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Old 28-03-2012, 05:33   #1
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36 Volt Solar Panel , 250 watts - Can I Connect to 12V Solar Regulator ?

Help, I bid for and won a 250 watt solar panel on ebay. It is rated at 255 watts, max power is 36V. Are they 12V nominal?? I am not sure if I have made a mistake and should try and change the solar panel for some others, before I pay for it?

Mono-Crystalline 250W
Size 1980 X 990 X 50 mm
Max Power Voltage - 36V Max Power Current -6.94A
Open Circuit Voltage - 44V Short Circuit Current - 7.62A
Module Efficiency 15.8% 125x125mm cells
Tolerance Wattage 0-10W
Cables Lenght -900mm
Allowable Hail Load - Steel ball falls down from 1M height

Can I hook this 250 watt panel up with my two existing 135 watt panels and run them through an appropriate solar regulator to charge my two 160 amp hour AGM sealed batteries? Or would I be better to get another two 135 watt, 12V panels, can you mix up the size of the panels and still connect them to the same regulator?

I was thinking of the westmarine NC25A-12V, expandable to 100A, solar and wind controller. Will also hook up two wind genny's to it.

FLEXCHARGE Regulator at West Marine

Any ideas or criticism would be most welcome?

All the best from Keith.
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Old 28-03-2012, 08:02   #2
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Re: 36 volt solar panel, 250 watts, can I connect to 12V solar regulator?

No. The charge controller you have will not handle this high of a voltage. If you had an MPPT controller then maybe, depending on its maximum voltage rating.

The panel you have bought is not intended for a 12 volt system (notice, open circuit voltage of 44 volts). You also do not want to mix this panel with your current ones if they are the typical panels made for a 12-volt system with an open circuit voltage of around 17-18 volts.

You would be better off getting rid of this and getting additional panels that have an open circuit voltage within a volt or two of your current panels.
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Old 28-03-2012, 09:16   #3
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Re: 36 volt solar panel, 250 watts, can I connect to 12V solar regulator?

With most MPPT regulators it will not be a problem with the 36v at MPP.
To Connect them to the batteries it would be best to use separate MPPT regulator. Don't parallel them with a normal 12 v panel.
The regulators you list are not MPPT so are not very suitable for a panel with a 36v MPP.
Solar and wind regulators are different. With solar you can disconnect the panel safely. With wind the generator speeds up with no load, so you need a different kind of regulator that diverts the power to a resistive load. There are a few regulators that will work with both wind and solar, but generally you are better with 2 separate products.
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Old 28-03-2012, 09:31   #4
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Re: 36 volt solar panel, 250 watts, can I connect to 12V solar regulator?

Agree with all the replies. I will be using panels like that one but my house bank will be 48 volts, and two of the above panels in series has the proper charge voltage for a 48 volt bank. For 12 volts banks, you want nominal output in the 17~18 volt range. Remember the 0.55 volt each cell produces is affected by temperature, plus for electron flow you need a voltage differential from the charging source to the storage source.
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Old 28-03-2012, 09:36   #5
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Re: 36 volt solar panel, 250 watts, can I connect to 12V solar regulator?

You will need a MPPT controller with a minimum of 44 V rated input voltage. The current rating could be as high as 30 amps. Many solar panel installers recommend safety factors that add 50% to the controller current rating. So if your controller is going to take 255 watts at 36 V and convert it to about 12 V then it is going to output about 20 amps. Multiply by 1.5 and you get a 30 amp rated controller. These aren't cheap.
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Old 28-03-2012, 15:52   #6
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Re: 36 volt solar panel, 250 watts, can I connect to 12V solar regulator?

Thank you all for your speedy replies and for confirming that I have made a big mistake in buying this solar panel!

Obviously, not all solar panels put out around 12V, it depends on the wattage and number of solar cells? Should I only match panels that are about the same wattage, what is the maximum wattage or voltage that I should marry with my existing 135 watt BP solar panels?

I have asked to cancel the purchase process and the seller has agreed to allow me to cancel the transaction process, phew!!!

I will buy two 150 watt solar panels and put them in parallel with the other two 135 watt panels??

I am also installing an eclectic energy, 400 watt, 12V wind genny to run alongside my aerogen 400 watt wind genny. I will run them all through the westmarine regulator, rated at 100 amps, which has the ability to connect 12V solar panles and wind gennys, the wind gennys can be automatically shunted to a resistive load when their output exceeds a predetermined level, which will slow them down.

"25 amp NC25A is a series regulator designed for alternative energy charging systems ranging from .1A to 25A. Ideal for solar (PV) and permanent magnet generators including outboard motors and smaller wind generators. Includes a charge divert feature for using excess charging source energy for other tasks, or for placing a load on permanent magnet charging sources such as wind generators to prevent over speed conditions. Draw: 5mA. Expandable up to 100A using an optional contactor. Green LED shows when panels are producing charge current and Red/Green LED display shows charging, divert and low battery levels.
223893 measures 3-7/8"W x 3-3/4"H x 1-1/2"D
343329 measures 1-1/2"W x 2-7/8"H x 1"D "


This is all going into 2 house batteries, soon to be 3 X 160 amp hour AGM, and running my new danfoss BD50F fridge freezer and other smaller loads.

