24v to 12v amp conversion

Thread Starter

Prebstar

Joined Apr 2, 2016
2
Hi,
I will be using a MPPT solar charge regulator to charge my 12v 125amp AGM batteries.
I have not got my solar panels yet, and came across some 180watt 24v panels at a good price, the MPPT controller is a 40 amp up to 60v, so that is ok.
My question is what power output can I expect from the panels compared to a 180w 12v panel as far as charging my 12v Agm battery, thanks
 

#12

Joined Nov 30, 2010
18,186
Twelve volts will not charge a 12 volt battery because there is not enough voltage to drive current backwards through the battery. If 12V is the peak voltage of the 12V panel, you have a non-starter. Check the datasheets for each panel and see how they act when loaded down to about 13 volts.
 

Thread Starter

Prebstar

Joined Apr 2, 2016
2
Twelve volts will not charge a 12 volt battery because there is not enough voltage to drive current backwards through the battery. If 12V is the peak voltage of the 12V panel, you have a non-starter. Check the datasheets for each panel and see how they act when loaded down to about 13 volts.[/QUOTE

Yes, I understand what you are saying, I was probably being too general saying they are'12v'. They are standard camping panels and depending on weather conditions can have a raw output of up to 17 or so volts.
Is it possible to work out a theoretical 12v out put for both the '12v' panel and 24v panel in amps at 12v??
 

#12

Joined Nov 30, 2010
18,186
Sure. That's what the manufacturers do when they characterize the panels. Unfortunately, I am not a manufacturer and I don't have your panels with me. In fact, I don't even know what brand or model number they are so I might go buy some and do the tests just for you. I'm afraid you will have to look them up or ask the manufacturer.
 

ErnieM

Joined Apr 24, 2011
8,011
Hi,
I will be using a MPPT solar charge regulator to charge my 12v 125amp AGM batteries.
I have not got my solar panels yet, and came across some 180watt 24v panels at a good price, the MPPT controller is a 40 amp up to 60v, so that is ok.
My question is what power output can I expect from the panels compared to a 180w 12v panel as far as charging my 12v Agm battery, thanks
If your specs are correct you can expect exactly the same power out of either one: 180 watts.

Practably the higher voltage panel may work a bit more efficiently than a lower voltage device as the switching losses thru the MPPT improve slightly with more voltage.

One former member here built chargers professionally had mentioned MPPT was simply not worth it on 12 volt panels as there was no gain in efficiency.
 
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