New project...

So I've gone thru 3 Li-Ion laptop batteries in the past 2 yrs.  Not sure =
how=20
long I'll keep this laptop, and after getting frustrated at prices of=20
replacement batteries and not trusting the serial-number-less ones on eba=
y,=20
I've hit upon another idea...  why not go gel-cell.

At the high level, each laptop battery is 10.8V @ 3.2AH, which is a power=
=20
capacity of about 35W.  In contrast, I saw a Yuasa 12V 7AH gel-cell (84W)=
=20
which is not very large or heavy, and is $23, so it's even more appealing=
=2E

Connection to the laptop, I'd probably use the power-port at the back, bu=
t the=20
external power adapter supplies 16V @ 3.36A.  Since I don't carry the=20
pluggable CD drive or floppy with me, I'll bet that the laptop will consu=
me=20
less than 3A (and I'll test to be sure).  That value's important to me fo=
r a=20
reason....

Raising the ~12V to 16V is easy, cause I have the dc-dc converter chip=20
already, and even a recently-built test ckt, which I can adjust to 16V by=
=20
changing just a few parts.  So cost is essentially zero there.  However, =
I=20
have a limit of 3A out.  But hopefully that won't be a problem.

Now, all I need is to figure out the charge and discharge characteristics=
 of a=20
(or this) gel-cell, and build a ckt to monitor the remaining power and on=
e to=20
charge the gel-cell.  I haven't found a suitable gel-cell charger ckt on =
the=20
net yet, but still looking.  And if I find the discharge specs, I'm sure =
I=20
can whip up a quick PIC-based (of course!) power monitor.  I can't even f=
ind=20
a website for Yuasa.

Any assistance/pointers appreciated.  And I'll even accept a "what the he=
ll=20
are you thinking" before I really get started.

Cheers,
-Neil.

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