24 volt panels to charge 12 volt battries

27 Posts
Mar 9, 2008 08:43 am
24 volt panels to charge 12 volt battries

Hi All
I have some 24 volt panels that put out almost 26 volts. My first question is would this be to high to charge a 12 volt battery bank?

Or would I be better off moving to a 24 volt battery bank?

If I move to a 24v battery bank would it be detrimental on the batteries to run a large 12 volt load from them?

Many thanks for the replies and advice...

Steve
 
9 Posts
Mar 9, 2008 05:49 pm
Re: 24 volt panels to charge 12 volt battries

26V is definitely too high to safely charge a 12V battery bank.  I think you should reconfigure the bank to be 24V which should be pretty easy unless you have an odd number of batteries in your battery bank.  I'm thinking that you could just put half of the batteries in series with the other half and be done with that part of it.

As for running a large 12V load from the mid point of the batteries, I'm not sure.  You could also look at a DC-DC converter to go from 24V to 12V.  I'm not sure what is practical in that arena.  If most of your loads are 12V in nature, then you could alternatively leave the bank at 12V and use the DC-DC converter (I seem to recall some charge controllers able to do this for you) between the panels and the battery bank. Hopefully someone else will chime in with more details about running a load in the middle.  I've wondered about that in the past myself.
 
27 Posts
Mar 9, 2008 06:45 pm
Re: 24 volt panels to charge 12 volt battries

Thanks Jonathan, I thought it would be the case...

Just have get answers for the rest of the questions...

Steve
 
578 Posts
Mar 10, 2008 11:26 am
Re: 24 volt panels to charge 12 volt battries

you said that you have 24v modules that put out almost 26 volts.  that tells me that you dont have 24v modules, but 18v modules.

look at these two examples

24v : http://store.altenergystore.com/Solar-Panels/150-Watts-Up-Solar-Panels/SolarWorld-SW175-175W-24V-Solar-Panel/p6107/

18v: http://store.altenergystore.com/Solar-Panels/150-Watts-Up-Solar-Panels/Kyocera-KC200GT-200W-18V-Solar-Panel-MC/p5854/

if you have modules with a higher nominal voltage than your battery bank, you should be using an mppt controller that can down convert voltages for you.
here is an example.

http://store.altenergystore.com/Charge-Controllers/Solar-Charge-Controllers/MPPT-Solar-Charge-Controllers/Outback-Solar-Charge-Controllers-MPPT/Outback-Mx60-60A12-48V-Mppt-Charge-Controller/p860/

james

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« Last Edit: Mar 10, 2008 12:15 pm by James Cormican »
 
27 Posts
Mar 10, 2008 12:01 pm
Re: 24 volt panels to charge 12 volt battries

Thanks James, Very usefull...

I'll have to rethink...

Steve
 
578 Posts
Mar 10, 2008 12:11 pm
Re: 24 volt panels to charge 12 volt battries

oops!

this was supposed to be the 18v example.  bad copy and paste.

http://store.altenergystore.com/Solar-Panels/150-Watts-Up-Solar-Panels/Kyocera-KC200GT-200W-18V-Solar-Panel-MC/p5854/

i will modify the existing post.  sorry about that.

AltE
"Making Renewable Do-able"
http://www.altEstore.com/

Tel: 877.878.4060 x107  or +1.978.562.5858 x107
Fax: 877.242.6718  or +1.978.562.5854
 
27 Posts
Mar 10, 2008 12:22 pm
Re: 24 volt panels to charge 12 volt battries

No problem, thanks again.

James can you explain:

Rated power
 Pr  SW165
 
Peak power
 Pmpp
 165W
 
Peak power voltage
 Vmpp
 35.3V
 
 
Peak power current
 Impp
 4.68A
 
 
0pen circuit voltage
 Voc
 44V

Short circuit current
 Isc
 5.10A

Fuse Rating  Ifuse  15A
 And how that equates to the rated wattage

Thanks
 
578 Posts
Mar 10, 2008 01:14 pm
Re: 24 volt panels to charge 12 volt battries

those stats point to a 24v module.  the 44voc and 35vmp give it away.  it probably has 72 mono or poly crystalline cells.

so that is fine to use, and you would probably see best results with your 12v batt bank if you invested in an mppt controller.

cheers,

james

AltE
"Making Renewable Do-able"
http://www.altEstore.com/

Tel: 877.878.4060 x107  or +1.978.562.5858 x107
Fax: 877.242.6718  or +1.978.562.5854
 
52 Posts
Mar 10, 2008 03:32 pm
Re: 24 volt panels to charge 12 volt battries

Hi Steve,

I would agree with James that MPPT is the way to go if your charging a 12v battery with a 24v panel. Here is some more infomation about the different ratings that solar modules have. This info will be in our How To section shortly.

