On 11/12/15 16:09, Percival P. Cassidy wrote:
have an 18V 2.4AH battery pack for Ryobi power tools that will no
longer take a charge and that the charger indicates is defective.
I've taken it apart and found that it has five pairs of cells that are
labeled:

"LS IMR-18650BB

18650 is the physical geometry: 18mm diameter, 65mm long, 0=round.

Any Li-ion 3.7V 18650 will do as a replacement (peak charge voltage
4.2V) - but get a matched set of 5.

I see on line numerous variants of the 18650 cells with various mAH
ratings but nothing with the "BB" suffix.

It's meaningless as far as you're concerned.

Is it worth the effort of trying to replace the defective pair, or is
there a way that I could try to restore them to life?

No. Replace the lot - you don't want a mis-matched string.

I don't have a spot-welder. If I use a Dremel cutting wheel to cut the
tabs on the defective pair, would it be OK to solder new ones in place
using copper flashing?

Buy replacements with tabs on. Soldering can damage the cell internally
unless you're very skillful and swift.

Avoid Ultrafire and other *fire Chinese brands and their Chinese clones
(often repackaged dead cells). They make fantastical claims of capacity,
but you're lucky if you get 1000mAH, and never as much as 2000mAH (they
often claim 4000 or 6000; no-one can build that).

If you can afford it, buy Panasonic NCR cells - about $12-$15/ea - which
if genuine will produce about 3400mAH at a much better sustained
voltage. Chalk and cheese against the Chinese cells.

Clifford Heath.

have an 18V 2.4AH battery pack for Ryobi power tools that will no
longer take a charge and that the charger indicates is defective.

I've taken it apart and found that it has five pairs of cells that are
labeled:

"LS IMR-18650BB
YT0288.different numbers on the ones I can see Made in China"

I see on line numerous variants of the 18650 cells with various mAH
ratings but nothing with the "BB" suffix.

Four of the pairs of paralleled cells show a voltage of 4.1x; the other
pair shows 2.1mV.

Is it worth the effort of trying to replace the defective pair, or is
there a way that I could try to restore them to life?

If I want to replace the defective pair, I assume that any 18650 cells
with at least 1200mAH capacity will work -- but in fact I don't see any
that low.

I don't have a spot-welder. If I use a Dremel cutting wheel to cut the
tabs on the defective pair, would it be OK to solder new ones in place
using copper flashing?

Perce

On Fri, 11 Dec 2015 00:09:14 -0500, "Percival P. Cassidy"
wrote:

have an 18V 2.4AH battery pack for Ryobi power tools that will no
longer take a charge and that the charger indicates is defective.

I totally agree with Clifford Heath. However, let me add a few
additional comments.

I don't have a spot-welder. If I use a Dremel cutting wheel to cut the
tabs on the defective pair, would it be OK to solder new ones in place
using copper flashing?

The cases on most 18650 cells are stainless steel. You won't be able
to solder to those. Copper flashing might make a connection, but at
the high currents involved, will probably give you intermittent
connections, corrosion, or heating problems. Spot weld or forget it.

You can buy 18650 cells with tabs that can be soldered:
https://www.google.com/#q=18650+with+tabs

I do something different, which might be of interest. Instead of
using 18650 cells, I use flat cells usually used in model airplanes,
cars, quadcopters, etc. Something like this:
http://www.hobbyking.com/hobbyking/store/uh_listCategoriesAndProducts.asp?cwhl=US&idCategor y=86&v=&sortlist=P&LiPoConfig=5&CatSortOrder=asc
The listing are for 5 cell batteries (5S), west coast warehouse, and
sorted by ascending prices. If you're lucky, you can find a 5S
battery pile that will fit in your Ryobi battery box. If not, you can
bash a big hole in the battery pack and improvise.

Note that all the batteries have a "balance charger" connector. I
won't go into detail now, but basically this is the way you avoid
killing a battery pack. Each cell is monitored individually with no
risk of overcharging any of them if another cell is low voltage.
https://www.google.com/search?q=balance+charger
The technique is SLOOOOOWLY creeping into the power tool biz.
https://en.wikipedia.org/wiki/Battery_balancing

If you decide to go this route, bug me as there are a few other things
that you'll need (power connector/adapter, balance charger, etc).



