Hi,

I'm replacing the battery in a GPS unit. Looks to
be an "A" cell (no, not AA or AAA), 3.7V 1800mAHr.
Of course, the battery has pigtails soldered to it
so I'll need something with either pigtails or solder
tabs as its replacement (I doubt I could add any
sort of battery holder in this small space!).

I went grep-ing Digikey and all I found were "lithium"
batteries but I suspect these are intended for use in
"nonvolatile (data) backup" (i.e., low current rates)
and not actually used to *power* something. (I think
the battery is intended to last about 8 hours so I'm
guessing the load to be about 250mA?).

Can someone clarify what I need to go looking for?
And/or a pointer to a source for same (qty 1).

Thanks!

D Yuniskis wrote:
Hi,

I'm replacing the battery in a GPS unit. Looks to
be an "A" cell (no, not AA or AAA), 3.7V 1800mAHr.
Of course, the battery has pigtails soldered to it
so I'll need something with either pigtails or solder
tabs as its replacement (I doubt I could add any
sort of battery holder in this small space!).

I went grep-ing Digikey and all I found were "lithium"
batteries but I suspect these are intended for use in
"nonvolatile (data) backup" (i.e., low current rates)
and not actually used to *power* something. (I think
the battery is intended to last about 8 hours so I'm
guessing the load to be about 250mA?).

Can someone clarify what I need to go looking for?
And/or a pointer to a source for same (qty 1).

Thanks!
google 18650.

spamme0 wrote:
D Yuniskis wrote:
Hi,

I'm replacing the battery in a GPS unit. Looks to
be an "A" cell (no, not AA or AAA), 3.7V 1800mAHr.
Of course, the battery has pigtails soldered to it
so I'll need something with either pigtails or solder
tabs as its replacement (I doubt I could add any
sort of battery holder in this small space!).

google 18650.

Thanks! Seems to be the right size and capacity;
but I need something with *pigtails*:

"Of course, the battery has pigtails soldered to it
so I'll need something with either pigtails or solder
tabs as its replacement (I doubt I could add any
sort of battery holder in this small space!)."

I haven't a clue as to how I could otherwise make the
connection to the battery (without risking explosion/damage).

On Thu, 30 Jul 2009 08:13:41 -0700, D Yuniskis
wrote:

spamme0 wrote:
D Yuniskis wrote:
Hi,

I'm replacing the battery in a GPS unit. Looks to
be an "A" cell (no, not AA or AAA), 3.7V 1800mAHr.
Of course, the battery has pigtails soldered to it
so I'll need something with either pigtails or solder
tabs as its replacement (I doubt I could add any
sort of battery holder in this small space!).

google 18650.

Thanks! Seems to be the right size and capacity;
but I need something with *pigtails*:

Ummm.... Find a picture of a pig. Note the tail. There's no
semblance to a battery tab.

"Of course, the battery has pigtails soldered to it
so I'll need something with either pigtails or solder
tabs as its replacement (I doubt I could add any
sort of battery holder in this small space!)."

I haven't a clue as to how I could otherwise make the
connection to the battery (without risking explosion/damage).

Ummm.... Google for "18650 tabs". There are also a mess of cells
available on Ebay using the same search key.

I've also been fairly successful with soldering wires onto the cells.
However, some cells use a stainless can, which won't solder. For
battery pack rebuilds, there's sometime not enough room for the
inevitable "lump" formed when soldering wires. That's not the case
with spot welded tabs, which lie flat.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

In article ,
Jeff Liebermann wrote:
I've also been fairly successful with soldering wires onto the cells.
However, some cells use a stainless can, which won't solder. For
battery pack rebuilds, there's sometime not enough room for the
inevitable "lump" formed when soldering wires. That's not the case
with spot welded tabs, which lie flat.

I usually cut off the spot welded tabs from the old ones and solder these.
But don't know how LiIon react to heat. You've got to solder quickly with
other types to avoid damage.

--
*All men are idiots, and I married their King.

Dave Plowman London SW
To e-mail, change noise into sound.

On Thu, 30 Jul 2009 19:01:04 +0100, "Dave Plowman (News)"
wrote:

In article ,
Jeff Liebermann wrote:
I've also been fairly successful with soldering wires onto the cells.
However, some cells use a stainless can, which won't solder. For
battery pack rebuilds, there's sometime not enough room for the
inevitable "lump" formed when soldering wires. That's not the case
with spot welded tabs, which lie flat.

I usually cut off the spot welded tabs from the old ones and solder these.

Yep. Same here. I inherited a large box of Metricom battery packs.
When I ripped them apart for the cells, I kept all the tabs. They
solver very easily and are quite handy. They're also quite sharp. I
have the blood stains to prove it.

But don't know how LiIon react to heat. You've got to solder quickly with
other types to avoid damage.

Dunno. I killed a few NiCads from overheating until I learned the
trick. I have a glass of water handy when soldering on the tabs. As
soon as the solder even looks like it's about to harden, I dump the
battery in the water. That keeps things quite cool and prevents the
heat affected zone from spreading.

