Charge indicator LED
As described, you could place a resistor from CHG to either battery+ or to Vin and an LED from CHG to ground. Resistor value depends on desired LED current. 

When CHG is low LED is off.
 When CHG goes O/C CHG is pulled high by R and LED is driven.

If you use say Vin = 16 V and want say 2 mA I_LED the R ~~= ( Vin - V_LED)/I_LED
~= (16-2) / .002 =~~ 6k8.



The LTM8062 comes in an LGA package which is liable not to be overly home-constructor friendly.  

It costs about $17 in 1's which is high if only basic functionality is going to be used. 

However, it will work with a range of battery chemistries and it has MPPT capability. If you need the fancier features it's a bargain. 

LTM8062 data sheet here.  

15 x 9mm LGA package.