Hey there. I guess you're getting swamped with requests. The specifics
on my battery (a 1400 power book) is that it's a 9.6v, and with NiMH
batteries can produce 3.5 AH. How would I know how many and what type of
cell to order? Would the outcome be better using lithium instead of
NiMH as your note suggests, or was that not meant for me?
Tom V
Okay Tom, you say your present battery pack outputs 9.6 V at 3.5 A/hr.
A single cell outputs 1.2 V at varying current, depending on the size.
Yu can make a guess at the size of the cells, based onthe battery pack
outside dimensions, assuming two rows of cells packed side-by-side, the
usual configuration for flat powerbook battery packs.
To get 9.6 V , you need 8 cells. To get 3500 mA/hr, you need something
like a C or D size cell, so if your pack is thinner than either of those
formats, you can assume two banks of 8 cells connected in parallel, each
outputting 9.6 V and at least 1750 mA/hr. If you don't have a battery
pack around that you're willing to cut open, which is the route I would
take regardless, then you might measure your pack, and figure out which
way the two side-by-side rows of eight are laid out inside, using the
cell dimensions from the Battery Merchant URLs I posted earlier. For
example, from the listing at www.batteriesplus.com/Product/roundcells.html,
I can see that one of the candidate cells (remember it must output
1750 mA/hr or better) is the following 4/5A size cell:
Cell model number Voltage Current Type Dimensions Cell Type
T6939H 1.2 2000 NiMH 17.0x43.0 4/5 A (F)
Two banks of these side by side would be:
(43mm long + 43mm long) X (17mm diameter X 8 cells) or
86mm X 136mm = 3.39in X 5.35in
which you can round up a bit, to allow for case thickness, tabs, and
internal wires. I've never seen a 1400 power cell, but I'll bet it's around
3-1/2" X 5-1/2" and about 3/4" thick, give or take. If it is, then
chances are pretty good that it uses 4/5A cells in this configuration.
You'll only know for sure when you open it up and peek inside! If you used
these cells, rated at 2000 mA/hr, you'll end up with a refurbished "new"
battery pack that puts out 4 A/hr, 500 mA/hr more than your existing rating.
You can find 4/5A size cells rated at even higher output, and considering
the trouble you're taking to replace the cells, going with the highest
current rating that will fit is a no-brainer. If it equates to another 15
minutes of working time on each charge, it's certainly worth it. Yes, it
will also take a little longer to recharge, and so what?
If you can find/steal/scrounge a dead 1400 battery somewhere, you can carve
that one up and determine exactly what cells you need, before looking at the
charts online to see what's available.
I'm delighted, that someone sells these oddball sizes: it means that I can
replace batteries in my rechargeable tools, instead of tossing them out
because it's cheaper to buy a new tool than to replace the battery pack.
Let me know how you make out : )
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