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

On 12/10/2015 9:09 PM, Percival P. Cassidy wrote:
have an 18V 2.4AH battery pack for Ryobi power tools that will no
longer take a charge and that the charger indicates is defective.

I've taken it apart and found that it has five pairs of cells that are
labeled:

"LS IMR-18650BB
YT0288.different numbers on the ones I can see Made in China"

I see on line numerous variants of the 18650 cells with various mAH
ratings but nothing with the "BB" suffix.

There are many variants of cells.
The ones designed for high current have lower capacity.
If you try to use laptop high capacity cells in a drill, you'll have
low performance and short service life. You're likely to find that
the correct cells you need cost about the same as a new pack.

Four of the pairs of paralleled cells show a voltage of 4.1x; the other
pair shows 2.1mV.

Is it worth the effort of trying to replace the defective pair, or is
there a way that I could try to restore them to life?

You can try to charge the dead pair with a 4V power supply current limited
to 100 ma or so.
Always wear eye protection!
Don't get in a hurry, or you may set the thing afire.
Do it in the garage in a bucket that can't burn if the cells catch fire
or explode.
I've had limited success with that in laptop packs. But don't get your
hopes up.
If it works, charge each pair individually to the same voltage.
Don't get in a hurry, it may take a long time for the current to drop.

If I want to replace the defective pair, I assume that any 18650 cells
with at least 1200mAH capacity will work -- but in fact I don't see any
that low.
NO, get the right type of HIGH current cells and replace them all.

I don't have a spot-welder. If I use a Dremel cutting wheel to cut the
tabs on the defective pair, would it be OK to solder new ones in place
using copper flashing?
DO NOT SOLDER DIRECTLY TO ANY CELL OF ANY KIND.
You can solder tabs together, if you're quick about it.

Perce
What's your objective?
If you want to play with battery packs, you're on the right path.
If you want to drill holes reliably, call up Ryobi and buy a new pack.
Last year at this time they all seemed to have lifetime battery guarantee.

On 12/12/15 03:05, Percival P. Cassidy wrote:
On 12/10/2015 08:22 AM, Clifford Heath wrote:
have an 18V 2.4AH battery pack for Ryobi power tools that will no
longer take a charge and that the charger indicates is defective.
I've taken it apart and found that it has five pairs of cells that are
labeled:
"LS IMR-18650BB
18650 is the physical geometry: 18mm diameter, 65mm long, 0=round.
Any Li-ion 3.7V 18650 will do as a replacement (peak charge voltage
4.2V) - but get a matched set of 5.
If I have to get a matched set -- of ten (five *pairs*)

When did your need for five cells become ten?

-- rather than of two, I might as well get two 4AH ones for $99.

To my knowledge, no-one has worked out how to make a 4AH 18650 cell yet.

The best cells are below 3.5AH, and five of those are already more than
$49 without building a case. Ryobi is Chinese now, so they're almost
certainly lying.

If you value high capacity, buy your own branded cells.

On 12/10/2015 08:22 AM, Clifford Heath wrote:

have an 18V 2.4AH battery pack for Ryobi power tools that will no
longer take a charge and that the charger indicates is defective.
I've taken it apart and found that it has five pairs of cells that are
labeled:

"LS IMR-18650BB

18650 is the physical geometry: 18mm diameter, 65mm long, 0=round.

Any Li-ion 3.7V 18650 will do as a replacement (peak charge voltage
4.2V) - but get a matched set of 5.

If I have to get a matched set -- of ten (five *pairs*) -- rather than
of two, I might as well get two 4AH ones for $99.

I see on line numerous variants of the 18650 cells with various mAH
ratings but nothing with the "BB" suffix.

It's meaningless as far as you're concerned.

Is it worth the effort of trying to replace the defective pair, or is
there a way that I could try to restore them to life?

No. Replace the lot - you don't want a mis-matched string.

See above.

I don't have a spot-welder. If I use a Dremel cutting wheel to cut the
tabs on the defective pair, would it be OK to solder new ones in place
using copper flashing?

Buy replacements with tabs on. Soldering can damage the cell internally
unless you're very skillful and swift.

