Third: Duo series batteries (10 cells in series, same specs. as PB500
"pack") _so far_ have needed at least 7 to 9 volts (I don't quite
remember). Their internal circuitry is much simpler and doesn't require
the memory correction of the PB500 batteries. Both the Duo and the 500
packs have a "circuit breaker" and fuse to protect the pack in case of a
short circuit. This is important for the following case:
The nickel cadmium (NiCad) and nickel metal hydride (NiMH) batteries use
a chemical composition which produce(s) waste product(s) under certain
conditions. I don't know how, but over time it/they build up unless the
battery voltage is brought down to a certain level. This buildup of
waste product(s) has been evident in all of the old batteries I have
worked with so far. It shows up as a battery with only a few minutes of
life. Sometimes this can be overcome using DeepDischarge or
BatteryAmnesia for 5 to 10 times (this is also a good idea of new NiCad
and NiMH batteries). The battery will then hold about 1 to 2 hours of
continuous usage at maximum output (harddrive running, full screen
brightness, etc.).
_IMPORTANT_ THE FOLLOWING IS NEVER TO BE DONE WITH A FULLY _CHARGED_
BATTERY, ONLY WITH A BATTERY THAT HAS BEEN FULLY _DISCHARGED_ IN THE
POWERBOOK OR A BATTERY THAT WILL NOT ACCEPT ANY CHARGE.
A FULLY CHARGED BATTERY CAN POSSIBLY MELT METAL WHEN DIRECTLY SHORTED
AND HAS TURNED SOME OF MY METAL EQUIPMENT CHERRY RED (and has melted
the plastic battery case)
Sometimes the above will not work and I have found that draining the
battery by short circuiting it helps, although a battery in this state
will need to be drained this way from time to time. The short
circuiting is hindered by the "circuit breaker" mentioned above. It can
be bypassed by opening the bar code side of a PB500 battery around the
label and exposing the flat wire on both sides of the breaker, then
connecting both sides with a wire (I haven't had to use this on Duo
batteries). The next step for both Duo and 500 batteries is to take two
thin sewing needles and bend them slightly. Insert them into the
positive (+) and negative (-) terminals on the battery with a pair of
needle nose pliers (they are marked and are different between Duo's and
500's). I use 14 gauge stranded copper wire with alligator clips at
both ends to make the actual short circuit. I usually start off with
about 4-6 feet of wire and sometimes a resistor of about 100 Ohms. If I
don't see a significant drop in voltage after 1 hour or the battery
doesn't heat up, then I take out the resistor (it's a good idea to use a
fan to keep the battery cool as the battery will heat up during
discharge). You can tell if the battery is discharging sometimes by a
small spark if you scratch the terminal needle with the alligator clip.
After about 1 hour or a measured voltage of approx. 15 millivolts _with
the wire connected_ you can stop, let the battery cool and charge back
up to the minimum voltage with the battery charger. I simply use two 14
ga. stranded wires with alligator clips on both ends and connect the
battery to the charger according to the normal position of a battery in
the charger, that is, I connect the positive end of the battery to the
charger contact where the positive end of a battery would normally go, etc.
I let the battery charge to about 5 to 9 volts and then try getting the
Book to recognize and charge it. If not, then I charge in the normal
battery charger more.
Fourth: The batteries can be disassembled by cutting with an Exacto or
sharp steak knife around the horizontal or flat "waist" of the battery.
For the Duo, first remove the locking cap, then cut carefully, with many
strokes, the waist. Be careful not to cut the flat ribbon cables inside
the case. Everything is _very_ tightly packed and I have torn cables in
the past. Once I start cutting all the way through, I twist a flat blade
screwdriver to split the rest of the case apart, only using the knife
again if the case won't split. I then give the case two or three more
strokes of the knife, then use the screwdriver again.
For the 500 battery, first remove the locking cap carefully with a flat
blade screwdriver (it will pry off, but take it slow, working first one
end, then the other, back and forth). Then cut around the "waist" of
the battery _except_ the flat end by the bar code. That is where the
microprocessor board is. On old Apple batteries, this can be pried out
with a screwdriver after cutting the other three sides, on the BTI
batteries, cut that side also, as it is one piece with the rest of the
case, but be very careful, that side has the microprocessor board under
it. You must also _not_ cut all the way through on the side with the
battery terminals. There is a ribbon cable under this side that can
easily be damaged.
Note: I have found that my BTI battery lock cap would not allow good
contact with the charging terminals inside the PB500. I inserted enough
cardboard between the cap on the lock side and the battery case to make
good contact. This was the cause of not charging, even though the
battery had 9V and was good before.
I open the battery case like a clamshell, from the curved side first,
very carefully and slowly as the ribbon cable on the terminal side will
get torn if the case snaps apart. Now you can check the individual
batteries for charge and conductivity and replace one or all. The tabs
that hold the batteries together can be torn off if need be, but I think
it would be better to cut them in half for reconnecting new cells later.
Be very careful to make a drawing of where the ribbons connect and of
how the batteries are tabbed together. New cells can be bought from
<www.digikey.com> and probably other online sources, or a local
electronics shop. They must be the same specifications as above or they
can have more milliamphours (e.g. 2000 or 2200 milliamphours). They
need to have tabs on them. Batteries will be destroyed if you try to
solder directly to them. The tabs can be folded together or soldered
(or welded if you have the proper equipment). If you solder the tabs
together, I have found that placing the batteries in water covering half
the battery or more preserves their original voltage. Soldering them
dry has _always_ decreased the battery strength by at least a little.
If the battery gets hot to the touch, it's too late, the chemicals start
degrading. Be as exact as you can and put the new cells back in the
same arrangement as before, with all the internal battery devices in the
same order. Be sure that the tabs are connected the same way as the
battery cells must fit in a _very_ compact arrangement to get the
battery case halves back to their original size. Some of the tabs have
specific arrangements so that they will fold in the appropriate
direction to make the whole pack fit properly. You need to use an
adhesive that won't stretch to put the case back together. I usually
use JB weld (a hard epoxy) around the cut area and clear tape to hold it
all together
and then I put a heavy weight on top until the epoxy dries. I have
taken to cutting the decals out of 500 batteries and taking the decal
off the Duo batteries to allow better cooling. I also often put the
batteries in the refrigerator before charging because I suspect that
battery life is shortened when they become warm to the touch. They also
seem to charge faster when they are cooler. I am not sure about whether
the batteries hold charge longer when they are cool.
The take apart URL's are:
<http://www.wwc.edu/~frohro/520_Fixes/520_&_540.htm> which has much
good 520/540 info.
Sorry, I couldn't find the Duo battery take apart tonight. If I do,
I'll post it here.
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