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I am planning to make a Solar Powered Battery Power Bank. I made one on a small scale and will scale it up. Anyway, there is a risk of rain short circuiting my DIY power bank.

I thought of sealing my NiMH batteries and other circuits in some water proof container, but for the solar cells and the soldered wires behind it itself, I was thinking of just covering it with some clear plastic. Would this be a good enough water proof solution?

I am planning to connect some mini-solar panels in parallel. Would there be any other solutions.

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    \$\begingroup\$ Measure the short circuit current with/without the plastic in the way. I found a 5-10% reduction depending on which plastic sheet I chose... \$\endgroup\$
    – user16324
    Feb 26, 2017 at 17:37
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    \$\begingroup\$ You can use heatshrink tubing on solder joints or coat with silicone. \$\endgroup\$ Feb 26, 2017 at 18:00
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    \$\begingroup\$ It will work for a little while. Clear plastic sheet in direct sunlight will become brittle and start falling apart within days to at most a few months unless it is specifically engineered for UV resistance (e.g., intended for use in greenhouses). I am afraid that your whole endeavor is not likely to survive long out in the elements. I suggest that you actually build a small greenhouse and put your project inside it. \$\endgroup\$
    – user57037
    Feb 26, 2017 at 18:54
  • \$\begingroup\$ To be more specific, the power bank is going to be mobile and small enough to hold in one hand. \$\endgroup\$ Feb 26, 2017 at 18:57
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    \$\begingroup\$ The bottom line is that clear plastic sheeting does not survive very long outside in full sun unless it is specialized for that purpose. Glass does not degrade due to solar exposure. \$\endgroup\$
    – user57037
    Feb 26, 2017 at 19:39

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It will definitely work, but it's interesting to talk about some consideration.

Depending of the technology of your panel, the spectral response may vary. It is likely that you are using a c-Si panel (this is the most common where you can see cells).

c-Si panel will convert most of the energy on the infra-red band of the spectrum from about 400 to 1'100nm that you mostly cannot see with your eyes.

A plastic that is transparent for you may not be transparent on this spectral band but you can very simply test that by putting the sheet in front of your panel and measuring any drop in the short circuit current (you won't see any significant difference in the open voltage).

Another point raised in the comments is the UV instability of polymer and you may want to have a plastic which is UV rated so it won't break appart after a few months.

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