North America Electrically conductive adhesives

[Doggggboy]

Does anyone have any experience or recommendations for an ECA that would work with a lithium battery pack?
I know there are various ECAs available but I'm not savvy enough to know if any would handle a Lithium pack. I know spot welding is used for joining the batteries in a pack but since I don't have a suitable spot welder I'm wondering if an adhesive would work to replace a dead cell.

 

[Susquatch]

Does anyone have any experience or recommendations for an ECA that would work with a lithium battery pack?

I've heard of them but never used them. I'm leery of them to be honest. Might require skills and technique I don't have any more..... and prolly never did. High current surges could get REALLY HOT! Not a good thing near lithium. Can't wait to hear what you learn.

 

[Xyphota]

I have used anisotropic conductive film and tape at work, but only for electrical signals, I don't think it could handle more than a few milli-amps. We purchase 3M branded stuff from digi-key, maybe they have another product that could work for you?

 

[Former Member]

Don't, welding is the correct way, soldering can work (I've done it and had great success), but to be fair it is hit and miss depending on your skills, prep and heat control.

Adhesives, heat is the issue.

 

[PeterT]

I wouldn't. Even a teeny harmless looking inter-cell balancing harness wire coming loose & poof. Lithium fires are not fun. Call around. We have a couple battery places (Calgary) & they have the spot welder & proper strip material. I had to get some tiny 1/3 AAAA round cells made into packs once upon a time, soldering was just not practical. The shop was reasonably priced. Also, depending on the joiner bar gauge & other factors, sometimes its not just one spot. I've seen multiple hits like a pattern.

Some lipo (I'm talking polymer here) have harness tabs where, depending on brand & other factors, they use solder that isn't the regular stuff. Special flux's are required & higher melting temp than our typical electronics grade. I haven't done this in a while but usually I stumble on posts where this is still the issue. The cannister (round cells) are pretty straightforward soldering though, Clean the metal with new stainless brush. Its better to have high heat, short duration than the opposite. If you show a pic we can be more helpful

 

[Tecnico]

Does anyone have any experience or recommendations for an ECA that would work with a lithium battery pack?
I know there are various ECAs available but I'm not savvy enough to know if any would handle a Lithium pack. I know spot welding is used for joining the batteries in a pack but since I don't have a suitable spot welder I'm wondering if an adhesive would work to replace a dead cell.

I’d be sceptical about ECAs providing a connection resistance comparable to a welded connection so, as mentioned, the joint may dissipate heat (heat up). I’d also be concerned about the bond failing mechanically (and of course electrically).

I’ve soldered nicads but, personally I’d want to read up on it before playing with lithium’s because of their reputation. I don’t think I took too high a risk with the nicads……….

You can get solder tabbed lithium cells from Canadianbatteries.com so that might be a good solution. Probably you can solder to the leftover tab in the pack after you take out the bad cell.

Now, I’d be interested to know what advice the experts have for replacing a bad cell, any concerns about uneven charging between new & old cells. I think some lithium packs have some sort of condition monitoring that knows about the cells and might get in the way of rebuilding a pack.

EDIT: @PeterT makes a good point, you may find you have a local shop that makes packs if that’s economical in your case.

D

 

[Ironman]

I have seen spot welding done with a pointed carbon rod and a 12 volt battery. hold it on firmly til the spot is red and remove. The danger of arcing could be ended by wiring in a starter relay and activating switch. Here is a poor video with carbons and an arc welder doing spotting

 

[PeterT]

Generally if you replace a bad cell with a good one in a pack, the charging/monitoring system accepts it as replacement family member as long as its within tolerance, same capacity, IR etc. But where it gets interesting is what the voltage state is relative to the other cells. If you put a more depleted 'storage state' cell amongst a fully charged pack, the charging algorithm can get confused & may complain or refuse to go on. Its basically always monitoring individual cell voltages, making decisions & distributing among them. Not sure how fully charged cell amongst depleted would fare much different but safest is run them all to depletion voltage & do surgery. Other systems are more operating mode, excessive heat, excessive current draw, min voltage over-drain protection etc. The electronics in tools can be sophisticated. I'm talking plain jane LI cells here. But many cells have electronics board under the lid, not just a roll of chemistry. Those you have to replace with identical types for sure.

 

[Doggggboy]

Thanks for the input guys. Seems unanimous that i'm looking for a unicorn.

 

[Susquatch]

We have a couple battery places (Calgary) & they have the spot welder & proper strip material.

Never thought of that! Great advice Peter! There is now hope for my trusty Dremel Stylus. I love that thing but Dremel discontinued it and I don't have battery welding capability to fix it. It is sitting in my basement workshop waiting for just such a miracle at my local battery shop to bring it back to life!

But many cells have electronics board under the lid, not just a roll of chemistry.

Love this description!

This is one of the things I HATE about Makita 18V batteries and Canon LaserJet Toner Cartridges too! I'd give both a frontal lobotomy if I could.

 

[Former Member]

The circuit boards accomplish a couple of things (some more some less):

Thermal control, in charging or use.
Charge control
Discharge control
Battery Health