Unfortunately this project has stretched to over a year longer than intended due to starting a business, consulting people and having a girlfriend, etc. Couple that with the fact that I don’t own some of the metalworking equipment I need to build my battery enclosure and holders, and time just runs away.
Because of that, the batteries sat in a box in my apartment.
So, one thing I was a little weary of over the last 6 months, is the health of my 180 cells. I charged them about 4-5 months ago one-by-one with an RC battery charger. They had never been charged before that and didn’t apear to be consistently charged from the factory. After charging, they all had basically the same voltage (I know SOC isn’t a real accurate measurement of SOC, but at the top/bottom, it’s fairly accurate).
Last night, dreading the chore, I measured all 180 of my batteries with a handheld multimeter. Not one was below 3.28V and they only varied about 0.06V amongst all of the cells. No dead cells. None had a large self discharge. I didn’t record the starting voltage for each cell bar-code, but I’m really happy with the fact that these things can sit for months and months and have no problems. When I do make the pack, I’ll start things slowly and not hammer on them too much just to wear them in properly.
Since it’s winter time, I’ve got some more free time, and I’m starting to work out the electrical system. A friend of mine is taking my extra frame and we’re going to make some mockups of the battery pack. We were considering spray foam, that way we can cut it away as needed and fiture out the final dimensions of the pack. He’s a welder so we should be ok on the enclosure side of things.