backup battery and case screws questions

Gennady Kupava gb at
Mon Oct 25 22:01:28 CEST 2010

В Пнд, 25/10/2010 в 11:14 -0400, Benjamin Deering пишет:
> It looks like I will be following your advice.  The hazmat shipping for 
> the lithium batteries was going to be 175% of the price.  I just ordered 
> some supercaps instead.
> Ben
> On 10/24/2010 12:51 PM, Martix wrote:
> > I suggest using double-layer super capacitor* intead of Lithium backup
> > battery. These capacitors stores energy for a long time, like a
> > battery and they have much longer lifetime. 0,2 F capacity should be
> > enough for RTC backup on several hours, maybe days.
> >
> > *
> >

I noticed in PCF manual:

	"Save" [about power states]

	In save state .... is supplied from either system voltage ... 
	or backup battery ... . Only ... and real-time click will 
	be active. __The GPIOs will maintain their state__ . 

Can 'maintaining GPIO state' be cause of our poor backup battery

Please, do not forget to share results. I'm not hw engineer guy, but
read about this capacitors and they sound exactly what's needed!
Personally i desoldered backup battery long ago (easy btw), found it is
dead and still can't find any replacement.


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