Chris Adams wrote at 02:40 PM 02/16/2005:
>> > The original batts. in StarMax are alkaline non
>> > rechargeable Ray O Vac 840/841 4.5 volt.
>>
>>Are these still available from any particular source like Radio Shack?
>>Or does one simply have to rig up the 3-AA battery configuration as
>>described?
>
>Might it be possible to use *any* 4.5v battery that physically fits if you can
>wire it up to the m/board connector?
Probably. Each of the battery technologies has a different cell voltage.
Standard alkaline cells are rated at 1.5 V, so the 840 has 3 of those in
series. NiCd cells are rated at 1.25 V, so three NiCd will only be 3.75 V. NiMH
cells are 1.2 V, so three of those in series will be 3.6 V.
But, the power curve on alkaline cells is a pretty straight, gradually
declining line between full and discharge, so the battery will actually spend
quite a bit of time below its rated voltage, and the circuits are designed for
that eventuality, taking a pretty wide voltage range.
OTOH, the two mentioned rechargeable technologies have power curves that are
pretty flat in the middle, then fall off rapidly when discharged. That means
they can spend a fair amount of time within the design voltage of the circuit.
But when they approach empty, they do it very fast.
I'm not real sure how Lithium batteries could fit into this scheme. I think
that Lithium cells run in the neighborhood of 3 V, so it might be too high with
2 series cells, or two low with one. Can't see any way of approximating 4.5 V.
------------------------
Michael Welch
Submissions Coordinator
Sr. Research Editor
[EMAIL PROTECTED]
Home Power magazine
www.homepower.com
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