Martin, 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.
Lot's of people think torquing is trivial. That would not be true of OEM auto manufacturers. If one does not take their lead... If people don't obtain the tool, look the torque up, and do it right, then they will either under or over torque (I am shrugging, but not unsympathetic). I can't really worry about all the people who strip out threads - I did a fair amount of that myself before deciding to do it right. If a DIY EVr does strip some out we can help them retap or helicoil the holes. It does happen. Here is a reference http://bit.ly/1dsHSCw Mike On Tue, Jan 7, 2014 at 5:01 AM, Martin WINLOW <[email protected]> wrote: > I'm slightly concerned that without qualification, inexperienced DIY EVrs > will start over-torquing there connections. Obviously, different size bots > will require different torques. When I bought my Thundersky cells in 2008, > I could not get a sensible answer out of them about what torque to use for > the bots (8mm in that case). Anyone care to offer a rule of thumb for the > usual 6mm and 8mm bolts used with most LiFePo4 cells? MW > > > > On 6 Jan 2014, at 14:22, Michael Ross wrote: > > > I recently took apart a nice little OEM battery pack and every terminal > on > > it was barely hand tight. I reassembled with SS socket head screws > instead > > of the Phillips screws, and torqued the 5mm bolts to spec. All you need > to > > do is torque them right and they will not loosen. Do not use lock > washers > > as they compromise the clamping force. If you look at bolted joints on > high > > quality equipment you will find properly designed joints with no > > lubrication or thread-locker - they just torque the right. I worked for > > Caterpillar and can vouch for their practices - needed to survive the > worst > > vibration environments imaginable. My Toyota cars over the last 30 years > > are all produced this way. I don't use conductive grease, I just go with > > clean and tight. > > > > For reference: > > > > 1 N m = 8.8in lb = 0.74bft lb > > > > I tightened the 5's to 35 in lb (4 Nm). > > > > Unfortunately, there are a lot of units for measuring torque. Inch > pounds > > are best for the small wrenches we have in the US. > > > > My joints were the terminals of 32120 cells, SS M5 screws, with nickel > > plated copper straps, and stainless steel flat washers (lock washers > thrown > > away). I am not sure what the terminal with the tapped threads is made > > from. It is s tamped and formed part, maybe SS, but could be a plated > > brass or copper... > > > > On Mon, Jan 6, 2014 at 7:26 AM, Mark Hanson <[email protected] > >wrote: > > > >> Hi Folk's, > >> last night a overvoltage battery balancer #22 shut down the charger at > >> 4.0V. At first I thought it was a bad OV balancer detector but after > >> replacing the circuit it still did it so I put a scope across the > battery > >> cell and noticed the charging pulsed waveform going from 3.3V to 4.0V > 60 hz > >> when adjacent cells were fairly solid (signifying a high impedance > >> condition). I thought I had a bad cell but after sanding under the > copper > >> strap & adding 3M dielectric grease & torquing back down, it charged > >> perfectly with no faults, back to low impedance. I found a few other > >> battery terminal bolts not tight after 20k miles (even with sealing > paint > >> on terminal bolts CALB 130). So it's best to tighten terminal bolts on > >> lithiums every 10k miles it seams. I used to tighten terminal bolts on > old > >> lead GC batteries every 500 miles but didn't think it was necessary with > >> lithiums but apparently they need it as well just less often. > >> Best Regards,mark > > _______________________________________________ > 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/bf3a5c29/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)