Top-of-the-line systems designed for complete reliability, even in the toughest tropical weather conditions, updated with a quick fit system for easy do-it-yourself hookup and removal without the assistance and expense of a refrigeration tech. Since pioneering marine 12V refrigeration systems more than 25 years ago, Adler/Barbour has continued to use the latest available technology to make these systems the most reliable of their kind. Both the Air-Cooled CU-100 (this page) and Air/Water-Cooled CU-200 use the high-performance Danfoss BD50F compressor, with up to 25% better cooling performance than the BD35F in the same size footprint!
How to Create a ColdMachine or Super ColdMachine System
Now you can custom configure a refrigeration system to your boat, taking into account available ice box space and the conditions in which you’ll use your boat. First, select the compressor/condensing unit that matches your performance requirements: the Air-Cooled CU-100 is excellent for temperate climates, while the Air/Water-Cooled CU-200 is the one to choose if you’re headed for the tropics.
Then, select an evaporator style that matches your box best (see below). Evaporators include all parts necessary to create a complete system, including the thermostat, mounting hardware, ice cube trays and owner’s manual. For installation flexibility, compressors may be installed up to 15' from the evaporator plate. Dimensions are listed for each component. Note: The CU-100 and CU-200 Cold Machines cannot be used with evaporators manufactured prior to January 2001. A Retrofit Adapter Kit is sold separately (Model 11930815). One-year warranty.
CU-100 Air-Cooled ColdMachine Compressor
Air-cooled Danfoss BD50F high-efficiency compressor for temperate climates. Extremely quiet running, this compressor is shrouded for maximum fan-forced cooling efficiency and features long-lasting, stainless steel construction. Quick-connect couplings, built-in troubleshooting diagnostics and modular phone jack thermostat/electronics connections make installation easy.
Amperage Draw: Approximately 4.5A–5.5A
Dimensions: 7-1/2"H x 10"W x 11-1/8"D
Weight: 17lb.


Thanks for all your help.

Keith.
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Old 28-03-2012, 17:32   #7
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Re: 36 volt solar panel, 250 watts, can I connect to 12V solar regulator?

Hang-on , read the specs guys the N25a-12 can cope with an input voltage unto 140V, thats more then enough. Fine its not a MPPT, so you'll move the panel away from its mac PV point, but so what.


remember PV panels are essentially current sources not voltage sources.

dave
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Old 28-03-2012, 20:54   #8
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Re: 36 volt solar panel, 250 watts, can I connect to 12V solar regulator?

Quote:
Originally Posted by goboatingnow View Post
Fine its not a MPPT, so you'll move the panel away from its mac PV point, but so what.

It will not do any damage, but the system will produce much less power than it should. The panel is limited to a maximum of 7A so at say 14v when the batteries are being charged the 250w panel will only produce 98w.
An MPPT is essential with these panels to get the other 150w back.
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Old 29-03-2012, 05:09   #9
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Sorry noelex. The charge controller presents a different. Impedence then the battery. Hence the panels voltage will be a function of its PV curve into that load. It will not be at 14 ( the output will ) do the losses are nothing like you stated. There will of course be some losses stepping down to 14 v but these regulators are switchers. So heat loss is low.

Remember PV panels are primarily current sources. The panel voltage at the controller input will be near the max power point ( as the PV curve is fairly flat ) but obviously only a tracking controller will get to the max point exactly. The difference between switched regulation and mppt is about 15% in panel efficiency.

( ps take say a 30 vac output transformer , rectify it and then feed it into a 5v regulator , does the transformer output fall to 5v , no. , while not identical the similarities are the same )
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Old 29-03-2012, 07:04   #10
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Re: 36 volt solar panel, 250 watts, can I connect to 12V solar regulator?

Quote:
Originally Posted by goboatingnow View Post
The difference between switched regulation and mppt is about 15% in panel efficiency.
This statement is too generic. This might be true if the open circuit voltage of a panel is ~15-16V for a 12V battery bank. For panels with higher open circuit voltage you can loose a lot more.

A have 3 Kyocera 135W panels and one Scheuten 195W Panel. Each panel has a controller, all but one are Morningstar Sunsaver MPPTs, the one is a simple PWM Morningstar Sunsaver 10, connected to one of the 135W.

The PWM controller doesn't start switching until battery voltage exceeds a treshold, then it starts switching to reduce current, to not overcharge the battery.

Currently my battery bank is at 13.2V, 10:00 in Miami, sunny.

Comparing 2 Kyocera 135W, but with different controllers:

Output of the simple PWN controller: 13.2V, input voltage (solar panel): 13.3V

Output of the MPPT controller: 13.2, input voltage (solar panel): 17.5

I calculate, I easily loose 17-18% on my 135W panel, connected to the simple controller. For the higher Voltage 195W panel I would loose 44-45%. See attached spreadsheet.

