Author Topic: Replacing NiCad cells in cordless drill pac  (Read 5695 times)

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Offline tomw

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Re: Replacing NiCad cells in cordless drill pac
« Reply #15 on: August 18, 2012, 01:20:38 PM »
Norm;

Got the drill pack yesterday. Could not connect to anotherpower to post that but finally came back just a bit ago.

No chance to endurance test but work nice and torquey out of the bubble wrap!

Thanks.

Tom

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Offline Norm

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Re: Replacing NiCad cells in cordless drill pac
« Reply #16 on: August 18, 2012, 01:45:00 PM »
Was hoping you got it.....
so far so good hmmm?

anxious to hear about further test....(if they are good that is ) :)
Norm.

Offline Norm

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Re: Replacing NiCad cells in cordless drill pac
« Reply #17 on: August 19, 2012, 08:19:41 AM »
Norm;

How do you think that new pack will react to the factory charger?

I guess the best thing to do is try it.

Can't wait to try it out and if it works I haver 2 or 3 more that are either flat out dead or so weak they are useless. Maybe I can find a way to allow more cells once I see how you did them. I have some PVC, Kydex and HDPE plastic I could maybe make an extender from that will stand up to the task.

  Rather invest in a more modern 18 volt setup with high tech batteries that are light and last long.

Thanks for the heads up.

Tom

 (How do you think that new pack will react to the factory charger? )
That's one of the things that I'm wondering....I hooked the sensor up
in the same location. Wondering if they have replacement sensors?
like on flea-bay....I imagine that it is a thermistor that shuts the charger
off or onto trickle charge when it get too hot but it also has to know if
the voltage is too high or too low.... ?
                           *********
 (I have some PVC, Kydex and HDPE plastic I could maybe make an extender from that will stand up to the task.)
Ed (windstuffnow) mentioned one time that he used a combination consisting of
stuff that you could use to make a rubber like mold of the part you wanted to
make a duplicate of then poured in the liquid plastic to cast the part....

I'm working on making my own clones of the pacs that my 14.4 Craftsman drill
uses....I have ideas how it could be done for your Milwaukee too.
We could have unlimited packs for our use !
I'll post pictures in the near future......


Offline MadScientist267

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Re: Replacing NiCad cells in cordless drill pac
« Reply #18 on: August 19, 2012, 08:45:50 AM »
Probably wont be much of an issue depending on how the charger terminates the charge. If it does it  solely by sensing NDV, there shouldn't be any issue. The only thing higher or lower capacity cells would cause is a change in charge time.

If it does it by timer, or a combination of timer/NDV and the cells are higher capacity than the originals, the pack might not reach full charge in a single pass.

The sensor should only be a thermistor, to terminate the charge either based solely on temperature (unlikely) or as a safety mechanism to terminate if things get too toasty.

Should be perfectly fine in most cases, provided the thermistor is roughly where it was originally, and any intermediate sense lines (if present at all) are connected between the cells identical to the original as well.

Steve
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Offline Norm

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Re: Replacing NiCad cells in cordless drill pac
« Reply #19 on: August 20, 2012, 09:44:37 AM »
On my 'smart charger' I fooled it by putting in
a thermistor from one of the battery packs that
Bruce sent me and it worked to some extent
the charger went to red light (fast charge) as i
remember it and I recall never quit,so I just shut it off Guess I could
put in a on off switch to connect the  thermistor
and shut it off when things got too warm could also
put in a timer and set it to a certain safe length of
time....

What I really need is an original sensor unfortunately
I threw the old ones away.....Hmmm
thanks for the input  Steve.
Norm.

Offline MadScientist267

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Re: Replacing NiCad cells in cordless drill pac
« Reply #20 on: August 20, 2012, 11:27:43 AM »
Eeek... Yeah that could put you in a bind.

It would be one thing if this was all slow charge from the git go. The current would taper off and if everything was limited ok, there wouldn't be any chance of runaway, etc.

With fast charging however, runaway is a very real threat. Be careful with this, as it can have some pretty nasty consequences under the right circumstances. It appears that your cell insulation is cardboard of some kind, so the typical retail heat shrink splitting thing doesn't threaten inter-cell shorting. But damage to the cells and probably more notable, the case for the battery (deformation) can occur, the latter potentially rendering the pack useless.

A timer isn't necessarily a bad idea, and is better than nothing. It can still leave you with cells hotter than you really want if, for example, the pack is for whatever reason not fully discharged.

