I am hoping this question isnt too basic for this forum but I am
trying to replace some rechargeable batteries (in a Roomba: I
understand that generally only one or two start malfunctioning over
time and that it is usually the same one). It MUST be easier than I am
finding it.

I can just about solder on a connection but these rechargeable C cells
(nickel metal hydride? I am pretty sure they aren't lithium!) always
seem to have some sort of electro-welded rectangular plate connecting
the batteries which wont come off with a normal soldering gun? Or do
I just have to apply an inordinate amount of heat at exactly the
position where the ;nick' seems to be in the plate? Given the amount
of heat I seem to have applied to it already with no effect
whatsoever, to me it seems that this might damage the cell?

Is there some trick to doing this please or am i supposed to use a
dremel wheel to cut the plates off, leaving just the electro-weld to
which I solder the wire for the new cell?

In article , Amanda Ripanykhazov wrote:
I am hoping this question isnt too basic for this forum but I am
trying to replace some rechargeable batteries (in a Roomba: I
understand that generally only one or two start malfunctioning over
time and that it is usually the same one). It MUST be easier than I am
finding it.

I can just about solder on a connection but these rechargeable C cells
(nickel metal hydride? I am pretty sure they aren't lithium!) always
seem to have some sort of electro-welded rectangular plate connecting
the batteries which wont come off with a normal soldering gun? Or do
I just have to apply an inordinate amount of heat at exactly the
position where the ;nick' seems to be in the plate? Given the amount
of heat I seem to have applied to it already with no effect
whatsoever, to me it seems that this might damage the cell?

Is there some trick to doing this please or am i supposed to use a
dremel wheel to cut the plates off, leaving just the electro-weld to
which I solder the wire for the new cell?

The connections are welded. Maybe several thousand degrees will
take it off. Normally you bend them off.

Soldering to batteries can be risky both safety and damage.
To solder, Dremel scratches in the metal. Use a very hot iron
at about 750 degrees F. Time is the important part. You want to
heat it up quickly and solder so it has time to cool. Metal strips can be replaced with ordinary
wire.

greg

I often wonder why people don't call the manufacturer first. Is it that
difficult?

I would contact iRobot and ask them what the recommended procedure is.

On the assumption that iRobot is not stupid, and knows that the batteries
will eventually have to be replaced, it seems reasonable that the wires from
the batteries connect to a push-on terminal on the main board. If this is
so, you'll have to get the iRobot batteries.

On Feb 19, 2:17*pm, "William Sommerwerck"
wrote:
I often wonder why people don't call the manufacturer first. Is it that
difficult?

I would contact iRobot and ask them what the recommended procedure is.

Thanks for that everyone: I will try it.

Obviously no one calls iRobot for this question. they just want to
sell their expensive batteries. The last thing hhey want is to advise
on how to take the battery compartment apart. They even go to the
length of putting special screws on it to prevent anyone taking it
apart (using a triangular headed screwdriver: Has ANYONE ever come
across that on any other unit of any type whatsoever?)

Amanda Ripanykhazov wrote:
On Feb 19, 2:17 pm, "William Sommerwerck"
wrote:
I often wonder why people don't call the manufacturer first. Is it that
difficult?

I would contact iRobot and ask them what the recommended procedure is.

Thanks for that everyone: I will try it.

Obviously no one calls iRobot for this question. they just want to
sell their expensive batteries. The last thing hhey want is to advise
on how to take the battery compartment apart. They even go to the
length of putting special screws on it to prevent anyone taking it
apart (using a triangular headed screwdriver: Has ANYONE ever come
across that on any other unit of any type whatsoever?)
Yes, it's common to prevent people who don't know what they're doing
from hurting themselves and suing the company. Certification agencies like
UL make a distinction between things that require a tool to open
and relax requirements in those areas. But people are idiots,
so vendors use fasteners that require uncommon tools to protect
them from themselves.
Your post suggests that you need that protection, but you're insisting
on learning the hard way.

REMEMBER THE SAFETY GLASSES.

I'd send you a picture of the battery pack that exploded after I
"fixed it" but it exploded so violently that I never found most of it.
The hot electrolyte spots on my glasses was my learning experience.

"William Sommerwerck" wrote in
:

I often wonder why people don't call the manufacturer first. Is it
that difficult?

I would contact iRobot and ask them what the recommended procedure is.

On the assumption that iRobot is not stupid, and knows that the
batteries will eventually have to be replaced, it seems reasonable
that the wires from the batteries connect to a push-on terminal on the
main board. If this is so, you'll have to get the iRobot batteries.





Or take the pack to a Batteries Plus store or other rebuilder and have a
new pack built. Usually at a lower cost than a new OEM pack.