Dirk
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Old 29-03-2012, 07:46   #11
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Re: 36 volt solar panel, 250 watts, can I connect to 12V solar regulator?

Sorry hold on there your statement

"battery voltage = Vin = Vout " of a simple controller

well thats just nonsense. Firstly the device NC25-12A is a switched mode buck convertor.

A simple linear regulator , on the other hand works by presenting a series or shunt impedance to either restrict or divert input current, By definition it present a much higher impedance then then battery, hence the regulator input voltage is primarily controlled by the regulator input source.

The primary looses in connecting a linear regulator is the IR2 heat looses in the equivalent controlling series or shunt resistance and the need to maintain PN junction temperatures below a critical point. Hence they are not very suitable for high voltage input low voltage output applications.

A switched mode regulator does not suffer the same looses as it uses an inductor and a PWM signal to transform the input voltage to a lower output voltage and with feedback controlling the pulse width , also achieve regulation. Because Ir2 loses are low, much higher voltages can be accommodated ( and in fact are to be encouraged). The input voltage of the regulator will primarily be determined by the PV panel, ( obviously the regulator input impedance changes with load).

Taking the PV or PI or VI curves of the panel will show the operating point, but the PV curves are fairly linear and flat ( which is why MPPT controllers are limited tho extracting a small gain).

The looses are nothing on the scale you mention because the PV panel is not dragged down to the battery voltage unless it is directly connectly. Hence while there is some looses in a switcher regulator over an MPPT regulator ( which is of course itself a switcher regulator, just with more software)its around 10-20% and only when the load( i.e. the battery) is actually demanding enough power from the PV panel to move the output voltage away from the MPPT point, outside of max power draw conditions , MPPT controllers deliver no benefit at all.


There seems to be a great mis-understanding of the basics of ohms law, thevinin equivalent circuits and regulation amongst sailors!!

I absolutly agree that connecting such a high voltage panel directly to a 12v battery would be nonsense as the very low impedance of the battery would drag the operating point of the panel to 12V , and on its PV curve this would mean it was putting out a lot less then max power. ( but then nobodies mad enough to connect any sort of large array directly to a battery right, surely not , no)


for those or you so minded, theres a very interesting series of Power supply video blogs on www.eevblog.com, Dave jones goes over in detail regulation both linear and switching etc in his design. ( for techies only)
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Old 29-03-2012, 07:50   #12
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Re: 36 volt solar panel, 250 watts, can I connect to 12V solar regulator?

Well, then, what am I doing wrong when I measure:

Comparing 2 Kyocera 135W, but with different controllers:

Output of the simple PWM controller: 13.2V, input voltage (solar panel): 13.3V

Output of the MPPT controller: 13.2, input voltage (solar panel): 17.5

??
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Old 29-03-2012, 07:55   #13
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Re: 36 volt solar panel, 250 watts, can I connect to 12V solar regulator?

Id love to know what the regulator is that has .1V across it and is actually able to do anything. perhaps you paid a lot of money for a toggle switch in disguise.

Note that some very early ( and poor ) regulator designs, merely connected the panel to the battery and then open circuited it when the voltage was reached, its certainly not a regulator and more of a toggle switch? na d in my opinion they are an abomination and for small panels only



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Old 29-03-2012, 08:02   #14
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Re: 36 volt solar panel, 250 watts, can I connect to 12V solar regulator?

That's my point, it isn't doing anything until battery voltage is getting to a programmed threshold, 14.4V in my case. Until then, the controller just connects the PV with the battery, drags down the solarpanel voltage to battery voltage. When the solarpanel voltage is less than battery voltage (at night) it disconnects. Above the threshold voltage for charging the battery, it reduces the current going to the battery starting the PWM. Then Vin goes up of course, but then the battery is already full!

The controller in question is the Morningstar Sunsaver 10 (PWM, no MMPT),

Edit: Just saw your added paragraph:
I think when these controllers are called "Charge controller" they behave the way I described. I believe the Flexcharge controller, mentioned by the OP is behaving the same, but I have a hard time finding facts on it, not just sales talk. I would be interested in specs of a controller you refer to: Not MPPT, but also not just a simple charge controller as I have in my setup.

Edit2: Found the manual of the flex charge nc25a:
http://www.pedalpowergenerator.com/d...25a_manual.pdf
Besides a lot of rambling on the charge efficiency, it says nothing how it handles the input Voltage. It does state, it is an On/Off controller on page 2, makes me think, it is a PWM, just like the one I have.

Thanks! Dirk
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Old 29-03-2012, 09:55   #15
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Re: 36 volt solar panel, 250 watts, can I connect to 12V solar regulator?

Actaully yes your right, if you read there charging algorithm page its a charge controller not a regulator. it switches the panels directly to the battery.

I think the cheap stuff must all be charge controllers.

perhaps most companies have just switched to MPPT for the higher end , after all its just a DC DC convertor with a bit more software.

Dave
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