Plant Mites SEM

"AA" Battery Charger

Projects, Experiments, Stuff Done for Personal Enlightenment or Just Fun

 

Bugs - Scanning Electron Microscope (SEM)

There were these geraniums that seemed to be full of webs and spiders that were so tiny, you couldn't observe without a magnifier.

I took a sample to my lab and placed them in the Phillips SEM and obtained the following images. These guys (or gals) look more like machines than living insects (although they were not alive in the hard-vacuum present!).

   An eye and a "hair". The hair is about 3µ across!

  An eye. Look at the structure that is <1µ across - the ripples and ridges.

       A baby.      Top of Page


     Battery Charger for disposable "AA" cells

            

 I found the concept on the Web, but it was not clear really who did it; when I discover, I will certainly give credit where credit is due!

It seems that if one supplies a CHARGE current for a given period, and then allows the battery to cool with no CHARGE current flowing, the Alkaline AA cells will not leak during charging; this is what occurs if one takes an Alkaline and tries to charge on a constant voltage (CV) supply.

Anyway, it works very nicely and is comprised of 2ea. 2N3904 NPN transistors arranged as a bistable multivibrator driving a MOSFET (heat sink in image). The ON time is about 2 seconds and OFF is about four seconds. For four "AA" cells I drive it at 6.5V from a bench-supply. ON-Current=350mA and OFF-current is <30mA. It takes about 24 hours to charge.

I plan on taking the Discharge Path resistors and making them variable to tweak the ON/ OFF times and improve the charge rate. There is no noticable warming of the cells during charging, but I have not measured beyond using the pinky.

Some cells are on their third charge demonstrate no apparent degradation of an ability to provide power. Some just "give up the ghost" and won't charge. Any use beyond the initial discharge is free-energy or maybe a free battery. A schematic is fortcoming; email me if you need one NOW!

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