25V To 12V Car Battery Charger.

Thread Starter

Kaiser Ed Bayawa

Joined Mar 19, 2015
64
Yes, I know. 11 - 12 VAC RMS has a peak voltage of ~ 15.5 - 16.9 volts.

So once you factor in rectifier forward voltage drops and the unavoidable line losses plus the very narrow duty cycle that the peak of the sine wave is above the voltage required to pass current through the system and 11 - 12 volts AC gives you a nice solid 14 - 15 volt DC average as needed for bulk charging a common LA battery without excessive overcharging. ;)

I've been repairing and rebuilding battery charges since I was a kid. Believe me I know my as applied to reality numbers for basic battery charging circuitry by now. :rolleyes:
Sir I unwind some turns until I get 12v but I notice a buzzing noise from the transformer.
Is it still ok sir?
 

tcmtech

Joined Nov 4, 2013
2,867
I don't know. There are a number of reasons that it could buzz.

Did you take the iron core part to get at the windings? If so that could be loose.

If you simply pulled the wire off the windings through the core the windings could be loose now.

Loose windings are easily fixed with a can of clear coat spray paint.
 
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