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Solar Web Page > Categories > General Discussion and Chat Page > Solar system diagram.
 
 


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Rick H Parker

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Posted Reply with quote  #11 
Just one thing confuses me and that is watts in series.

Perhaps this will help you.

Power is a rate (quantity / time) not a quantity that one can count.  Power is the rate in which energy is transferred or converted to a different form of energy. 
Watts is the unit of measurement for electrical power. Trying to add "watts" in series is like is like trying to add the velocity of two people riding a tandem bike.

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Rick H Parker
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Electronics Engineering Technologist

Aussiemike

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Posted Reply with quote  #12 
Thanks Willie will make sure wires are correctly sized.
stmbtwle

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Posted Reply with quote  #13 
Watts are a unit of power, right? So with two people riding a tandem bike you get twice the power (assuming they're both pedaling). And if you gear it right, it WILL go faster.

If you have two 100w panels, that's 200w... series OR parallel.

Otherwise why spend money for the second panel?
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Willie, Tampa Bay
Aussiemike

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Posted Reply with quote  #14 
Very good analogy.
Aussiemike

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Posted Reply with quote  #15 
In my schematic on post #8 the 4 x 12v panels will have an open voltage of maybe 60v.
Does the following data on the back of my MPPT controller forbid me from using such controller?

40A specifications:
Size: Approx. 24.9x17.9x15.6cm/ 9.80x7.05x6.14"
Nominal system voltage: 12/24V auto work
Rated charge current: 40A
Rated discharge current: 40A
Battery input voltage range: 8V~32V
Max. PV input power: 520W(12V); 1040W(24V)
Self-consumption: ≤20mA (12V); ≤16mA (24V)
Discharge circuit voltage drop: ≤0.18V
Temperature compensation coefficient: -3mV/

TIA
Mike
stmbtwle

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Posted Reply with quote  #16 
Assuming you mean the line highlighted in red. That is the BATTERY voltage, so you're good.

The data shown doesn't show the maximum allowable PV voltage. Can you download the manual? If there is any question you can reconfigure your solar array to 24v instead of 48v. The amps however will double to 30+A, and you'll have to size your wiring and fuse accordingly.

That would be 2 sets of 2 panels, same as the batteries.

Are you going to be using a separate inverter? While it doesn't affect the charging side, it may require heavier wiring (and fuse) between the batteries and inverter.
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Willie, Tampa Bay
Aussiemike

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Posted Reply with quote  #17 
Thanks again Willie.
I have downloaded the specs from their site and think I know the answer but will run it by you first before I make changes.

epever.jpg 



Aussiemike

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Posted Reply with quote  #18 

Max PV input power has no mention of 48v

but

Max. PV open circuit voltage states

100V(at minimum operating environment temperature) 92V(at 25℃ environment temperature)

Is that safe to assume it's ok?
stmbtwle

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Posted Reply with quote  #19 
Yes you're good. The allowable power for charge controllers is determined by the output amps to the "system" (as determined by the batteries). so you could put more power into a 24v system than 12v. When they mention "12v-24v" they mean SYSTEM voltage, and you have a 24v system.

Note the "MPPT voltage range". This is the ideal input voltage. It needs 2v more than the batteries, up to 72v. It will still work up to 100v but probably in a "safe" mode. Above 100v it may get "expensive".

At 48-60v you're right where you want to be.


I see that the recommended wire size is given too. You can use larger wire but not smaller.
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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
Aussiemike

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Posted Reply with quote  #20 

 

That 6 AWG is for PV to controller and to battery?
What distance would I be safe to use that size wire?
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