Avoid Ultrafire and other *fire Chinese brands and their Chinese clones
(often repackaged dead cells). They make fantastical claims of capacity,
but you're lucky if you get 1000mAH, and never as much as 2000mAH (they
often claim 4000 or 6000; no-one can build that).

If you can afford it, buy Panasonic NCR cells - about $12-$15/ea - which
if genuine will produce about 3400mAH at a much better sustained
voltage. Chalk and cheese against the Chinese cells.

Clifford Heath.

On 12/11/2015 12:51 AM, Jeff Liebermann wrote:

have an 18V 2.4AH battery pack for Ryobi power tools that will no
longer take a charge and that the charger indicates is defective.

I totally agree with Clifford Heath. However, let me add a few
additional comments.

I don't have a spot-welder. If I use a Dremel cutting wheel to cut the
tabs on the defective pair, would it be OK to solder new ones in place
using copper flashing?

The cases on most 18650 cells are stainless steel. You won't be able
to solder to those. Copper flashing might make a connection, but at
the high currents involved, will probably give you intermittent
connections, corrosion, or heating problems. Spot weld or forget it.

You can buy 18650 cells with tabs that can be soldered:
https://www.google.com/#q=18650+with+tabs

I do something different, which might be of interest. Instead of
using 18650 cells, I use flat cells usually used in model airplanes,
cars, quadcopters, etc. Something like this:
http://www.hobbyking.com/hobbyking/store/uh_listCategoriesAndProducts.asp?cwhl=US&idCategor y=86&v=&sortlist=P&LiPoConfig=5&CatSortOrder=asc
The listing are for 5 cell batteries (5S), west coast warehouse, and
sorted by ascending prices. If you're lucky, you can find a 5S
battery pile that will fit in your Ryobi battery box. If not, you can
bash a big hole in the battery pack and improvise.

Note that all the batteries have a "balance charger" connector. I
won't go into detail now, but basically this is the way you avoid
killing a battery pack. Each cell is monitored individually with no
risk of overcharging any of them if another cell is low voltage.
https://www.google.com/search?q=balance+charger
The technique is SLOOOOOWLY creeping into the power tool biz.
https://en.wikipedia.org/wiki/Battery_balancing

This battery pack does have connections from every between-cells
connection to the PC board, so I am assuming that this was supposed to
be part of the balancing circuitry.

I can buy two of the 4AH packs for $99, so replacing all ten cells (five
*pairs*) in the present one would probably cost about the same for less
capacity as one new one.

Perce

On 12/11/2015 03:01 AM, wrote:

I have an 18V 2.4AH battery pack for Ryobi power tools that will no
longer take a charge and that the charger indicates is defective.

If you're in the US, you might check with your local Batteries Plus
store. I had some DeWalt 12 V NiCd packs rebuilt by them for pretty
reasonable money, a couple of years ago. They have cells with tabs,
and the spot-welder to correctly join the tabs together.

I did ask at my local Batteries Plus, who told me that they don't
rebuild Li-Ion battery packs. Their after-market battery packs are
outrageously expensive.

Home Depot sells a brand new Ryobi P105 battery - probably the same one
you have - for $59+tax. That listing also claims that the battery has
a 3-year warranty; is it possible that your battery is younger than
that?

The defective one is a P104, and I have no idea when I bought it. Even
if it were, theoretically, in warranty, I've voided the warranty by
taking it apart and peeling off the adhesive foam covering the ends of
the cells; it never occurred to me that it *might* still be in warranty.
It appears that Ryobi warranty service is obtained by returning items to
a service center -- no indication that one can simply exchange a
defective item at Home Depot.

A two-pack of the 4AH P108 packs is only $99. I don't know whether
that's a year-round deal, but I did take advantage of the same deal
around this time last year. I suspect that's a year-end deal, as a
single P108 is the same price.

Perce

On Fri, 11 Dec 2015 11:13:35 -0500, "Percival P. Cassidy"
wrote:

This battery pack does have connections from every between-cells
connection to the PC board, so I am assuming that this was supposed to
be part of the balancing circuitry.

I wasn't aware of that. Progress lurches forward, usually when I'm
not looking.

