welding question (laptop battery repair)

[gorobei]

so my laptop battery wouldn't fully charge indicating a bad cell, and eventually started overheating if i tried to charge it. its a fujitsu which later models had a recall so they discontinued that model of battery. so buying a replacement is just gambling on it having a similar fault.

so i pulled the battery pack apart without damage (with 3days of swearing and multiple spudgers). i found the 18650 cell model number and ordered replacement panasonics.

i managed to mostly salvage the wiring harness attached to the charge controller though some of the spotwelds tore a bit of the nickel strips.

the clearance inside the battery case is ridiculously tight so i dont think i can get away with soldering wires to replace the nickel strips harness. so.......

my options are:

1. buy a specialty battery electronics spot welder tool from ebay for $150 and never use it again.(not really an option)
2. life hack a car battery and solenoid into a welder https://www.youtube.com/watch?v=b_kGgPVrcCI (sketchy)
3. ask a welding shop if they can weld it.

So my question is: will a commercial MIG/TIG welder or stick welder be able to do a low enough volt/current to not damage the 18650 battery terminals or burn through the nickel strips? (i have the old cells so i can provide a test unit, but i dont have any extra nickel strips/tabs )
there are also some cheap chinese $50 stick welder units on amazon so they probably would be much lower rated on the lower voltage end and less likely to burn thru.

i've placed the new cells and harness inside the laptop and it seems to charge fine(no usage/hours limiter in the charge controller) so all im looking to do is secure the cell terminal connections. i could just kapton tape them and shove shims to apply pressure, but a single weld would probably be better.

any constructive feedback would be appreciated.


bigclive's explanation on why lithium-ion cells go bad and become a fire hazard : https://www.youtube.com/watch?v=gYFuVbZmu5M

 

[Skunk-Works]

You can't use a MIG, it would be TIG and at a very, very low amperage.

 

[Skunk-Works]

Even then, I'm not sure a TIG welder is safe to use on batteries.

 

[PottedMeat]

TIG/Stick/MIG - nooooooooo, if someone offers - make sure to record it and stick it on youtube

they say even soldering will damage cells, but i've done it before on flashlight cells and haven't had a problem (BOOM!)

liberal application of flux, a high wattage iron to apply a bit of leaded solder quickly can work.

 

[paperfist]

You don't have a local car battery shop? Mine does replacement on laptop batteries, power tool batteries, etc.

There was one type they wouldn't touch but I can't remember which. It was the go boom kind. They had pics of burnt legs, faces, all kinds of good stuff.

 

[gorobei]

TIG/Stick/MIG - nooooooooo, if someone offers - make sure to record it and stick it on youtube

they say even soldering will damage cells, but i've done it before on flashlight cells and haven't had a problem (BOOM!)

liberal application of flux, a high wattage iron to apply a bit of leaded solder quickly can work.

the bigclive vid covers the myths, the amount of lithium is minuscule and not reactive enough to start the fire. the main factor is when one cell reverses polarity and creates an electroplating effect on the insulator between the annode/cathode which acts as a bridging resistor leading to a rapid discharge creating the heat. there's another vid from some guy who actually builds battery packs for work, he takes a flir and compares soldering vs spotweld, unless you are holding the iron on there for 15 min it is aparently safe enough to solder. assuming you dont work with fully charged cells it shouldnt be an issue.

You don't have a local car battery shop? Mine does replacement on laptop batteries, power tool batteries, etc.

There was one type they wouldn't touch but I can't remember which. It was the go boom kind. They had pics of burnt legs, faces, all kinds of good stuff.

what parts are they replacing on laptop/tools? like i said i dont think this model of battery package is readily replaceable. all the online sites just list every model and no indication of stock status much less true oem quality. so sorting thru all the reviews is pointless given all the fake customer feedback entries.

 

[paperfist]

the bigclive vid covers the myths, the amount of lithium is minuscule and not reactive enough to start the fire. the main factor is when one cell reverses polarity and creates an electroplating effect on the insulator between the annode/cathode which acts as a bridging resistor leading to a rapid discharge creating the heat. there's another vid from some guy who actually builds battery packs for work, he takes a flir and compares soldering vs spotweld, unless you are holding the iron on there for 15 min it is aparently safe enough to solder. assuming you dont work with fully charged cells it shouldnt be an issue.

what parts are they replacing on laptop/tools? like i said i dont think this model of battery package is readily replaceable. all the online sites just list every model and no indication of stock status much less true oem quality. so sorting thru all the reviews is pointless given all the fake customer feedback entries.

They are doing what it seems like you are trying to do and that's replacing the cells themselves while keeping the OEM pack/connectors intact.

 

[gorobei]

They are doing what it seems like you are trying to do and that's replacing the cells themselves while keeping the OEM pack/connectors intact.

do you have a website?

 

[Jerem]

If I understand correctly the clearance is so tight you can't get a soldering iron to it. That being the case there is no way you can get a mig/tig to fit and get a ground connection in there as well. No welding shop is going to try it either, It isn't worth their time or effort. My thoughts go toward buying the spot welder and put it up for sale when you are done

 

[paperfist]

do you have a website?

http://www.yorkvillebattery.com/

 

[gorobei]

http://www.yorkvillebattery.com/

ok, cool. i'll try to find something like that around here.

 

[gorobei]

If I understand correctly the clearance is so tight you can't get a soldering iron to it. That being the case there is no way you can get a mig/tig to fit and get a ground connection in there as well. No welding shop is going to try it either, It isn't worth their time or effort. My thoughts go toward buying the spot welder and put it up for sale when you are done

not exactly. at the factory, the cells are assembled in a jig and paper thin nickel foil strips are spot welded to form the harness. the whole thing is then taped together in a cluster of cells end to end and charge controller board in a very precise package. when they drop the cluster in the cheap ABS plastic case there is almost no extra space or wiggle room. because the nickel strips are so thin and the support structure inside the case cuts off some area, you cant add any extra space to the wiring harness. some of the cells are butting up right against each other, even a 1mm wire with insulation used in place of the nickel strips would keep it from fitting back in the plastic case.
https://www.youtube.com/watch?v=VrDnTXqoqjM covers the issue.

 

[Skunk-Works]

so sorting thru all the reviews is pointless given all the fake customer feedback entries.

www.fakespot.com

Works great with Amazon.

 

[PottedMeat]

even a 1mm wire with insulation used in place of the nickel strips would keep it from fitting back in the plastic case.

you can get metal strip connectors from old 9V batteries, several inches worth. tinning and fluxing the strip, the terminal, then tacking them together + the kapton or whatever spacer they put in should be compact enough

 

[gorobei]

so i found a store: interstatebatteries.com that seems to do repairs on cordless hand tool battery packs. i'll swing by with the bits to get an estimate, i've already done the hard part by getting the case open and sourced the replacement cells.

 

[Red Squirrel]

Whatever you do make sure it's being recorded, and have a class D fire extinguisher handy.

Seriously though, if you're careful you can solder them, though it's not really ideal. It slightly damages them. The trick is high heat for short duration.

The proper way is a spot welder, which basically uses quick bursts of high current to create a "tac" weld. You can make one using a microwave oven transformer that you rewind so that the secondary only has a few turns. You end up with a relatively low voltage but high current output.

Something like this: https://youtu.be/o1NFbchHeM8?t=58s Actually this one seems to just use a big battery, guess that works too. You just need a high current source.