Author Topic: Solar system voltage?  (Read 1107 times)

ProGeek

Solar system voltage?
« on: January 08, 2018, 10:35:40 AM »
So I have a couple of 24V panels. Actually the max panel voltage is 30V. I know I need a charge controller that take 24V input. My question is can I setup batteries as 12V or do they have to be 24V too? How much efficiency would I be loosing by keeping the battery bank 12V? I already have a largish 12V inverter. Do I need to get a 24V inverter?
If the freedom of speech is taken away then dumb and silent we may be led, like sheep to the slaughter.

RWS

Re: Solar system voltage?
« Reply #1 on: January 08, 2018, 11:24:40 AM »
You can charge a 12 VDC battery from a 30 VDC panel.  Just use a 12 charge controller.  Some charge controllers will do either.  They will auto recognize the voltage, then turn on the panel.  Some larger charge controllers will do 12, 24 or 48 VDC charging.  Inverters are voltage specific, ie 12, 24 or 48 but not either. 
My recommendation on inverters is use the highest voltage inverter you can find in the capacity range you want.  The reason is 1.  Your battery is never big enough.  By putting 12V  batteries in series, you get twice the capacity.  2.  By raising the battery voltage allows you to use smaller wire.  It's easier to work with.
The only time I would use a 12v inverter is for a very portable low capacity system.

Starlady

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Re: Solar system voltage?
« Reply #2 on: January 08, 2018, 11:38:21 AM »
Solar system voltage!

Wow, can they even measure that?

I mean............the SUN, yikes.
"We can't solve problems by using the same kind of thinking we used when we created them." Albert Einstein

RWS

Re: Solar system voltage?
« Reply #3 on: January 08, 2018, 12:04:02 PM »
Solar system voltage!

Wow, can they even measure that?

I mean............the SUN, yikes.
It's the DC voltage that comes out of a solar panel in full sunlight.  Ont the data plate on the back of the panel is OCV (Open circuit Voltage)  and max load volatge which is the voltage you should have with the panel supplying full current to a load ie under load.  Shade half your panel and watch the voltage.  Interesting !

Solar system voltage!
Also could be the battery voltage in a battery system.
Solar radiation is measured and use is solar panel standardization.  My local weather shows me the soar radiation among other variables.         http://www.georgiaweather.net/index.php?content=calculator&variable=CC&site=VIENNA

Lilburner

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Re: Solar system voltage?
« Reply #4 on: January 08, 2018, 01:14:57 PM »
My new favorite thing in the whole world.

http://www.westmountainradio.com/product_info.php?products_id=epic-pwrgate

And when I say new, I mean brand new. I had to get on a waiting list to get mine about two months ago. I believe they're shipping from stock by now.

It's got 4 sets of plugs. DC in, batt, out, and solar. It manages all four seamlessly.

You can tweak things like battery chemistry, battery and output voltage, etc. It takes up to 30V on the solar.

Go ahead. You know you want one.

A strong conviction that something must be done is the parent of many bad measures.
~ Daniel Webster

Starlady

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Re: Solar system voltage?
« Reply #5 on: January 08, 2018, 02:01:05 PM »
"It's the DC voltage that comes out of a solar panel in full sunlight."


The amateur astronomer in me was puzzled there for a minute.

;)
"We can't solve problems by using the same kind of thinking we used when we created them." Albert Einstein

Fixit

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Re: Solar system voltage?
« Reply #6 on: January 08, 2018, 08:21:56 PM »
I could be wrong but the way I read this
https://theinverterstore.com/product/aims-40-amp-solar-charge-controller/
You could configure your solar panels anywhere from 15vdc to 150vdc and still charge a 12vdc battery bank . This would solve a wire gage problem on long runs from panels to charge controller . Then you put your controller close to your battery bank .

revckd

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Re: Solar system voltage?
« Reply #7 on: January 08, 2018, 09:39:01 PM »
Man, I forgot how much I learn from you guys on here. Battery chemistry... I wouldn't have thought of that one, guess I got something else to research.
revckd
KM4PHQ

Bellatores et Venatores in Christo
A prudent person foresees danger ahead and takes precautions. ~ Proverbs 27:12

RWS

Re: Solar system voltage?
« Reply #8 on: January 09, 2018, 06:31:48 AM »
I could be wrong but the way I read this
https://theinverterstore.com/product/aims-40-amp-solar-charge-controller/
You could configure your solar panels anywhere from 15vdc to 150vdc and still charge a 12vdc battery bank . This would solve a wire gage problem on long runs from panels to charge controller . Then you put your controller close to your battery bank .
In the early days, solar charge controllers would take up to 60 VDC and charge a 12VDC battery.  It was a novel thing to string two solar panels in series so that they could be a few feet further away.  Then they came up with 150DC charge controllers.  The first one I installed was 72ft from the solar array.  Just 2 years ago they came out with 600VDC charge controllers.  I installed two with each having a 10 panel array.  The reason for two was one array was facing East on an existing boat house.  The second array I oriented South West to get the evening sun.  A third array was South facing.  With 600VDC charge controllers allows more flexability on location as you can have the panels 100-115ft away with no problem.  People seem to like big trees shading their house.  I use 48VDC battery banks and recommend any inverter 3kw and up to do the same.

