[Gta04-owner] various powermanagement issues

Andreas Kemnade andreas at kemnade.info
Mon Oct 19 08:41:54 CEST 2015

On Mon, 19 Oct 2015 07:28:16 +0200
"H. Nikolaus Schaller" <hns at goldelico.com> wrote:


> Approx. 3 seconds after the TPS autoboots with an empty battery, we have
> U-Boot up and running. And hacking U-Boot is much simpler and more flexible.
> It may be not well known that our U-Boot has some additional commands:
> 	http://projects.goldelico.com/p/gta04-uboot/page/NewCommands/
> and there is: 
> 	• systest ch[arge] - enable battery charger and print mV levels
> So the solution could be as simple as adding a "systest charge" command
> (potentially slightly modified to better integrate into a script) to the boot.scr
> to enable more power drawn from USB and unburden the battery.
> I love simple solutions where all components are already on the table :)
> In this case for ca. 4 years...
> So we have to ask ourselves why nobody did solve it in that long time frame.
> Are such things not known?
The answer is quite simple.
1. My initrd-thing works (I have published here on the list) except for
some batteries at the end of their life. My 350mAh-battery has begun to
getting thick. So I will not use the battery anymore. Uboot-hacking
would have giving we approx 1 week more use time if it would work. So
no practical need to fix that using uboot. Except that my system fully
boots on first try when there is power available.
The reason for that topic was just because I wanted to know how to best
live with bl6c batteries. Now I have found out that MADC gives at least
some information.

2. More logic than just enable charger is needed.
Reason: Booting the system (after booting the kernel) gives quite high
currents, especially if peripherals are enabled at powerup time. That
means that there might be even some discharge.
And further on it feels that there is some hidden logic which lets the 
GTA04 boot when there are red traffic lights in the vicinity on my bike
or I have to start climbing a hill so that there is less than 500mA
charging current. 
The autamatic charging has some logic making it switch to slow charging
mode, which means limiting IUSB(!!) to 100mA when battery goes below
approx 3.2V. or something like that. Therefore I enable linear charging
and disable most things in my script and then wait until Vbat reaches
3.45V (I just noticed that my script still does that via bq27000 and
not via MADC in12). Then I check whether the GTA04 sits in my bike
holder via accel sensor. If not I switch back to automatic charging.
The root fs is mounted then (and power-consuming things like
journal replay can start. Shorter red-phases can be handled using that

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