[Nut-upsuser] Ablerex MARS

[Charles Lepple]

On 4/22/06, Carlos Rodrigues <carlos.efr at mail.telepac.pt> wrote:
> Right now megatec just calculates a linear approximation. It doesn't
> give accurate values, but it is enough to have a fuzzy idea of the
> charge left (like saying "it's almost noon" instead of "it's 12:45"),
> and I'm not seeing how to plot a more accurate charge that fits all
> the models that megatec is supposed to support (especially given I'm
> no electrical engineer).

Don't get me wrong - I spent less than five minutes with the battery
charge code for tripplite_usb.c (shamelessly ported from tripplite.c).

I should have just said that a battery is more complicated than a
linear "bucket of charge", and left it at that :-)

I think that the solution that APC and MGE apparently use (probably
others as well) on their PDC HID UPSes is better - do the charge
calculation in an on-board microcontroller, and calibrate it as part
of the final QA stage. If the manufacturer can't afford a couple extra
cents for a microcontroller that can do that math, the components will
probably drift over time anyway (making PC-side charge calculations
futile).

> Now, I've introduced these values to megatec, and I've commited it to
> SVN. Can you (not Charles) check if they are acceptable now?
>
> On 4/22/06, Charles Lepple <clepple at gmail.com> wrote:
> > On 4/22/06, lonely wolf <wolfy at nobugconsulting.ro> wrote:
> > > The voltage doesn't look to have a linear dependency with the charge ...
> >
> > Here's the charge curve used by the Tripp-Lite driver:
> >
> >    http://boxster.ghz.cc/projects/nut/browser/trunk/drivers/tripplite.c#L456
> >
> > Generally speaking, measuring the voltage to find charge is a bit
> > problematic unless you take into account the amount of current flowing
> > in or out of the battery as well (a real-world battery has non-zero
> > Thevenin resistance, so it is not a pure voltage source). The best you
> > can do is plot voltages over time (as reported by the UPS), and try to
> > fit the curve.
> >
> > --
> > - Charles Lepple
> >
> > _______________________________________________
> > Nut-upsuser mailing list
> > Nut-upsuser at lists.alioth.debian.org
> > http://lists.alioth.debian.org/mailman/listinfo/nut-upsuser
> >
>
>
> --
> Carlos Rodrigues
>


--
- Charles Lepple