PWM controller PV input voltage measurement

[squowse]

One of the cheap PWM controllers, 12V battery, 20Voc panel.

Is it normal for the PV input to read the same voltage as the battery?

Fluctuates between 13.9 battery voltage, and 15.3 or something in quick spikes every couple seconds.

 

[littleharbor2]

Totally normal. The fluctuation you are seeing is likely the controller switching on and off to maintain float voltage.

 

[squowse]

Totally normal. The fluctuation you are seeing is likely the controller switching on and off to maintain float voltage.

OK, I’m used to MPPT controllers where the solar input stays higher than the battery side.

 

[squowse]

OK, I’m used to MPPT controllers where the solar input stays higher than the battery side.

The battery side doesn’t fluctuate. Maybe it isolates the two connections every few seconds to check the solar voltage.

 

[littleharbor2]

OK, I’m used to MPPT controllers where the solar input stays higher than the battery side.

Actually any controller will have it's output voltage controlled by the battery voltage.. You'll see the output voltage is just slightly higher than actual battery voltage.

 

[RCinFLA]

PV panels are illuminated level based current sources. PWM SCC's are just 'ON-OFF' connection between PV and battery.

They control battery charge voltage by chopping on and off. When battery needs charging, the switch is almost continuously 'ON' so panel voltage will drop to battery voltage with the PV's illumination generated current going to battery.

You only need a PV panel voltage a few volts greater than battery voltage. You can put a much greater panel voltage on PWM controller but will lose potential PV power when the loaded panel voltage drops to battery voltage. This is where the MPPT controller DC to DC converter benefits the delivered PV power.

MPPT controllers need more panel overhead voltage above battery for DC to DC converter stable operation and the MPPT search process needs a high enough panel voltage above battery voltage to allow the MPPT controller to detect where the MPPT point is by varying load on panel and detecting the peak in output.

Most MPPT controllers will drop to direct ON-OFF PWM mode if they do not detect a definitive peaking as they do their MPPT scan.

 

[squowse]

Actually any controller will have it's output voltage controlled by the battery voltage.. You'll see the output voltage is just slightly higher than actual battery voltage.

Im talking about the solar PV input side, not the output voltage. The output voltage will be the battery voltage.

 

[squowse]

PV panels are illuminated level based current sources. PWM SCC's are just 'ON-OFF' connection between PV and battery.

They control battery charge voltage by chopping on and off. When battery needs charging, the switch is almost continuously 'ON' so panel voltage will drop to battery voltage with the PV's illumination generated current going to battery.

You only need a PV panel voltage a few volts greater than battery voltage. You can put a much greater panel voltage on PWM controller but will lose potential PV power when the loaded panel voltage drops to battery voltage. This is where the MPPT controller DC to DC converter benefits the delivered PV power.

MPPT controllers need more panel overhead voltage above battery for DC to DC converter stable operation and the MPPT search process needs a high enough panel voltage above battery voltage to allow the MPPT controller to detect where the MPPT point is by varying load on panel and detecting the peak in output.

Most MPPT controllers will drop to direct ON-OFF PWM mode if they do not detect a definitive peaking as they do their MPPT scan.

Interesting- thanks