Sears tools

"Ernest Christley" wrote

I baby my batteries with the tenderest of loving care. I made two battery
packs last 10 years, using it for nearly everything, and the batteries
were still good enough to pass on to a brother-in-law.

The new set was shot in six months. From Ron's experience, it may be that
DeWalt has de-emphasized their 9V line.

Could be; I know they want your to buy the 16 volt ones, and now, the 24
volt ones.

It could be that they are pushing a 9 volt pack too hard during charging.
The same charger is used for 9.6 to 18 volt, I know for a fact. Perhaps
that is too many volts to feed into the 9.6 batteries.
--
Jim in NC

"Ernest Christley" wrote

Dang-it! I bet you're right.

I noticed the batteries coming out of the new charger a lot warmer than
the came out of the old one. I bet I would still have decent batteries if
I had kept the old charger.

Perhaps you could stick a voltage regulator chip into the charger, or
experiment to find a resistor that would drop the voltage to a reasonable
level.
--
Jim in NC

"Morgans" wrote in message
...

"Ernest Christley" wrote

Dang-it! I bet you're right.

I noticed the batteries coming out of the new charger a lot warmer than
the came out of the old one. I bet I would still have decent batteries
if I had kept the old charger.

Perhaps you could stick a voltage regulator chip into the charger, or
experiment to find a resistor that would drop the voltage to a reasonable
level.
--
Jim in NC

The voltage regulator is the only correct solution, although I don't recall
the proper shut-off voltage. Ideally, the charger should provide a fairly
quick charging current and then shut off, or else drop to a couple of
milliamps when the fully charged voltage is reached.

IIRC, if the batteries are to last, the correct voltage varies with
temperature and should be controlled within about 0.1 volt. I don't recall
the correct voltage for a full charge, but 9.6 volts sounds like a stack of
8 nicad cells; so the figure of 11.6 volts sounds possible for some fairly
normal temperatures. However, that is a distant and somewhat foggy
memory--so it is only usefull as a starting point to search for the correct
numbers.

I hope this helps.

Peter

Um...last time I checked, Nicad batteries were charged with a constant
current source, not a constant voltage soure. You can use a regulator
IC with a properly connected resistor to make a constant current source.

Scott


Peter Dohm wrote:
"Morgans" wrote in message
...

"Ernest Christley" wrote


Dang-it! I bet you're right.

I noticed the batteries coming out of the new charger a lot warmer than
the came out of the old one. I bet I would still have decent batteries
if I had kept the old charger.

Perhaps you could stick a voltage regulator chip into the charger, or
experiment to find a resistor that would drop the voltage to a reasonable
level.
--
Jim in NC


The voltage regulator is the only correct solution, although I don't recall
the proper shut-off voltage. Ideally, the charger should provide a fairly
quick charging current and then shut off, or else drop to a couple of
milliamps when the fully charged voltage is reached.

IIRC, if the batteries are to last, the correct voltage varies with
temperature and should be controlled within about 0.1 volt. I don't recall
the correct voltage for a full charge, but 9.6 volts sounds like a stack of
8 nicad cells; so the figure of 11.6 volts sounds possible for some fairly
normal temperatures. However, that is a distant and somewhat foggy
memory--so it is only usefull as a starting point to search for the correct
numbers.

I hope this helps.

Peter




--
Scott
http://corbenflyer.tripod.com/
Gotta Fly or Gonna Die
Building RV-4 (Super Slow Build Version)

Scott wrote:
Um...last time I checked, Nicad batteries were charged with a constant
current source, not a constant voltage soure. You can use a regulator
IC with a properly connected resistor to make a constant current source.

Most of the current issue batteries (certianly the XRP Dewalts) are
NOT NiCad. Mine are LiIon.

Only the dumbest-ass slow nicad chargers were simple constant current
chargers. The rapid chargers all used the pack temperature to regulate
how much current they put in them.

Scott wrote:
Um...last time I checked, Nicad batteries were charged with a constant
current source, not a constant voltage soure. You can use a regulator
IC with a properly connected resistor to make a constant current source.

Most of the current issue batteries (certianly the XRP Dewalts) are
NOT NiCad. Mine are LiIon.

Only the dumbest-ass slow nicad chargers were simple constant current
chargers. The rapid chargers all used the pack temperature to regulate
how much current they put in them.

After I wrote that, which is obviously the wrong sequence, I did a quick
search and found that a constant current plus voltage/temperature sensing
was preferred. My recollection of the fully charged voltage was also much
too high!

Peter


"Scott" wrote in message
.. .
Um...last time I checked, Nicad batteries were charged with a constant
current source, not a constant voltage soure. You can use a regulator IC
with a properly connected resistor to make a constant current source.

