Rather strange voltages during ac charging

[fivewin]

A friend bought this and during charging a 7Ah vrla he measure with mm the battery status, 3.9 volt. He unplugged and without charging the battery shows 12.6v.

Then he measured the output of the charger without connecting to to the battery, different voltages
Can someone explains how a smartcharger works. Or is this one broken.

[fivewin]

Here is the charger

[Mike90250]

most chargers need to sense battery voltage before they will completely turn on

[Sunking]

A friend bought this and during charging a 7Ah vrla he measure with mm the battery status, 3.9 volt. He unplugged and without charging the battery shows 12.6v.

Are you sure the charger was connected because that is not likely possible. If the battery is in decent health with a resting voltage of 12.6 volts (12.6 indicates good health), then pulled down to 3.9 volts with the charger connected reversed polarity would have generated a lot of smoke and fire.

Then he measured the output of the charger without connecting to to the battery, different voltages Can someone explains how a smartcharger works. Or is this one broken.

Doesn't mean anything.

Connect the battery first, then plug the charger in.

[fivewin]

Mike, your are right. Its a newly bought charger and you have to wait few seconds after connecting to the battery b4 plug in to an ac socket.

Thanks, he = happy now