, but it will certainly be a lead sled coming in at a svelte 3200lbs. I've ordered custom springs (Springworks) for the rear struts to help accommodate the extra 700-800 lbs on that axle. May have to beef up other components, too. Time will tell.

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