200W 24V panel to 12V

[lorenz]

I have a 24V 200W panel, but my car is 12V. I was told that I could use a regulator to make it a 12V solar panel, but I also have been told that this would effectively reduce the panel to 100W panel. Is there any one in the know and be able to explain why?

[MarineLiner]

Welcome onboard and thanks for joining.
Yes, the power reduced but not 50% directly.
It's called inefficiency.
We had discussed it more than once. Also about the panel voltage and charging.
I'll come back with the link soon. Or we can use the tags below.

[lorenz]

Wow, how quick was that!!!! Thank you so much. I scanned though the links you have provided, but was not find the information I need. Can you give me an estimate how much I would loose?

Cheers Lori

[MarineLiner]

I scanned though the links you have provided, but was not find the information I need.
Can you give me an estimate how much I would loose?

[lorenz]

Thanks, yes I have used the tags.

To my solar story. I have ordered a 12V 200W panel, but when it arrived the panel was 24V 200W. The retailer offered to send me a regulator that would take care of this. I agreed as long as the panel would still provide 200W. Now

[MarineLiner]

[QUOTE=lorenz;10005]I have ordered a 12V 200W panel, but when it arrived the panel was 24V 200W. The retailer offered to send me a regulator that would take care of this. I agreed as long as the panel would still provide 200W.
Now

[MarineLiner]

Can also use "Search" from main menu of this screen, type: power loss
then click go.

[lorenz]

Thanks, it is a Monocrystalline solar panel, but I have no idea what brand.
The regulator is a “CMP 24 Solar regulator” http://solarcontroller.en.alibaba.co...24_series.html

[MarineLiner]

We should wait for Mike and SunKing who know better than me.
Mean while keep on searching on this forum board.

[Mike90250]

You need to locate the actual tech data for the panel. It will list the voltage that the panel produces it's max power. VmaxPower. Without that label, or a $15,000 piece of test gear, you will have no data to really work with. If the panel is a 18V nominal, it may have a Voc (Volt open circuit) of 22-24V. But by the time controller losses are factored in, a panel that has it's max power at about 18V is right for a 12 v battery charger.
Only a MPPT style charge controller can "match" a higher voltage panel, to a lower voltage battery, and maintain the total system wattage. PWM controllers just cycle a electronic switch on and off, to give an average charge voltage.
When a high voltage panel is connected to a low voltage battery, via a PWM or plain wire, the watts decrease.

Or I could just attach a picture, and it's pretty obvious what happens when you go below the panels peak power spot.

(pic from http://chuck-wright.com/SolarSprintP...rSprintPV.html )

[Sunking]

Ok there are two types of charge controllers. Shunt and MPPT

A shunt regulator is really nothing more than a electronic variable resistor. They are very inefficient because Current Input = Current Output. So let's say your 200 watt panel Vmp = 18 volts, Imp = 11.1 amps (18 volts x 11.11 amps = 200 watts). OK your battery is at 50% SOC which = around 12.2 volts. With this info we now can look at what is going on. The input voltage to the regulator is 18 volts, and input current is 11.11 amps. On the output of the regulator is 12.2 volts, and since input current = output current we know the output current is 11.11 amps. So at the input we have 18 volts x 11.11 amps = 200 watts. On the output we have 12.2 volts x 11.11 amps = 135 watts. What happened to the missing 65 watts? It is being burnt off as heat in the regulator or wasted giving you only 67% efficiency. Cool huh?

OK a MPPT controller is a different animal. It is a true DC to DC switch mode regulator. It takes the DC input power, converts it to AC, and converts back to DC and has an efficiency of around 95 to 97%. So at the input we have the same 18 volts x 11.11 amps = 200 watts, but on the output we have 12.2 volts x 15.6 amps = 190 watts or 95% efficient.

So what is the difference between the two? Hint look at the currents or AMPS.

[crxvfr]

lorenz, it sound like I'm in the same boat as you. I have a 200 watt 24 volt panel and wanting to use a 12 volt battery system. I ended up buying a morningstar sunsaver mppt for $206. Read the specs on whatever you consider buying. So far as I am understanding things, the sunsaver mppt will only handle 200 watts of panel power with a 12 volt battery system, so expanding is out of the question unless I go to 24 volt batteries.

[lorenz]

Thank you all, you guys have been terrific. Don’t know where to go from here, but it appears the best way forward is with the correct panel.

Cheers from down under

[Uechi Kid]

If I understood correctly, a MPPT controller would solve you issue.