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Let's say I have a lithium-ion battery like the this one. and let's also say that I have a solar cell like one of the following this or this. i know that charging a lithium io battery is tricky and ideally involves ramping up the voltage at larger amperage followed by a flat voltage and lower amperage If I'm not super concerned with performance, is it possible to simplify the process and trickle charge the battery over a longer period of time? Also, if the voltage output of the solar cell is less than optimal, would that effect the performance of the battery?

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  • \$\begingroup\$ You're going to need to boost the voltage from the solar panel. If you boost it to 5V, you can use the charger that is recommended for the battery. \$\endgroup\$ – Dampmaskin Nov 22 '16 at 15:14
  • \$\begingroup\$ It might be possible to design a charge controller that mates that panel to your battery. But it would be a lot easier to get a much bigger panel with higher voltage and current output, and use an off-the-shelf charge controller. You can't just directly connect the panel to the cell, I don't think. \$\endgroup\$ – mkeith Nov 22 '16 at 15:40
  • \$\begingroup\$ It's best to avoid links that just say "this", because links often go dead. Also because it requires the reader to have to click the link for the sentence to even make sense. \$\endgroup\$ – Bort May 4 '17 at 10:38
  • \$\begingroup\$ As the crucial data regarding the solar cell was in a link that no longer works, this question is pretty much pointless now. \$\endgroup\$ – Finbarr Oct 24 '17 at 11:15
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LT3652 is one of the best solar charge controller chip for small applications. It has inBuilt MPPT and Programmable Charge Rate Up to 2A with input voltage range of 4.95V to 32V (40V Abs Max)

there is a Sparkfun board called Sunny buddy which uses the same chip. Schematics and layouts are available.

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You want to charge a 150 mAh battery using a 20 mA solar cell. A full charge would require more than one day, especially when there are clouds in the sky. But even at a day without clouds, you won't get the 20 mA from sunrise to sunset, when the solar cell is optimal aligned to the sun at noon. In the night the battery should not discharge thru the solar cell, you should insert at least a diode between both.

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    \$\begingroup\$ Do not put a diode in series with this solar panel. The Voc is only 4.4V. Vmpp is 3.8. With a diode it basically will not charge at all. Basically, it is more trouble than it is worth to use this solar cell. \$\endgroup\$ – mkeith Nov 22 '16 at 16:30

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