Modified Battery Charger Circuit Problem Discussed

The included circuit was designed and built by Mr.Vinod Chandran, however there's some issue with the circuit which has been addressed in this article. Let's learn the discussion between Vinod and me.

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 the fault, if you are the 
connecting meter prods across the battery terminals, it should show the 
average voltage of the battery and the supply voltage...not sure why 
it's showing a higher voltage. Is your meter OK?

 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.

Hi Swagat,
Atlast 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.
Regards
Vinod chandran

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