I just bought a float charger from Harbor Freight for my car battery. I hooked up a voltmeter with no other load and the output voltage reading from the float charger was rapidly fluctuating back and forth from 0 volt to 2V and sometime up to 8V but never reached 13+ volt like it was supposed to. However, when I hooked up the float charger with the car battery (load), the output voltage was no longer fluctuating and it slowly and steadily rose from 12.6 volt to 13.7 volt like it was supposed to and 400 mA current was flowing steadily through it.
Is that no-load fluctuating voltage a normal behavior? What is the reason?
Is that no-load fluctuating voltage a normal behavior? What is the reason?
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