Hello Electrified Miata Fans! I am now semi-recoverd after the battery fire. Thanks to Teresa for her encouragement to relocate this phase of the project to the garage.
First, we created a new workspace in the garage, with a large exit in case we have any other incidents.
Two car nights have happened since the last time I wrote. Thank goodness for the team. They pulled together, created solutions and made progress.
The guys came over on the first car night and popped the top and bottom off the
battery that caught fire.
We already knew we had to move the bus bar forward, as having the bus bar too close to the cells is what caused the short and subsequent flame out of 2 cells. We also decided that a plastic insulator between the cell and the bus bar would be a good idea. We were about to find out how well the bus bars were actually attached to the battery. Did I mention that the battery pack that caught fire was still fully charged? Before the incident, all 20 cell voltages were either 3.88 or 3.89 volts. After the incident, the cell voltage was 3.87 on the two effected cells - basically unchanged. Wow!! Did I mention that I've become quite sensitive to certain sounds, like pop and hissing?
Watching the guys pull the bus bars off the batteries, I could feel my heart racing. The pop and crinkle as the RTV grudgingly gave way while pulling the plastic off the
cells sounded just like the start of when the pack caught fire. If the bus bar edge dug into the cells and cut the thin plastic insulator, we could easily re-create the conditions that caused the first fire. Of course we were safer in that we're now working in the garage. Yikes!! I'm still nervous working around these little cylinders of energy. We removed the bus bars from 2 of the 3 batteries. There were a few small dents in the battery that caught fire, so I removed those cells as well as all the cells that were in proximity to the extreme heat.
I didn't get a lot done that first week after the fire. Personally, it has been a struggle for me. Fear can create all kinds of reasons not to work. Normally, I don't mind taking calculated risks. Having the battery catch fire as I tightened a bus bar has pushed me to thinking about the risks. I'm not interested in another fire and spend a lot of time thinking about alternatives. Taking time off and going to COTA for the weekend helped a lot.
The guys came over on the 2nd car night and removed the top from the 3rd pack and again removed the bus bars.
This time we used plastic to protect the battery from dents and shorts. It was still tough for me to listen to all that popping and snapping. RTV is good stuff being both a good insulator and a nice glue with elastic properties. Now that all the damage is un-done, we can start on the rebuilding processes.
Ed and I cut some plastic spacers from the thin plastic he has laying around. We also cut a new top and bottom for the ones that were fire blackened.
Now I have all the parts I needed to finish re-building.
Before the incident, we had 3 nearly finished packs. We now have 1 pack that has been rebuilt, and 2 packs in progress. Of those two packs, one will be easy as all it needs is installing new bus bars with plastic insulators and re-attaching all 44 power leads with Loc-Tite. The larger mid-size pack will need 17 cells replaced and re-wired in addition to installing the new insulated bus bars. Whew! This set back is finally contained and we'll be back on track soon
The goals for next week are to finish the 2nd pack and have the 3rd pack ready for assembly. After than, we can get back to attaching the the transmission to the Leaf motor and spinning it. The coupler weighs in at 3.3 pounds, which replaces the 31 pounds of Miata clutch assembly. Removing 28 lbs of rotating mass should be worth a little bit of extra performance! Extra performance always sounds good to me! Thanks for reading! Hope y'all are staying healthy and having fun.
Bill likes cars that understand the 'go fast now' pedal