Actually It Is Based on Lead Acid Battery. It also has an article reference link to "Lead Acid Battery Charging" that apparently appeared in Solar Navigator in 2005.

Go to the article link previously provided:
http://www.edn.com/article/5...o_LEDs.php

Near the top of the web page click the "View as PDF" button. This is necessary because the article page only shows a badly edited section of the design idea.

Next look at the statement that bridges the end of the first PDF page and the beginning of the second page:

"The figure uses a 12V lead-acid battery indicator as an example, but you can extend the design to accommodate other types of chargeable batteries".

Personally I think the idea presented in the article has a modicum of cleverness to it but I would never include such circuit in something I designed and I would use quite different words to describe the circuit operation. Since both LEDs in the circuit see a current change and thus an intensity change, since there is a wide variation of how folks perceive LED intensity and since the definition of the %Charge level of the battery as derived from looking at the LEDs is fully subjective I would use caution of claims I made for such a type of circuit.


Michael Karas