[ltp] Auxilliary external batteries

[Theodore Ts'o]

On Tue, May 13, 2003 at 03:36:28PM +0000, Robert Hajime Lanning wrote:
> On Tue, 13 May 2003, Bob Toxen wrote:
> > Keep in mind that all these auxiliary external batteries are is a
> > 12V rechargeable battery, charger, and inverter.  My R31 used about
> 
> No, there is no need for an inverter.  Not AC.  The brick that comes
> with my TP600X outputs 16Volts DC at 3.36 Amps.  These external
> batteries are just 16Volt high current batteries.  I don't plug the
> power supply into the battery, I plug the battery directly into the
> notebook.

Absolutely true.  Also the case is that all of these auxiliary
batteries (both the Electrovaya and the Valence) have a much higher
energy density than as sealed lead-acid battery.  In fact, both
companies have what seems to be an identical business strategy; they
were started to commercialize some exotic, patented battery chemistry
which is supposed to be allow for lighter, higher capacity batteries
than the standard Lithion Ion batteries (which are themselves much
lighter and have a higher energy density that lead-acid batteries).
Both companies are producing these external batteries more as a way of
marketing their propeitary battery technology and to show it off as a
proven technology.  It's clear that what they really want to do is to
license their battery technology to laptop manufacturers, since that's
where the big money is....

> >      50W inverter: $25 at www.microcenter.com (about 0.3 pounds)
> >         or about the same price at www.batteriesplus.com
> >      7.5 AHr 12V sealed lead acid battery would weigh 6 pounds
> >         Model CLTXPA12-7.5F via www.batteriesplus.com $26
> >      Battery charger (1A would recharge in about 10 hours)
> >         2.5 pounds via www.batteriesplus.com $17
> >      ===========================================================
> >      Total cost $68
> >      Total weight 8.8 pounds

So your solution gives you 90Wh, buth with a 75% efficient inverter,
that's an effectively 67Wh battery.  To compare, the Valance N-Charge
battery is 65 Wh, but it's 9" x 11" x 0.51", and it weighs 1.95 lbs.
Yes, it costs $199, but at least for me, the volume difference of the
inverter + 50W inverter is at least as important as the weight factor.

Actually, I've just purchased the VNC-130 Model, which gives you
120-130Wh, weighs 3 pounds and comes in the same form factor.  And
it's $299.  

Is it expensive?  Yup.  But is it worth it?  I think so....

						- Ted