--
Jim Yanik
jyanik
at
localnet
dot com

Amanda Ripanykhazov wrote:
I am hoping this question isnt too basic for this forum but I am
trying to replace some rechargeable batteries (in a Roomba: I
understand that generally only one or two start malfunctioning over
time and that it is usually the same one). It MUST be easier than I am
finding it.

I can just about solder on a connection but these rechargeable C cells
(nickel metal hydride?
You sure they're not sub-C?
They're spot welded.
DO NOT SOLDER TO THE NEW BATTERIES. GET BATTERIES WITH TABS AND
SOLDER TO THE TABS.
Replace 'em ALL at once. Weak ones will be killed by the new ones.
"Not exactly, but that's the result."
I am pretty sure they aren't lithium!)
If you're gonna replace cells, shouldn't you be CERTAIN
what they are? Last thing you want is a robot running around
your floors ON FIRE!
always
seem to have some sort of electro-welded rectangular plate connecting
the batteries which wont come off with a normal soldering gun? Or do
I just have to apply an inordinate amount of heat at exactly the
position where the ;nick' seems to be in the plate? Given the amount
of heat I seem to have applied to it already with no effect
whatsoever, to me it seems that this might damage the cell?

Yes, it will.
Is there some trick to doing this

If you're gonna solder on batteries,
Wear safety glasses. Put 911 on speed dial.
Order up a whole set of tabbed cells to replace the ones
(actually ALL of them)
you ruin by overheating. Make sure you understand the charging
regimen so you can order the correct type of cells.

Now you're ready to ruin some new cells. Have at it.

OR,
you can take it back where you bought it and say, "fix it!"

please or am i supposed to use a
dremel wheel to cut the plates off, leaving just the electro-weld to
which I solder the wire for the new cell?

Amanda Ripanykhazov wrote:
I am hoping this question isnt too basic for this forum but I am
trying to replace some rechargeable batteries (in a Roomba: I
understand that generally only one or two start malfunctioning over
time and that it is usually the same one). It MUST be easier than I am
finding it.

I can just about solder on a connection but these rechargeable C cells
(nickel metal hydride? I am pretty sure they aren't lithium!) always
seem to have some sort of electro-welded rectangular plate connecting
the batteries which wont come off with a normal soldering gun? Or do
I just have to apply an inordinate amount of heat at exactly the
position where the ;nick' seems to be in the plate? Given the amount
of heat I seem to have applied to it already with no effect
whatsoever, to me it seems that this might damage the cell?

Is there some trick to doing this please or am i supposed to use a
dremel wheel to cut the plates off, leaving just the electro-weld to
which I solder the wire for the new cell?




Hi Amanda, You might want to look at this link, it details what to expect.

http://www.robotreviews.com/hack2/battery.shtml

Theres a good link to thread of advice on which cells to buy etc

Good luck, I'm about to try the same on my Roomba, JC

On Feb 19, 4:18*pm, Archon wrote:
Amanda Ripanykhazov wrote:
I am hoping this question isnt too basic for this forum but I am
trying to replace some rechargeable batteries (in a Roomba: I
understand that generally only one or two start malfunctioning over
time and that it is usually the same one). It MUST be easier than I am
finding it.

I can just about solder on a connection but these rechargeable C cells
(nickel metal hydride? I am pretty sure they aren't lithium!) always
seem to have some sort of electro-welded rectangular plate connecting
the batteries which wont come off with a normal soldering gun? * Or do
I just have to apply an inordinate amount of heat at exactly the
position where the ;nick' seems to be in the plate? Given the amount
of heat I seem to have applied to it already with no effect
whatsoever, to me it seems that this might damage the cell?

Is there some trick to doing this please or am i supposed to use a
dremel wheel to cut the plates off, leaving just the electro-weld to
which I solder the wire for the new cell?

Hi Amanda, You might want to look at this link, it details what to expect..

http://www.robotreviews.com/hack2/battery.shtml

Theres a good link to thread of advice on which cells to buy etc

Good luck, I'm about to try the same on my Roomba, JC

Hi JC

Yes, I had seen that and have two batteries to do: So my problem is
probably in getting enough good cells in one of them if I can figure
out how (as Mike would put it) to join up two separate tabbed cells
without having a spot welder

It is noteworthy that the on line 'experience based' instructions say
that you can solder where there was spot welding beforehand. (They
dont tell how to get the tabs off in the instructions which I saw,
which is why I posted here)

