# 24v, 12v, Panels, Charge Controller and Battery

Registered Users Posts: 33 ✭✭
Since I'm a raw beginner at this, I think I've missed some simple points that make a huge difference.  Can someone clarify for me?

I thought if you have a 12v battery or battery bank, that you had to have a 12v panel or Array of panels.   Apparently this is not true.  Resources say that I can have a 24 volt panel connected to a CC (either PWM or MPPT) and the CC will convert the incoming power to match the connected 12v battery.  Is this true?

Also, the resources say that I can even mix 24v and 12v panels  and there is no harm done to the CC or the 12v battery.  Of course, connecting the PA in Series or Parallel makes a big difference in the effectiveness of the current transferred to the battery.

Does this mean that any reliable CC will safely do this as long as I'm not overloading the 10amp, 20amp, etc. rating?

Finally, in doing all of this, what is the absolute bottom line in battery charging?  Is the main goal to get the highest Amps possible?  Are the Amps what I'm actually trying to improve the most for sake of charging a system, as opposed to getting minor adjustments from 13.1 or 13.6 or 14.1volts?

• Solar Expert Posts: 5,592 ✭✭✭✭✭
Charge controllers;

MPPT type will convert the voltage to proper charging voltage for the battery bank, They will down convert the voltage and use most of the wattage coming in. You will want to have @ 30% more voltage than is required for charging (@14volts per 12v system) so typically you will want 12volt panels in series.

PWM do not down convert, rather limit the voltage coming in. While higher voltage panels can sometimes be used (check the controllers limits) the 'extra' voltage is just lost. When correctly sized panels are used there is about a 10% loss using this type charge controller.

Panels or strings of panels should be with in 10% of each other to prevent large system losses and avoid confusing MPPT type controllers searching for best conversion.

Charge controllers, control the voltage presented to the battery bank. These voltage parameters vary by battery type and manufacturer. Check with the manufacturer for proper set points.
Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
- Assorted other systems, pieces and to many panels in the closet to not do more projects.
• Registered Users Posts: 33 ✭✭
Thanks!   So, ONLY a MPPT CC will allow me to efficiently use the 24v panels with a 12v battery bank?

• Solar Expert Posts: 5,592 ✭✭✭✭✭
edited March 2017 #4
Thanks!   So, ONLY a MPPT CC will allow me to efficiently use the 24v panels with a 12v battery bank?

Yes! Often in small system <1000 watt array, it can be cheaper to use an PWM controller. large panels can be less than half the cost but come with high shipping rates. In addition PWM controller are typically 1/3rd the cost of MPPT controllers.
Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
- Assorted other systems, pieces and to many panels in the closet to not do more projects.
• Registered Users Posts: 4,495 ✭✭✭✭✭
Another factor is distance to array. For longer runs, using an MPPT controller allows for more panels in series, higher voltage, lower current, and thus smaller wire.
Off-grid.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
• Registered Users Posts: 33 ✭✭
The smaller wire for the run is a great help to one application I'm looking at.  Thanks.

• Registered Users Posts: 33 ✭✭
As asked in the initial question:

>>Finally, in doing all of this, what is the absolute bottom line in battery charging?
>>Is the main goal to get the highest Amps possible?  Are the Amps what I'm actually
>>trying to improve the most for sake of charging a system, as opposed to getting
>>minor adjustments from 13.1 or 13.6 or 14.1volts?

What I mean is, What is the factor that is most important to the charging of batteries?  Of course, I need the proper voltage, but if one CC gives a tiny edge over another (PWM vs. MPPT) in voltage, is that less important than one that gives better amperage output?  Same question for the 24v vs. 12v Solar panel array... Am I better off to choose between the, based upon whichever will dump more amps into my battery array?

• Solar Expert Posts: 5,592 ✭✭✭✭✭
What I mean is, What is the factor that is most important to the charging of batteries?  Of course, I need the proper voltage, but if one CC gives a tiny edge over another (PWM vs. MPPT) in voltage, is that less important than one that gives better amperage output?  Same question for the 24v vs. 12v Solar panel array... Am I better off to choose between the, based upon whichever will dump more amps into my battery array?
"Charge controllers, control the voltage presented to the battery bank. These voltage parameters vary by battery type and manufacturer. Check with the manufacturer for proper set points. "

The charge controller will maintain proper charging voltage. Most PWM will have a couple choices of charging profiles and the more expensive/higher quality will let you set your own charging voltage points. MPPT type will have a microprocessor of some type and are typically offer user settings.

Both should maintain very similar voltage set points for your battery bank...

The choice typically is a straight price/value assessment. MPPT typically will deliver about 10% more energy and are somewhat more flexible, but require a higher incoming voltage. PWM will tend to be cheaper, but work cost effectively with a more narrow VMP panel range.

Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
- Assorted other systems, pieces and to many panels in the closet to not do more projects.
• Registered Users Posts: 33 ✭✭
Thanks for the elaboration on your previous statement.  Do you know of a website or something that I can view comparisons for different voltages on Panel Arrays?  I'd like to see the differences in amperage that is output to the battery via both PWM and MPPT charge controllers.  It seems like the videos I was watching showed much more substantial amperage outputs to the batteries when using higher voltage panels with a MPPT controller.
• Solar Expert Posts: 5,592 ✭✭✭✭✭
I am not aware of any...
Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
- Assorted other systems, pieces and to many panels in the closet to not do more projects.
• Solar Expert Posts: 3,844 ✭✭✭✭✭✭
Thanks for the elaboration on your previous statement.  Do you know of a website or something that I can view comparisons for different voltages on Panel Arrays?  I'd like to see the differences in amperage that is output to the battery via both PWM and MPPT charge controllers.  It seems like the videos I was watching showed much more substantial amperage outputs to the batteries when using higher voltage panels with a MPPT controller.