Conversion Process - Electrical - Battery fire Forensics and prevention finding.....

Please note this article is the August 2008 findings of this case.......
The article is from Bill Moore - EV World Insider


Battery Fire Forensics
Early in June 2008, an engineer with Central Electric Power Cooperative of Columbia, South Carolina was driving a Toyota Prius that had been converted by Boulder, Co-based Hybrid's Plus to a PHEV 15 plug-in hybrid. The day was hot, the maximum temperature got up to 98 F (36.6 C). After driving an estimated 40 miles, he noticed the Prius' engine beginning to rev at high RPMs and a warning light come on. He pulled onto the shoulder of the road and inspected the vehicle, assuming the acrid smell coming from the vehicle was the engine over-revving. He pulled back onto the road and drove a few more miles before noticing the warning light again and a strong smell of burning fabric, which quickly filled the cabin with smoke. Pulling off the road, he got out of the vehicle and noticed the right side of the rear cargo compartment was on fire, which eventually consumed the vehicle, igniting an intense forensics search as to the cause. The results of that research are now available in the following PDF:
Report of Investigation: Hybrids Plus Plug In Hybrid Electric Vehicle. The 33-page report prepared for the National Rural Electric Cooperative Association and the U.S. Department of Energy's Idaho National Laboratory by eTec in Phoenix, concludes...

Here is the summary
The likely cause of the fire is improper assembly of bolted joints with electrical lugs. These joints became loose causing excessive heating which led to the rupture of individual battery cells which resulted in significant short circuiting of the battery ultimately resulting in the vehicle fire. The batteries were designed so that a spacer should have been placed between the fuse blade and the electrical lug so that the plastic battery cover would not be in compression. Compressed plastic has a tendency to creep which would result in loss of clamp load on the fastener. Inspection shows that the brass washers that were intended to be the spacers were instead installed underneath the bolt head (between the bolt and the lug which served no purpose). Additionally, there was no locking mechanism (lock washer, safety wire, adhesive, etc.) that prevented the bolt from backing out of the nut. It is likely that the bolted joint became loose over time and during regular vehicle operation which resulted in a high-resistance connection causing those components to increase in temperature. A123 Systemsí design guidelines appear to be violated in several areas which may have contributed to the severity of this incident.

A timely reminder to do the right thing when it comes to dealing with high current connections in our conversions. I also highly recommend using a torque wrench on battery terminals (bolt style terminals) to ensure they are not over tightened causing internal damage. Once again, remember any connection will work to start with but it's the longer term connection issues that will cause problems. This can result from all the things mentioned in this report.

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