Solar wrapped batteries charge themselves
February 26, 2009 From the files of “why don’t they make that?” comes a rechargeable battery with integrated solar cell charger. The “SunCast” prototype uses flexible solar cells from IFE and some C sized NiMH rechargeable batteries. Scientists at IFE have been experimenting with the production of flexible solar cells and were kind enough to send some samples to the “SunCast” battery designer Knut Karlsen.
The flexible solar cells are rated at 1.8v and are wrapped around the batteries and connected to the positive and negative terminals with some flat wires from a broken camera lens. Once connected the solar cells act like a very weak trickle charger.
There is no other circuitry so Knut plans to make a second version that includes some electronics to check when the cell is full to prevent over charging, as well as add some capacitors to charge the batteries more efficiently. With added circuitry the battery would then need to be smaller if it all needs to fit within the same dimensions as a C-cell battery.
While it seems like one of those ‘so obvious it must be good’ ideas many readers will note that putting batteries in direct sun light for extended periods may not be such a great idea. As the battery cells are cylindrical only a small percentage of the solar cell will be in direct sun light at any one time therefore considerably reducing their efficiency. The flexible solar cells have no output current quoted and as the inventor himself has not tested the prototype, it may in fact be a good idea to hang on to that plug in battery charger just a while longer.
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The milliamp hour rating of the battery - with the fill up rate of the wrap around panel.....
Your going to be waiting a LONG time for a battery to become fully charged.
Though the tester could have simply cut a tab and used a multimeter to test the output of the cells, and then done some tabulation to give an approximate recharge time of a battery laying or standing vertically in a sunny position.....
He didn\'t do that which was slack for a reviewer of electric products....
But the system has SOME merrit...
But methinks, a plain flat panel solar charger - would be a better way to do it - with the height and circumference of the cells wrapped around the battery - about 60 to 70% of the potential harvesting area is lost. to shielding and low incident angularity.
I mean it\'s a nice idea... but a PROPER charger that the batteries can be slotted into with a small solar charger - as a dedicated charging station, is a MUCH more effective and efficient use of resources.