This might be of interest if you want to repair your battery pack:
"Cell Re-balance of Ryobi One+ 18V Li-ion Battery (130501002)"
https://www.ifixit.com/Guide/Cell+Re-balance+of+Ryobi+One%2B+18V+Li-ion+Battery+%28130501002%29/13286
"Rebuilding Ryobi 18v Batteries"
http://toolboyworld.com/eBay/Ryobi_Batt_Rebuild.htm
Looks like the balancing circuitry is in the battery pack, not the
charger.

I can buy two of the 4AH packs for $99, so replacing all ten cells (five
*pairs*) in the present one would probably cost about the same for less
capacity as one new one.

http://www.homedepot.com/p/Ryobi-18-Volt-ONE-High-Capacity-LITHIUM-Battery-2-Pack-P122/204321540
I would not trust the battery capacity (ma-hrs) as stated on the
label. However the goood price and less risk of buying these is
probably better than trying to rebuild a pack.


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

On 12/11/2015 12:59 PM, Jeff Liebermann wrote:

This battery pack does have connections from every between-cells
connection to the PC board, so I am assuming that this was supposed to
be part of the balancing circuitry.

I wasn't aware of that. Progress lurches forward, usually when I'm
not looking.

This might be of interest if you want to repair your battery pack:
"Cell Re-balance of Ryobi One+ 18V Li-ion Battery (130501002)"
https://www.ifixit.com/Guide/Cell+Re-balance+of+Ryobi+One%2B+18V+Li-ion+Battery+%28130501002%29/13286

I might try that.

"Rebuilding Ryobi 18v Batteries"
http://toolboyworld.com/eBay/Ryobi_Batt_Rebuild.htm
Looks like the balancing circuitry is in the battery pack, not the
charger.

He deals with minor voltage differences between cells, not the huge
differences I have (mV only, from the one paralleled pair).

I can buy two of the 4AH packs for $99, so replacing all ten cells (five
*pairs*) in the present one would probably cost about the same for less
capacity as one new one.

http://www.homedepot.com/p/Ryobi-18-Volt-ONE-High-Capacity-LITHIUM-Battery-2-Pack-P122/204321540
I would not trust the battery capacity (ma-hrs) as stated on the
label. However the goood price and less risk of buying these is
probably better than trying to rebuild a pack.

Any less trustworthy than the alleged 2.4Ah capacity of the present one?

Perce

On Fri, 11 Dec 2015 15:52:58 -0500, "Percival P. Cassidy"
wrote:

Any less trustworthy than the alleged 2.4Ah capacity of the present one?

Well, I don't know if Ryobi tests their cells, where they get them, or
what they're charger is doing to them. If they're like most laptop
and UPS computah battery manufacturers, the prime directive is to
quickly kill the batteries in order to sell the customer a replacement
battery or UPS. I suppose cordless tools are much the same.

If you want the best cells, various individuals have already done the
work:
http://lygte-info.dk/review/batteries2012/Common18650Summary%20UK.html
http://www.torchythebatteryboy.com/p/18650-batteries-chargers.html
http://www.candlepowerforums.com/vb/showthread.php?257543-LiIon-18650-battery-comparison
Also, search on candlepowerforums.com for battery tests:
http://www.candlepowerforums.com

I do my own using a West Mountain Radio CBA-II. For example, here's
an Ultrafire 3000 that manages to barely squeeze out 850 ma-hrs at 1C:
http://802.11junk.com/jeffl/LiPo/
http://802.11junk.com/jeffl/LiPo/Ultrafire%20LiPo%203000%20ma-hr%2018650.jpg
http://802.11junk.com/jeffl/LiPo/Ultrafire%2018650%20test.jpg
I know garbage when I buy it.

Note that your 2400 ma-hr battery is usually rated at 0.2C or 480 ma
discharge current. The test is also at room temperature. Vendors
sometimes cheat and test the batteries in a water bath. The problem
is that your drill probably draws about 30A, split between two strings
of cells or 15A per cell, or about 6C. If you look at the typical
LiIon 18650 family of curves, 6C isn't even on the graph. Much
depends on at what voltage you want to declare the battery to be
discharged. Panasonic uses 2.5v. Good quality LiIon batteries do not
loose much capacity at these discharge rates. Junk drops drastically
in capacity. Without knowing more about what you have, and testing
the cells, I can't guess(tm) the capacity at 15A discharge.

