[time-nuts] Measurement of noise voltage density on batteries

Charles Steinmetz csteinmetz at yandex.com
Fri Sep 5 21:51:28 EDT 2014

Gerhard wrote:

>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.

Best regards,


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