Amanda Ripanykhazova

Hi Amanda,

Amanda Ripanykhazov wrote:
On Feb 19, 4:18 pm, Archon wrote:
Amanda Ripanykhazov wrote:
I am hoping this question isnt too basic for this forum but I am
trying to replace some rechargeable batteries (in a Roomba: I
understand that generally only one or two start malfunctioning over
time and that it is usually the same one). It MUST be easier than I am
finding it.
I can just about solder on a connection but these rechargeable C cells
(nickel metal hydride? I am pretty sure they aren't lithium!) always
seem to have some sort of electro-welded rectangular plate connecting
the batteries which wont come off with a normal soldering gun? Or do
I just have to apply an inordinate amount of heat at exactly the
position where the ;nick' seems to be in the plate? Given the amount
of heat I seem to have applied to it already with no effect
whatsoever, to me it seems that this might damage the cell?
Is there some trick to doing this please or am i supposed to use a
dremel wheel to cut the plates off, leaving just the electro-weld to
which I solder the wire for the new cell?
Hi Amanda, You might want to look at this link, it details what to expect..

http://www.robotreviews.com/hack2/battery.shtml

Theres a good link to thread of advice on which cells to buy etc

Good luck, I'm about to try the same on my Roomba, JC

Hi JC

Yes, I had seen that and have two batteries to do: So my problem is
probably in getting enough good cells in one of them if I can figure
out how (as Mike would put it) to join up two separate tabbed cells
without having a spot welder

It is noteworthy that the on line 'experience based' instructions say
that you can solder where there was spot welding beforehand. (They
dont tell how to get the tabs off in the instructions which I saw,
which is why I posted here)

In general, you don't want to remove the tabs unless absolutely
necessary. Use them as "attachment points" to which you *can*
solder. Trying to make a connection to the battery (cell)
itself is an exercise in frustration and danger (batteries don't
like heat; soldering irons are hot -- do the math)

If you *must* remove the tabs, you can usually just wiggle
them back and forth repeatedly until metal fatigue causes
them to fail. You will end up with a small cluster of
"bumps" on the battery case as the "welds" usually stay behind
(i.e., you will find an equivalent number of *holes* in the
removed tab)

Amanda Ripanykhazov wrote:
On Feb 19, 4:18 pm, Archon wrote:
Amanda Ripanykhazov wrote:
I am hoping this question isnt too basic for this forum but I am
trying to replace some rechargeable batteries (in a Roomba: I
understand that generally only one or two start malfunctioning over
time and that it is usually the same one). It MUST be easier than I am
finding it.
I can just about solder on a connection but these rechargeable C cells
(nickel metal hydride? I am pretty sure they aren't lithium!) always
seem to have some sort of electro-welded rectangular plate connecting
the batteries which wont come off with a normal soldering gun? Or do
I just have to apply an inordinate amount of heat at exactly the
position where the ;nick' seems to be in the plate? Given the amount
of heat I seem to have applied to it already with no effect
whatsoever, to me it seems that this might damage the cell?
Is there some trick to doing this please or am i supposed to use a
dremel wheel to cut the plates off, leaving just the electro-weld to
which I solder the wire for the new cell?
Hi Amanda, You might want to look at this link, it details what to expect.

http://www.robotreviews.com/hack2/battery.shtml

Theres a good link to thread of advice on which cells to buy etc

Good luck, I'm about to try the same on my Roomba, JC

Hi JC

Yes, I had seen that and have two batteries to do: So my problem is
probably in getting enough good cells in one of them if I can figure
out how (as Mike would put it) to join up two separate tabbed cells
without having a spot welder

It is noteworthy that the on line 'experience based' instructions say
that you can solder where there was spot welding beforehand. (They
dont tell how to get the tabs off in the instructions which I saw,
which is why I posted here)

Amanda Ripanykhazova

Hi Amanda, I haven't checked out the construction of the Roomba battery
as yet but I'm guessing your problem is the original links between the
batteries is not an easily solderable metal, maybe stainless steel?. In
the link I gave you they are replacing all the batteries so soldering to
the original batteries was not a required. The metal case of the
batteries can usually be soldered to but its not recommended as others
have stated. You may need a special flux and a high wattage iron to make
decent connection to the original welded tags. JC

Amanda Ripanykhazov wrote:
On Feb 19, 4:18 pm, Archon wrote:
Amanda Ripanykhazov wrote:
I am hoping this question isnt too basic for this forum but I am
trying to replace some rechargeable batteries (in a Roomba: I
understand that generally only one or two start malfunctioning over
time and that it is usually the same one). It MUST be easier than I
am finding it.

I can just about solder on a connection but these rechargeable C
cells (nickel metal hydride? I am pretty sure they aren't lithium!)
always seem to have some sort of electro-welded rectangular plate
connecting the batteries which wont come off with a normal
soldering gun? Or do I just have to apply an inordinate amount of
heat at exactly the position where the ;nick' seems to be in the
plate? Given the amount of heat I seem to have applied to it
already with no effect whatsoever, to me it seems that this might
damage the cell?

Is there some trick to doing this please or am i supposed to use a
dremel wheel to cut the plates off, leaving just the electro-weld to
which I solder the wire for the new cell?

