eVFR Electric Motorcycle Conversion » V2.0: Batteries and BMS

V2.0: Batteries and BMS

Its been a busy season. I went to Ashland, OR to visit Brammo and Barefootmotors (will write about that this weekend hopefully). The weekend after that I went to Spokane, WA for Thanksgiving with my relatives. I haven’t had a ton of time to sit and do stuff on the battery side of things.

Last night, I brought my batteries inside from the garage. The temperatures have been very low this last week, and I feared the batteries might get damaged. I sat down for about an hour and measured each and every battery. Out of 195 batteries that I had sitting there (6 more are at Synkromotive, 1 in my car), one was 2.8V, two were 3.19V and 2 were 3.22V. The rest were between 3.28V and 3.33V. Not bad for sitting almost 3 months.

So my plan this weekend is to make some progress with the batteries. I want to put small batches in parallel to equalize, and bring them all up to ~3.65V with a 3.7V DC-DC converter and power supply I’ve got. After letting them charge, I’ll disconnect and let them all balance between eachother and settle. This will ensure a balanced pack before building. If it isn’t pre-balanced, the BMS will take a long time to balance the cells by itself. People often make the mistake of not balancing the pack before assembly, which can cause them many problems down the road.

Hopefully I can finish equalizing cells this weekend. If I do, I’m going to see if I can borrow a CBA-II from Phil Hochstetler (to do a 3-4C discharge on each cell to make sure they’re all in good shape for the pack. I can log each battery and save the graphs. It’l help knowing how each battery (barcoded) progresses over time.

I don’t know if I’ll have time to get much more done before I go visit family in Roanoke, VA for Christmas. I leave the 24th of December and return the 4th of January. Once I get back, I need to contact my welder to get the fabrication started while I do some battery setup and test.

Thats it for now. Should be a fun January and February now that I’ve got pretty much everything.

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