Wednesday, August 26, 2009

Pop go the NiCads, not quite yet!

After nearly punching a rear opening through my garage and capsizing the HOA President, what more could I fear? Over the next week in July, my test runs got braver, as did my application of the accelerator. I got temporarily stranded once when an improperly wired 12V fan relay melted a wire, but it all nearly came to a stop when I heard a loud snap, crackle and pop during a spririted takeoff, and looked back to see an orange glow under a blackened lexan cover. Ripping off the cover, some tiny flames licked to life where a busbar had melted against a glowing red stainless terminal bolt. What they say is true, boys- retorque your cable connectors after the first round of testing! One loose battery connection can ruin your day. In this case, it only cost a pair of busbars, and left a molten brand in the top of one battery cell...
Well, the cell wasn't seriously damaged, and replacing a bolt and busbar is a simple matter, so it's back into action. However, I was replacing with a virgin cell that had not been properly commissioned, and for that matter, neither had my pack. I had just given it a shallow charge, awaiting installation of my E-Meter, which was sitting on the workbench of an EV Elder awaiting a clean bill of health (it never powered up on the first install). SO, rather than charging properly by counting amps and having a full-time voltage monitor, I forged ahead with a handheld DVM, first paralelling the new cell with a neighbor or two to bring it a bit closer to the rest of the pack. Then I overcharged, and decided to water the cells per the manual. Piece of cake. However, since I hadn't been able to count amps, apparently the cells weren't fully charged after all, and after a small successful test run, the cells foamed and spewed electrolyte on the next charge. I had prematurely filled them, and they expelled the excess. This caused a number of shorts between adjacent cells, and also via the stainless steel battery clamps. In total, five cells had holes burnt through their plastic cases, ranging from a barely perceptible pinhole, to a serious snot hole.

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