I'm trying to make a voltage Indicator light for 2, 7.2 lithium batterys. Each battery set is 7.2 volts and 1700 MHa each battery. Id like to use a dual Bi-Color LED 5mm that would light up green when the battery is between 8.2 to 7.7. Then orange between 7.6 to 7.2 then red from 7.2 to 6.6. I had read on the Internet were it said to use a LM358 op-amp I'm not sure if I can use it. Any suggestions would be great fully appreciated.

 

use LM393 instead of LM358. Google for "window comparator" and see how it work...

Allen

 

You will need a voltage reference, too. I recommend the TL431

 

This can be modified for the voltage range you need.
http://www.reuk.co.uk/12-Volt-Battery-Monitor-Circuit-with-LM3914.htm

 

As jjw posted, these were available from Online stores some time back for about 7 Dollars.

Something like this.

 

As jjw posted, these were available from Online stores some time back for about 7 Dollars.

View attachment 90187 Something like this.

I wanted to thank you all for such a quick respond. I"m going to try the options you have all gave me I "ll let you know with one i used.