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Mylar to increase efficiency of solar battery charger?

by syntotic
Tags: battery charger, bopet, mylar, solar cell
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syntotic
#1
Sep15-13, 04:53 AM
P: 7
I just got my hands on a solar battery charger with a set of usage specifications that makes me believe it will only be useful some four days a month and will take more or less such time to charge a single set of batteries, despite promises on the contrary in the instructions. Since the case is flimsy and needs some protection, I conceived the idea of adding some parasol made of mylar. Mylar is reflective and heat conserving, intuitively it seems it will help the charger, even under low Sun conditions, to charge batteries faster. Can anyone comment?

I suspect on the other hand that such parasol would be pointless if the charger itself has some inbuilt limit, so for instance it might help in cloudy days but be futile on sunny days because of different properties of mylar.

Furthermore, since mylar is heat reflective, case protection with added mylar may modify the device s heat properties to affect its capacities, irregardless of the parasol, (this would be true also of other protections, though mylar can be easily used in layers for additional flexibility). I hope it will diminish the danger of leaving-the-device-inside-a-car-warning, at least, though such concern seems to be specific to the charger I have and more likely than not will not test it. I can, of course, incorporate some design into the mylar parasol, like chosen angles, size and substrate, to better adequate it to the solar cell design, if it can help the charging efficiency issue.

I am also considering adding a stepper motor governed by photoresistors to orient the charger as need be, in which case the parasol can become even more complex. Mylar is a good solution, though the same problem applies to using mirrors, on principle.

It is important to answer these questions speaking generally, attending to properties of solar cells and battery charging and mylar, since there are other chargers in the market with different capcity specifications that would similarly benefit (or be harmed), by the mylar protection/parasol add-ons.

Danilo J Bonsignore
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mfb
#2
Sep15-13, 09:07 AM
Mentor
P: 12,053
Where do you want to add the mylar and how do you expect positive effects from that?

Mirrors to increase the radiation falling on the solar cells will certainly speed up charging if the sun shines, but then you can get thermal issues. On a cloudy day, mirrors don't help.
I don't see why the battery charger could be colder than the environment - and if that is not the case, thermal insulation won't reduce its temperature. Reflecting parts of incoming sunlight that do not hit solar cells might be useful if the sun shines, but I would expect the device to be designed to handle that.


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