Jeff Liebermann wrote:
On Thu, 30 Jul 2009 08:13:41 -0700, D Yuniskis

spamme0 wrote:
D Yuniskis wrote:
Hi,

I'm replacing the battery in a GPS unit. Looks to
be an "A" cell (no, not AA or AAA), 3.7V 1800mAHr.
Of course, the battery has pigtails soldered to it
so I'll need something with either pigtails or solder
tabs as its replacement (I doubt I could add any
sort of battery holder in this small space!).
google 18650.
Thanks! Seems to be the right size and capacity;
but I need something with *pigtails*:

Ummm.... Find a picture of a pig. Note the tail. There's no
semblance to a battery tab.

Note the following: ;-)

"Of course, the battery has pigtails soldered to it
so I'll need something with either pigtails or solder
tabs as its replacement (I doubt I could add any
sort of battery holder in this small space!)."

I haven't a clue as to how I could otherwise make the
connection to the battery (without risking explosion/damage).

Ummm.... Google for "18650 tabs". There are also a mess of cells
available on Ebay using the same search key.

Thanks. When I saw these were commonly used in laptop battery
packs, I just fished a couple of laptops out of the trash and
cannabilized the battery packs until I found cells with "decent"
open circuit voltages. Made sure I cut the tabs that connected
them to their neighbors so I would have a fair bit to work
with. Soldered some pigtails on and was able to replace the dead
battery in the GPS unit easily!

Rescued GPS unit: $0
Rescued Li Ion cell: $0
Working GPS unit: priceless

wink

I've also been fairly successful with soldering wires onto the cells.
However, some cells use a stainless can, which won't solder. For
battery pack rebuilds, there's sometime not enough room for the
inevitable "lump" formed when soldering wires. That's not the case
with spot welded tabs, which lie flat.

I've never had luck trying to solder to these cans
(partly out of fear of letting the can get too hot!).

I've a friend who will make me a little welder but I
would have to fetch it from him (out of state) -- its
just not worth the effort for something I do so rarely!

Thanks, all, for the pointers!

Jeff Liebermann wrote:
On Thu, 30 Jul 2009 08:13:41 -0700, D Yuniskis

spamme0 wrote:
D Yuniskis wrote:
Hi,

I'm replacing the battery in a GPS unit. Looks to
be an "A" cell (no, not AA or AAA), 3.7V 1800mAHr.
Of course, the battery has pigtails soldered to it
so I'll need something with either pigtails or solder
tabs as its replacement (I doubt I could add any
sort of battery holder in this small space!).
google 18650.
Thanks! Seems to be the right size and capacity;
but I need something with *pigtails*:

Ummm.... Find a picture of a pig. Note the tail. There's no
semblance to a battery tab.

Note the following: ;-)

"Of course, the battery has pigtails soldered to it
so I'll need something with either pigtails or solder
tabs as its replacement (I doubt I could add any
sort of battery holder in this small space!)."

I haven't a clue as to how I could otherwise make the
connection to the battery (without risking explosion/damage).

Ummm.... Google for "18650 tabs". There are also a mess of cells
available on Ebay using the same search key.

Thanks. When I saw these were commonly used in laptop battery
packs, I just fished a couple of laptops out of the trash and
cannabilized the battery packs until I found cells with "decent"
open circuit voltages. Made sure I cut the tabs that connected
them to their neighbors so I would have a fair bit to work
with. Soldered some pigtails on and was able to replace the dead
battery in the GPS unit easily!

Rescued GPS unit: $0
Rescued Li Ion cell: $0
Working GPS unit: priceless

wink

I've also been fairly successful with soldering wires onto the cells.
However, some cells use a stainless can, which won't solder. For
battery pack rebuilds, there's sometime not enough room for the
inevitable "lump" formed when soldering wires. That's not the case
with spot welded tabs, which lie flat.

I've never had luck trying to solder to these cans
(partly out of fear of letting the can get too hot!).

I've a friend who will make me a little welder but I
would have to fetch it from him (out of state) -- its
just not worth the effort for something I do so rarely!

Thanks, all, for the pointers!

snip

I've a friend who will make me a little welder but I
would have to fetch it from him (out of state) -- its
just not worth the effort for something I do so rarely!


I'd like to hear more about the welder design.

I messed around with low-voltage transformers, but never
got consistent welds. Was VERY sensitive to contact
resistance. About half the welds didn't stick.
The other half blew thru the tab.

Gave all that up when a CD welder
showed up on ebay for $15. It'll put 7000Amps into a milliohm.
Get MUCH more consistent tab welds.

If you have a chance to get an affordable tab welder,
you'll find other uses for it. And you'll have a lot of new
friends in need of tab welding ;-)

mike

Re the discussion on making connections to battery cells: the summary
of the content so far is that soldering is dangerous, weldingis the
way to go, but is not trivial.

