Vinod: I am attaching the circuit image of
the charger with hysteresis feature. (with my modification.). This
charger is working good. But i need your suggestions and confirmation.
Swagatam: Using a transistor won't give accurate results, moreover the setting part
would become very tedious. The circuit is technically correct, if you can
adjust the tripping point correctly, then it might just work.
Vinod: I am going to test this circuit. I already build this in general
board. automatic cut-off is set in 13.6v now. All i want to wait for
the battery to discharge around 12v. I will inform you the result.
Vinod: I made the charger (hysteresis) but there is a problem. i will attach
the image to explain the problem. When i connect multimeter in that
particular red dots, the voltage shows 16.8.(0.43 A) but when i
disconnect battery from the charger and measured again. then there is
no problem. the out put is 14.2. And the other pin of the
relay(through the current limiting resistor) will deliver a clean
output voltage of 13.9 (0.033A). Why this is happening ?. The only
change i have made from this circuit is to grab the green LED and R1
from there and connect it after the D6.
Swagatam: It's difficult to understand and troubleshoot the fault, if you are connecting meter prods across the battery terminals, it should show the dropped voltage level of the battery ... this problem can happen only if the source current is too high and not at the recommended 1/10th level of the battery AH, make sure to use an input that is specified with the above current limit
You can repeat the checking by switching OFF the power supply and then again switching ON the power supply keeping the meter connected to the points A and B.
At last i made a charger that suits my needs. this is the
schematic.(plz look attachment). Until battery gets 13v this is a
constant current charger(400-500mA). After 13v, charging current is
25mA. And the LED's indicate the charging stages.