I attached a LM2596 board to a 8.4V Li-ion battery pack to feed my 6V circuit. The question is, can I charge the battery with 9V through output of LM2596?
Many Thanks.

 

No.

 

I looked at the LM2596. There is a large diode from OUT to Vin that will cause output current to flow back into the input.
I have not tried it!
Battery, LM2596, load. Normal operating mode. If you lift up on the output to any voltage above 6V the PWM will go to 0 duty cycle. Lifting the load above the battery by 1V will cause current to back flow into the battery. The diode is large and my guess is that it will withstand 3A.
This is not the normal way of doing things. There is not current limit or voltage limit and no overcharge limit!

 

I looked at the LM2596. There is a large diode from OUT to Vin that will cause output current to flow back into the input.
I have not tried it!
Battery, LM2596, load. Normal operating mode. If you lift up on the output to any voltage above 6V the PWM will go to 0 duty cycle. Lifting the load above the battery by 1V will cause current to back flow into the battery. The diode is large and my guess is that it will withstand 3A.
This is not the normal way of doing things. There is not current limit or voltage limit and no overcharge limit!

Ron: He is trying to get 9V by running a boost converter off an 8.4V battery and use the output to charge the battery. In other words, a feee energy device.

 

I'm pretty sure the LM2596 is buck only.

 

If it were synchronous it would transfer power the other way (but it isn't).

 

Ron: He is trying to get 9V by running a boost converter off an 8.4V battery and use the output to charge the battery. In other words, a feee energy device.

I think you are right.
Amazing how many people think you can bootstrap a device to get more energy out then you put in.

 

Ron: He is trying to get 9V by running a boost converter off an 8.4V battery and use the output to charge the battery. In other words, a feee energy device.

Wrong! I have another charging source. In fact, I was trying to mod a 6V device which had its own battery and charger circuit. Since I want to replace the battery with an 8.4 li-ion battery pack, I needed to reduce voltage with LM2596. So I just wondered if I can avoid extra wiring.