very slightly loose battery connection problem

[alsmith]

Not a question, just info in case the info can help someone else.

My bike started cutting out within seconds of the battery being connected (at the farest point from home of course). When I got home it turned out to be one very slightly loose screw on the battery connection-and I mean slight! It looked ok, the spring washer was compressed but the wire/ring connecter could be rotated with some resistence on the battery post. The screw hardly turned at all when tightening up but it sorted the problem.
I really didn't expect such a minor thing to have such a massive effect. I think I'm going to repace all of the spring washers and screws with new/better quality parts- maybe allen screws would be a better choice then the cross heads.

Does anyone happen to know the screw thread and length use on the headway cells, and any relevant experience / advice?

 

[wineboyrider]

Maybe some type of dielectric loc tite?

 

[dnmun]

you should verify that the screw does not bottom out into the top of the actual cell inside. if it goes too far it could damage the cell itself.

 

[Ypedal]

problem with stiff buss bars is that they will cause the screws to back out if the pack flexes at all even a tiny bit..... the orange blocks should be secured solidly together and prevent the cells from twisting when hitting bumps etc.....

i would tighten them all ( careful not to strip them ) and then lock it all down with a bit of hot glue. )

 

[alsmith]

It's not bottoming out.

The blocks are property linked together. I'm not sure hot glue would help, the movement to tighten wasn't really noticable.

I think I'll try takng the connections apart and using contact cleaner on it, that might be enough to sort it. I can check to see if the spring washers have flattened but they aren't expensive to replace.

 

[Punx0r]

A little dab of Loctite (non-permanent variety) on the threads should help. Apparently, testing on vibration machines shows that spring washers are generally ineffective at preventing loosening, rather they often worsen the problem...

 

[dnmun]

if you put insulating materials onto the threads then the threads will not be able to conduct current. a major current path imo.

 

[alsmith]

if you put insulating materials onto the threads then the threads will not be able to conduct current. a major current path imo.

Yes, I know people who've had issues with this (friend with his moped, maintainance engineer at a factory I worked at), then had difficulty finding the cause.

 

[Punx0r]

Apologies, I thought the underside of the connecting link was the primary current pathway.

One of the most effective ways to ensure a threaded fastener stays done up is to ensure it's tightened enough to ensure adequate preload (stretch). If a reliable torque specification is available from the cell manufacturer then I would take the time to apply it.

 

[alsmith]

I had wodered what the spec is but couldn't find one.

 

[Punx0r]

If you the dimensions of the screw and the grade (or measure and guess) you can look up the appropriate torque setting. Proper design specified that the female thread be stronger than the male, so it's a safe bet if the thread in the cell is good, but that might be a big "if"...

 

[dnmun]

headway has the screw length spec somewhere, but i forgot it now. i think they expect the screw to cover the little link thingy and the flat washer and the lock washer too.

the problem with the headway screw torque is that on the negative end the terminal where the screw tightens into will rotate if you over torque it too.

i think it is the negative end that has the minimal clearance between the screw and the case inside so if the screw is too long or if you use a long allen screw like some do to make the cans mate into a serial connection then the screw can penetrate the case on that negative end.

i think they have vent and popup type over voltage protection device on the positive end. but not sure.

 

[alsmith]

There's been at least one post here about a loose post problem.

added
just found [img=[url=http://s1120.photobucket.com/user/al5mith/media/A3FJ52_6KQP7.jpg.html]

[/url]]this pic c/o elife bikes[/img]