Author Topic: Voltage/current limiter for solar panel  (Read 5337 times)

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Offline luckyx182Topic starter

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Voltage/current limiter for solar panel
« on: March 15, 2016, 11:58:28 pm »
Hi, I'm building solar powered weather station and I'm looking for some circuit which would limit the outputting current and voltage. This max. output current and voltage should be adjustable depending on used battery.  I'm going to use 6V 330 mA solar panel, 4 1300 mAh AA NiMh batteries in series and paralel , so I think I need 3,6 - 3,8 volts and 260 mA max. out of the desired circuit. Can anybody help please?

Offline han

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Re: Voltage/current limiter for solar panel
« Reply #1 on: March 16, 2016, 12:26:00 am »
I suggest use typical commercial a viable MPPT module.
you can find lot in aliexpress:


Offline Kleinstein

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Re: Voltage/current limiter for solar panel
« Reply #2 on: March 16, 2016, 04:46:36 pm »
Charging NIMh from solar is tricky: the only reliable way to detect the end of charging / full cells is via the temperature rise and resulting drop in voltage. This only works well when the charging current is constant, which is difficult from variable solar cells also a relatively high charging current (e.g. > 500 mA is preferred to get enough heating).

So I don't see a need to limit the current. The voltage of the solar cells will also not rise very much above 8 V, and drop with load. At this low power an reasonably matching voltage, you might get away without a MPP charger.
So the big question is how to reasonably detect the end of charging - thats really tricky. A charge counting chip might be an idea - so measure the charge and hope to get good conditions to do a charge at high reasonably high current to do charging by temperature form time to time. 

So it would be much easier with a single Li based cell.

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