In my experience, manual cutoff as a sole charge termination method is a really bad idea. I have always ultimately ended up destroying the pack due to runaway, because lets face it, babysitting a pack waiting for it to hit temperature is like watching grass grow. Eventually boredom will turn into doing something else with the idea of "check on that in a few minutes". Invariably (with me at least), "Oh crap!" will come to your mind (if not your mouth), and you will return to the charging location only to find chernobyl has shown up for round 2. Sans nuclear hazards.

You are right, best bet is an original sensor, or at least knowing the spec of said sensor. They are not all created equal, but you know that already.

You'll find a solution, I'm sure.

Steve
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Offline Norm

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Re: Replacing NiCad cells in cordless drill pac
« Reply #21 on: August 20, 2012, 02:28:44 PM »
Now don't panic, I was just thinking out loud.....actually I have been
satisfied with not having it run on fast charge....I just hook it up to one of the 14.4
batteries and when plugged in the green light goes on (slow trickle charge)
and takes about 12 hrs. or so to reach about 15 volts from there .

Oh for another thing I sometimes charge them with my pedgen no danger of
overcharge there I'd fall asleep and stop pedaling long before the cells got even
body tempature.
Norm.

Offline MadScientist267

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Re: Replacing NiCad cells in cordless drill pac
« Reply #22 on: August 20, 2012, 10:33:53 PM »
LOL I hear ya, just wanted to throw that out there just to be on the safe side. Fried too many myself to not warn someone else about it...  :o :-\

Slow charge is better anyway, the cells will accept the charge better, and your 2x4 might be all the more religious for it. ;)

Pedgen? Haha, you mean like manual human labor, to charge batteries? Why on earth would anyone do that?  ;D

Eh, who am I kidding. It would certainly do ME some good to make one, get on it, and make some juice with it. It's just that I'm a touch short on space at the moment... Hmmm, maybe next to the panel on the roof?

I get'll back to you on that... Hahaha

Steve
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Offline frackers

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Re: Replacing NiCad cells in cordless drill pac
« Reply #23 on: August 21, 2012, 12:02:50 AM »
Many years ago I got a matched set from a guy that had all the gear to make packs from boxes of 1000 Sanyo cells. Each cell would be charged and discharged at the C rate 5 times and the voltage tracked. The software he used would then match up cells so they were as close as possible. His top packs were used by the model car guys and a nominal 7.2 volt sub C cell pack and produced over 9.5 volts and could run 50 amps without a cell going reversed. He expected to get 2 packs like that per 1000 cells and so they were priced appropriately :) They were prized because the particular class of racing required that only a 6 pack of sub-C NiCd cells could be used.

I bought an average pack, 7.4 volts but good for 40 amps (i.e. 30C) and his tip for charging was to flatten the pack with a couple of car headlight bulbs to get down to a couple of volts and then change at 5C until there was a 10C temperature rise in the pack - job done!! Note that you can only do this with matched cells.

His rigs could cycle 80 cells simultaneously and as you can imagine the spare bedroom it was set up was pretty warm.

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Offline Norm

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Re: Replacing NiCad cells in cordless drill pac
« Reply #24 on: August 21, 2012, 09:27:41 AM »
So right now I got a 14.4v pack consisting of 12 - 1.3 amp/hr NiCads
checking 2 in series at a time I was getting like .2 from each set of two
if I was lucky ....so I zap each set of 2 with a wall wart output 12 volts 800Ma.
then each set read close to 2 volts (nominal voltage 2.4) total voltage then was
11.92 target voltage will be 16.
Charging with this wall wart I figured about 3 watts. Not fast enough?
So then started charging with my 3 VW panels that are in series and
figured it is charging about 7 watts in the morning sun that is about 45 degrees
above the horizon (crude calculation) you experts please don't laugh I get by.....
with a little/lot of help from my friends....(you guys!)
took it off charge and now reads 16.45, each two cells in a series reads 2.74-2.76
I try to have it read 16.2 after disconnected with each set not varying more than
.02 from each other (equalized?) then I hook it to the drill and drill 16- 5/8 inch
holes in the side of a 2x4 bearing down on the drill and as fast as I can maybe
about 5 or 6 seconds per hole if it passes this test I figure they will last awhile?

Norm.

Offline MadScientist267

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Re: Replacing NiCad cells in cordless drill pac
« Reply #25 on: August 21, 2012, 10:54:49 AM »
From what I can gather the rate isn't so bad, but you might not be hitting full depending on just how fast you're putting the juice in.