Scott


Peter Dohm wrote:
"Morgans" wrote in message
...

"Ernest Christley" wrote


Dang-it! I bet you're right.

I noticed the batteries coming out of the new charger a lot warmer than
the came out of the old one. I bet I would still have decent batteries
if I had kept the old charger.

Perhaps you could stick a voltage regulator chip into the charger, or
experiment to find a resistor that would drop the voltage to a reasonable
level.
--
Jim in NC


The voltage regulator is the only correct solution, although I don't
recall the proper shut-off voltage. Ideally, the charger should provide
a fairly quick charging current and then shut off, or else drop to a
couple of milliamps when the fully charged voltage is reached.

IIRC, if the batteries are to last, the correct voltage varies with
temperature and should be controlled within about 0.1 volt. I don't
recall the correct voltage for a full charge, but 9.6 volts sounds like a
stack of 8 nicad cells; so the figure of 11.6 volts sounds possible for
some fairly normal temperatures. However, that is a distant and somewhat
foggy memory--so it is only usefull as a starting point to search for the
correct numbers.

I hope this helps.

Peter




--
Scott
http://corbenflyer.tripod.com/
Gotta Fly or Gonna Die
Building RV-4 (Super Slow Build Version)

"Ron Natalie" wrote in message
...
Scott wrote:
Um...last time I checked, Nicad batteries were charged with a constant
current source, not a constant voltage soure. You can use a regulator IC
with a properly connected resistor to make a constant current source.

Most of the current issue batteries (certianly the XRP Dewalts) are
NOT NiCad. Mine are LiIon.

Only the dumbest-ass slow nicad chargers were simple constant current
chargers. The rapid chargers all used the pack temperature to regulate
how much current they put in them.

That's actually a couple of good points, and there should be some
information on the battery packs stating what they are.

A google search leads to a lot of information about each of the battery
types, along with the obvious conclusion that there are a lot of
questionable chargers out there for each of the types.

By the way, my old AEG screwdriver (also sold as Milwaukee) uses a 2 cell
NiCad battery pack--which explains why time alone will destroy the batteries
even though the charger appears to be pretty good.

Anyway, thanks for a good reminder to REALLY examine the tool, the battery
and charger, and the litterature when buying tools in the future.

Peter

"Ron Natalie" wrote

Most of the current issue batteries (certianly the XRP Dewalts) are
NOT NiCad. Mine are LiIon.

Only the dumbest-ass slow nicad chargers were simple constant current
chargers. The rapid chargers all used the pack temperature to regulate
how much current they put in them.

I think most of the newer non LiIon Dewalt batteries are nickel metal
hydride. Only a couple years ago, they were still NiCads.

Dewalt chargers for non LiIon batteries do not sense temperature. They have
only a positive and negative lead, and there is nothing in the charger to
sense temperature externally, as if that would do much good, anyway.

They do use peak detecting charge technology, though.
--
Jim in NC

On Sat, 17 Nov 2007 19:33:26 -0500, "Morgans"
wrote:


"Ron Natalie" wrote

That's a shame. Nearly all of my tools now are from the 18V
Dewalt line to include:
I've had no problem with the XRP batteries.

One big difference in how long they last, is how you treat your batteries.

One of the biggest battery killers is running them until they won't hardly
turn the tool motor without any load on it. You should stop using the
battery, and get a fresh one immediately after the RPM starts to drop
noticeably.

If you run your battery real hard, let it cool for at least 30 minutes, and
an hour or two is better, before you charge it. After it is fully charged,
it should be allowed to cool down a bit before you use it again.

All this requires is enough batteries to do your job with some resting time
between cycles. An extra couple batteries go a long way towards making all
of them last much longer.

Also, some of the Dewalt chargers come with a button on them, that you push
to run them through several cycles of discharge and recharge, to condition
them. I think that helps them out a bit, but it should not be over used.
All batteries, and it does not matter which brand, have a limited number of
cycles in them, before they start to go bad.

Another thing I do, is to take the pack apart when it goes bad, and right
after charging, read each individual cell's voltage. It will be very
apparent that a few are totally zapped. If you have at least two bad packs,
you can remove the bad cells from one, borrow cells from the other, and have
a good battery pack, for a while, at least.

There is a battery shop in my area that you can take the packs too and
they will replace the cells for you. I believe it was $75 the last
time I priced having the cells replaced for an 18V battery pack and
that was for the higher Miliamp batteries. The owner said that he
gets a lot of contractors in to have the cells replaced with the
higher miliamp cells and they constantly brag about how much better
they are than the new ones off the shelf.