Need help selecting components for solar a battery charger.

Try it without the diode. This type of diode will drop about 0.6V leaving only 0.9 for the battery.

 

Get 2 more of the solar cells and connect them all in series. You don't need any diode.

 

Sir Simon . . . . . .


" I want to make a single cell AA solar charger that can charge a single AA 1900mAh eneloop battery in English winter time, So that's about 7hrs light per day. "


I gots to knows ?

What is this light source type, and its voltage current specs, that you perceive is going to be consuming X amount of milliamperes from a 1.2 VDC @ 1900 mah AA Sanyo eneloop
battery for about 7 hrs of light per day ?

That voltage spec only meets an incandescant lamp of the penlight category . . .that I know of.
That 1.2 voltage is also below common LED's operating thresholds, unless you use a germanium transistors converter circuit to up the 1.2 . . .and less . . . .voltage.
In either case , this lighting level intensity, seems to be in the illumination magnitude of a nightlight or a reading booklight. . . . used "for a cold English winter time night".

If you are figuring upon a total run time from the battery alone and computing it out as 1.2 Volts X 1.9 amps for a combined capable stored wattage of 2.28 watts.


Recalculate . . . . . as you don't have that TOTALLY deep of a storage well.

Figure on the lighting load gradually dropping the effective voltage of the cell to its safe recommended FINAL discharge state of .9 volt output.
Sooooo figure on your having had a voltage decrease of 1.2VDC down to .9VDC as having supplied you with .57 watts of power
during that discharge transition period.
So, in re-figuring, what can you do with .57 watts of power, in computing, with the lights voltage and current requirements, in order to come up with an X period of operating time ?

As far as the solar cells, I would be getting some "seconds"/ "cosmetics" / "breakers" from the larger 3 by 6 units that are MASS manufactured and used so PROFUSELY in large solar
panel arrays, and figure the number of series cells at .5VDC that will get my required voltage and current requirements, along with being somewhat above the LEVEL of lighting wattage
and time duration that you need.

I'm DEFINITELY tending to overshoot on those solar panel series output voltage specs, with the number of overcast days and shorter winter daylight time .
More initial voltage and current capability can readily be corrected thru a series FET constant current generator .

The most common 3 by 6 cells can be bought and scored to like sizes with a cut off wheel chucked in a Dremel tool, and guided along a clamped on wood strip and then snapped and series soldered
via jumpers to get the required multiples of .5VDC per cell.

Surplus cells:

http://stores.ebay.co.uk/ML-Solar-World-Wise-Solutions/Broken-Solar-Cell-/_i.html?rt=nc&_fsub=1811315014&_sid=854676534&_trksid=p4634.c0.m14&_sop=15&_sc=1

Seems like youse U.K's guys have to pay thru the nose for postage !

I usually just go for the cheapest items just out of the E-bay bidding threshold and just entering into the Buy it Now category, unless you like playing the E-bay bidding war . . . .or just having bidders luck .

Now . . . .feedback . . . .on your lighting level needs aspects . . . . is it a night light level or booklight . . .or even . . . (put on sunglasses) MORE ?


73's de Edd