Hi Amanda, You might want to look at this link, it details what to
expect.

http://www.robotreviews.com/hack2/battery.shtml

Theres a good link to thread of advice on which cells to buy etc

Good luck, I'm about to try the same on my Roomba, JC

Hi JC

Yes, I had seen that and have two batteries to do: So my problem is
probably in getting enough good cells in one of them if I can figure
out how (as Mike would put it) to join up two separate tabbed cells
without having a spot welder

It is noteworthy that the on line 'experience based' instructions say
that you can solder where there was spot welding beforehand. (They
dont tell how to get the tabs off in the instructions which I saw,
which is why I posted here)

Amanda Ripanykhazova

Amanda, Lark Battery (www.larkbattery.com) should be able to sell you what
you need. Their contact info is
LARK BATTERY CENTER
8302 NW 39th Expressway
Bethany, OK. 73008
(405) 946-5275


Send them an email describing what you need and get a quote from them. They
will sell you individual cells with tabs so you can build the battery
yourself, or if you wish, they will construct the battery for you (at no
additional charge). I have done business with them before, and I can
attest to their quality.
You will have to describe the battery construction or send a picture so
they can construct it. From the web link posted above, it looks to be 12
sub-C cells in series, arranged in a 6x2 pack. There appears to be some
additional wiring attached to the pack, so you'll have to attach it to the
new pack.
Lark Battery are good folks. No affiliation; just a satisfied customer.

Cheers,
--
David
dgminala at mediacombb dot net

In article
,
Amanda Ripanykhazov wrote:
I am hoping this question isnt too basic for this forum but I am
trying to replace some rechargeable batteries (in a Roomba: I
understand that generally only one or two start malfunctioning over
time and that it is usually the same one). It MUST be easier than I am
finding it.

I can just about solder on a connection but these rechargeable C cells
(nickel metal hydride? I am pretty sure they aren't lithium!) always
seem to have some sort of electro-welded rectangular plate connecting
the batteries which wont come off with a normal soldering gun? Or do
I just have to apply an inordinate amount of heat at exactly the
position where the ;nick' seems to be in the plate? Given the amount
of heat I seem to have applied to it already with no effect
whatsoever, to me it seems that this might damage the cell?

The easiest - but more expensive way is to buy 'tagged' cells. These can
them be soldered without damage to the cell - a very real possibility if
you solder to them direct. But since they're less common on the retail
market the prices tend to be high. You might find somewhere local that can
weld tags to batteries for you. If you're lucky like me. ;-)

--
*Despite the cost of living, have you noticed how it remains so popular?*

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

Just to add, it's sometimes cheaper to buy a different make of battery
that may be on offer and rob it of its cells to fix another.

--
*Reality is a crutch for people who can't handle drugs.

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

Just to add, it's sometimes cheaper to buy a different make of
battery that may be on offer and rob it of its cells to fix another.

This is not generally a good idea. Replacing the bad cells in one battery
with new, good cells, is likely to cause cell reversal during operation. You
should generally replace all the cells.

It's also useful to have some way of measuring each cell's capacity while
discharging it, so you can roughly match the cells' capacities.

On 20/02/2010 12:17 PM, William Sommerwerck wrote:

Just to add, it's sometimes cheaper to buy a different make of
battery that may be on offer and rob it of its cells to fix another.

This is not generally a good idea. Replacing the bad cells in one battery
with new, good cells, is likely to cause cell reversal during operation. You
should generally replace all the cells.

I think that's what he means. Rob one (unusable brand) battery to
replace the cells of your (wanted brand) battery. As long as the cells
themselves are the same, it's all good.

It's also useful to have some way of measuring each cell's capacity while
discharging it, so you can roughly match the cells' capacities.

The cells are sometimes stamped, if not, you can get a clue from the
label of the battery case (the outside plastic case). They may not give
you too much information other than the brand and model, but they
usually do state the Ampere/hour capacity.

Just to add, it's sometimes cheaper to buy a different make of
battery that may be on offer and rob it of its cells to fix another.

This is not generally a good idea. Replacing the bad cells in one battery
with new, good cells, is likely to cause cell reversal during operation.
You
should generally replace all the cells.

I think that's what he means. Rob one (unusable brand) battery to
replace the cells of your (wanted brand) battery. As long as the cells
themselves are the same, it's all good.

Perhaps. But the principle stands -- replace all the cells.


It's also useful to have some way of measuring each cell's capacity
while discharging it, so you can roughly match the cells' capacities.

The cells are sometimes stamped, if not, you can get a clue from the
label of the battery case (the outside plastic case). They may not give
you too much information other than the brand and model, but they
usually do state the Ampere/hour capacity.

It's ampere-hour, not Ampere/hour. Big, big difference.

