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)