Sunday, September 09, 2007

Make a what outta who, take two? (or, the reincarnation of baby Optima)

(note the maniacal look of glee...)


(already looking deceptively young)

Creative retasking of salvaged components is one of the more satisfying aspects of this project for me, and the prototype Baby Optima had been bugging me for a while. The yellowtop color and tidy size that fit perfectly atop the original VW air cleaner stand were too good to pass up. Besides the prototype being an interesting footnote in EV history, this particular baby had cranked up John Wayland's generator cart during many record-breaking races. However, rebuilding it as a battery out of Cyclon cells, though clever, would give only an 8.0 Ah battery, not much reserve capacity should the dc-dc EVer conk out. Also, it was on the wrong side of the motor bay for clean wiring, and the position of Godzilla 003's coolant pipes were just begging for a reservoir atop that stand. So, I accepted; bent to the will of Zilla, and decided to convert the little Optima into a coolant reservoir.
Now, this battery had been sitting for years, it didn't get above 10v when I hit it hard with a recharge, and had been purposely shorted out for a couple of days to prepare it for decommissioning. HowEVer, sitting unconnected overnight, it actually recovered a bit of charge. What's the worst that could happen, eh? So I went to it with the hacksaw, and when the blade started to sparkle, I went ahead and checked voltage. 8.56, not too shabby for a battery with a sawblade shorting out three cells!

Cutting off the top was easy enough. Slicing throgh the cell interconnects was the only work involved, as they wanted to send the blade off course.

With the top off, the little six-pack lay exposed to the world. Of note, is that one cell was discolored in comparison the the rest, perhaps the reason that the battery wouldn't charge up.

Extracting the spiral cells proved to be a challenge. I screwed in the largest lag bolt I could find, and the cell sizzled with displeasure, but the big screw simply pulled out of the matrix when pried up with a crowbar. After several short starts (yes, a very bad pun...), I wound up simply drilling out the contents of each cell with a large spade bit, simply shaking and prying out the contents after they were shredded and loosened up. I didn't get an entire spiral cell suitable for dissection, but the following photo shows one section, complete with a piece of grid, the reddish-brown electrolytic paste, and the tyvek felt separator.

After extracting the lead and bagging it for disposal (this should be an interesting negotiation with the battery recycler), I cleaned up the case (wiping instead of rinsing or sweeping in order to minimize dust and water contamination, and securely bagging the paper towels for disposal).

To get the case ready for reuse, I squared off the top edge, which was pretty ragged from my hack job, with a belt sander. I also used a sautering iron to melt the plastic back into a couple of nicks and pinholes incurred while drilling out the contents. Then a Dremel tool was used to trim the remaining case material out of the battery top, and I cut off the hollow lead battery posts flush with the lid, in preparation for mounting hose nipples. Multiple hardware treks and redesigns were required, but in the end, I used 90 degree barbed fittings, threaded into the battery posts, and epoxyed a brass pickup tube into both fittings. (Yes, brazing would be better, but my torch was out of gas.) This way, the direction of flow doesn't matter, there will be no splashing sound, as there would be if the coolant return wasn't plumbed under the surface, and the warm coolant will be returned to the bottom of the reservoir, encouraging convection currents. However, the biggest encouragement of all for thorough mixing will be the pattern of holes I drilled as coolant passages within the reservoir. I also cut the bottom of each tube at a sharp angle so that ht tube would nearly touch the bottom of the reservoir, but have less potential for suction against the bottom or blockage by silt.

All that remained to do was seal on the top with silicone, mount the reservoir on the stand, and hook up the plumbing.
Keen observers will note that the 'positive' coolant fitting has not been connected. Installation of the coolant pump and radiator still must happen, and as with all else on the Karmann Eclectric, that involves some custom fitting, and must wait for another day!!
I case you're wondering about how this system will be filled and purged, there are actually two vents in the top of the Optima case. One, the grey porous ceramic disk that only vents under pressure, and the other, a 1/8" diameter 'straw' that stuck down into the battery about an inch. I cut this off level with the top so that it will vent air instead of liquid, and will rid some sort of porous cap for it (visible inside the rectangle atop the Optima lid). The vent will be the highest point in this system, so it the cooling system should purge itself. Initial filling will be through the upper hose, but coolant can be topped off through the vent hole.

Thanks for Reading,