July 11, 2008

Tomorrow we leave for Rehoboth, Delaware to spend a week at a beach house with my extended family. A friend is covering my class for those days which is nice, but I feel really torn...

There's so much work to get done on this project and I'm just getting to the interesting parts. My motor has finally arrived and I'd like to get busy and put her in there! Oh well, I guess I'd better grab a little resting and recreating while I can.

I'm finally in a position to begin serious testing on the BB-600 cells. Today I put 3 of the 12 volt modules in parallel on my big charger set for 35 Amps. Over a period of an hour the charging current decayed from 29 Amps down to 20 Amps, where it stayed for the next three hours. At that point I guesstimate they had almost 90 Amp-hours in them, and the voltage read 14.11 Volts. At about 3 in the afternoon I began a (nominally) 6 Amp overcharge -- the meter on the charger read 5. By 7:30 PM the charge current had decayed to 4.7 A and the voltage had also dropped to 13.9 V. I think the cells are not really completely full (for instance the overcharge is supposed to be 4 hours at the C/10 rate which would be 9 Amps for this configuration) but this is as close to completely juiced up as I've ever gotten any of them.

Decided to do my first cell watering! I added de-mineralized water until all the cells had an electrolyte level about .125 inches above the aluminum side rail. Some (2 or 3) cells were about .25 inches above the rail so I left them alone, but most were at or below the level of the rail. After the watering I gave them another half hour on the 35... I mean 20 Amp charger to top them off. None of the cells vented noticably and when I measured there voltages cell by cell, they are now amazingly close to one another.

spreadsheet with voltage readings.

I really wanted to do a discharge test, and running in the brushes on the new motor would be a nice way to do it! Having started the process a few days ago and having become concerned about the noise and how HOT the wire I was using got I opted for some basic instrumentation. I purchased a shunt and ammeter (intended for installation in the instrument cluster) some time ago, so I wired them into my test rig. The motor makes a disturbing amount of noise and draws 50 AMPS with no load on it! After just 10 minutes I shut her down. I wonder how much self-discharge will happen over the next week while I'm away? Anyway it's now after 9:00 PM and the spouse is packing single-handed --- time for me to call it a night.