I'm beginning to doubt what I thought I knew

**Sunking** · 09-29-2015, 11:35 PM

Hope you have not bought anything, you are screwed if you have. . Two huge mistakes you are making.

1 is using expensive battery panels. Grid tied panels are 1/2 the cost and you only need two of them.

2. With 5 panels only give you two possible configurations. Either all in series or all in parallel That is what happens when you work with Prime Numbers. Now here is the bad news. 5 panels in series exceeds your Charge Controller Maximum Voltage Open Circuit rating. Which means you can only wire them in Parallel which is the last thing on earth you want to do. Very expensive and inefficient.

3. Lastly you did not mention what voltage battery battery you are running, but if 12 volts will take a 45 amp controller. This part you will find real Funny. Since you are forced to wire all your panels in parallel means you have to use 12 volt battery because you bought battery panels, and they do not have enough voltage to run a 24 volt battery.

So yep you screwed up before you even got started. Example if you intended to use 12 volts was a huge mistake in the first place, but you should have noticed if operating at 12 volts your controller can only input 240 watts @ 12 volt battery with 500 watts of panels. With 5 panels you can only run 12 volts because to use them as 24 volts requires even number of panels wired in Series which you cannot do unless you loose or gain a panel.

With 5 panels now requires you to buy expensive combiners and over current protection devices, and some real large feeder cable.

**sensij** · 09-29-2015, 11:40 PM

OK, so your battery bank is 325 Ah @ 24 V. That battery bank will want 32 A (C/10) to keep the batteries mixed, so the 20 A charge controller is undersized.

Also, that 100 V limit on the charge controller probably applies to the Voc. The Voc of your 12 V panels is likely to be around 21.5, so 5x will be more than 100 V and too much for the charge controller, even before you correct the voltage for the minimum temperature the array will see.

500 W of panels will deliver through an MPPT charge controller a max of around 20 A @ 24 V, and usually much less, so in that respect, they match the charge controller, but aren't enough to support the entire battery bank. You really need more panels (probably double what you have, wired in parallel with your existing 500 W series) and a bigger charge controller (40 A, with a 150 Voc limit) to support that battery.

What loads are you planning to run? How many Wh do you plan to consume each day? You really need to make sure your panels will deliver enough energy to keep from deficit charging your batteries, and killing them prematurely.

**Wooden Indian** · 09-29-2015, 11:43 PM

Originally posted by Sunking

Hope you have not bought anything, you are screwed if you have. . Two huge mistakes you are making.

1 is using expensive battery panels. Grid tied panels are 1/2 the cost and you only need two of them.

2. With 5 panels only give you two possible configurations. Either all in series or all in parallel That is what happens when you work with Prime Numbers. Now here is the bad news. 5 panels in series exceeds your Charge Controller Maximum Voltage Open Circuit rating. Which means you can only wire them in Parallel which is the last thing on earth you want to do. Very expensive and inefficient.

Yes I have already purchased it all. Delivered last night.

I was going all in series and thought the 90 volts (at peak 18 volts X 5) could be handled by the controller because of where it says * Max. Solar Input Voltage: 100VDC. I don't know why some deep section of my brain just started screaming at me today.

So, speak to me like I'm a child ( I feel that way now), how can I make this work using what I have? Remove one panel from the equation and run 4 until I can upgrade the MPPT?

edit: My power needs are quite limited. We are going Off Grid to live a different life not heavily dependent on power. Running a laptop and desktop PC, 3 cell phones, possibly some TV (32" LED) on some evenings, a small thermoelectric cooler, and of course a few LEDs in the evenings or lighting. I have generators to cover for and large draws like tools and the clothes washer.

edit 2: Bank is 12 volt not 24 and 360 AH (late night brain toot).

**Sunking** · 09-30-2015, 12:14 AM

Originally posted by Wooden Indian

Yes I have already purchased it all. Delivered last night.

I was going all in series and thought the 90 volts (at peak 18 volts X 5) could be handled by the controller because of where it says * Max. Solar Input Voltage: 100VDC. I don't know why some deep section of my brain just started screaming at me today.

Your 12 volt panels Voc is 22 to 23 volts, at 75 degrees and gets higher as the temps drop. even without running any numbers 5 x 22 volt panels in series is 110 volts which is greater than the controllers input puts the brakes on that option. It is pointless to carry on with the Voc Temp Correction for cold temps in your area which now puts the panel Voc voltage up around 150 to 160 volts input to the controller significantly exceeding your controller input of 100 volts. You would need a controller with 200 volt input. With your controller 3 panels in series is max in series. 4 and 5 is out of the question. So you need to loose 1 panel, or gain 1 panel, and operate at 24 volts. Your controller can only handle 2 of your panels at 12 volt battery.

**Wooden Indian** · 09-30-2015, 12:28 AM

Originally posted by Sunking

Your 12 volt panels Voc is 22 to 23 volts, at 75 degrees and gets higher as the temps drop. even without running any numbers 5 x 22 volt panels in series is 110 volts which is greater than the controllers input puts the brakes on that option. It is pointless to carry on with the Voc Temp Correction for cold temps in your area which now puts the panel Voc voltage up around 150 to 160 volts input to the controller significantly exceeding your controller input of 100 volts. You would need a controller with 200 volt input. With your controller 3 panels in series is max in series. 4 and 5 is out of the question. So you need to loose 1 panel, or gain 1 panel, and operate at 24 volts. Your controller can only handle 2 of your panels at 12 volt battery.

