So it's a buck converter hooked up to two TP4056 Lithium battery chargers, hooked up to two 18650 batteries in series.
I drew a picture of the circuit. The diode(s) has a 0.5v drop.



I want the other part of the circuit (the part not shown) to be able to use 8.4v. Does anyone know if this circuit works, as far as not buying the parts, and hooking the parts up..

The batteries from top to bottom.
TOP : LEFT-NEGATIVE, RIGHT-POSITIVE.
BOTTOM : LEFT-POSITIVE, RIGHT-NEGATIVE.

Or maybe this one..?

 

Neither will work, the Diode is shorting out the battery....

What do you want to achieve?

 

Neither will work, the Diode is shorting out the battery....

What do you want to achieve?

Charge each battery individually, and then output 8.4 to the load.

 

According to this guy (Must LITHIUM BATTERIES be BALANCE CHARGED ? #15).
He talks about 18650 batteries. So idk.. Still learning.

Also, here's a video he did on charging (How to Charge Lithium Batteries).

He knows A LOT about 18650 batteries. He's been doing this for 2+ years, no problems. He has a van powered by 18650 batteries.

 

then you will need a battery management pcb like this, and charging it with a 9-12 v supply..

http://m.ebay.co.uk/itm/2S-5A-PCB-P...%3A9efff54f15a0a9c558dff7fffff1cb0f%7Ciid%3A2