So to give a little back story. I haven't really riden to work yet, primarily because the roads and trails around here aren't really advantageous of commuting from where I'm at. I live in DC and so typically Metro is an option but not where I'm at, I'd have to drive and then park to metro which would cost more than what I'm already paying now for parking at my work ($180/mo). I got the idea that I could bike to work by saving a ton of money from parking and auto expense. However, that really hasn't panned out yet. My SO and I are looking to move this summer to a place closer to our work and so that'll give me the opportunity to finally bike to work. I built an ebike last summer and started with the battery. I used a combination of cheap chinese cells and older brand name cells. Some of which I have some concern about... So this is where I'm at. Through riding last summer I was able to put over 100miles on the bike and I had a blast. I took a nasty spill in the parking lot of Marriott International in the fall and that was my wakeup call that this bike isn't so much a bike anymore...when you're going 30+mph... So anyway. Back to the bike. I have the stock controller which says 26A 48V, but I can comfortably do 33-34A which gets me close to 1500W. This is awesome for accelerating and getting up to full speed. On a fully charged battery I can do about 35MPH. Riding comfortably is around 20-25MPH. In a single ride I've riden around 20 miles and still had plenty of charge left. I think I was down to around 44V.
So the battery. I built the battery as cheap as possible using copper wick wire and used cells, some new. Some of these cells only got me around 1500mAh but I didn't test every single cell... So here's my dilemma. I'm going to take apart my current battery of 91 cells. Discard the cells I retest that achieve under 1900mAh and replace them with a bargin! I found older NCR18650 Panasonic 2700mAh cells for $1.6/cell. Not all of the cells will be replaced as this would be quite expensive, but only the cells that fail the test will be replaced. Also, I'm adding a parallel group to reduce my load per cell. Since I'll get around 1400-1500W that means at full charge I'll draw close to 4A per cell, or 2C from a standard 2000mAh cell which most of them are. I'm really hoping the Panasonic cells perform really well and help the battery out. lol. I also had some design flaws in my first battery that I hope to fix with this new one. I designed the battery to hug the top rail of my bike as you'll see in the picture below. Problem was I didn't have my bike at the time I built it so I didn't measure the diameter of the bike tube correctly and so the cells ended up being too wide... Hopefully through this redesign I'll be able to make a more compact battery. Basically I'm attempting to make it look like it's part of the bike rather than one of those dolphin packs you commonly see.
If anyone is interested in purchasing the Toshiba battery pack that has the panasonic cells in it: https://www.ebay.com/itm/NEW-Toshiba-Li ... 1438.l2649
The battery is probably upwards of 10 years old. The cells in the test battery I got were around 3.4V, charged them up and they still get over 2700mAh at 1A discharge. Pretty exciting!
For now I've purchased a new soldering iron (last one died somehow). More wick wire from china which will take awhile... and the 24 panasonic cells. I also have LG 18650 S3 cells that I will include in replacing the older cells. These cells are 2200mAh cells rated for 4A discharge max which should work just fine.