solar panel Requirement. Help needed.

SimonF1
SimonF1 Registered Users Posts: 1 ✭
edited January 2016 in Solar Beginners Corner #1

First of all, Hello and hope everyone is having a great new year so far.

I know very little about electronics and just need a little help getting the right components.
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.

ive already got a 1.5v 0-300ma solar cell but for some reason even after 7 hours charging it does not have any power in the battery.
Please I don't want a similar setup that I have to recalculate.

I just need a link for the solar cell I need and from ebay uk would be best place for me to get it from.

I already have some 1N4007 diodes that im hoping to use in the circuit, I place one diode in the live side from the solar cell wire with the stripe facing away?.

Please can anyone post me a link for the solar cell I need.

Kind Regards
Simon


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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #2

    Hi Simon, Welcome!

    See if you can find the charging parameters of the Eneloop, I did a quick search and came up with nothing.

    I have charged NiMH batteries with a small solar panel, 5 'AA's with a 6 volt nominal, 6-700 MAh panel. I can't recall if they were the simple high capacity NiMH or the Lower capacity slower self discharge like the Eneloop. but I recall they could handle constant over charging, dissipating the over charging by heating up. I'm sure this wasn't good for the battery, but it wasn't dangerous by the specs.

    As to solar charging, a solar panel will likely produce about 70% of it's rating and then only in direct sun light. So "...7 hour of light" if indirect and not full sun might produce nothing in the way of charging amps. The solar cell/panel might produce full voltage with no available/meaningful charging current available. 

    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • zoneblue
    zoneblue Solar Expert Posts: 1,220 ✭✭✭✭
    #3
    Well theres a number of basic principles you need to grasp. If a solar panel is labelled at 1.5V that might be the Voc or the Vmp. In either case its not enough to charge a NiMH cell. I suggest you spring for something with 36 cells, a charge controller and what not. Then use that to power a buck converter, and/or a constant current circuit. All NiMHs charge using a constant current until the voltage, temp and cell pressure peak. You can do this wih peak detection or more simply time it. 14 hours at 0.1C will take a flat cell to fully charged.

    However to keep things really simple, if you got two of the cells that you have in series i think till charge just fine. Solar cells are constant current generators, so 300mA is what the cell produces in full sun, and the voltage will swim around depending on how much a load you place on it. Dont forget a siicone diode drops 0.7V. A niMH starts charging at about 1.3V, and completes around 1.6V. Thus two of your cells will produce 300mA at up to 3V. 300ma happens to be pretty good for the eneloops which can be charged at anything from 50mA upto 1A. When the sun goes down your charger 'shuts off". Awesome.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


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