Cells with the same mAh rating from the same company nevertheless vary in
capacity. I've had to return new cells for replacement because they were way
out of spec.

"William Sommerwerck" wrote in
:

Just to add, it's sometimes cheaper to buy a different make of
battery that may be on offer and rob it of its cells to fix another.

This is not generally a good idea. Replacing the bad cells in one
battery with new, good cells, is likely to cause cell reversal during
operation.

You also have OLD cells with lots of charge cycles mixed with new cells,and
the old cells will fail sooner.

You should generally replace all the cells.

Agreed.

It's also useful to have some way of measuring each cell's capacity
while discharging it, so you can roughly match the cells' capacities.


agreed.

--
Jim Yanik
jyanik
at
localnet
dot com

On Feb 19, 7:42*pm, Jim Yanik wrote:
"William Sommerwerck" wrote :

Just to add, it's sometimes cheaper to buy a different make of
battery that may be on offer and rob it of its cells to fix another.

This is not generally a good idea. Replacing the bad cells in one
battery with new, good cells, is likely to cause cell reversal during
operation.

You also have OLD cells with lots of charge cycles mixed with new cells,and
the old cells will fail sooner.

You should generally replace all the cells.

Agreed.

It's also useful to have some way of measuring each cell's capacity
while discharging it, so you can roughly match the cells' capacities.

agreed.

--
Jim Yanik
jyanik
at
localnet
dot com

You can solder to the tabs or to the remains of the tabs where you
have pulled them off. Scratch the metal before you solder to get them
to take the solder. Use flux also. Replace all batteries, using NMH
rather than NiCad, as they have larger capacity. they are sub-C, I
have had to replace my wife's roomba batteries, so know first-hand

On 20/02/2010 2:16 PM, hr(bob) wrote:

... Replace all batteries, using NMH
rather than NiCad, as they have larger capacity...

This can't usually be done, because the end of charge algorithms on the
smart chargers won't won't be compatible with the different cell technology.
It's very possible a charger for NiCads can grossly overcharge NiMh.
You had better HOPE the circuitry has a timeout value, otherwise you'll
melt them down to a shapeless blob.
If nothing else, this will bring the life of your new NiMh's down.

Even float charging (which was routinely done in cheap equipment for
NiCads) is a bit iffy when you get to NiMH cells.

On 20/02/2010 12:42 PM, Jim Yanik wrote:

This is not generally a good idea. Replacing the bad cells in one
battery with new, good cells, is likely to cause cell reversal during
operation.

You also have OLD cells with lots of charge cycles mixed with new cells,and
the old cells will fail sooner.

Sure, but surplus battery packs would more then likely be very similar,
if not a little on the depreciated side.

In article ,
William Sommerwerck wrote:
Just to add, it's sometimes cheaper to buy a different make of
battery that may be on offer and rob it of its cells to fix another.

This is not generally a good idea. Replacing the bad cells in one
battery with new, good cells, is likely to cause cell reversal during
operation. You should generally replace all the cells.

Well, yes. I wasn't suggesting otherwise. The majority of cordless tools
use sub-C sizes of different types and capacities - and of course number
according to the voltage. If you can buy one on special offer it might be
able to supply a set of cells to replace those in the faulty unit at a
lower cost than buying individual tagged replacement cells. I've done just
this a few times. For example, with the move to LI cells some are selling
off their NiMH cells at discount. Same with NiCads.

It's also useful to have some way of measuring each cell's capacity while
discharging it, so you can roughly match the cells' capacities.

Usually on the battery case or tool spec if not the individual cells.

--
*The more I learn about women, the more I love my car

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

It's also useful to have some way of measuring each cell's capacity
while discharging it, so you can roughly match the cells' capacities.

Usually on the battery case or tool spec if not the individual cells.

Let me repeat this... The capacity printed on the cell is its nominal
capacity. It is NOT the capacity of that particular cell. Individual cells
can sometimes differ 20% or more from this value -- usually on the low side.

It's important to match the capacity of nicad and NiMH cells, because they
have a very abrupt cutoff. This means that one cell can drop way low, while
the other cells are at a voltage high enough to continue powering the
device. If you let the device run long enough after this point, the weak
cell will drop to zero volts, then reverse, possibly causing it to leak or
explode.

In article ,
William Sommerwerck wrote:
Usually on the battery case or tool spec if not the individual cells.

Let me repeat this... The capacity printed on the cell is its nominal
capacity. It is NOT the capacity of that particular cell. Individual
cells can sometimes differ 20% or more from this value -- usually on the
low side.

And you think makers of low end tools care about this?

It's important to match the capacity of nicad and NiMH cells, because
they have a very abrupt cutoff. This means that one cell can drop way
low, while the other cells are at a voltage high enough to continue
powering the device. If you let the device run long enough after this
point, the weak cell will drop to zero volts, then reverse, possibly
causing it to leak or explode.

