Battery Pack Repair - Is it worth it?

[Bicurico]

Hi,

As a test equipment addict, I own a pretty reasonable collection of TV/CATV/SAT field meters. I doubt there are many people with a bigger collection, but then, Youtube has taught me that there is always someone who does it faster, quicker, crazier, etc.

Anyway, one of the problems I have is that many of my portable test equipment units work with battery packs and those tend to age, even if you don't use them. Also, not charging them regularily (guilty) has a bad effect on them.

For years I have looked at how 18650 cells are used for these battery packs and Chinese seller offer spot soldering machines for 100-200 Euro. You then need the metal stripes to connect the cells and the cells - lots of them.

Now my questions are:

- The spot welder devices come with an alert that you need so many amperes on your houses switchboard. Is that really problematic? How much power is needed?
- How dangerous is it to handle the 18650 cells and trying to spot solder them?
- Where to get them at a reasonable price?

While I would like to keep all instruments in prestine conditions with full capacity battery packs, the truth is that I seldomly use them and when I do, it is on my desk where I can attach the power source.

It seems that the DIY approach to renew battery packs is still quite costly, considering that the average battery pack uses at least 12 cells if not much more.

Also, with new EU import laws and taxes, I don't know if the 18650 cells can be sourced cheaply.

And yes, I know that the battery pack is normally as good as the worst of the cells. Often you only need to replace a few to get almost full capacity back again.

Still I wonder, if it is worth it, especially considering the switchboard requirement and the possible danger hazards.

Your opinions please.

Regards,
Vitor

[tunk]

Are these reasonable prices: https://eu.nkon.nl/rechargeable/li-ion/18650-size.html

[jpanhalt]

I have a homemade capacitor-discharge tab welder.  It uses very little current.  I can't imagine any home not having sufficient service for that.  Now, if it is not CD, then there might be a problem, but I doubt it.

As for use, at the time I built it, almost all of my batteries were NiCd or LiMH for several model airplanes, and I used it quite a bit.  I have never used it with LiPo, but I have used it occasionally with batteries like the 18650 but lower capacity.  I had terrible luck with "18650" batteries.  Tabs went on fine, and there were no obvious problems, but the batteries died after only a few charge cycles.  Could have been cheap or fake batteries.

One thing to consider is that bulk batteries are often sold with or without tabs.  Those with tabs may even be cheaper.  Once the tab is welded, you can just solder the tabs.  It takes a little more space lengthwise, but may still be adequate for  your instruments.

[Algoma]

Not much power is needed, most seem to use current limited charging of a capacitor bank over a few seconds, for rapid pulse dischage, its often all low voltage (~12V). There really isn't much need for high power when spot welding batteries, unless you're doing large industrial batteries.

- How dangerous is it to handle the 18650 cells and trying to spot solder them?
  its an instant spot of heat that is quickly disspated into merely the surface of the material.. Its possible, but very unlikely to cause an issue. It usually takes a fair bit of abuse to cause an issue with an 18650 (though not impossible) .. its all pretty safe, provided the batteries have an actual safety vent for pressure like they're supposed to, in the event of an failure.

- Where to get them at a reasonable price?
   Good ones are the challege to find, Banggood and Aliexpress are a source of a whole range from useless cheap scrap, to reasonable quality that may likely last quite a while.  Typically you get what you pay for (Dont go for the cheapest ones)


My source of 18650 cells is old laptop batteries.. quickly sort out the dead cells (they self discharge) and you often get a few that have some pretty good life in them.

[abdulbadii]

- The spot welder devices come with an alert that you need so many amperes on your houses switchboard. Is that really problematic? How much power is needed?
- How dangerous is it to handle the 18650 cells and trying to spot solder them?
- Where to get them at a reasonable price?

While I would like to keep all instruments in prestine conditions with full capacity battery packs, the truth is that I seldomly use them and when I do, it is on my desk where I can attach the power source.

It seems that the DIY approach to renew battery packs is still quite costly, considering that the average battery pack uses at least 12 cells if not much more.

Also, with new EU import laws and taxes, I don't know if the 18650 cells can be sourced cheaply.

And yes, I know that the battery pack is normally as good as the worst of the cells. Often you only need to replace a few to get almost full capacity back again.

Still I wonder, if it is worth it, especially considering the switchboard requirement and the possible danger hazards.

Your opinions please.

Regards,
Vitor

if don't mind spend time research, google great sites about the battery, i found that Battery University one of the best out of few.

no pain, its far easier than learning E circut / science
then can understand what we should do everytime ecounter  any battery/power problem

then considering based on that knowlegde and on market availability, it's not worth creating a battery pack, this meant for open, easy choice on space needed for it.
try to obtain Li-ion 18650s each with tiny bump on positive battery terminal, and try get their holders too, then do everything cell by cell so that can be better maintained, healthy, optimum battery lifetime, and far easier handling as no need pesky resistance welding...
with the trade-off battery space, a bit expensive 4/more slots high quality & control charger, and few extra kits needed