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Subject: AW: Bug: Battery Charging with low voltage

AW: Bug: Battery Charging with low voltage

From: Matthias Klumpp <>
Date: Tue, 1 Feb 2005 18:05:53 +0100


THX to everybody, picking up that item (once again ;-)))

Following some replies to the comments that were done:

# ----------------------------------------------
# Reply by: Dan Richardson
# ----------------------------------------------
# My JBR6 works with a 9v adapter and Rockbox.
# My JBR15 drains, just like yours.
# Both work fine with the same 9v adapter and the stock Archos
# firmware.

I'm glad to here, that there are the same problems somewhere else too.
That prooves it's not only my JB behaving like that.

# ----------------------------------------------
# Reply by: [IDC]Dragon
# ----------------------------------------------
# It starts to consider it only after 40 sec, too late if your cells are

Well, at least the "F1+ON" option helps getting out that trap with low power
during power on.

# It's known that it would be better to enable charging asap, by the
bootloader perhaps,
# and cut this later if not needed.

I'm surprised why that wasn't done already (no time / fear of having a too
aggressive charger strategy...) ?

# I don't really dare to mess with the charging algorithm.
# Looks overly complex to me, like if we would do a high current charge.

Never change a running system ? - Why not trying it at least ?

# We can't adjust the charging current, only enable or disable charging.

Ok, that was new for me.
But why I do measure 30mA with the Archos FW and only 15mA with Rockbox then

# You're right, determing the battery status is difficult for us.
# If in doubt and before the 1st measurement, Rockbox doesn't charge.

Couldn't there be a setting like "aggressive charge" for all those who don't
worry to loose their batteries ?

# ----------------------------------------------
# Reply by: Jerry Van Baren
# ----------------------------------------------
# Question: Is your power plug switched with the car ignition (most are)?


# If so, you are NOT powering your RockBox constantly as
# you imply by stating that it is connected always.

Sorry, but your wrong.
While switching on/off ignition, the adapter and therefore the JB is
charged/not charger - that's clear.
The mentioned problem occurs, if I drive long distance (>4h) w/o stopping
the car (and also not switching off ignition).
Therefore I said "it is connected always".

# My advice is do NOT turn deep discharge on because <snip>

IMHO: Turning deep discharge on or off does have no significant effect in
that special case I mentioned.
I measured total run times of (a) 5h (deep discharge = on) and (b) 7h (deep
discharge = off).
The difference between (a) and (b) is likely due to the fact, that I started
(a) with NOT FULL batteries, but (b) with COMPLETELY FULL charged batteries.

# If your power source is switched with the ignition,
# this will really mess up the RockBox charging algorithm <snip>

Sorry again:
If I drive in cycles of e.g. 30min->ign. off->ign. on->30min driving a.s.o.
(e.g. city), I'm running out of battery power two times a year !
That's what I observed during the last 2 years. Means the charging algo.
keeps my batteries at least in the shape to work (don't know at which level

# Archo's battery charging algorithm is probably:
# 1) Start charging immediately
# 2) Charge full tilt until you see a peak or a many hour time limit
# This is much more aggressive than RockBox.

This is what (IMHO) could probably be done with a new setup option
"aggressive charge".

# ----------------------------------------------
# Reply by: Dan Richardson
# ----------------------------------------------
# I see the same problem Matthias does, with one of my two JBRs.
# <snip>
# Mine is hardwired to the battery.
# <snip>
# Deep discharge has no effect on the issue on my JBR.
# I've walked through every permutation of charging setting.
# No joy.
# <snip>
# Rockbox's algorithm is not aggressive enough.
# It works for some JBR V1s, but not for all.

Confirms all my tests, thanks ;-))

# ----------------------------------------------
Sorry for the long mail, but I really would like to give a maximum of
information and support for those interested in that topic and those
probably helping in finding a way to get one step forward.
Now looking for new mails :-O)))))

Best wishes


Received on 2005-02-01

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