ProGeek

Re: Solar system voltage?
« Reply #9 on: January 12, 2018, 11:08:16 PM »
Thanks. I'm guessing it's more efficient to run the panels at 24V and the batteries at the same voltage. How much efficiency would I loose with 24V in and 12V batteries?
If the freedom of speech is taken away then dumb and silent we may be led, like sheep to the slaughter.

RWS

Re: Solar system voltage?
« Reply #10 on: January 13, 2018, 06:19:13 AM »
Thanks. I'm guessing it's more efficient to run the panels at 24V and the batteries at the same voltage. How much efficiency would I loose with 24V in and 12V batteries?
Well of course you would loose a little due to heat, however they have designed the equipment to minimize the heat generated.  My experience is you would not notice it.

John Galt 1

Re: Solar system voltage?
« Reply #11 on: January 13, 2018, 08:05:41 PM »
There are 2 types of solar charge controllers.
PMW controllers are inexpensive ($18-$60) and they work well when the panels are rated at roughly 140% TO 200% of the battery voltage.   (17-24v panel feeding a 12v battery)    They usually aren't very programmable and will do an ok job with panels rated for less than 24v charging a 12v battery.     Using a PMW controller with a higher voltage panel (like 40v) to a 12v battery will work but you're losing over half the energy the panel is putting out.     I can explain why if you need more information.

MTTP type controllers are the most efficient and work well for higher voltage panel strings.      MPPT controllers take the super high voltage and convert the high volts to more amps dramatically increasing the efficiency of the power sent to the batteries, but they are expensive, between $240 to over $1000 depending on input voltage and amp capacity.

For a few small panels wired in parallel feeding a 12v battery a PMW controller is fine.       If you're running over 1000 watts in panels or high voltage panels a MPPT controller is worth the extra cost.

I have 3 solar systems, from a 200 watt one using a PMW controller charging a 12v battery to run my small shop fridge to a Conext 80-600 MPPT controller charging the 48v battery bank my home runs off of.     

RWS

Re: Solar system voltage?
« Reply #12 on: August 04, 2018, 12:02:27 PM »
Times are moving up system voltages as new equipment becomes available.  I just started a new install at a Mini Farm just down the road from me.  The owner just got his grid tied system up and running.  Now that his meter is running backwards most of the daylight hours, he wants an off grid system to run the well, lights and freezers.
The grid tied system is a Solar Edge 6000 Watt system that uses power optimizers, one at each panel.  The optimizer is a MPPT charge controller combined with a rapid shut down of voltage coming off the panels when the inverter shuts down.  This leaves the system safe for fire fighters to turn on the fire hose.
Yesterday we (home owner & I) installed a new back panel (3/4" plywood) to mount new equipment on.  This morning when I took over my painters scaffold he had it painted.  I told him light brown would not show dirt as easily.
Next step is to remove one string of florescent lights and install 4ea porcelain light sockets for LED bulbs.  Power will come from the off grid lighting panel.
What I started to say and digressed is the battery for Solar Edge "StoreEdge" system runs at 400VDC.  Power comes right off the series string of PV panels.  Oh, the batteries are made by LG and are LI-Ion.
The existing inverter is right beside where we are going to install the new inverter.  I told the home owner that if the grid ever did go down long term that he could move one string of panels from the grid tied inverter to the off grid inverter thus doubling his off grid power.  Sounds like a plan to me.....

RWS

Re: Solar system voltage?
« Reply #13 on: August 07, 2018, 12:47:11 PM »
Florescent lights gone and LED light bulbs installed in porcelain fixtures.  The fixtures were $1.49 ea.  I was surprised as I was expecting 4 or 5 bucks.
The string of LED lights will be powered from the new off grid lighting panel I installed this morning.  I knocked out two 3/4" knock outs in the upper back of the panel, installed 3/4" EMT sweeps up thru the perlin into square boxes.  I thought this would give a neater look with fewer conduits coming to the panel.  It is a nice lighting panel with 2ea neutral busses and two ground busses already installed right out of the box.

RWS

Re: Solar system voltage?
« Reply #14 on: August 09, 2018, 01:31:09 PM »
Ground rod installed.  I use "CadWeld" one shot moulds to weld the #6 copper ground wire to a 5/8" copper clad ground rod.