Yes, you can connect two or more LiFePO4 batteries in parallel to increase capacity while maintaining the same voltage.
[PDF Version]
Connecting PV panels in series increases the voltage but amps remain the same, but in parallel connection, current and power output increase.
[PDF Version]
The short answer is, yes, you can mix solar panels that have different wattages. Different wattage panels have different voltage and amps.
[PDF Version]
How to connect solar panels together in parallel: Join the positive (+) cables of all the panels into a single one, then do the same with all the negative (-) cables. For this, you will need branch connectors or a combiner box.
[PDF Version]
