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From: Lee on 14 Dec 2009 05:40
On Dec 13, 5:31 pm, D Yuniskis <not.going.to...(a)seen.com> wrote:
> Hi,
>
> Replacing rechargeable battery packs in consumer kit
> is a bane I suspect most of us share.  You can't
> "solder" to individual cells.  And, you usually can't
> slip a battery holder in place to make the connections
> for you.
>
> Sure, you can buy premade packs in a wide variety of
> configurations.  But, these often come at a premium
> in price (to pay for the added labor of their fabrication)
> *and* you can't just pick them up "off the shelf"
> (well, *some* configurations are available like this
> but not "in general").
>
> Has anyone come up with a clever way around this problem?
> Is there a poor man's approach to welding tabs onto
> batteries?  Or, some other conductive fastener that
> doesn't put the cell at risk in the process?

You might try replacing the heating element of a large 120 volt
powered soldering iron with a pair of spot welding points. I'm
thinking of the type with a 1 pound transformer, with a trigger switch
and usually a light to illuminate the work area - they create large
amounts of low voltage current. Buy using just the right size area of
contacts, one might get lucky enough to make a one second spot welder
that could be just the ticket for doing this. This is how it's done
in the first place. The end does get hot, but cooler than soldering.
You can solder if you do it very fast.

How about getting the manufacturers to change all those custom sized
NiCad batteries to standard sized cells so we could just change them
out at a local Radio Shack instead of buying expensive Digi-Key one
off replacements?

One option is to buy the pack at "Bats R Us" place where they spot
weld them as needed. Sometimes a good price can be agreed upon, other
times you are lucky if they take money instead of your first born.
From: Dave Plowman (News) on 14 Dec 2009 05:46
In article <isw-09B9A0.20565613122009@[216.168.3.50]>,
isw <isw(a)witzend.com> wrote:
> In article <hg40gr$sba$1(a)aioe.org>,
> D Yuniskis <not.going.to.be(a)seen.com> wrote:

> > Hi,
> >
> > Replacing rechargeable battery packs in consumer kit
> > is a bane I suspect most of us share. You can't
> > "solder" to individual cells.

> You can do it easily, IF you use the proper solder and flux. Look for
> something that can solder stainless steel.

Ordinary solder works just fine. It's overheating the cell that's the
problem.

--
*Do infants enjoy infancy as much as adults enjoy adultery? *

Dave Plowman dave(a)davenoise.co.uk London SW
To e-mail, change noise into sound.
From: D Yuniskis on 14 Dec 2009 06:10
Dave Plowman (News) wrote:
> In article <hg40gr$sba$1(a)aioe.org>,
> D Yuniskis <not.going.to.be(a)seen.com> wrote:
>> Sure, you can buy premade packs in a wide variety of
>> configurations. But, these often come at a premium
>> in price (to pay for the added labor of their fabrication)
>> *and* you can't just pick them up "off the shelf"
>> (well, *some* configurations are available like this
>> but not "in general").
>
>> Has anyone come up with a clever way around this problem?
>> Is there a poor man's approach to welding tabs onto
>> batteries? Or, some other conductive fastener that
>> doesn't put the cell at risk in the process?
>
> You can buy most cell sizes with tags already welded on - so you can then
> solder them together. From most decent electronics suppliers.

Yes, that was the "premade packs" option I mentioned.
These are almost always "specials" -- with added cost
and lead times.

You can also buy "single cell packs" (i.e., a cell
with tabs) but assembling these into complete
batteries usually results in a battery pack that
is too large to fit into the space available.
(in addition to being more expensive than
"regular cells")
From: Dave Plowman (News) on 14 Dec 2009 06:24
In article
<043d824c-8727-4587-b813-c11ef3d6f752(a)b36g2000prf.googlegroups.com>,
Lee <melee5(a)my-deja.com> wrote:
> How about getting the manufacturers to change all those custom sized
> NiCad batteries to standard sized cells so we could just change them
> out at a local Radio Shack instead of buying expensive Digi-Key one
> off replacements?

In terms of numbers made I'd say sub C is a standard size - pretty well
every cordless tool I have uses them. But supply and demand determines
aftermarket prices for bare cells.

--
*I used up all my sick days so I called in dead

Dave Plowman dave(a)davenoise.co.uk London SW
To e-mail, change noise into sound.
From: Wild_Bill on 14 Dec 2009 10:40
Some battery users need to weld lots of cells together on a regular basis,
and they sometimes build their own welding equipment.
I found numerous online examples of home-built welders when I searched for
battery pack welding or some similar terms.

The types of welding processes used are resistance welding, and capacitor
discharge spot welding.
Resistance welding is performed by a low voltage, high current secondary
winding on a large transformer. The winding may be made from large gauge
cable and may only be a few turns. A timer circuit is used to energize the
transformer for very brief periods, some tenths of a second. The high
current passing between the 2 tips creates the spot welds.
Capacitor discharge welding is performed by a large bank of high value
electrolytic capacitors (rated/capable of rapid discharge) which are
charged, then discharged thru the tips applied to the strap. Some commercial
versions are microprocessor controlled with numerous features.

Fixtures are often used to apply pressure to the tips, for more consistent
welds.

Nickel strip is available in coils (McMaster Carr), and straps are cut to
length, then welded to the cells.
Spot welding is typically done as 2 spots at once, with 2 tips pressed
against the strap simultaneously. When the current passes from one tip to
the other, 2 welds are made. This is then repeated, providing 4 spot welds
per cell contact, for very reliable connections.

Cells purchased with tabs already welded to them are fairly easily trimmed,
then joined with solder, which doesn't heat the cell as much as trying to
solder directly to the cell.
Fiberglas tape can be used as an insulating gaurd between straps and cell
cases, and to cover straps after assembly.

I've only encountered one piece of test equipment where the battery
compartment was so tight that a new pack made with tabbed cells almost
didn't fit.

--
Cheers,
WB
..............


"D Yuniskis" <not.going.to.be(a)seen.com> wrote in message
news:hg40gr$sba$1(a)aioe.org...
> Hi,
>
> Replacing rechargeable battery packs in consumer kit
> is a bane I suspect most of us share. You can't
> "solder" to individual cells. And, you usually can't
> slip a battery holder in place to make the connections
> for you.
>
> Sure, you can buy premade packs in a wide variety of
> configurations. But, these often come at a premium
> in price (to pay for the added labor of their fabrication)
> *and* you can't just pick them up "off the shelf"
> (well, *some* configurations are available like this
> but not "in general").
>
> Has anyone come up with a clever way around this problem?
> Is there a poor man's approach to welding tabs onto
> batteries? Or, some other conductive fastener that
> doesn't put the cell at risk in the process?

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