diy solar

diy solar

Helicoils in Cell Terminals

@Sillyputty , Thanks for sharing your misadventure in battery repair, and I'm glad the damage and cleanup wasn't too bad.

If I'm ever in this situation, I would probably give it a go, but definitely have it on the list of work that must be done outside, where the smoking remains can be kicked out into the yard.
 
You'll find out one way or another if it's a quality machine shop! ?
It’s back from the shop now with a new M7 grub screw and nut installed. The guy said he drilled down about an extra mm and i inwardly winced, but the battery is connected up in my system now and working, so all is good ?

The cost was just 100 Swedish kronor - about $10…
 
It’s back from the shop now with a new M7 grub screw and nut installed. The guy said he drilled down about an extra mm and i inwardly winced, but the battery is connected up in my system now and working, so all is good ?

The cost was just 100 Swedish kronor - about $10…

Good deal. Given the risk involved, that's a bargain.
 
@Sillyputty , Thanks for sharing your misadventure in battery repair, and I'm glad the damage and cleanup wasn't too bad.

If I'm ever in this situation, I would probably give it a go, but definitely have it on the list of work that must be done outside, where the smoking remains can be kicked out into the yard.
No problem - we all learn from the experiences, good and bad, that we post here. If (a very big IF) I ever decide to do this again, I'll seperate the battery into individual cells (as was done when I did the original terminals that turned out OK) and use a drill press with a solid depth-stop on the spindle travel or the bit itself, with the former being preferable.
 
Agreed, some things are just better left to people with the proper gear

Or naivety?
And he did that for ten lousy bucks??

use a drill press with a solid depth-stop on the spindle travel or the bit itself, with the former being preferable.

And a hold-down for the cell?
I have workpieces jump up to swallow the bit. (especially drilling holes in walls of boxes, where I'm drilling through.)
I think my most reliable drill-stop is a copper tube slipped over the bit.
 
you can make a stopper out of polyurethane rod cut it to exact length for your drill bit, or if you are using a mill you would not even need that. Anybody with a machine shop has step blocks and jigging blocks to lock down pieces prior to attempting to machine them.
 
Length of stopper does not need to be precise, because position of drill in chuck is adjustable.
Benefit of stopper around drill bit is, if drill bit slips deeper in chuck, that doesn't result in going too deep.
(I once tried a stopper in the form of a pass-through plastic drill chuck, which simply slipped.)

Yes, milling always has workpiece secured. Drill press often not, except against rotation by workpiece or vice hitting upright.
In the case of cells, tall and skinny, you're going to be gripping a plastic (or bulging metal wrapped in plastic) workpiece. Good thing current flow between case and electrode is minimal.

Machinist has to really go out of his way to make a hold-down for these tall rectangular cells. He might be tempted to restrain against rotation by the base; better by the thick plastic block of the top, although torque needed is quite low. For a production-type operation on many cells, could make a frame to fit over top, but this was for single piece.

I used to do a lot of machining in high school & JC shop, now just use a cheap drill press. I have a junk Harbor Freight drill/mill/lathe combo I picked up, but vertical spindle is nearly seized, haven't figured out how to pull apart or otherwise get loose.
 
Ok thanks. I was asking because one of my Lishen 272Ah cells has stripped a thread (my fault of course) and I was expecting to have to put an M6 helicoil in. Having taken it to a local machine shop though they advised a better and stronger fix will be to drill out to M8 1.0mm fine thread, which I’ve left in their hands to do (with clear warning to use an end stop to drill no lower than existing hole depth).
M8x1,0 might look stronger on paper but personally I’d go for helicoil. Helicoil takes the tear and wear away from the weak aluminium
 
Given that what's done is done, idea is to not wear the aluminum threads you now have.
"7mm grub screw" - that fits Allen wrench? It can be restrained against turning while working a box-end or crow's foot wrench.
At the small torque involved, squeezing moving wrench and stationary Allen wrench between your fingers will rotate nut without applying any torque to grub screw/cell terminal interface.

People here have used various locktite etc. to keep stud fixed in the threads (avoid any reaching contact surface.)
 
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