I have some 18650 cells that need to be connected in series. So I was looking to use bus wire but I found a couple people sell it on eBAy .. So does anyone have experience with ebay bus wire or another idea?? Also I am trying to add much length to each cell.

 

Is using a battery holder not an option?

https://www.sparkfun.com/products/12900
https://www.aliexpress.com/w/wholesale-18650-battery-holder.html

I recommend caution with AliExpress; there's not much that can go wrong with a battery holder, but buy low quantity before making a large purchase...

 

Is using a battery holder not an option?

https://www.sparkfun.com/products/12900
https://www.aliexpress.com/w/wholesale-18650-battery-holder.html

I recommend caution with AliExpress; there's not much that can go wrong with a battery holder, but buy low quantity before making a large purchase...

The contact resistance of battery holder terminals is usually too high for lithium battery applications.

All my lithium cells are rescues from recycling bins, they have connecting straps between cells that looks like either low grade stainless or high nickel steel. Its not impossible to solder that if you use an active flux. Soldering directly to the cell would be a bad idea - whenever possible, I leave some excess strap clear of the cell to solder onto. Even if that doesn't work out, the strap where its spot welded on, at least has a higher thermal resistance than soldering directly on the cell.

Most of the time - I use the wire from scrap PC PSUs that went to the Molex connectors, if volt drop along the leads is an issue; I double it up.

 

The only difference between "bus" wire and every other copper wire is that it doesn't have insulation. How hard is it to take the insulation off some copper wire?

 

The only difference between "bus" wire and every other copper wire is that it doesn't have insulation. How hard is it to take the insulation off some copper wire?

Probably better if the TS doesn't remove the insulation - long runs were mentioned.

I'd go completely the other way - Flat braid earth strap and insulate with heatshrink sleeve.

Usually I just go with whatever wire is to hand that looks chunky enough for the job.

 

Probably better if the TS doesn't remove the insulation - long runs were mentioned.

I'd go completely the other way - Flat braid earth strap and insulate with heatshrink sleeve.

Usually I just go with whatever wire is to hand that looks chunky enough for the job.

I have used normal wire before and also tired using solder wick .. But I am looking for a more solid connection and bus wire is flattened wire which saves space . Plus it makes the battery packs more rigid.

 

The only difference between "bus" wire and every other copper wire is that it doesn't have insulation. How hard is it to take the insulation off some copper wire?

Bus wire is usually plated with a low oxidizing metal, like tin, or tin/lead.

 

You could try charging up a large capacitor and making a spot weld that way.

 

You could try charging up a large capacitor and making a spot weld that way.

Years ago I worked for a firm that made capacitor discharge stud welders - the capacitor bank was similar size to a car battery. A big SCR dumped it into the stud when triggered.

Lithium cell bus strips are spot welded - which is something different entirely.

 

Two suggestions:
1) Use the braided shielding from some shielded cable that you have flattened. Nowadays, one needs to add a precaution. Be sure it is copper and solderable.
2) Buy nickel strip that is used for welded battery tabs. It is thin (use 2 or 4 mil) , flexible, takes almost no space, and is easy to solder. Tin the battery ends, place the strip over an end, heat the strip to complete the joint.

Just noticed Ian's comment. I do have a DIY spot welder for the tabs, but I also solder them on occasion. Lithium scells are more sensivive to heat than NiCd or NiMH. I have soldered LiFePO4 .

John

 

Two suggestions:
1) Use the braided shielding from some shielded cable that you have flattened. Nowadays, one needs to add a precaution. Be sure it is copper and solderable.
2) Buy nickel strip that is used for welded battery tabs. It is thin (use 2 or 4 mil) , flexible, takes almost no space, and is easy to solder. Tin the battery ends, place the strip over an end, heat the strip to complete the joint.


John

Soldering directly to a lithium cell is dangerous!!! - I only do it when there is a bit of bus strip spot welded on that increases thermal resistance to the cell casing. If there is a free end of bus strip on the cell, its safe to solder to that.

That stuff doesn't solder easily, I use an aggressive active flux so the iron is in and straight out quick.

 

Soldering directly to a lithium cell is dangerous!!! - I only do it when there is a bit of bus strip spot welded on that increases thermal resistance to the cell casing. If there is a free end of bus strip on the cell, its safe to solder to that.

That stuff doesn't solder easily, I use an aggressive active flux so the iron is in and straight out quick.

"That" stuff means what? Of course, I don't try to solder to cotton fiber or aluminium. But soldering to nickel is no harder than soldering to gold plate. Are you sure your soldering iron is properly tinned?

John

 

"That" stuff means what? Of course, I don't try to solder to cotton fiber or aluminium. But soldering to nickel is no harder than soldering to gold plate. Are you sure your soldering iron is properly tinned?

John

My iron is properly tinned, and I know at least two ways to solder aluminium.

The bus strip has to be spotlessly clean to solder, and strong flux makes the operation quicker when the tip is close to the cell casing.

If you want to heat up a lithium cell - you go right ahead.