Incidentally, if you're considering buying or building a battery spot
welder (I am), this might be interesting:
http://www.ebay.com/sch/i.html?_nkw=battery+spot+welder
I made my own CD (capacitor discharge) system, but it sucks and is in
need of replacement.

Good luck.
--
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 in message
...
On Fri, 11 Dec 2015 00:09:14 -0500, "Percival P. Cassidy"
wrote:

have an 18V 2.4AH battery pack for Ryobi power tools that will no
longer take a charge and that the charger indicates is defective.

I totally agree with Clifford Heath. However, let me add a few
additional comments.

I don't have a spot-welder. If I use a Dremel cutting wheel to cut the
tabs on the defective pair, would it be OK to solder new ones in place
using copper flashing?

The cases on most 18650 cells are stainless steel. You won't be able
to solder to those.

The flux I bought in a plumbers supply yard works perfectly OK on stainless,
but sometimes needs the stainless to be lightly abraded.

Often I see a warning on lithium cells not to expose to more than 212F - or
boiling water in other words.

Whenever I need to solder lithium cells; I just trim back the stainless
strip so it still has a bit spot welded to the cell - its just that little
bit more thermal resistance between the iron and the cell.

A fully charged cell can provide a fair bit of entertainment if the heat of
soldering melts the seal and causes a short - solder first, charge later.

On Fri, 11 Dec 2015 21:26:03 -0000, "Ian Field"
wrote:

The flux I bought in a plumbers supply yard works perfectly OK on stainless,
but sometimes needs the stainless to be lightly abraded.

Paste or liquid flux? I've had no luck soldering stainless with
either. Mostly, I try to solder to button cells, not 18650, which
might be different. The paste flux made for copper pipe doesn't seem
to work for stainless. For example;
http://www.homedepot.com/c/flux_and_solder_HT_BG_TH
Can be used on all materials except aluminum and
stainless steel.

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

On 12/11/2015 12:59 PM, Jeff Liebermann wrote:

This battery pack does have connections from every between-cells
connection to the PC board, so I am assuming that this was supposed to
be part of the balancing circuitry.

I wasn't aware of that. Progress lurches forward, usually when I'm
not looking.

This might be of interest if you want to repair your battery pack:
"Cell Re-balance of Ryobi One+ 18V Li-ion Battery (130501002)"
https://www.ifixit.com/Guide/Cell+Re-balance+of+Ryobi+One%2B+18V+Li-ion+Battery+%28130501002%29/13286
"Rebuilding Ryobi 18v Batteries"
http://toolboyworld.com/eBay/Ryobi_Batt_Rebuild.htm
Looks like the balancing circuitry is in the battery pack, not the
charger.

I tried boosting the voltage of the low-voltage pair but without much
success so far. I don't really have a suitable power source.

When I plug that pack into a P117 charger, the red light flashes "for
ever" ("Testing"), but after a looong time changes to the slow flash
indicating "Defective." When I plug it into a P125 charger, I get the
"Charging" indication for just a minute or two, then it switches to
"Charged," but of course it isn't: that one pair of cells still shows
only in the mV range.

Perce

On 12/11/2015 1:22 PM, Jeff Liebermann wrote:
On Fri, 11 Dec 2015 15:52:58 -0500, "Percival P. Cassidy"
wrote:

Any less trustworthy than the alleged 2.4Ah capacity of the present one?

Well, I don't know if Ryobi tests their cells, where they get them, or
what they're charger is doing to them. If they're like most laptop
and UPS computah battery manufacturers, the prime directive is to
quickly kill the batteries in order to sell the customer a replacement
battery or UPS. I suppose cordless tools are much the same.

If you want the best cells, various individuals have already done the
work:
http://lygte-info.dk/review/batteries2012/Common18650Summary%20UK.html
http://www.torchythebatteryboy.com/p/18650-batteries-chargers.html
http://www.candlepowerforums.com/vb/showthread.php?257543-LiIon-18650-battery-comparison
Also, search on candlepowerforums.com for battery tests:
http://www.candlepowerforums.com

I do my own using a West Mountain Radio CBA-II. For example, here's
an Ultrafire 3000 that manages to barely squeeze out 850 ma-hrs at 1C:
http://802.11junk.com/jeffl/LiPo/
http://802.11junk.com/jeffl/LiPo/Ultrafire%20LiPo%203000%20ma-hr%2018650.jpg
http://802.11junk.com/jeffl/LiPo/Ultrafire%2018650%20test.jpg
I know garbage when I buy it.

Note that your 2400 ma-hr battery is usually rated at 0.2C or 480 ma
discharge current. The test is also at room temperature. Vendors
sometimes cheat and test the batteries in a water bath. The problem
is that your drill probably draws about 30A, split between two strings
of cells or 15A per cell, or about 6C. If you look at the typical
LiIon 18650 family of curves, 6C isn't even on the graph. Much
depends on at what voltage you want to declare the battery to be
discharged. Panasonic uses 2.5v. Good quality LiIon batteries do not
loose much capacity at these discharge rates. Junk drops drastically
in capacity. Without knowing more about what you have, and testing
the cells, I can't guess(tm) the capacity at 15A discharge.

Incidentally, if you're considering buying or building a battery spot
welder (I am), this might be interesting:
http://www.ebay.com/sch/i.html?_nkw=battery+spot+welder
I made my own CD (capacitor discharge) system, but it sucks and is in
need of replacement.

Good luck.

It's not clear how those welders work. Looks like timed pulse??

I spent a LOT of time messing with battery tab welding.
You need a LOT of heat QUICKLY.
I put a SSR on the primary of a modified microwave oven transformer
and counted the number of cycles of 60 Hz. to set the power delivered.
Problem with low voltage is that it is extremely sensitive to
resistance in the path.
I could get very good welds about 80% of the time. On average,
I got all good welds on about 0% of the packs.

You really want a fixed amount of energy delivered independently
of contact resistance.

Capacitive discharge is the way to go. But, to get repeatability,
you need to be switching the energy at high voltage. It's not
easy to switch 1000 amps or more.

I gave up on DIY when I found a 125 Watt-Second CD system on ebay for
cheap. That puppy can put 7000A single pulse into .001 ohms.
Repeatability improved dramatically. Battery doesn't even get warm.

On 12/11/2015 08:41 AM, Clifford Heath wrote:

have an 18V 2.4AH battery pack for Ryobi power tools that will no
longer take a charge and that the charger indicates is defective.
I've taken it apart and found that it has five pairs of cells that are
labeled:
"LS IMR-18650BB
18650 is the physical geometry: 18mm diameter, 65mm long, 0=round.
Any Li-ion 3.7V 18650 will do as a replacement (peak charge voltage
4.2V) - but get a matched set of 5.
If I have to get a matched set -- of ten (five *pairs*)

When did your need for five cells become ten?

Reread my original message in which I referred to four *pairs of
paralleled cells* showing 4.1x Volts and the other *pair* showing only
2.1mV.

-- rather than of two, I might as well get two 4AH ones for $99.

To my knowledge, no-one has worked out how to make a 4AH 18650 cell yet.

That's why they use *paralleled pairs* of 18650 cells.

The best cells are below 3.5AH, and five of those are already more than
$49 without building a case. Ryobi is Chinese now, so they're almost
certainly lying.

If you value high capacity, buy your own branded cells.

BTW, a few years ago I found a Web site dealing with battery packs for
power tools that reported that all the packs they had disassembled used
the same Sanyo 18650 cells -- including the RIDGID packs with the
lifetime warranty and the Craftsman "19.2-volt" (for how many seconds
after they come off the charger?) ones.

Perce

"Jeff Liebermann" wrote in message
...
On Fri, 11 Dec 2015 21:26:03 -0000, "Ian Field"
wrote:

The flux I bought in a plumbers supply yard works perfectly OK on
stainless,
but sometimes needs the stainless to be lightly abraded.

Paste or liquid flux? I've had no luck soldering stainless with
either. Mostly, I try to solder to button cells, not 18650, which
might be different. The paste flux made for copper pipe doesn't seem
to work for stainless. For example;

Some plumbing is stainless and any good plumber's yard will stock flux for
it.

The one I bought from had regular and active flux - I bought the latter and
it works just fine on stainless.