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Solar Lithium Ion/Polymer charger - v2
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Solar Lithium Ion/Polymer charger - v2

by czuvich on Fri Apr 26, 2019 3:12 pm

I had a couple of questions about the Solar Lithium Ion/Polymer charger:

1) Is it possible to wire a panel directly into the board (without using the barrel jack connector/adapter)? If so, where and do I need to add a Schottky diode?

czuvich
 
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Re: Solar Lithium Ion/Polymer charger - v2

by adafruit_support_bill on Fri Apr 26, 2019 3:40 pm

You should be able to charge cells using a 5v panel in good solar conditions. You need abou 4.5v minimum for the charge controller to work.
You can connect to the DCIN slder pads next to the USB connector. A protection diode would go on the positive side with the anode end toward the panel. See diode "D1" on the schematic.

Note that there will be a voltage drop across the diode. Schottky diodes have a lower Vf than most. But you can expect about a 0.3v drop.

https://cdn-learn.adafruit.com/assets/a ... 1396904194

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Re: Solar Lithium Ion/Polymer charger - v2

by czuvich on Fri Apr 26, 2019 3:56 pm

Thank you! One more question, can it handle open circuit voltages up to 10V? I have some 5.5V solar panels that can peak on very sunny days at 10V. I noticed the the back of the component say 5V - 6.5V, and I saw some of the solar panels on here at 7.7V peak. Thanks so much!

czuvich
 
Posts: 109
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Re: Solar Lithium Ion/Polymer charger - v2

by adafruit_support_bill on Fri Apr 26, 2019 6:17 pm

The absolute maximum rating for the MCP73871 is 7.0v. Open-circuit voltages from solar panels are often several volts higher than their nominal voltage. But they do tend to drop quickly with even modest loads. We have not seen any issues with the 6v nominal panels we carry in the store.

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Please be positive and constructive with your questions and comments.