SuperDutyFWC said:
Really interesting questions. When talking to the manufacturer of the panel, the technician stated, and I'm paraphrasing, that the voltage of the panel doesn't matter. It charges at a certain amp/hr and the voltage you see 12v vs 24v is irrelevant to the charging. It's really more about the output of the batteries. He stated you can charge 12v batteries in parallel or series, in a 12V or 24V system with any panel. The 12V vs 24V is really talking about the system, the electrical needs coming from the appliances. Do you have a 12V or 24V system of appliances puling electricity from your batteries, regardless of input. Meaning, you can use two 12V to achieve 24V for your 24V system and use the same solar panel as you would with two 12V batteries in a 12V system.
Basically he said they are marketed as 12V or 24V panels not because of the power they generate, but based on how people typically use them, for their power needs in a 12V or 24V system.
That being said, the 100W panel specs show, max system voltage 1000V, 100W, 18V, 5.56 amps. The 300W panel shows max system voltage 1000V, 300W, 32.48V, 9.91 amps.
Edited to add: even the charge controllers don't seem to "care" about the voltage, whether 12V or 24V. The Zamp 30A controller, as an example allows either.
Hmmm... I have questions about this info... much of it does not agree with what I know.
1) "the voltage of the panel doesn't matter. It charges at a certain amp/hr and the voltage you see 12v vs 24v is irrelevant to the charging. It's really more about the output of the batteries."
Well, yes and no. How the panel generates power is largely irrelevant to the battery voltage. It is generally more efficient in a large home/commercial system to run higher voltages as it reduces power losses. Just like the power lines coming from hydro/gas power plants run at very high voltages.
And yes, the output to the batteries needs to be what the batteries want to consume.
2) He stated you can charge 12v batteries in parallel or series, in a 12V or 24V system with any panel.
Also true. Which is why we can use dual 6V batteries instead of 12V batteries in our campers. But since we are ultimately going to want 12V, our batteries are wired/configured to create 12V, not 6V or 24V.
3) The 12V vs 24V is really talking about the system, the electrical needs coming from the appliances. Do you have a 12V or 24V system of appliances puling electricity from your batteries, regardless of input. Meaning, you can use two 12V to achieve 24V for your 24V system and use the same solar panel as you would with two 12V batteries in a 12V system.
Also true. And we need 12V for our campers.
4) Basically he said they are marketed as 12V or 24V panels not because of the power they generate, but based on how people typically use them, for their power needs in a 12V or 24V system.
Not in my experience. The terminology of 12V or 24V is definitely a derivative of how the cells on the panel are configured. A 12V panel will output much more than 12V and generally less than 24V. This Renogy 160W panel does 22.9V at 8.37A -
https://www.renogy.com/160-watt-12-volt-monocrystalline-solar-panel/
A 24V panel will put out more than 24V - this Renogy 320W panel puts out 40V and 9.6A. That's a very different way to generate the power... more volts, less amps.
https://www.renogy.com/320-watt-monocrystalline-solar-panel-120-cell/
5) even the charge controllers don't seem to "care" about the voltage, whether 12V or 24V. The Zamp 30A controller, as an example allows either.
Umm.... yes they do. Unless you are using a 30A PWM style controller, in which case neither panel will create the advertised amount. PWM style controllers "throw away" any voltage over what the battery needs (best case 14.5V or so + 0.5V = 15.1V) and it is just that 15.1 * the max current of the panel that you will get in the way of power. Meaning that both of the above panels would see only:
15.1* 8.37 = 126W
15.1* 9.6A = 145W
A good MPPT controller will get much more out of these panels if feeding a 12V battery array.
