[time-nuts] Measurement of noise voltage density on batteries
csteinmetz at yandex.com
Fri Sep 5 21:51:28 EDT 2014
>I have made some measurements on the noise voltage density in
>batteries. The short result is: 1. NiCd rulez. 2. Size DOES matter.
Nice work! (But not exactly news.) As noted in the NIST paper you
quote, the noise of batteries is very closely correlated with their
internal resistance, because the primary noise mechanism is Johnson
noise and NiCads have the lowest internal resistance of commonly
available batteries. As you discovered, the internal resistance of
many NiMH batteries rises when current is drawn (one of the great
drawbacks of NiMH batteries for high-drain uses such as model
aviation and even high-lumen flashlights).
It would be nice to see measurements under load for all of the
batteries (using a more suitable lithium battery -- perhaps a CR123A
or a similarly-sized or larger rechargeable lithium), and results for
small SLA batteries.
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