A typical figure used with NiCd is 125% of nominal while charging, but the panel may struggle a little toward the end there. this figure however is dependent somewhat on the charge rate.

A 12V nominal panel ironically enough is pretty close to its peak power output near end of charge with a 14.4 nominal battery provided there is full sun. As long as its got the gonads to be able to push enough to hit that 125%, you should be able to reach full charge.

One of the more peculiar (and useful) aspects of NiCd (and NiMH to a lesser extent) is the phenomena of Negative Delta Voltage, or NDV. Put simply, it refers to the fact that when a cell is full, the voltage starts going down instead of continuing to rise like most other chemistries. This is only by a small amount, and is typically associated with a rise in temperature of the cell. The good smart chargers utilize both of these conditions to determine when to terminate charge.

At high rates without intervention, this results in thermal runaway. At low rates, the current doesn't rise enough to worry about it. Regardless of rate though, NDV is present, and on a 14.4 nominal pack, can be in the handful of tenths of a volt range. Higher rates (more accurately, higher cell temperatures) will result in a bit more, possibly as much as a whole volt. Smart chargers usually "discover" it in the early stages, and will either terminate at a preset drop, or start a timer that lets any weaker cells play catch up.

Hopefully this helps; the idea in giving you this info is so that rather than thinking inside or outside the box, you can think like the box. ;)

On the zapping, it works, with one caveat (that can ruin your day in an enclosed pack) - Zapping only gets rid of a portion of the dendrite(s) that are shorting the cell. Ultimately this means that while you've opened up the cell so it can charge, the "seed" is still there, and can creep up on you when the cell is near depletion. When you have a string of cells, it can be nearly impossible to "single out" the offending cell and clear the dendrite again. The more cells in the string, the harder it gets.

Frackers - As far as insane charge rates, not me. It shortens the lifespan of the cell, doesn't fully absorb the charge (up to 50% less absorption), and if not monitored VERY closely can result in not only failure of a cell, but potentially catastrophic failure. I don't recommend it.

Steve

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Offline Norm

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Re: Replacing NiCad cells in cordless drill pac
« Reply #26 on: August 22, 2012, 09:40:09 PM »
 Thanks for all the info Steve , sure glad I don't have to do this
for a living.....does make for a nice hobby tho'  :)

been doing too much thinking today time for a Tylenol    :)
Norm.

Offline WooferHound

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Re: Replacing NiCad cells in cordless drill pac
« Reply #27 on: August 23, 2012, 10:08:39 AM »
sure glad I don't have to do this
for a living.....does make for a nice hobby tho'  :)

You could be the only cordless drill battery rebuilder in the world. I think you could make a few dollars at it.
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Offline Norm

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Re: Replacing NiCad cells in cordless drill pac
« Reply #28 on: August 23, 2012, 09:11:45 PM »
No doubt about it I could make a few dollars right now I'm
just feeling my way around.....very cautious I want to make
sure any batteries I send are completely satisfactory....
Maybe you'd like to try a set Wooferhound ?
 Anyway on with some details....
for an 18 volt cordless they pay only about $6 for postage & handling
and they get 3 stacks (5 in a stack) and some ribbon linkage.
continuing from reply #4 and glancing briefly at #7 to see how
I arranged them at first but now do it this way basically .....
They are lettered A1& A2, B1&B2,C1&C2, etc.
 cutting the tabs between the pairs only
then next step taking one pair at a time cut the connecting
ila_rendered
ribbon with scissors and fold over and it looks like this
ila_rendered
after they are spliced back together.
after all 7 pairs are spliced back together they are turned
upside down and the first pair with the negative end in the
center and + toward the bottom, now next pair with a slight
gap (so you can see that it's the next pair) and the negative
close to the + of the first pair, same way with the next pair.
ila_rendered
when they are arranged just right they are bundled with a 
cable tie,
now the pairs are tabbed and soldered together.....plus to negative, plus to negative
etc.
ila_rendered
the bottom cell (negative) is the first of the second bundle,
on the second bundle  the top middle will be the positive
terminal.....
this is how the cells on this one particular brand of 18 volt is
arranged and of course others may differ.
Hope this is clear to every one....
Norm.

Offline Norm

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Re: Replacing NiCad cells in cordless drill pac
« Reply #29 on: August 23, 2012, 09:18:15 PM »
Whoop....that last pair in the last picture should have been turned around
so the bottom cell would be with the positive end.....