[Gta04-owner] charging gta04 on my bicycle

[Alexander Lehner]

On Fri, 11 Jul 2014, Dr. H. Nikolaus Schaller wrote:

> Hi,
> the charger is a little critical about the VBUS voltage. It reports an issue if >5.2 V and drops charging if <4.4 V.
>
> But charging is only (re)started if VBUS goes below ca. 1.5V.
>
> So there is a situation for VBUS voltages where it does not charge even if you have 5.0V.

Is this related to the GTA04 only or does the charger of the GTA02 behave 
the same?

I used my GTA02 with a self-soldered step-down converter and was at least 
able to keep the battery charge at live for a whole day cycling.

> Andreas has modified things to make it work on a bike:
> http://www.ohsw.de/gta04-otg.pdf
> http://www.ohsw.de/gta04-bike.pdf

This is quite impressive!!!

I also remember that there were tools which could change the power drain 
of the GTA in stages like 100mA, 500mA and 1000mA.

100mA is sufficient for charge only in standby or turned off.
While 1000mA is hard to achieve with a bicycle dynamo.

Another option which I evaluated successfully was this solar charger:

http://www.solarc.de/shop/product_info.php?language=en&info=p32_e-GO--Professional.html

It has some buffer batteries inside (AA or block cells) and you can feed 
it additionally with an external power supply.

So:

Sun   -\
dynamo ->  eGo  -> USB

Con: more weight and costy
Pro: has a very intelligent charging system and output power regulation


A.