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Subject: Again ;-) - Battery Power Problem with USB + proposal
From: Matthias Klumpp (Matthias.Klumpp_at_gmx.de)
Date: 2004-11-05


Hi,

I know this is maybe a "boring" and often repeated story for you, but I'm
simply not able to understand the Rockbox behaviour related to battery
charging.

I'm using a JBRV1, now with flashed V2.3 (previously a CVS version from mid
of August 2004).
The JB is only operated in my car with power car adapter connected always,
so it should never run out of battery power.
Due to that known battery charging problems, I tried to rule out any root
cause for running out of battery by replacing the original batteries with
new 2200mAh NiMH batteries.
For several months I was not connecting my JB anymore via USB, so I don't
know if the behaviour is new in 2.3 or if it was already in the older SW I
was using.

Here are some details what happened/what I've done:

(1) In the car: Remaining battery time with power adapter connected
displayed 5h.
(2) At home: Switching the JB on, starting from the File Browse Screen,
battery symbol displayed '?'
(3) Connecting Archos power adapter
(4) Connecting USB cable
(5) Doing some file copy stuff
(6) After aprox. 15 minutes (!!!!) I got a disc write failure
(7) No access via USB possible anymore
(8) Disconnecting USB cable
(9) Switching off/on JB (power connected)
     -> ATA Error -1 (I remebered that batteries might be low)
(10) Trying to start with F1-ON (power connected)
     -> Archos SW starts
     -> Rockbox tries to spin up HDD
     -> ATA Error -1
(11) Leaving the JB switched off for aprox. 30 minutes
(12) Trying to start with F1-ON (power connected)
     -> Archos SW starts
     -> Rockbox starts
     -> File Browse Screen is displayed
     -> Backlight is switched off
     -> Charging Batteries splash screen is displayed
     -> Battery symbol displayed '?'
(13) Guessing it will charge now, I left it for 1h
(14) Trying (10) again (with same result)
(15) Repeating (11)-(13) but now leaving the JB with that splash screen for
aprox. 5h
     -> when I returned the display was off
     -> batteries were completely (!!) empty
(16) Trying to start with F1-ON (power connected)
     -> Archos SW starts
     -> Rockbox is NOT loaded
     -> Archos SW charging screen is displayed
(17) Leaving it that way over night
(18) Next morning 'Battery Charged' is displayed
(19) Switching off/on (no F1-ON, no power connected)
     -> Rockbox boots perfectly
     -> Remaining battery time displayed 6h.

Would anybody be able to explain that behaviour ?
Why is the JB draining so much battery power with USB and power connected ?
Why is the SW obviously NOT charging batteries while displaying the charging
splash screen ?

---------------------------------------------------
I wrote the 1st part yesterday. As I was not able to get that item out of
mind, I "brain stormed" a little bit ;-))

The JBR's are charge controled by SW not by HW, right ?

Anyhow there must be some capacity sensing HW:
(a) just by voltage
(b) with a current sensing resistor for capacity measurement
Right ?

if (a):
Voltage is braking down only when HDD tries to spin up.
So it's necessary to spin the HDD up (means applying a load) to know the
battery volatge under load.
Why not entering the charge mode directly after low voltage with load was
detected ?

if (b):
Why not measuring the battery capacity BEFORE spinning up the HDD ?
Is it because this would delay the time until the JB has booted up with
fully charged batteries ?

Would it be a suitable solution to have a second key combination (like
F1+ON) to force battery charging while powering on ?
That case we could use that "forced charging" to pump up the batteries at
least a little bit, so next time booting the SW comes accross that first
loss of power while spinning up the HDD with low batteries and in sequence
enters the normal charging procedure.

---------------------------------------------------
Uuuuh, this was getting a pretty large mail.
Hopefully somebody is reading this ;-)))

Many thanks in advance for your help and explications

Greetings

Matthias

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