Despite having used re-chargeable batteries from long before they became a
domestic item, I've never known one to explode. But then I've always
insisted on decent chargers.

--
*Why is the man who invests all your money called a broker?

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

On Feb 19, 10:54*am, Amanda Ripanykhazov
wrote:
I am hoping this question isnt too basic for this forum but I am
trying to replace some rechargeable batteries (in a Roomba: I
understand that generally only one or two start malfunctioning over
time and that it is usually the same one). It MUST be easier than I am
finding it.

Two cautions: if this is a battery of multiple cells in series, you
must
replace ALL cells at once. It is important that all the cells have
the same batch number and age if they are charged and discharged
in series.

Second caution, the contents of these (NiCd or NiMH) is a caustic
liquid, buy tabbed cells rather than trying to get the case up to
soldering
temperature. The tab ends can take solder temperature or spotwelding
without hazard.

No real tricks, just a few techniques that can make battery pack
building/rebuilding easier.

Don't reuse old cells or the old welded connecting strips for new battery
packs. If the old cells have leaked, the pack connector copper leads may
also be damaged if the leakage has reached the ends of the stranded copper
leads. The liquid that's leaked out of the cells can wick up into the
stranded copper leads.
Replace the pack leads with the same gage wire (or larger) if any damage is
visible.

Choose new cells of the correct physical size and reasonable capacity,
fresh, flat top cells with soldering tabs already attached. Solder the tabs
to connect the cells together, not wires or other material directly to the
cells. Some dealers will add tabs to cells for free.

Cells with tabs used to be made with the 2 tabs oriented 180 degrees apart
(looking down at the top of the cell, one tab points left, the other tab
points right).
The cells I purchased recently from 3 different sources have the tabs both
pointing in the same direction.
Lay the cells out side-by-side in a line with alternating + & - tabs
adjacent to each other, and all the tabs pointed upward.
To get the tabs to meet and overlap, make a 45 degree bend close to the
welds, which changes the direction of the tab to 90 degrees.
By making the 45* bend close to the weld, the tabs won't stick out past the
sides of the cells.

Clean the tabs and tin them with solder using flux.. as they overlap, tin
the top of one tab, and the bottom of the other. With the cells neatly hot
glue tacked together, apply an additional small amount of solder to the area
where the tinned tabs overlap, and press the tabs together with a tool until
the solder cools.
I place a small square of fiberglass tape under the joined tabs as extra
insurance so the + tabs can't short circuit to the cell case (even though
there is an insulating washer under the plastic skin).

If the original battery pack utilized a thermal protection device, one
should definiely be installed in the new pack. Many times a thermal switch
is marked with the temperature rating. Temperature rise during charging can
be detrimental to the useful life of the battery pack, and also to the
capacity of the cells.
Thermal protection switches with leads can be soldered to tabs of the cells.
The polyswitch types of devices should be spot welded directly to the cells.
Any other components (diodes, precision resistors) that were part of the
original battery pack should be checked for normal values.

Connector leads can be soldered to the appropriate tabs, and shrink tubing
over the soldered connection and the end of the lead will offer some
support/strain relief for the leads.

There are dealers that also sell the shrink wrap to cover the cells, for
making a neat and secure battery pack.

A few simple guidelines will prevent most problems.
Don't solder directly to cell terminals.
Don't allow cells to get hot while charging.
Don't overcharge battery packs. One of the best ways to prevent overcharging
is to use a manually reset timer to limit the amout of time for charging.
Don't over-discharge battery packs. When the device/tool starts to run
slower, stop using it and recharge the battery pack.

Many rechargeable consumer devices are supplied with very poor quality
chargers (just a transformer and a diode was the cheapest method).
If you can't get a reasonable service life from the battery packs, you might
consider choosing another method of charging the battery, whether that means
removing it to connect it to a better quality charger, or modifying the
device with an external connector for safely connecting a better quality
charger.

In some cases, it's just better to have more than one battery pack, that can
be easily swapped by means of an external connector.

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


"Amanda Ripanykhazov" wrote in message
...
I am hoping this question isnt too basic for this forum but I am
trying to replace some rechargeable batteries (in a Roomba: I
understand that generally only one or two start malfunctioning over
time and that it is usually the same one). It MUST be easier than I am
finding it.

I can just about solder on a connection but these rechargeable C cells
(nickel metal hydride? I am pretty sure they aren't lithium!) always
seem to have some sort of electro-welded rectangular plate connecting
the batteries which wont come off with a normal soldering gun? Or do
I just have to apply an inordinate amount of heat at exactly the
position where the ;nick' seems to be in the plate? Given the amount
of heat I seem to have applied to it already with no effect
whatsoever, to me it seems that this might damage the cell?