There's another possibility that I've seen read about but have no
experience with: conductive glue. From a commercial battery website I
saw (http://www.smallbattery.company.org....ire-glue.htm):

"Wire Glue - electrically conductive adhesive

Wire Glue utilizes the latest advances in microcarbon technology to
bring you a highly conductive glue at a fraction the price of
competitive products which use precious metals such as silver.

Wire Glue allows you to make low voltage AC and DC electrical
connections without soldering or heating.

There is no requirement to measure out and mix hardeners. Simply stir
and apply the glue to your surface and let it cure overnight. By
morning, you will have a reliable, permanent and electrically
conductive bond!

Cost-effective replacement for silver-loaded epoxies.

This lead free formulation is ideal for bonding all types of low
voltage electrical connections.

Wire Glue is not intended for high voltage or high current
applications. In high power circuits Wire Glue may become hot and give
off burning smells."

From another page on the same site:

"Can you make the tabbed cell I require?

We do not add tabs to order... Order a bare, untagged cell from us and
then carefully remove the existing tags from your dead cell. Apply the
Wire Glue to your cell's surface and to the tag, pop them together and
let it all cure overnight. By the morning your problems will be
solved."

This also suggests that you should be able to get similar but more
expensive silver-based glue. What current either will handle sensibly
I don't know - a data sheet would help.

HTH

D Yuniskis wrote:
spamme0 wrote:
D Yuniskis wrote:
Hi,

I'm replacing the battery in a GPS unit. Looks to
be an "A" cell (no, not AA or AAA), 3.7V 1800mAHr.
Of course, the battery has pigtails soldered to it
so I'll need something with either pigtails or solder
tabs as its replacement (I doubt I could add any
sort of battery holder in this small space!).

google 18650.

Thanks! Seems to be the right size and capacity;
but I need something with *pigtails*:

"Of course, the battery has pigtails soldered to it
so I'll need something with either pigtails or solder
tabs as its replacement (I doubt I could add any
sort of battery holder in this small space!)."

I haven't a clue as to how I could otherwise make the
connection to the battery (without risking explosion/damage).

buy cells with tabs.
do not solder to lithium cells!!!!! unless you have very good fire
insurance, medical insurance and a death wish.
Your wife will be very angry six months later when the GPS
sets her car on fire. So, if the battery doesn't hurt you, she will.

Just in case you missed it....DO NOT SOLDER DIRECTLY TO ANY BATTERY,
ESPECIALLY LITHIUMS. People will tell you they do it.
Are you feeling lucky?

You need a battery tab welder if you try to use non-tabbed cells.

Virtually every lithium ion laptop battery pack
ever made contains tabbed 18650 cells. Buy an old battery pack
and take it apart...carefully.
Sometimes, you can talk the radio shack guy to give you one from his
recycle bin. Or ask the IT guy at work.

Cut the tabs. You can (carefully) solder to the remaining part of the
tabs if they're 1/4 inch or more without overheating the cell.


Your gps (probably) takes significantly less peak current
than a laptop, so a weak laptop pack that's not completely dead
may provide useful cells for your application.

On Fri, 31 Jul 2009 00:37:21 -0700, spamme0
wrote:

buy cells with tabs.
do not solder to lithium cells!!!!! unless you have very good fire
insurance, medical insurance and a death wish.

Well, you're right. Heat will cause a Li-Ion battery pack to
deteriorate rather rapidly. There's also the fire danger. Several
web sites recommend against soldering directly to the can on Li-Ion
cells. For example:
http://www.electronics-lab.com/articles/Li_Ion_reconstruct/
http://www.panasonic.com/industrial/battery/oem/images/pdf/panasonic_liion_precautions.pdf
"Do not short circuit, overcharge, crush, mutilate, nail penetrate,
incinerate, reverse polarity, heat above 100 degrees Celsius, solder
directly on the metal can."

I guess I've been lucky as my method of dunking the battery into water
after soldering seems to have prevented any problems. However, in the
future, I probably won't take the chance. It's too risky.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Jeff Liebermann wrote:

On Fri, 31 Jul 2009 00:37:21 -0700, spamme0
wrote:

buy cells with tabs.
do not solder to lithium cells!!!!! unless you have very good fire
insurance, medical insurance and a death wish.

Well, you're right. Heat will cause a Li-Ion battery pack to
deteriorate rather rapidly. There's also the fire danger. Several
web sites recommend against soldering directly to the can on Li-Ion
cells. For example:
http://www.electronics-lab.com/articles/Li_Ion_reconstruct/

http://www.panasonic.com/industrial/battery/oem/images/pdf/panasonic_liion_precautions.pdf
"Do not short circuit, overcharge, crush, mutilate, nail penetrate,
incinerate, reverse polarity, heat above 100 degrees Celsius, solder
directly on the metal can."

I guess I've been lucky as my method of dunking the battery into water
after soldering seems to have prevented any problems. However, in the
future, I probably won't take the chance. It's too risky.

Especially once you know what happens when you mix lithium and water - the
lithium catches fire.