[Bulk] [Diy_efi] supercap

[Steven P. Donegan]

The Dallas chip seems to support super cap or battery - I chose a super
cap for no specific reason beyond cheap/available. And the circuit we
are discussing is the data logger, not the ECU - so if the data logger
dies it's not a vehicle stopping event. The ECU will have a bit more
hardened power supply taking all of the lists input to date.

On Tue, 2007-02-27 at 11:04 +1100, Bill Washington wrote:
> Bevan, Steven,
>     Any thoughts on using a rechargable battery - (2 or3 cell)NiMH 
> probably, for the RTC, and higher temp range 100uF electros for the 
> reservoir caps on the remainder of the circuit? - the NiMH could be 
> trickle charged by Diode during normal operation and diode switched to 
> the RTC at power down - the RTC would then operate at full rail voltage 
> minus one diode drop during normal operation, and NiMH minus one diode 
> drop at power down. Configuration, etc would depend on the Min operating 
> voltage of the RTC...
> Thoughts?
> 
> Regards
> Bill
> >
> >   
> >
> > ------------------------------------------------------------------------
> >
> > Subject:
> > Re: [Diy_efi] PCB layout/circuit design
> > From:
> > Bevan Weiss <kaizen__ at hotmail.com>
> > Date:
> > Tue, 27 Feb 2007 08:01:17 +1300
> > To:
> > diy_efi at diy-efi.org
> >
> > To:
> > diy_efi at diy-efi.org
> >
> >
> >
> >
> >> Bevan Weiss wrote:
> >>
> >>> I haven't looked into temperature ratings for super caps lately, but 
> >>> last I looked they weren't great.  Something like -5degC to 45degC..
> >>
> >> Eep. is that failure at -5 degrees, or simply that they lose their 
> >> charge? (the latter isnt much of a problem in our case unless they 
> >> REALLY lose it)
> > That's rated temperature.. so outside of that anything can happen.  
> > Generally you'll get a deviation from the rated capacitance.  In most 
> > cases it will fall significantly.  With lower temperature generally 
> > the ESR will also increase (much like a battery), and the leakage 
> > current will also decrease.
> > It's not a big issue so much, apart from the slightly increased 
> > possibility of container rupture (which would be a bad thing).  Super 
> > caps tend to work best in situations where they aren't hot or cold.. 
> > otherwise batteries tend to do a better job.
> >>
> >>> I applaud you for taking on this design in such a public manner.  
> >>> Sorry if it seems like we're telling you how to suck eggs, just want 
> >>> to make things easier for you :)
> >>
> >> I'm no expert on analogue electronics either, so Im here for all the 
> >> learning I can get too :-)
> >> _______________________________________________
> >> Diy_efi mailing list
> >> Diy_efi at diy-efi.org
> >> Subscribe: http://lists.diy-efi.org/mailman/listinfo/diy_efi
> >> Main WWW page:  http://www.diy-efi.org/diy_efi
> >>
> >>
> >
> _______________________________________________
> Diy_efi mailing list
> Diy_efi at diy-efi.org
> Subscribe: http://lists.diy-efi.org/mailman/listinfo/diy_efi
> Main WWW page:  http://www.diy-efi.org/diy_efi