Compaq (off topic)

From: <(>
Date: Tue Jul 21 00:35:38 1998

> Date: Mon, 20 Jul 1998 15:50:33 -0400
> Reply-to:
> From: Charles A Davis <>
> To: "Discussion re-collecting of classic computers" <>
> Subject: Re: Compaq (off topic)

> Max Eskin wrote:
> >
> Hi Max:


And Chuck's comments on batteries snipped as well...

To clearify;

Main battery is charged by two types of process; charging (or rapid
charging) and trickling charging.

Still, the voltages and currents used to charge that main battery
does changes.

Example: 12V NiCd rated at 2000mAh battery pack, uses 10 cells in

Rapid charge is around 1amp or so in order to get under 2 hours and
around 2V rapid charging voltage per cell. That's why usually I see
18V power bricks paired with portables that uses 12V NiCd pack plus
that said power pack also stated around 2A max or so in order to meet
both rapid charging AND have some enough current left over to power a
running portable.

Trickling charge is around 1.3V or so per cell with controlled
current to give very low current around less than 100mA or less to
that pack. Norminally fully charged voltage is 1.25V per cell.

Max commented on 3 batteries in a portable like this LTE Lite, That
little pack with 6 cells is 7.2V standby battery pack. In certain
situations for example if you wanted to swap batteries in midstride
without cutting power or reboot that machine or put a computer in
deep sleep, that part dips into that pack for this.

Anything else ususally uses cmos battery either 3.0V lithium
coin or 3.6V NiCd battery.

First thing you will see problems on those CMOS battery is bad time
keeping when pc is off or in deep sleep in extended time and at worst
problems powering up and down or losing cmos data configuration.

Both Lite and Elites uses siimple power bricks norminally 12~18V
around 2A max, no sensing feedback from computer. Just like a coax
plug but in Compaq's infinite wisdom used oddball 3 pin connector.
Grr. Yes, I did split those power brick for that Lite and Elite
when I check for solder joints, it's simple PSU no tricky extra
circuits anything else besides simple PWM circuit.
Charging circuits is inside that battery pack with that yellow LED

Jason D.

PS: For several reasons, I always split open all power bricks when I
aquire anything that is portable or whatever or is tasked to repair
any portables at component level work IS to check on the condition of
those capacitors and solder joints condition. One of my SLT power
brick died because of this by clusmy user who had no idea that PSU is
not working right before me! Blown PWM IC, couple of resistors burnt
to crisp and no one dropped in to tell me those two resistor values
when I requested these info and power MOSFET (expansive as hell at
around $15 to $20 each and hard to ge). BTW, that SLT power brick
is model 2682 or 2687 but it's lighter depsite it's same size but the
DC power cable is *deatachable* from power brick. Anyone have that
one? If so, find 2 screws under that rubber feets and would be
mucho appreciated to report on those resistor values for this R500
and R512??? They're dull green fusiable resistors in 1/4W size
connected directly between that MOSFET switcher and the PWM ic.

Jason D.
Received on Tue Jul 21 1998 - 00:35:38 BST

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