and what should be the value for R2 1R5 ?

 

No. The minimum sense voltage for the TL431 is 2.5 volts.

 

No. The minimum sense voltage for the TL431 is 2.5 volts.

Thank you for advice.
May i ask about how is the minimum sense voltage should have to charge the 1.5V Ni-mh ? and have any recommended component for me ?

 

An operational amplifier would work with a sense voltage less than 1.5 volts.

 

a simple circuit here for nicd or nimh

http://alectronicx.blogspot.co.uk/2010_08_01_archive.html

 

An operational amplifier would work with a sense voltage less than 1.5 volts.

Erm..how can i connect with the op amp ? if i use LM324N

 

Erm..how can i connect with the op amp ? if i use LM324N

I can not seem to make myself redesign this circuit for you. It is the wrong circuit in the first place. It does not have the features necessary to protect NiMH batteries.

 

If you want the cell to be protected against over voltage and over current, I could change a couple of resistor values to make the below SLA charger useable for NiMH-cells.

Get the full page at:
http://www.sentex.ca/~mec1995/circ/SLAC.htm

 

Thanks, It seem good,but my project need have 2 color LED monitoring the battery. Do you have any other suggestion ?

If you want the cell to be protected against over voltage and over current, I could change a couple of resistor values to make the below SLA charger useable for NiMH-cells.

Get the full page at:
http://www.sentex.ca/~mec1995/circ/SLAC.htm

 

How u all think about this circuit can function well ?

 

Your project?

Is this a school project of some kind?

The text in your Post #10 reads like gibberish. It's probably just an English as Second Language issue, but you are going to need to really work at making that text more readable before we can do much.

 

Your project?

Is this a school project of some kind?

The text in your Post #10 reads like gibberish. It's probably just an English as Second Language issue, but you are going to need to really work at making that text more readable before we can do much.

Actually it is one of my school homework.
I need to design an solar panel battery charger circuit. It is with the function of LED monitoring in state charging or full.

 

Actually it is one of my school homework.
I need to design an solar panel battery charger circuit. It is with the function of LED monitoring in state charging or full.

The post #10 sure makes me think of a famous quote from Pulp Fiction

Well, it being homework changes the game a bit, as you are the one supposed to make it!
So, I'll stick to give you some pointers.

Another game changer is that it is supplied from a solar panel, as this means that you have to avoid losses as much as possible.

The circuit in #10 is an odd X-mas tree of inferior design, better start from the bottom and make a block diagram of what you think it must contain. Then post that here for review.

You might wanna take a look at the datasheets for LM393 (dual comparator) and LM339 (quad comparator), as they may be quite helpfull in solving the task.

If it's within the boundaries of your assignment,, you might consider a fairly simple so-called flash-charger, which has a single LED on when charging and when it reaches full, it will pause until the terminal voltage of the cell has dropped a little and then charge to the limit again etc. - the flashes will become shorter, as the cell is topped up after the initial charge.