[Tfug] Source for notebook batteries?

[Bexley Hall]

Hi Jim,

> Looking at pictures in the various how-tos, the factories
> are usually using "tabbed" batteries and soldering the wires 
> to the tabs.

Argh!  Time to get pedantic, I guess.  :<

The batteries (def: two or more *cells* wired together)
typically have each of the cells connected to their
(electrical) neighbors with flat "tabs".  I.e., one end of
the tab is welded to the anode of cell #1 while the other
end is wired to the cathode of cell #2.  (this puts the
cells in series.  In some BATTERIES, you might have several
cathodes or anodes wired together as there might be multiple
"chains" of cells sharing a common connection point -- see
my previous post).

At the two ends of the "battery" (a series of cells, in this
example), wires *sometimes* connect the "battery" to:
- the external terminals of the battery pack
- an internal charge controller (some batteries even have
  LED indicators that show the depth of discharge even when
  the battery is not installed in a device)
- some other protection network
etc.

Often, a PTC device (sometimes even a real *fuse*) is installed
in series with the cells (*anywhere* that it may be convenient
to do so since anyplace is as good as any other!).

Sometimes, these "tabs" actually provide the connections instead
of "wires".

> There's no practical difference between that and "wires soldered
> to the batteries" unless you want to really nit-pick.

The difference is *you* can't solder to the batteries (without
damaging the batteries or risking personal injury).

You *can*, however, solder to the tabs *if* you have them long
enough and have a soldering iron with enough thermal mass
(the battery/cell will act as a nasty heatsink so toy soldering
irons are just an accident waiting to happen:  by the time you
get the tab hot enough to "take" the solder, you have probably
also heateed up the adjcaent cell a considerable amount!).

When I try to rescue a battery pack, I look to see how many cells
are salvageable (i.e., capable of taking/holding a charge).
Then, I look at where they are mechanically/electrically located.
Ideally, they are all contiguous so I only have to isolate
"bad cells" at the "ends" of the chain of cells.

I cut the metal tab connecting each of the "end" GOOD cells
from the neighboring bad cells (if any).  I do this as close 
to the bad cell as is possible.  My goal is to end up with
1/2" to 1" of usable "tab" in the process.

If I have a string of one or more *other* "good" cells that
need to be attached to the *end* of this first series, then
I presumably have a comparable amount of "tab" on that
other string to work with.  Depending on the mechanical
configuration that I need to end up with, I may solder
those two tabs together directly (this is harder than soldering
a wire to each tab!) *or* solder a pigtail onto one tab and
terminate the pigtail on the other tab.  (now I've got a loop
of wire that has to get crammed into the battery casing)

I recently did this with a GPS whose internal battery
(which happened to be a single Li Ion cell) had died.
End result:  GPS with NON REPLACEABLE battery is now
still in use!

However, I *do* have to stress how easily you can screw
things up by doing them yourself.  Batteries *look*
innocuous (and magical!) but can cause you lots of
grief if you abuse them (and, they are frighteningly
easy to abuse!)

If you can afford a laptop, you can afford a replacement 
battery!  :>  Comes with the territory...

> The best replacement cell option appears to be to score
> tabbed cells to replace the size/voltage of what you have
> now, with a small boost in amp-hr rating acceptable, crimp

You also have to be wary of cells that *seem* better
than comparable cells.  "How is it that these folks
are able to get greater energy density than everyone else?
Have they defied some law of fiziks?"  They could be using
thinner insulators, etc.

> tab connectors to the factory wires
> and slip those onto the tabs on the new cells.
> 
> You have no cause for "no, no, no" because nothing I'm
> saying disagrees with Don's post.
> 
> Don notes that some brands of replacement cells might be
> bad.  I agree completely.  Buying individual cells is the ONLY way
> to know the actual brand which can be researched.  Buy a sealed
> unit from Dell OR Ebay and you have no clue what's in there and 
> can't find out.

Well, if you buy something with Dell's name on it, then *Dell*
presumably has vouched for the suitability of those components
with your laptop.  (of course, there is no guarantee that
this was done correctly!  Can you spell "recall"?).

OTOH, if you roll your own battery and it catches fire and
burns down your house, don't even *think* of trying to sue
the laptop maker!  (and, if someone is injured in that
fire, better be prepared to swallow their medical costs!)

(Boy, gotta love how I abuse punctuation in THIS post!  :> ) 

--don

!@^&%#.+= just in case any of those puntuation marks feels "left out"