12V system with 36V system - PWM functioning

[pedro322]

Hi guys,

planning to mount small solar system for my shed. And I have one spare 36V solar panel 460W (Vmp 35.31, Imp 13.03, Voc 41.9, Isc13.8). From understanding how PWM works it will only get 12V-14V from solar panel in which the power is around 160-180W. This is then transferred to the battery, right? And other excess power is wasted. (battery voltage 12.8, lifepo4 min 50Ah, probably 100Ah) And now my question is:

If the PWM regulator is marked for max 100V PV and 30A and the max PV input power for 12V system is less or equal to 360W this is value corresponding to 12V panels (actually around 18-20V) and its marking max input for this voltage panel type and in my case if the solar panel is around 36-42V and PWM is taking only 12V then this panel is as "max 200W for 12V", right?

Thanks!

 

[chrisski]

What model PWM do you have?

The 100 volt max makes me think it is an MPPT which will be close to 0 loss. PWM controllers normally have a 20 ish max input.

 

[pedro322]

What model PWM do you have?

The 100 volt max makes me think it is an MPPT which will be close to 0 loss. PWM controllers normally have a 20 ish max input.

Just simple cheap one Powmr Pstar-30A

I was also thinking about Powmr keeper 1220 but it is offering max 60V and 260W for 12V and not sure how its will be handling overpanelling in this case as the input will be around 36V and 13A and will be converting it to its max (in this case 20A as I would like to limit charging current ao battery is not “loaded” withing one-two hours)

 

[chrisski]

I can’t comment.

I was sure this was an MPPT controller, but it’s a 12,24, 36, 48 volt PWM. That explains the 100 VOC, but normally on a PWM, there’s a separate limit for each voltage, but not this.

 

[pedro322]

I can’t comment.

I was sure this was an MPPT controller, but it’s a 12,24, 36, 48 volt PWM. That explains the 100 VOC, but normally on a PWM, there’s a separate limit for each voltage, but not this.

Fully understand, thanks.

I will be probably switching for something better as I don't want to burn shed down or damage battery.

 

[mikefitz]

switching for something better

The PWM only allows current flow from the panel , thus with a typical charging volts of 13.5 and panel current of 13 amps, that's 175 watts maximum. Long term PWM with a lithium battery is not recomended