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Environment

Solar wrapped batteries charge themselves

February 26, 2009
Solar wrapped batteries charge themselves
The solar rechargeable battery
The solar rechargeable battery
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The solar rechargeable battery
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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.

Paul Evans

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8 comments
Abandonvehicle
Now this could inspire more devices being made with transparent battery covers.
jcfdillon
if solar thin film photovoltaic collector will be blocked from incoming sunlight, you could put the battery or batteries on top of a mirror surface so that the batteries will take advantage of the solar thin film better. otherwise, the batteries can be manufactured with smaller thin film area on them, such as only half of the battery that will be exposed to sunlight. you mentioned the problem of the batteries getting too hot in sunlight; a small portion of the electricity can be used to power a small fan to increase cooling rate for a large array of these batteries; the heat produced in this way could be used to heat the hot water for a household, while the batteries can be the battery to provide solar elecricity at night. so you would have a combined photovoltaic electric collector with battery array and solar hot air, which can be applied to direct air heating and/or preheating the hot water supply partially to reduce other fuel consumption.
Polly Aylor
Since putting batteries in direct sunlight is generally a bad idea, why not coat a battery-operated device with cheap solar cells and let the device charge it's own batteries.
Dr.A.Jagadeesh
Good Concept. But it needs much more refinement for practical applications.
Dr.A.Jagadeesh Nellore(AP),India
Ronny Detroit
Polly Anne is right-on: Flat panel on the device case and let each device charge its own batteries.
Mr Stiffy
Hmmmm NICE idea.. but the words \"WEAK trickle charger\" is not wrong.
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.
kellory
A mirror will double the output of a solar cell, but the shaded side will produce no power. A simple solution would be to stand the batteries upright, and place a pair of mirrors to the backsides of the solar panels much like fun house mirrors, reflecting light to all sides at once. tucking the batteries into an alcove made from three mirrors coming together at right angles (1 under, and two to the sides) would greatly increase it's charge rate, as long as it does not get too hot. It would not require close tracking for best angle, and would cost next to nothing to produce, could even be made to fold down flat when not needed.
Paul Russell
I don't think anyone is ever gonna beat a solar panel connected to a car battery. And unlike these ones, it can be charged while in use, just put an inverter on the battery and you could power anything, from charging your MP3 player or Cell phone, to your CD player, or even larger stuff like laptop or televisions, assuming you've got the power