This circuit will indicate the battery charge level, thus giving us idea when are we going to charge or replace it with a new one. Initially when a 12V (marked) lead acid battery is fully charged, the voltage is around 12.7V (100% charge).When the battery is left uncharged for period of time, it starts to loss its charge and there come a time when the battery voltage drops to 10.5 (0% charge).See table below for voltage vs battery charge.
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjIVIkCrTm4f4tfkWOmyhLZ0jLJna-4qo8TV_RKAu3QxcIg4q_I7Bvajia0xZzTewt7zp_Yall1Qmi2f2GP3XCQJm6_wsbHHnMo2GugXHIeH4BB3acGwsc8RXfpLRFJmYvHKCUgbsPsv0xu/s320/12V+battery+voltage++vs+charge.jpg) |
battery voltage vs charge |
Operation summary:
When battery voltage is above 12.2V (70%-100%), all LED is on. When voltage is between 11.7V to 12.2V (30%-60%), only LED2 is on. When voltage drops below 11.7V, all LEDs are off.
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg3wuIY0nvDsx0VYi_8R5njUYdNMj_HrK2GDmYvrhX6lGRygMkvwaqxGgFXAqP7bdBw8moqZQJOCjuN1SnBRHxdo_XbMFHbV6ZT201__6J4Nr6EafrPleHJ0QXtTIpE5Xp4-lr6qNk9HTPl/s400/battery+discharge+monitor.jpg) |
indicator schematic |
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhhd48BUjiJ3GyF1aBu1fnQsc7MDFUUw-BrhQJoQuCdK6epufmoYU3H6dK0E5c56QqsusBy6H9hy4QgL88ybJOvHbz5-YXtQmIxBJD7Bu10V0xA3cJ2QUtXBHsW_udSzhEIetCqhaUdNS_t/s320/LM+393+internal+connection+and+pins.jpg) |
LM393 pins and internal connections |
Part List:
LM393 comparator
R1 -120 ohms
R2 -560 ohms
R3 -560 ohms
R4 -12 kilo-ohms
R5 -4 kilo-ohms
R6 -2.7 kilo-ohms
R7 -2 kilo-ohms
R8 -2 kilo-ohms
D1 -5.1V zener diode
LED1,LED2 -red, orange, yellow and either LEDs
How can do with 6 volt- need help !
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