I connect a 5v 5w solar panel a usb port and a 3.7v 2.5A lipo with pcb.
 If I connect a phone to usb port it doesn't charge, but if I remove the battery from the circuit, it does.
I suppose it's because battery pcb downgrade the voltage to 4.2v or there is not enough energy to serve both.
There is a simple way to prioritize the usb or make them share?
Thanks in advance for your help

PS
Sorry to eventual mistakes but I'm still learning electronics.
I did not blow anything yet, thanks also to t

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Summary of requirement:

Given:

* 5V 5 Watt PV panel
* Cellphone with "USB" "5V" charger input.
* Single cell LiPo 3.7V nominal 2500 mAh.

Requirement: 

* Use PV to charge phone if connected.
* Otherwise charge battery.
* If possible share PV energy between phone and battery if both present.

Problem:

Connecting the panel to the LiPo loads it to battery voltage which is too low a V to operate the phone charging circuit.