[Gta04-owner] battery problems

[Andreas Kemnade]

On Sun, 18 Aug 2019 15:19:22 +0200
"H. Nikolaus Schaller" <hns at goldelico.com> wrote:

> Hi,
> 
> > Am 17.08.2019 um 20:17 schrieb Andreas Kemnade <andreas at kemnade.info>:
> > 
> > Hi,
> > 
> > I have these kind of replacement "batteries" for the gta04.
> > 
> > https://misc.andi.de1.cc/gta04-batteries-small.jpg  
> 
> Nice!
> 
> > 
> > The right one works, but dimensions are not perfect and feels
> > more fragile. The left one worked shortly but then I had no output at
> > the terminals. There seems to be some problem between the gta04-side
> > battery - terminal and the B- test point.
> > 
> > A picture of the protection circuit is here.
> > https://misc.andi.de1.cc/prot-circuit-small.jpg
> > 
> > As I do not have too much spare protection circuits, do you have
> > any advice what I should take better care of for the next one?  
> 
> The role is to protect the battery cell and not the device powered
> by it.
> 
Well, it is just the best mechanical fitness I have.

> Well, you can bridge it if you connect an external power supply
> and not a battery which does not survive a short-circuit.
> 
> > 
> > Furthermore with the right one looking at the display is easier
> > and I could check current consumption.
> > 
> > The whole thing is interesting because it would allow me to run
> > git bisect run with a closed gta04a5. Currently I am using the letux3704
> > for it.  
> 
> I remember there was a schematics of the HF08 battery (fuel gauge
> and protector) but I did not find it any more.
> 
> Here is an application note by TI and I assume that the HF08
> battery is not very different:
> 
> 	http://www.ti.com/lit/an/slua456/slua456.pdf
> 
> Most important is that the current sense shunt resistor and the
> battery protection FETs are in the - side of the battery. So
> if there is a GND connection between the power supply and the
> USB shield this effectively bypasses the protection and the
> shunt resistor.
> 
Well, I guess the shunt resistor is low compared to that bypass.

> Or did I misunderstand the problem and you are looking for better
> mechanical design? There you might use three small screws contacting
> the battery springs of the GTA04.
> 
yes, it is about the mechanics. I just want to avoid trashing another
protector pcb. I do not know the reason why that one got
apparently damaged.
The microsd adapter is already better than my screw approach. I
have checked power consumption of wifi in 2.6.32 (which does not have
hdq) using such a screw-based adapter.

> Yet another idea would be to design a new "protector PCB" which
> only has the three golden battery contacts on one side and some
> solder points on the other. Since they are quite small, they
> are not expensive to be produced by e.g. aisler.net.
> 
hmm, the contacts are just thing chemical NiAu? Or is hard gold needed
here?

Regards,
Andreas