Conflicting advice on series vs. parallel for charging 12v Bank. Please advise.

[Mike90250]

I assume the two 12v panels wired in series would charge a 24v battery. Am I wrong on this?

Could be. We need the
Vmp ___
Voc ___
specs to insure that the panels match correctly. The scant specs 8.29v & 22.92v you gave, made no sense.

Generally, 2, 12V nominal system voltage panels in series, would charge a 24V battery. But this is strange stuff and the numbers don't make sense.

[MikeB]

What is
Vmp ___
Voc ___



Very strange #'s A Voc of 23V will never be able to charge a 24V battery

Please check the panel specs again. You may have replied with the wrong #'s Voc should only be about 30% higher than Vmp

I'm sorry, the Vmp is 18.21 voc is 22.92

[MikeB]

What is
Vmp ___
Voc ___



Very strange #'s A Voc of 23V will never be able to charge a 24V battery

Please check the panel specs again. You may have replied with the wrong #'s Voc should only be about 30% higher than Vmp

I assume the two 12v panels wired in series would charge a 24v battery. Am I wrong on this?

[Mike90250]

What is
Vmp ___
Voc ___

it's 8.29 & 22.92

Very strange #'s A Voc of 23V will never be able to charge a 24V battery

Please check the panel specs again. You may have replied with the wrong #'s Voc should only be about 30% higher than Vmp

[Gajetest]

Gajetest hope this is helpful

I have two 12v-150W panels that I plan to wire in series for 24V, with tracer 20amp mppt CC, and 4-6v batteries connected in series, with 12/24 1500W inverter to run a small fridge. Is this the best plan or should I connect the batteries in series, parallel for 12V.
Thanks in advance.
Greetings,
Well I don't know the model of your refridgerator the going average is around 600 watts to run tht could mean 1000 or more to startup. My advice get a Kill-o-Watt measurer it will tell you how much your fridge uses at startup and running. Two very different numbers. If your in an Ideal sun recieveing place you have about 4 to 5 hours of charge time to fill your batteries and still tun your fridge full time realize the fridge uses more power durring the day as the door is opened and closed a lot. You have a 1500 watt inverter or 1.5K inverter. two 150 watt solar panels will not be able to run this refrigerator without seriuosly depleting your batteries. And

If you do that you will be buying new batteries a lot. Which makes saving money not feasible.
You also need to hook up a meter to your panels at full sun and see what you ar really getting from them. Remember they have to charge your batteries and run your rifrigerrator 24/7. You did not write down what your Amp hours are on your batteries. So since they are 6 volt I'll guess 250ah? Also what is your inverter power input 24 or 12 if it is 12 DO NOT series the 6 volts to get 24 or you will smoke your inverter. From what you said I'm guessing its a 12 volt pure sine wave inverter. It has to be pure sine wave even if your fridge would work on a modified sine wave inverter it would burn up the mothor in the fridge.
So as I see it you have one choice series and parallel the six volt batteries to give you 12 volts and the most amp hours you can get out of them. 2 6 volt batteries joined in a series will give you 12 volts, and I was guessing that you have at least 250 amp hours so that will give you 25o amp hours and 12 volts. Paralleled the two 12 volt batteries you now have. And you will have 12volts and 500 amp hours. Now times the amp hours by the voltage and it gives you 12 * 500 am hours which equals 6000 watt hours or 6 KWH.
I have a Frigidaire 26 cf Side by Side. Manufactured 07/2004 (did I also mention I'm cheap?) I tested it on a Kill-o-Watt meter for 24 hours. In the 24 hours it used 2.9 KWH. This is why you need to see how much your panels actually produce so you can make the right storage choice.

Now on my hypothetical arrangement above at full charge it was 6 KWH. That is if your amperage is 250 or more you’re okay with storage. If less calculate as long as you at least have 4KWH of storage you are okay. Cannot stress this enough do not try to drain your batteries below 50% they will die on you.
Now what do your panels produce in their 4 to 5 hour window? Testing them will let you know for sure and do not trust what it says on the panel. Your panels have to put out enough power to run your refrigerator and on top of that charge on your batteries to full capacity. Do not run your batteries below 50% percent or they will fail on you very quickly. If your panels can't produce enough power then you need to spend a little more and get some more panels. I would be surprised if two 150 Watt panels will be enough to accomplish this. You will not know until you test them to see their real output.
If you would like me to help you figure it out go to my site Gajetest.com there you will find an info email address. Give me the output of your panels amperage at peak sun-time. The amp hours on your batteries are rated at. What voltage they read when they are fully charged and you test them with a multi-meter. And if you do not have a Kill-o-Watt Meter; give me the year and the brand of your refrigerator. Or it may tell you start-up and running Watts inside of the door or on the back by the motor.

