I am planning to use this small solar panels to charge a 18650 cell with this charger module and power a low power project with it.

I've never worked with solar cells, although I have read a lot from them. I understand the need for diodes on them to prevent a battery discharge, but I'm having a little problem.

As far as I know, any diode has a voltage drop. Let's say 0.6V on average in my experience.

If I connect those 5V panels in parallel with the charger, would I run in under voltage problems? In the description is stated that input voltage should be 5V.

But then series panels would be more or less 9V and we are clearly on the over voltage side.

Are diodes necessary in this application? Would the charger prevent the battery discharge? I'm kind of confused arranging this power setup and would appreciate any help.


1 Answer 1


If you incorporate a cheap, off-the-shelf charging module between the solar cells and the battery you will solve all the problems, over charging and back flow through the solar cell. A typical one is here Many other similar modules are available on eBay and Banggood. Again other suppliers are available.

  • \$\begingroup\$ Tp4056 was the first hit when looking for lithium chargers. I was more appealed for my link because of the out+- terminals but I can't determine what are the differences between the modules. Apparently both are based on tp4056, but I see 2 ic more on my link than yours. Do you know what is the deal? \$\endgroup\$
    – David P.
    Commented Aug 29, 2019 at 12:26
  • \$\begingroup\$ Answers that are mainly just links to other sites do not have lasting value, particularly if they just recommend commercial products. You should discuss why a charging module should be used and describe the important characteristics. \$\endgroup\$ Commented Aug 29, 2019 at 13:13

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