Just wonder whats the max voltage for a pulse charger? here is a circuit that tested a ~17V when input a 12V, is it normal? can it damage the battery? or can I go a larger inductance?

 

...here is a circuit that tested a ~17V when input a 12V...

Do you mean that you saw 17V at the battery poles, without the battery in the circuit? That wouldn't surprise me. What matters to the battery is the average current.

 

Do you mean that you saw 17V at the battery poles, without the battery in the circuit? That wouldn't surprise me. What matters to the battery is the average current.

Thank you.
yes, I didn't put a battery yet, just measured the voltage by an oscilloscope.
This circuit said be able to desulfates, my battery sit there for few years, I just want to reuse it.

 

That’s fine. That’s the new impulse chargers that are suppose to desulfate the lead plates. You can’t check voltage without the load. It’s probably checking for load voltage between the charge pulses.

I tried one this year for my motorcycle and it seems to be working. Usually have to get a new battery every 2 years. But it’s now past that mark.

 

Just wonder whats the max voltage for a pulse charger? here is a circuit that tested a ~17V when input a 12V, is it normal? can it damage the battery? or can I go a larger inductance?

View attachment 176816

The Yuasa Little Red Book of Batteries suggests remedial pulse charging at about 29.5V.

Basic old style chargers with iron cored transformers are usually "impedance wound" - that basically means they have lousy regulation. The off load voltage will be higher than you expect. A mildly sulphated battery takes a little more than the "usual" charge voltage range to get things moving. A transformer with lousy regulation, at least has a go at being a current source - this avoids the charging current rising to the point where it causes the plates to buckle as the acid comes out of the plates and thickens the electrolyte.

A healthy battery should load the charger down somewhere near about 11V as it picks up and then start climbing to about 14.4v as charging progresses.