Help me understand controller capacity

[Tracerocks]

I’m confused on this.

I want to use a 450 watt panel that puts out 40 volts and 11 amps.

When I use this on my 24v system will the controller halve the input voltage and double the amperage? Meaning do I need a 22 amp controller?

Or is the input ratings on charge controllers independent from system voltage that it is connected to?

 

[sunshine_eggo]

Controllers are rated in OUTPUT amps.

e.g., a 30A controller can put out about 30A * 28V = 840W

20A * 28V = 560W. 20A will do you fine.

 

[Ampster]

Yes that is the rating. However my understanding is that it is important to not exceed the input voltage of the controller. Also headroom is recommended in the event of a cold clear day where your panels could put out more voltage. Yes, the input spec can be independent of the output. The output in many cases can be user adjusted.

 

[Tracerocks]

Ok. So say I hook up 3 450 watt panels in parallel, voltage stays at 40, amps triple to 36.

When hooked up to my 24 v system am I looking at an 80 amp controller?

 

[sunshine_eggo]

3 * 450W = 1350W

1350W/28V = 48A or 50A controller.

 

[Tracerocks]

Thanks@ sunshine_eggo!

I have my brain wrapped around this now!

 

[upnorthandpersonal]

Always remember: