Solar panels and battery selection using the Solar Charger Shield V2.2

Hardware
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Hi everybody,

first of all I would like to apologize for the, probably very basic and stupid questions for you, but I'm not an electronic expert..

I'm implementing my project using an Arduino Mega 2560 (I need more pins.. this is the most important reason that it drives the Arduino choice)
I'll put my project in an external environment without the electricity source. For this reason my idea is to use a battery with a solar panel as power input to charge the battery.
I also applied some low-power techniques in order to reduce energy consumption as much as possible.
Regarding the solar panel and battery connections I purchased this Arduino Solar Shield.

And here I'm a bit (a lot) confused about the choice of the battery and the solar panel(s) to be purchased.
First of all, my idea is to use multiple (2 or 4) solar panels in order to exploit as much as possible the solar light (multiple positions) but I'm not able (I'm not sure) about the solar panel selection to purchase.
Considering that the maximum current that the solar shield could be delivered is 700mA can I use 4 solar panels like this

(applying also 4 applying 4 diodes to avoid reverse current)?

About this the possible number or size of the solar panels Do I need to consider the amount of th Current at Peak Power?
For example, using 4 solar panels with 170mA as Current at Peak Power, 4*170 = 680 that it's > of the current of the solar shield.
So, is this wrong? Do I reduce the amount of the panels or do I use a different panel?

About the Solar input voltage it's 4.8~6V.
These are the specifications about the solar panel:

  • Dimensions: 100x80x2.5(±0.2) mm
  • Typical voltage: 5.5V
  • Typical current: 170mA
  • Open-circuit voltage: 8.2 V
  • Maximum load voltage: 6.4V
    Maximum load voltage, Open-circuit voltage are > Solar input voltage. Is it a risk?

About the lipo battery, can I use a battery 3.7v and about the mAh value as high as possible (for example this https://www.amazon.it/2100mAh-Lithium-Polymer-Replacement-Bluetooth/dp/B095BTSMYH/?th=1 ?)
What about the maximum current value (in this case 5A)? Is it ok?
In case, can you suggest me something else?

2

LiPo's freeze and break at 32F and fail when temps get too high.

Best battery choices for solar are either Lead Acid or LiFePo4. I pick LiFePo4's.

Solar panels, a 10W or 20W 12V loaded >=13.8 unloaded solar panel.

A MPPT solar charger is a better choice.

Between the solar cell and the MPTT charger should be a diode to prevent the solar panel, at night, from becoming a load on the battery. The prevention of nighttime solar panel discharge extends the life of the solar panel.

Diode example,

Those controllers do not have a battery draining display and can run various types of batteries.

3

You have a lot of ways to expand your I/O. HCMOS logic such as the 74HC595 (output) or the 74HC165 (input) are low power and inexpensive. There are also I2C port expanders such as the PCF9555, my favorite but it has a register the PCF8574 and PCF75 do not. These are 8 and 16 I/O devices that can generate an interrupt for you. For normal operation they connect to the I2C bus which will control many of these devices.

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