jstept's blog

I ordered two new 20Ah LiFePO4 cells from Sam at Yesa on Tuesday to replace the two that were damaged (see "Fire is Bad"). Cost was $70 per cell and shipping from Hong Kong was $45. The cells arrived last night along with an individual cell charger. Sam asked me to send him a picture of the cell arrangement in the pack so he could have the tabs soldered in the correct orientation.

The red arrows indicate the bad cells.

I took my damaged pack over to Synkromotive today to have some experts take a look at it. We took voltage readings of each of the 12 cells. They each read about 3.3V, except for two cells. One of them read just about zero, and the one with the obvious damage read about 1.8V. Their advice was to just replace the bad cells and keep going. They also briefly studied the BMS that came with the batteries, and deemed it satisfactory.

I had a harrowing experience yesterday while I was riding the Rezistor home from work. I smelled something funny (it always starts that way, doesn't it?), looked down, and saw smoke coming out from under the seat. I pulled over, cut the power, got off, and saw the paint on the exterior catch fire. I blew out the fire, lifted the seat, and saw some arcing between the corner of the battery pack and the inside of the scooter body. I disconnected the battery pack immediately.

Rode the Rezistor to work yesterday and today. I haven't been able to find any electrical outlets on the outside of the (very old) building I work in, so I had to improvise.

This weekend I rode the Rezistor to Spring Scoot, a scooter rally held annually each year here in Portland. It basically served as the initial test run and range tests. I started with a 6.6 mile ride on Friday night and rode progressively longer distances Saturday and Sunday. I finished with a 14.5 mile ride Sunday evening, much of it at full throttle. There seemed to be juice left when I got home, although my headlight (and presumably the rest of my accessories) seems to have given out a few blocks earlier. The controller, motor, and power cables were only a little warm.

The replacement controller from Team Delta arrived on Wednesday. Fantastic service from Dan, considering I just explained the problem to him on Sunday. I installed it and, at first, got the same "MOSFET short circuit" error message from the controller as before. I wondered if the contactor might be faulty, so I took that out, fiddled with it as much as I could (which wasn't much) then reinstalled it. But then it occured to me that the 12V converter might be faulty, so I left that disconnected. That must have been it, because the scooter worked after that.

On Sunday I contacted Dan at Team Delta, who sold me the motor and controller. I described what was happening with the Sevcon Millipak controller and he was able to clarify things for me.

Well, it's been an exciting week. I spent much of last Saturday getting the brakes working, installing the levers, cables, and switches. The brakelight switches install in-line in the brake cables within the headset, so I had to figure out where to cut the cable housings to get them in the right spot.

I haven't blogged in a while, but it's not because I haven't been making progress. It's just that when I get free time, I'd rather spend it building than typing and uploading photos. Here's a summary of what I've been doing:

I had to reconfigure LiFeP04 battery pack 1 so it fit better in the space below the seat. This involved cutting the tape that held it together, cutting and resoldering some of the links between the cells, and extending some of the wires to the BMS.

HUGE thanks to my friend Arden for helping me assemble the drivetrain. A fellow member of the Oregon Scooter Club, Arden has an amazing shop with machining and welding capabilities. He probably saved me over $100 in machine shop costs, as well as providing some of the raw materials.