PV modules’ power output is rated in Watts. A Watt is an instantaneous measurement of electrical power. Power is a rate, much like miles-per-hour on your speedometer shows the rate at which your car is traveling. Power is not the same as energy. Electrical energy is expressed in Watt-hours (Wh) and is a quantity. Electrical energy is like the number of gallons of gas in your fuel tank. Your electric utility bill shows the number of kilowatt-hours (kWh, or thousands of Watt-hours) you use per month. So how does the wattage rating of a solar panel affect the amount of energy the panel produces? Simple-- with all else being constant, a higher-wattage solar panel will produce more energy over time than a lower-wattage panel. A 100-Watt module will produce twice as much energy as a 50-Watt module at the same location during the same period of time. It’s worth mentioning also that solar modules’ rated wattage is based on what the modules produce under laboratory-controlled conditions, called Standard Test Conditions (STC). STC allows solar panels to be compared to each other using the same metric. However, because these rated wattages represent ideal laboratory conditions, it is likely that the module will produce less wattage in actual use.

PV modules also have voltage and current ratings. The rated wattage of a panel is equal to its operating voltage multiplied by its operating current: Watts = Voltage x Amps. The amount of energy in Watt-hours that a panel will produce is a product of the wattage of the panel and the number of hours of full-intensity sunlight, or insolation, that it receives. For example, a solar panel that outputs 100 Watts for two hours will produce 200 Watt-hours of energy. The actual number of Watt-hours a panel produces will very likely be less than this theoretical value due to many factors that affect the efficiencies of the system components. There are standard factors used to correct for real-world energy losses, but to the present focus is the basic electrical principles.

Voltage

PV modules have three different voltage ratings that it’s handy to understand. The nominal voltage of a panel could also be called the “conversational voltage.” When we talk about the voltage of the panels and the other components of the system, we’ll most often use the nominal voltage. Nominal voltage actually refers to the voltage of the battery that the module is best suited to charge; the term is a “leftover” from the days when solar panels were used only to charge batteries. The actual voltage output of the panel changes as lighting and temperature conditions change, so there’s never one specific voltage at which the panel operates. Nominal voltage allows us, at a glance, to make sure the panel is compatible with a given system without having to look at the exact voltage. The second voltage rating is the maximum power voltage (Vmp). This is the highest voltage the panel can produce while connected to a system and operating at peak efficiency. The third voltage is open circuit voltage (Voc). This is the maximum voltage that the panel can produce when not connected to an electrical circuit or system. Voc can be measured with a meter directly contacting the panel’s terminals or the ends of its built-in cables.

Current

Panels also have two different current ratings: current at maximum power (Imp) and short circuit current (Isc), both listed in Amps. The maximum power current is similar to Vmp: it’s the maximum current available when the panel is operating at peak efficiency in a circuit. Similar to Voc, the short circuit current is the current measurement your meter would show when in contact with the positive and negative terminals of the panel while not connected to a system or load.

All these electrical characteristics are used to help determine the size of the PV system and components. These specifications can be found on the label on each solar module as well as on manufacturers’ specification sheets.


« Last Edit: Mar 10, 2008 03:35 pm by Chris Brown »
 
27 Posts
Mar 10, 2008 03:41 pm
Re: 24 volt panels to charge 12 volt battries

Thanks Chris, just the explaination I needed. I'll have some more questions soon

Thanks again

Steve
 
1 Posts
Oct 29, 2014 02:36 am
Re: 24 volt panels to charge 12 volt battries


Hi All
I have some 24 volt panels manufactured by solar panels manufacturer that put out almost 26 volts. My first question is would this be to high to charge a 12 volt battery bank?

Or would I be better off moving to a 24 volt battery bank?

If I move to a 24v battery bank would it be detrimental on the batteries to run a large 12 volt load from them?

Many thanks for the replies and advice...

Steve

Hello friend bit old thread but have you made the right change? I do have similar query so can you help me out..
« Last Edit: Oct 30, 2014 02:33 am by Fritz Ashton »
 
47 Posts
Nov 18, 2014 02:07 pm
Re: 24 volt panels to charge 12 volt battries


Hello friend bit old thread but have you made the right change? I do have similar query so can you help me out..
[/quote]

Fritz, let us know the specs of your panel, and we can figure out what charge controller you need to make it work.

Amy
altE Store
Solar Queen
 

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