Newbie trying to figure how power is pulled from the system batteries only or controller/inverter

[h2ocean]

hello all I will ask the question first and them babble about my thoughts on design.
I can find tons of info on putting PV power into the batteries and inverters but if my batteries are fully charged and the panels are producing does the inverter still take its power from the batteries or does the charge controller pass the excess power to the inverter. I am sure this will probably not be a simple answer and i do not have any equipment yet since i want an answer before i buy the wrong thing.

Now for the babblings, This all started with the batteries, I am a maintenance tech and replaced the batteries in 2 scissor lifts only to have management scrap one of them 2 weeks later. they are rated in Amp hours @ time and the calculation tells me i can pull 15 amps for 20 hours from each of the 6 batteries so they would easily rum my fridge and freezers for a week with no problem. they are wired 36V in the lift and i have the charger for the 36V system so i would like to keep them that way but i would need 48V panels and the used panels I can find are 24 r 36 volt so i will probably end up series/parallel wiring them into 3 12V strings unless i buy 2 more $1000,00 i don't want to spend and have 24V system.

Panel wise i am looking at about 940-1200 watt depending on if i get 260 or 325 panels.

thanks for any knowledge you can offer, my main confusion is am i going to be making extra power that will not be used until the battery levels drop which from the calculations will be days with the small load on the battery bank

 

[DIYrich]

It depends. If you buy a component system, then each component does what it does. The charge controller takes PV and turns it into regulated DC voltage. That current is shared by the battery and inverter. Inverter takes power first. If enough current is left over, it charges the battery. If the battery is full (voltage?) It should then be the signal to convert excess to AC to keep the voltage down. So everything goes over the battery bus.

All-in-one may be a little smarter. It should see that the batteries are full and convert all the PV to AC, and push the excess to the grid.

 

[h2ocean]

so in a component system the charge controller will convert the excess to AC? or will the DC just be be sent to the bus? i will look and see if an all in one is comparable to component pricing but i won't have a grid tie in to send the excess.

 

[Mattb4]

hello all I will ask the question first and them babble about my thoughts on design.
I can find tons of info on putting PV power into the batteries and inverters but if my batteries are fully charged and the panels are producing does the inverter still take its power from the batteries or does the charge controller pass the excess power to the inverter. I am sure this will probably not be a simple answer and i do not have any equipment yet since i want an answer before i buy the wrong thing.

...

The answer is simple. Charge controllers job is to charge the battery. There is no excess power because panels do not produce power without being loaded. How can the panels be loaded to their full potential? Either by having a battery demanding power for charge or other loads taking the power from the SCC and battery that are in parallel. Do not confuse grid tie setups with this that are always presenting a load that is basically infinite for a inverter to want to supply. Pure grid tie systems do not have charge controllers.

There are hybrid controllers for sale that allow both grid tie and also energy storage. These units have two missions. Parallel with grid to take advantage of the loading potential as well as all the extra power from the grid and also use solar to provide battery charging for home backup. Some of them get very complicated in how they ensure that solar panels are always being loaded to their potential.

ETA: It comes down to understanding parallel power sources. Whether AC or DC.

 

[h2ocean]

thank you MattB4 that is the exact answer i was looking for I had assumed (we know what that stands for) that the panels produced all the time........evidently not the case and the solution i was looking for.
thanks so much