Is there some trick to doing this please or am i supposed to use a
dremel wheel to cut the plates off, leaving just the electro-weld to
which I solder the wire for the new cell?

"Wild_Bill" wrote in
:

Don't overcharge battery packs. One of the best ways to prevent
overcharging is to use a manually reset timer to limit the amout of
time for charging. Don't over-discharge battery packs. When the
device/tool starts to run slower, stop using it and recharge the
battery pack.

Many rechargeable consumer devices are supplied with very poor quality
chargers (just a transformer and a diode was the cheapest method).
If you can't get a reasonable service life from the battery packs, you
might consider choosing another method of charging the battery,
whether that means removing it to connect it to a better quality
charger, or modifying the device with an external connector for safely
connecting a better quality charger.

My wife & I each have coldless drills, which we use intermitently for
household repairs & projects. The only way to make sure we have a
charged battery handy for emergencies is to leave one in the chargers.
Even though these are reasonably high quality chargers (Ryobi & DeWalt),
I'm sure we are shortening the life of the batteries.

It occured to me that one option might be to put the chargers on a timer,
so that they are on for half an hour a day. That should top them off,
without cooking them. The catch is that I'm not sure what sort of load
the charger presents when it is off. I could just end up discharging the
battery through (at a minimum) diode leakage. As long as the leakage is
low, that might actually be OK, ot it could produce a nasty memory effect
in the NiCd's.

Any thoughts or comments?

Thanks!

Doug White

My wife & I each have coldless drills, which we use intermitently
for household repairs & projects. The only way to make sure we
have a charged battery handy for emergencies is to leave one in
the chargers. Even though these are reasonably high quality
chargers (Ryobi & DeWalt), I'm sure we are shortening the life of
the batteries.

You probably are. I would not charge the batteries until they began to run
down, then recharge no more than four hours (or whatever the manual
recommends as the maxium charging time).

I own an inexpensive 12V Ryobi drill, which gets similar intermittent use.
The charger /does not/ shut off automatically. Indeed, there is nothing to
indicate that the charge is complete! I am very careful about when and how
long I charge it.

The battery does not quickly self-discharge. I've never had a time it wasn't
ready. So, after each use, I'll recharge it for 15 minutes or so.

A 12V battery pack has eight nicad cells. It's important not to repeatedly
run down the battery, as you're increasing the chance of reversing the
lowest-capacity cell in the pack.


It occured to me that one option might be to put the chargers on a timer,
so that they are on for half an hour a day. That should top them off,
without cooking them.

A half hour a week -- or even a month -- would probably be enough.


The catch is that I'm not sure what sort of load the charger presents
when it is off. I could just end up discharging the battery through (at a
minimum) diode leakage.

That would be several hundred K.

"William Sommerwerck" wrote in
:


A 12V battery pack has eight nicad cells. It's important not to
repeatedly run down the battery, as you're increasing the chance of
reversing the lowest-capacity cell in the pack.

my 9.6V Makita stick has EIGHT cells,wouldn't a 12V pack have TEN cells?
1.2V per cell.


--
Jim Yanik
jyanik
at
localnet
dot com

Amanda Ripanykhazov wrote:
I am hoping this question isnt too basic for this forum but I am
trying to replace some rechargeable batteries (in a Roomba: I
understand that generally only one or two start malfunctioning over
time and that it is usually the same one). It MUST be easier than I am
finding it.

I can just about solder on a connection but these rechargeable C cells
(nickel metal hydride? I am pretty sure they aren't lithium!) always
seem to have some sort of electro-welded rectangular plate connecting
the batteries which wont come off with a normal soldering gun? Or do
I just have to apply an inordinate amount of heat at exactly the
position where the ;nick' seems to be in the plate? Given the amount
of heat I seem to have applied to it already with no effect
whatsoever, to me it seems that this might damage the cell?

Is there some trick to doing this please or am i supposed to use a
dremel wheel to cut the plates off, leaving just the electro-weld to
which I solder the wire for the new cell?



The thing to take away from this thread is that EVERYBODY knows exactly
what to do, they just don't agree...violently!!
Be VERY CAREFUL acting on ANY information from this thread.

You MIGHT get more reliable info from
sci.chem.electrochem.battery

There's a reason that the label says, "don't open this battery pack."
This thread is why...

The thing to take away from this thread is that EVERYBODY
knows exactly what to do, they just don't agree... violently!!
Be VERY CAREFUL acting on ANY information from this thread.

Whether or not the consensus view on this issue is correct, replacing
rechargeable batteries with non-OEM devices is NOT something someone with
little understanding of rechargeable batteries should do. I would simply buy
the iRobot batteries and forget about it.