And I can tell you what you need to do
Gajetest

[cmclane28]

Thanks very much for the clarification. I will wire the panels and batteries in series and the 20a mppt controller does double the watts at 24v. And I do have a generator for backup.

It is somewhat difficult to find reliable information for small systems and I really appreciate this solar forum.

Glad I could help. I'm a bit new to all of this myself. It's amazing how much I've learned over the last couple of months, and the help provided on this forum has been great.

[MikeB]

If your charge controller is only rated for 200 watts (I assume that's if you have a 12V battery bank), and you are going to use a 12 V battery bank, your 2 - 150 watt panels are going to be too much because they will be putting out 300 watts no matter which way you wire them (Series: 36+v x 8.29 amps or parallel: 18+v x 16.58 amps). Typically the wattage rating for the charge controllers is double if you go with a 24V battery though, so assuming that's the case I'd wire the panels in series and wire your 4 - 6v batteries in series for a 24 volt system. Assuming they are rated around 230 Ah that would give you about 2,700 usable watt hours (realistically less because of normal inefficiencies), so as to not run your batteries down past 50%. Not sure what your fridge uses in watts, but you mentioned it was a small one so I think that would work fine. Of course if you have a couple cloudy days in a row you'll need to find a way to help charge the battery bank.

Thanks very much for the clarification. I will wire the panels and batteries in series and the 20a mppt controller does double the watts at 24v. And I do have a generator for backup.

It is somewhat difficult to find reliable information for small systems and I really appreciate this solar forum.

[cmclane28]

No it's 8.29 & 22.92. So I assume I can still have the panels in series, for 24v, and the batteries in series and parallel for 12v. And I assume that's my only choice without buying more panels for the time being. I also have a 50w panel I used for years for lights & small tv at this cabin and I had planned on just leaving it out of this new array. However I'm curious, is there any way to include the 50w panel or is it simpler and better just to leave it out.

I really appreciate your time and expertize. I don't know if you're allowed to recommend controllers & inverters, but if you are, what would be an adequate choice on a limited budget.

thank you again

MikeB

If your charge controller is only rated for 200 watts (I assume that's if you have a 12V battery bank), and you are going to use a 12 V battery bank, your 2 - 150 watt panels are going to be too much because they will be putting out 300 watts no matter which way you wire them (Series: 36+v x 8.29 amps or parallel: 18+v x 16.58 amps). Typically the wattage rating for the charge controllers is double if you go with a 24V battery though, so assuming that's the case I'd wire the panels in series and wire your 4 - 6v batteries in series for a 24 volt system. Assuming they are rated around 230 Ah that would give you about 2,700 usable watt hours (realistically less because of normal inefficiencies), so as to not run your batteries down past 50%. Not sure what your fridge uses in watts, but you mentioned it was a small one so I think that would work fine. Of course if you have a couple cloudy days in a row you'll need to find a way to help charge the battery bank.

[MikeB]

Mostly - yes

a 24V battery system needs to charge at nearly 31V at times - Will the "12v" panels in series go that high? What is the
Vmp _____
Voc _____
spec on the label ?

No it's 8.29 & 22.92. So I assume I can still have the panels in series, for 24v, and the batteries in series and parallel for 12v. And I assume that's my only choice without buying more panels for the time being. I also have a 50w panel I used for years for lights & small tv at this cabin and I had planned on just leaving it out of this new array. However I'm curious, is there any way to include the 50w panel or is it simpler and better just to leave it out.

I really appreciate your time and expertize. I don't know if you're allowed to recommend controllers & inverters, but if you are, what would be an adequate choice on a limited budget.

thank you again

MikeB

[Mike90250]

Mostly - yes

a 24V battery system needs to charge at nearly 31V at times - Will the "12v" panels in series go that high? What is the
Vmp _____
Voc _____
spec on the label ?

[MikeB]

is your fridge 12V or 24v ? That's your answer.

If it's 120VAC, then you need a pure sine inverter to run it, and I would advise to use a 24v system with a 1,000w inverter. You need a large inverter to be able to start the motor in the fridge.

