IM-17 Batteries

[Chuck Moore]

How much current are you drawing? Some of the newer
Low Dropout Regulators pull in the 10's of uAmps range.

Chuck
>
> From: Garey Barrell <k4oah at MINDSPRING.COM>
> Date: 2004/05/10 Mon AM 12:45:17 CDT
> To: HEATH at LISTSERV.TEMPE.GOV
> Subject: Re: IM-17 Batteries
>
> Bob -
>
> It doesn't look like an alkaline battery would last even 10 hours
> at a 10 mA load before it's terminal voltage drops to less than
> 8.5V.  A lithium is a little better, but even it would only last
> about 40 hours at a 10 mA load before dropping to 8.5V.
>
> The alkaline drops 0.5-1V quickly , then slopes down at a
> somewhat slower rate.  End of life for an alkaline is 4.8V!
>
> Probably the closest approach would be to use 8-10 AA cells and
> regulate to 8.4V.  Not really a viable solution unless it's a big
> product.!
>
> 73, Garey - K4OAH
> Atlanta
>
> Bob And Bettina Groh wrote:
> > Regarding 'low drop out regulators' - there are a bunch of them today
> > that will (at 'light' loads) that will regulate well with only 50 mV or
> > so across them. You would need one of the adjustable one's with some
> > precision resistors (or a pot) to set the output voltage.  Should work
> > great and, with SMD devices, could be built up in quite a small space.
> > Good point about the discharge characteristics.  If any other info
> > needed, I would be glad to look into the matter and provide a 'paper'
> > design.
> >
> > 73
> > Bob Groh, WA2CKY
> >
> > Garey Barrell wrote:
> >
> >> John -
> >>
> >> There really isn't a good replacement for a mercury cell.  There are
> >> many ways to get 8.4 V from a 9V battery, but the absolute voltage isn't
> >> the problem.  All batteries EXCEPT for the mercury battery have a
> >> "slope" discharge curve.  i.e., the voltage starts to decrease almost
> >> immediately, and continues until it reaches the minimum that will
> >> operate the equipment.
> >>
> >> On the other hand, a mercury battery has an almost flat discharge
> >> "curve" until just before end of life when it drops like a rock.  This
> >> is important for things like watches, light meters for photography,
> >> voltmeters or anything else that relies on a stable voltage.
> >>
> >> Photographers have gone to great lengths to make accommodations to keep
> >> their light meters accurate.  The only "good" answer is a voltage
> >> regulator, but not many regulators will regulate with less than a volt
> >> to work with.
> >>
> >> 73, Garey, K4OAH
> >> Atlanta
> >>
> >>
> >>
> >> John Barkow wrote:
> >>
> >>> Anyone know of a replacement for the 8.4V mercury battery for this
> >>> unit other
> >>> than a 9V battery?
> >>> Thanks, John kd6pt
> >>>
>
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