Electronic – Need to limit current to maximum 1.6A

To get the I/V-Curve of the solar panel (and therefore the Maximum Power Point), I would suggest you use a circuit with feedback to change the current sourced from the solar panel. This is possible with a variable current source like this:

^{simulate this circuit – Schematic created using CircuitLab}

Vref determines the current sinked from the solar panel. The current is calculated as follows:

\$I=\frac{V_{ref}}{R_2}\$

Therefore, from the knowledge of the Vref and the measurement of the solar panel voltage, you can easily determine the maximum power of your panels

For reference: The circuit is from "A collection of Amp Application by James Wong (Analog Devices): http://www.analog.com/media/en/technical-documentation/application-notes/28080533AN106.pdf

I will answer but I want to point out that your panel can only supply 7.15W according to the information in your question. In order to charge a single LiPo cell at 2A, the maximum output power would be 2A * 4.2V = 8.4W. It is physically impossible for output power to be higher than input power. But it is still a good idea to increase the charge rate to 2A. This will allow the charger to extract as much power as it can from the panel.

Here is a link to the datasheet for the part: http://cds.linear.com/docs/en/datasheet/3652fe.pdf

Here is what you should do:

1) Change R1 to 50 mOhms. This sets the charge current.

2) Change D1 to MBRS340 (available from several vendors). The diode in the Sunny Buddy may get over-loaded if you go to 2A charge.

3) Change L1 to 10uH capable of 2.5 to 3A. E.g., Bourns p/n SDE0805A-100M. It is tricky to calculate ripple current for a solar panel, because Vin max does not occur during Iout max. But 10 uH should give you low ripple current.

I did not study the whole design. I am assuming other things are set up in a reasonable fashion (such as the charge timeout and float voltage). I definitely recommend you review the datasheet, and, if Linear has a reference design for this part, review the reference design schematic and any notes or datasheet available for it.

Good luck!