hp50g change low battery threshold voltage
davoremard
I'd like to lower hp50g internal low battery threshold
(the one that displays Lowbat(S) after powering ON)
to appear when battery voltage drops below 4.5V
(currently I get it below 5V)
While running hp50g on 500mAh NiMH batteries I get low
battery warning too early. Few hours after charging it shows
lowbat(S) while the batteries can hold 4.8-4.9V steady even at
CPU load and could run more than a week
of my usual usage.
Checking with btmon program and comparing with connecting a
voltmeter directly to the battery compartment while hp50g is on,
both readings are consistent.
(maybe btmon shows 0.05V less than voltmeter)
I got low battery when btmon shows 4.97V
(while the btmon needle is in battery
"good" area, not yet stepped into "warn"
area).
I'd like to lower hp50g internal low battery threshold
to around 4.5V. Is there some application or at least
Saturn or ARM9 location to
poke the modified voltage threshold value?
Best regards, Davor
sc_u...@hotmail.com
> While running hp50g on 500mAh NiMH batteries I get low
> battery warning too early. Few hours after charging it shows
> lowbat(S) while the batteries can hold 4.8-4.9V steady even at
> CPU load and could run more than a week
> of my usual usage.
Battery monitors will not run well with Ni-MH cells. The reason is
that unlike alkalines, Ni-MH batteries do not lose voltage at a
constant rate. They tend to hold their 1.2V until just before they run
out of gas. That's when the voltage suddenly drops without warning.
New alkalines will deliver 1.6V fresh and under no load, but once the
machine is on, alkalines will never output 1.5V.
I use 900mAh Ni-MH batteries and my low-bat warning comes very late.
Usually by the time the status indicator turns on, the calculator
already cannot stay on for long periods of time (i.e. several
minutes). However, turning it off and letting it "rest" for a short
time before restarting it will usually clear the annunciator, though
it always comes back momentarily, especially under the load of a CPU-
intensive calculation such as numerical integration.
S.C.
davoremard
sc_use...@hotmail.com wrote:
> On Sep 26, 4:45�am, davoremard <davorem...@gmail.com> wrote:
> > While running hp50g on 500mAh NiMH batteries I get low
> > battery warning too early. Few hours after charging it shows
> > lowbat(S) while the batteries can hold 4.8-4.9V steady even at
> > CPU load and could run more than a week
> > of my usual usage.
>
>
> Battery monitors will not run well with Ni-MH cells. The reason is
> that unlike alkalines, Ni-MH batteries do not lose voltage at a
> constant rate. They tend to hold their 1.2V until just before they run
> out of gas. That's when the voltage suddenly drops without warning.
I'm aware of that is normal NiMH behavior. However it has some
curve slope as it discharges but quite small so with some
tuning of the voltage, we can set the indicator to appear more
early or more late regarding the battery remaining capacity
> I use 900mAh Ni-MH batteries and my low-bat warning comes very late.
> Usually by the time the status indicator turns on, the calculator
> already cannot stay on for long periods of time (i.e. several
I'd rather prefer mine to behave like yours, to receive low battery at
the
end of battery capacity.
I think my hp50g voltage monitor is somehow set up too high and
triggers
low battery too early. I hope there is some ARM register that we can
change
to adjust it so it could fit each battery. With some tweaking we
should be able
to detect 1 hour warning before NiMH battery runs out.
Davor