Re: [electricboats] Finally Starting The Build

I used these screws from McMaster Carr:
https://www.mcmaster.com/92605A134/

They have a flat tip and I thought that would help get more engagement of the threads.  I did not use locktite.  I applied contact grease to the threads and all contact surfaces of the battery terminals and bus bars.  I considered the threaded studs contact surfaces.  I made my bus bars from 3/4" x 1/4" copper bar and the holes are much closer to 6mm.  One hole is a tight clearance fit for the stud the other is slightly elongated. I figured every square mm of contact was useful in a high current application like this.  And I thought locktite would act as an insulator and inhibit contact between the screw and the threads though it might improve the hold of the studs and that could be more important? 

I torqued the studs to spec with a torque limiting driver and used SS nuts to hold the bus bars down.  They were the type with a serrated flange but I can't find that order reference right now.   When I tightened the nuts holding my bus bars I held the stud from turning as I tightened down the nuts.  I connected the BMS leads to the bus bars with separate 10-24 brass screws in threaded holes in the bus bars rather than ring terminals under the nuts holding the bus bars to the studs.  I didn't want anything adding to the task of holding the bus bars to the studs.  

I don't know how much strength there is in the terminal threads on these batteries but I am sure they would be easy to strip.  But I seem to recall reading somewhere that the real issue was inside the cell where the pouches connect to the terminal or the cross bar that the terminal attaches to.  The torque spec may have to do with protecting that part not the threads in the holes.    I can't confirm that this was an issue at all.  I just recall seeing something about it.  It could have been speculation. 
 

Dan Pfeiffer

 

On 2021-08-20 1:57 pm, Randy Cain wrote:

I'm using steel m6 grub screws from Monsterbolts (both ebay and amazon) torqued to 4Nm with loctite 242. I'll then slip a plastic sleeve over it since the lugs have 8mm or 9mm holes and don't need to contact the stud anyway.