The basic problem is that manufacturers often charge too much for
replacement batteries. If the battery pack is used in current models (no pun
intended), it shouldn't be expensive.

In article ,
William Sommerwerck wrote:
The thing to take away from this thread is that EVERYBODY
knows exactly what to do, they just don't agree... violently!!
Be VERY CAREFUL acting on ANY information from this thread.

Whether or not the consensus view on this issue is correct, replacing
rechargeable batteries with non-OEM devices is NOT something someone
with little understanding of rechargeable batteries should do. I would
simply buy the iRobot batteries and forget about it.

Assuming someone has reasonable DIY skills and sticks to tagged
replacement cells of the same type as the originals there's little to
worry about. It's certainly not any more hazardous than many common tasks
people take on.

--
*Marriage changes passion - suddenly you're in bed with a relative*

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

Assuming someone has reasonable DIY skills and sticks
to tagged replacement cells of the same type as the originals
there's little to worry about. It's certainly not any more hazardous
than many common tasks people take on.

I would still be cautious. For one thing, you want to be sure the
replacement cells have at least the same capacity as the originals. Higher
is probably okay, lower is almost certainly not.

If a battery dealer can make up a pack for you, it might be a good idea to
take the old pack in and have them do it. However...

My experience with non-OEM Li-ion cells has been that, even when they come
from a recognized manufacturer, they quickly deteriorate. They're a complete
waste of money. Nicads and NiMH cells aren't so critical, but there is the
possibility that the charger for the product might have been designed for a
particular battery from a particular company, and might not work correctly
with other batteries.

Just to dump on Mr. Allison again... I've replaced the nicads in several
Polaroid #365 electronic flashes with MAHA 2200mAH tabbed NiMH cells. The
original cells were designed for rapid charge, and the charger is supposed
to fully recharge them in one hour. The charger works fine with the NiMH
cells, and shuts off properly (even though it's probably not at would be
full charge for those cells).

"William Sommerwerck" wrote in
:

The thing to take away from this thread is that EVERYBODY
knows exactly what to do, they just don't agree... violently!!
Be VERY CAREFUL acting on ANY information from this thread.

Whether or not the consensus view on this issue is correct, replacing
rechargeable batteries with non-OEM devices is NOT something someone
with little understanding of rechargeable batteries should do. I would
simply buy the iRobot batteries and forget about it.

The basic problem is that manufacturers often charge too much for
replacement batteries. If the battery pack is used in current models
(no pun intended), it shouldn't be expensive.

Manufacturers don't want to sell replacement parts.
Also,replacement parts are handled differently than manufacturing
stock,they get inventoried and taxed,and those costs get added to the part
price.



a realistic alternative is to go to a rebuilder and have them make you a
new pack from new cells.(of the same type/chemistry as OEM.)

--
Jim Yanik
jyanik
at
localnet
dot com

The basic problem is that manufacturers often charge too much for
replacement batteries. If the battery pack is used in current models
(no pun intended), it shouldn't be expensive.

Manufacturers don't want to sell replacement parts.

True, but they are legally obliged to. Unfortunately, there doesn't seem to
be much enforcement of the laws.


Also, replacement parts are handled differently than manufacturing
stock, they get inventoried and taxed, and those costs get added to
the part price.

True, but... That doesn't change the fact some companies -- such as
Thomson -- GOUGE. Please tell me how two AAA NiMH cells with a little cable
and socket can sell for almost $25. And this is a current-production
battery.

"William Sommerwerck" wrote in
:

The basic problem is that manufacturers often charge too much for
replacement batteries. If the battery pack is used in current models
(no pun intended), it shouldn't be expensive.

Manufacturers don't want to sell replacement parts.

True, but they are legally obliged to. Unfortunately, there doesn't
seem to be much enforcement of the laws.


Also, replacement parts are handled differently than manufacturing
stock, they get inventoried and taxed, and those costs get added to
the part price.

True, but... That doesn't change the fact some companies -- such as
Thomson -- GOUGE. Please tell me how two AAA NiMH cells with a little
cable and socket can sell for almost $25. And this is a
current-production battery.




A company(Fortune 500 at the time) I used to work for would raise
their parts prices as the product that the parts went into got closer to
the end of support period.
I was told this was to "encourage" customers to buy a newer instrument,by
raising the cost of repairs.

It didn't matter that the parts were "in current production".

--
Jim Yanik
jyanik
at
localnet
dot com

In article ,
mike wrote:
The thing to take away from this thread is that EVERYBODY knows exactly
what to do, they just don't agree...violently!!
Be VERY CAREFUL acting on ANY information from this thread.

You MIGHT get more reliable info from
sci.chem.electrochem.battery

There's a reason that the label says, "don't open this battery pack."
This thread is why...

I'd also stay indoors if I were you...

--
*You never really learn to swear until you learn to drive *

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