Drok power supply as a charger suddenly responding differently.

[RichNorman]

I am using a 20amp adjustable voltage power supply from DROK as a charger and it's' worked great up to today when something changed. It does not have the adjustable current knob.

Behavior before: The voltage with no load would be set at 14.4v to 14.6v and then when you hooked it up, the voltage would drop to 13.something on the screen and gradually increase as the SOC increased ultimately ending with the display showing the non-load setting of 14.4v and charging would stop.

Behavior today: Same settings, but now the displayed voltage of 14.6v does not drop when hooking it to a battery in need of charge. It remains at 14.6v and multi-meter measurement shows it is putting out that voltage. It seems to go through the same cycle of heating up and running the fan as needed and the battery seems to charge just fine.

Any thoughts on what may have broken perhaps with the power supply? Why is it suddenly not varying voltage under load?

 

[fafrd]

I am using a 20amp adjustable voltage power supply from DROK as a charger and it's' worked great up to today when something changed. It does not have the adjustable current knob.

Behavior before: The voltage with no load would be set at 14.4v to 14.6v and then when you hooked it up, the voltage would drop to 13.something on the screen and gradually increase as the SOC increased ultimately ending with the display showing the non-load setting of 14.4v and charging would stop.

Behavior today: Same settings, but now the displayed voltage of 14.6v does not drop when hooking it to a battery in need of charge. It remains at 14.6v and multi-meter measurement shows it is putting out that voltage. It seems to go through the same cycle of heating up and running the fan as needed and the battery seems to charge just fine.

Any thoughts on what may have broken perhaps with the power supply? Why is it suddenly not varying voltage under load?

Have you measured the voltage of your battery?

Charging a ‘mostly-full’ battery with a voltage over 13.5V or 14V is going to translate to a different charge voltage than charging a ‘mostly-empty’ battery with a voltage under 13V or 13.5V…

 

[Bud Martin]

It sounds like the batteries may be full. Do you have clamp-on DC Amp-meter to check the charging current?

 

[fafrd]

It sounds like the batteries may be full. Do you have clamp-on DC Amp-meter to check the charging current?

Just disconnecting he battery from the charger (or turning off the charger) and measuring battery voltage with a multimeter will accomplish close-enough to the same thing…

Another question for the OP: how much are you discharging between daily charge sessions and do you have any way to quantify / estimate that discharge in terms of SOC % (or Ahs)?

 

[RichNorman]

I was charging the battery after extended use over the weekend and the standing voltage was dithering between 12.9 and 13v. I am aware a fully charged battery wouldn't pull the displayed voltage down on the charger.

 

[fafrd]

I was charging the battery after extended use over the weekend and the standing voltage was dithering between 12.9 and 13v. I am aware a fully charged battery wouldn't pull the displayed voltage down on the charger.

Do you own a multimeter?

 

[RCinFLA]

If it voltage regulates the current limiting circuit feeds into it and there is only a few parts for current limiting, There is a 4 milliohm shunt feeding an LM321 op amp. Output of op amp goes through schottky diode to voltage feedback point.

Check if pin 3 of op amp which is also center wiper of CC pot varies as you adjust CC pot. My first guess would be bad CC potentiometer.
Also check the 5v 78L05 regulator that supplies the op amp. I have seen the regulator blow out if too high input voltage is put on buck DC-DC input.

 

[RichNorman]

Do you own a multimeter?

Yes. That is how I measured the the voltage I listed in the response you quoted.

 

[RichNorman]

If it voltage regulates the current limiting circuit feeds into it and there is only a few parts for current limiting, There is a 4 milliohm shunt feeding an LM321 op amp. Output of op amp goes through schottky diode to voltage feedback point.

Check if pin 3 of op amp which is also center wiper of CC pot varies as you adjust CC pot. My first guess would be bad CC potentiometer.
Also check the 5v 78L05 regulator that supplies the op amp. I have seen the regulator blow out if too high input voltage is put on buck DC-DC input.

Thank you so much for the suggestion. I was not real clear which unit I am using. My apologies.

The DROK unit I am using is an AC to DC unit the same or similar to this unit. https://www.droking.com/ac-power-su...-to-DC-0-24V-20A-Adjustable-Voltage-Regulator

The schematics gave me something to use to poke around with. It's interesting that the DROK unit comes with an extra pontentiometer. I will swap them and see what happens. Thank you again.

 

[RCinFLA]

I have one of those also. Ten turn pots are really poor quality on those also. I had to replace one of them on mines.