Series Connections Bolts and Nuts
- Micah Black
After being previously advised to not use fujilock fasteners on the series connections for the battery modules, and learning more about the types of fastener retention through the investigation of the clickbond standoffs, I figured it would be good to revisit this topic.
Research on bolt loosening:
https://www.boltscience.com/pages/vibloose.htm
https://www.boltscience.com/pages/Why_nuts_and_bolts_can_self-loosen.pdf
The research on bolt loosening above shows research with extreme transverse loading. It is not representative of the loading that will be on the battery pack connections, but it is a good example of what can happen, and what will happen if we are not careful.
Prevailing Torque and Fujilock Nuts:
https://www.fastenermart.com/prevailing-torque-lock-nuts.html
https://www.mefaco-intl.com/wp-content/uploads/Fujilok.pdf
While the prevailing torque locknuts do seem useful, in practice they just minimize the issue. The loading torque from vibrations, etc must exceed this prevailing torque threshold before being
Conclusions:
There is absolutely NO substitute to proper preloading of bolts
Critical fasteners in the battery box should be regularly checked and have a quick visual identification of loosening
A sharpie mark in the mated position should be used, and checked regularly.
Locktite should be used where necessary - on busbar connections, fuse connections, relay connections, etc.