Hi Jukka, Is that "tight enough" ± a smidge? I am going with the torque wrench.
I watched a class once where people tried to control applied torque by feel with the max hold set, but hidden, then check the max after to see how well that worked. It was just terrible. A person might get it right once, but they were unable to do very well repeatedly. Then a set of seemingly identical joints were torqued, and the un-torquing checked. Again, no correlation to the applied torque. I don't really doubt that you are able to do this and have no trouble - this doesn't look like a very demanding application to me. But some people think that these joints will loosen over time. My contention is this loosening is not because the joints are prone to loosening, but that they were not torqued correctly to begin with, and maybe sometimes not enough. If you torque them right, they won't loosen - ever. Mike On Tue, Jan 7, 2014 at 6:01 PM, Jukka Järvinen <[email protected]>wrote: > Well.. The whole pole assembly (in these certain prismatic cells) has been > under doubt for a decade now. Some failures but not as much as one would > think. > > Many of you know the foils inside the cell are compressed together and > drilled with one or two holes. There are similar holes in the Al or Cu pole > assembly. Foils are tightened with stainless steel bolt and nut against the > pole blocks. Some washers included. And this is inside the cell where they > may be soaked in electrolyte. If the connection gets loose it will fail. On > some I've found just black goo where the bolt was supposed to be. > > The idea is that the current goes where it most easiest go. Through tight > copper-copper or Al-Al connection. That steel bolt has no chance of > transferring any significant amount of current. > > I would keep all lubricants and pastes away from the cell poles. As long as > they are dry they will work nicely for a decade. Clean and dry makes it > easier to find the loose connections. At every service I test drive the > vehicles and after some driving I measure every pole bolt manually for > heat. If the heating occurs (more than others) on any bolt that is already > tight it indicates internal bolt failure. Cell has to be changed. > > Early indication is higher voltage drop with high discharge current but the > capacity seems to be there. BMS detects this failure easily. > > As the depth of threads and length of bolts are not exact I tighten the > bolts manually 'tight enough'. After few thousand poles and bolts it's in > the wrist. The big problem is on cells that have been unbolted for a dozen > times. The Al pole looses it's threads. It happens when unbolting. Al > sticks to the stainless steel threads and we have nice hole on the pole > with no threads left. Depending on the case I change the whole cell or just > drill a bit bigger hole and rethread it for a bit larger bolt. > > Spring washers and lockable bolts will keep the connection perfect at any > condition. > > -Jukka > > 2014/1/7 Lee Hart <[email protected]> > > > Michael Ross wrote: > > > >> It is necessary to have a properly sized torque wrench, the willingness > to > >> look up the proper torque setting for the materials involved, and a > >> willingness to spend the time getting all of the bolts right. The > >> alternative is you take a chance on shortening the life of an expensive > >> pack, or running out of power in transit. It is a choice one makes not > >> torquing well... http://bit.ly/1dsHSCw > >> > > > > Good advice, Michael. Thanks for the reference! (That's a new way to look > > it up.) > > > > It should be noted that sometimes the manufacturer's choice of materials > > and recommended torque is woefully ignorant. For example, a stainless > steel > > screw in aluminum is a bad design choice. It's likely to be electrically > > bad, and is also likely to gall and seize in time. > > > > -- > > "Obsolete" means nothing more than "the salesmen would prefer you buy > > something else." -- Dave McGuire > > -- > > Lee Hart -- See my Xmas projects at www.sunrise-ev.com/projects.htm > > _______________________________________________ > > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > > For EV drag racing discussion, please use NEDRA ( > http://groups.yahoo.com/ > > group/NEDRA) > > > > > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: < > http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20140108/c80cde7e/attachment.htm > > > _______________________________________________ > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > For EV drag racing discussion, please use NEDRA ( > http://groups.yahoo.com/group/NEDRA) > > -- Put this question to yourself: should I use everyone else to attain happiness, or should I help others gain happiness? *Dalai Lama * Tell me what it is you plan to do With your one wild and precious life? Mary Oliver, "The summer day." To invent, you need a good imagination and a pile of junk. Thomas A. Edison<http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html> A public-opinion poll is no substitute for thought. *Warren Buffet* Michael E. Ross (919) 550-2430 Land (919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google Phone (919) 631-1451 Cell (919) 513-0418 Desk [email protected] <[email protected]> -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20140107/b8e31c77/attachment.htm> _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