The fridge will be 120V and I had planned on 1500W pure sine wave inverter. So if I get this correct, you are saying going 24V with the batteries then a 1000w inverter will do the job?

The Tracer 20A controller is rated for 200W. Will it work for the 2-12v 150 panels wired in series. Am I correct that would be 24v, 150w?

[Mike90250]

is your fridge 12V or 24v ? That's your answer.

If it's 120VAC, then you need a pure sine inverter to run it, and I would advise to use a 24v system with a 1,000w inverter. You need a large inverter to be able to start the motor in the fridge.

[MikeB]

need advice

I have two 12v-150W panels that I plan to wire in series for 24V, with tracer 20amp mppt CC, and 4-6v batteries connected in series, with 12/24 1500W inverter to run a small fridge. Is this the best plan or should I connect the batteries in series, parallel for 12V.
Thanks in advance.

MikeB

[Gajetest]

Wow! A poor guy ask for a little help and yu'all get into a equipment measuring match

And I'm keeping this PG you know what I mean when I say you 'all measuring your equipment.

I see you have a 12 volt system. Well right there even for emergency situations 12 volt systems tend to be a might unstable 24 volt is better 48 is best 96 volt I think is a might overkill. You have to series and parallel just like you have to do with your power storage system. To get the all-important amp hours you need to get your watt hours without spending or purchasing to many panels. I went for solar trackers gives me the most sun power time as it moves my panels like a sunflower always facing the sun.
You say your system uses 1.5KWH or around that I’m too lazy to scroll back up and get the number you placed I hope I'm close, and mean no disrespect like I said I’m just lazy. There are about a hundred calculators online that will tell you what you need in power and panels and some good math was demonstrated here.

The average American household of 4 uses 16.5KWH in a 24 hour period. Mine is 2 people and I use 17.5KWH in a 24 hour cycle, computers and gadgets I’m always working on puts me in a higher power bracket plus there is no energy crisis so I use electricity in abundance. And I sure as hell don’t give my CLEAN energy to a power company who sells me trash power to use in my home. Hook an oscilloscope to your pure sine wave inverter, and then do the same test to what’s coming out of your wall from the Power Company. Your inverter power will look like spring water compared to the Mississippi Mud they send through all their capacitors and whatnot. However, if you have been keeping up with the power companies; then you know their switching to micro-grids. Like they are already doing in Europe, and will start leasing and charging for equipment and wattage hours.

So you might want to start thinking on a larger scale before they jump and catch you by the short hairs. All I'm writing is documented so if some ijit wants to try and bash me; better do some reading. And you’ll find I really will not care or listen to negative junk. We got a good thing here I’m glad I joined. I like to see all the information that is available open and to be shared. We in America are behind in renewable energy systems. Above 90% could not even tell you what an inverter is or 99% wouldn’t have a clue to what a Gasifier-generator is. Let’s keep the dialogue to the point please. I’m a wind bag and I know it. But I’m reaching 60 years too fast and I’m tired of the damn 1%-ters treating us like mushrooms.

All I'm saying we got some CEO's out there that are planning more nuclear reactors, can you wrap your head around that? We don't need them. Anyone can go Off-Grid at a low cost. Don't look at brand names look at specifications of the equipment you buy. Let’s use good forums like this one to come together to share and take back what is already God given and free. Well I probably wrote too much, but I can’t help it. We need to help each other and not wait for some company to drop a ready-made will fit all power system on our door. And to all of you fellow tinkerers well met gentlemen.

[Sunking]

Honestly, you should have an attitude adjustment! If you actually plug the specs into the sizing calculator, the calculator itself states "Array power (Wattage) excessive". It's not my verbage, it's the verbage of the calculator itself. I CAN add you know. Four panels in series is 157V, which I think maybe might be less than 200V. When you input the number however as two 2-panel strings, the calculator gives you a green OK.

What does that tell you?

Power = P1 + P2 +P3..... Makes no difference if the panels are series or parallel 4 panels of 280 watts = 1120 watts all day long everyday. You are trying to compare 3 different Controllers with different power ratings at 12 volt battery. The maximum Power Input at 12 volts is:

Classic 150 = 1380 watts
Classic 200 = 1137 watts
Classic 250V = 878 watts
Classic 250KVS = 800 watts

From the charts it is real easy to see only the Classic 150 and 200 should be considered operating at 90/70 volts or less input voltage. The OP IMO should only be looking at the Classic 150. Regardless either the Classic 150 or 200 with those panels are 2 x 2.