AVR-Chat

Thanks Ken,

In the series/parallel combination I was looking at I will be looking 
at about 2.2 - 2.3V then, that means around 4A being drawn from each 
series combination - yikes!!!!!

Cheers
Col

--- In AVR-Chat@yahoogroups.com, Ken Holt <kholt@m...> wrote:
> 
> 4 NiMH batteries is a good starting point, but remember that you'll
> only get 4.4 - 4.6V (series total) over most of the discharge curve.
> 
> 
> At 06:17 PM 7/30/2004 -0000, you wrote:
> >--- In AVR-Chat@yahoogroups.com, "C Sizer" <aussiecol39@y...> 
wrote:
> >
> >> ... I want to use 4 x 2300mAh AA
> >> batteries in serial/parallel to
> >> provide me with 3V.
> >
> >Sounds like alkaline cells at 1.5 volts each.
> >
> >> The printer runs on 5V but consumes
> >> over 3.5A peak, so I require a DC-
> >> DC converter circuit... to provide
> >> 3V at 5A peak.
> >
> >You mean to provide 5V/3.5A, which will suck six amps or more from 
> >your 3V battery. I don't think this will work. The internal 
> >resistance of alkaline cells will be too high and your 3 volts 
will 
> >sag something terrible.
> >
> >Like everyone else, I suggest you switch batteries.  Use four NiMH 
AA 
> >cells to get 5V and regulate down to 3V. I don't think you'll need 
to 
> >buck down, just use a linear regulator, unless you're taking a lot 
of 
> >current at 3V. Although the capacity of the NiMH cells won't be 
2300 
> >mA.h (I use 1800 mA.h cells but I think now you can do a bit 
better) 
> >I think they will actually last longer. This is because the 
alkaline 
> >cells will never give you full capacity at such a high discharge 
rate 
> >and you're avoiding power loss in the boost converter. High 
quality 
> >cells will be able to keep the voltage up because NiMH cells have 
a 
> >low internal resistance. For example, the 7.2 volt 6.5 A.h modules 
in 
> >my car have an internal resistance just a bit over 10 milliohms. I 
> >can get 60 amps or more from the 300 volt battery and the voltage 
> >stays up at 275 volts.
> >
> >Graham.
> >
> >
> >
> >
> >
> > 
> >Yahoo! Groups Links
> >
> >
> >
> > 
> >
> >