Thank you. I am so glad I reached out for help. Running an odd number (3 batteries) won't work then, I can add one battery making it 4, running a 24 volt system, and drop one panel. Of course my inverters are 12 volt so... yeah, awesome.

Because I need power before I'll be able to get a new controller and or different inverters, it sounds like I need to run 2 panels when I get there, order a new controller and inverters that can run 24 volts instead of 12. Man... I should have reached out sooner.

**sensij** · 09-30-2015, 12:28 AM

Originally posted by Sunking

Your controller can only handle 2 of your panels at 12 volt battery.

I agree with this. At 12 V, that charge controller is only rated to accept 260 W of PV input. You need a new charge controller if you want to use more than two panels, no matter how you wire it.

To support 360 Ah @ 12 V, you should probably target C/8 = 45 A, but C/12 is 30 A and as long as you are above that, you aren't in too deep of a hole. Your 500 W gets you 42 A or less, so not ideal, but probably close enough for now.

Something like this should work:

Amazon.com

http://www.amazon.com/dp/B00YCI48F4

As Sunking said, your Voc for 5 panels in series is about 110 V. 136% of 110 V = 150 V, and it would take operating at around (25 - 100 deg) = -75 deg C before you exceeded the voltage input (assuming ~-0.35%/deg C Voc thermal coefficient). As long as you use a 150 V 40 A charge controller, you can put your 5 panels in series and stay with the 12 V battery voltage.

Edit: With Amazon Prime, you get free two day shipping. Might still be possible to order it now and get it by Monday.

**Mike90250** · 09-30-2015, 01:32 AM

Originally posted by Wooden Indian

.... Running a laptop and desktop PC, 3 cell phones, possibly some TV (32" LED) on some evenings, a small thermoelectric cooler, and of course a few LEDs in the evenings or lighting......

a small thermoelectric cooler That one item is a deal breaker. Thermo electric cooling is about the very least efficient form of cooling. Next is the desktop computer and the laser printer. Laptop can still suck 95w, unless it's a new efficient model.
Don't forget the video source, DVD player or Sat receiver ?

So the 500w can manage the phones, LED's and laptop, depending on the power they all draw and the sun that you have.

But there is a lot of re-thinking for you to do if you are unable to return the gear.

My suggestion, get one more PV panel, and run 2 strings of 3 panels.
The MPPT is going to be less efficient the more disparity between the solar voltage and battery voltage.
If the controller is robust enough, it will be able to throttle back to prevent overheating or damage, or if it frys, you have a reason to get a good one (Midnight, Morningstar, Xantrex, Steca, Outback

Going to a 24V system would be my next suggestion, but that means new inverters !

**Rainwulf** · 09-30-2015, 04:47 AM

Im with the put the panels in series party, but get a much better controller.

This is mine http://www.ebay.com.au/itm/161199831018
Software control, very efficient, you can graph all the data, or export it to excel, and the big winner is its 60 amps, and can take 145 volts worth of panels.
You can also use a computer to vary the charge voltages which is ideal for when you are maintaining your bank using the maxsmoke method thats stickied in this forum.

And for cheap panels, grid tie panels are so damn cheap.. i have been picking up panels for less then 50 cents a watt.

**Wooden Indian** · 09-30-2015, 05:49 PM

Originally posted by Rainwulf

Im with the put the panels in series party, but get a much better controller.

This is mine http://www.ebay.com.au/itm/161199831018
Software control, very efficient, you can graph all the data, or export it to excel, and the big winner is its 60 amps, and can take 145 volts worth of panels.
You can also use a computer to vary the charge voltages which is ideal for when you are maintaining your bank using the maxsmoke method thats stickied in this forum.

And for cheap panels, grid tie panels are so damn cheap.. i have been picking up panels for less then 50 cents a watt.

Yeah. I stupidly picked up this one http://www.amazon.com/gp/product/B00...ilpage_o06_s01
so... yeah. I'll have to hold off on replacing it until I get on the property so it's delivered while I'm there, and I'll try to stretch thin on a couple hundred watts in series until then... maybe 3 days or so.

Going with another 120 AH battery and a 6th panel as well. Then, once I can afford to change out my inverters, I'll go 24 volt on the bank. Sure wish I would have become a member here sooner. I look forward to being here and learning from y'all.

**paulcheung** · 09-30-2015, 09:03 PM

Things are gone bad already. Unless you can return all the items you have purchased. Otherwise you have to try make things work. If it were me, I will try to see how to spend the least additional money make it work.

I would buy another 30 or 40 amps MPPT charge controller like Tracer 40 Amp MPPT and connect 3 panels in series, then use the 20 amps MPPT you already have to connect the other 2 panels in series. So just buy another Charge controller then all the things will work as long as you don't have high amperage draw in each inverter like 100 amps 12 volts.

**Rainwulf** · 10-01-2015, 08:09 AM

Originally posted by paulcheung

Things are gone bad already. Unless you can return all the items you have purchased. Otherwise you have to try make things work. If it were me, I will try to see how to spend the least additional money make it work.

I would buy another 30 or 40 amps MPPT charge controller like Tracer 40 Amp MPPT and connect 3 panels in series, then use the 20 amps MPPT you already have to connect the other 2 panels in series. So just buy another Charge controller then all the things will work as long as you don't have high amperage draw in each inverter like 100 amps 12 volts.

Yea, this system will work as long as you arent using a lot of power at all, so it really comes down to the question:

What kind of loads are you trying to power?

**Wooden Indian** · 10-01-2015, 09:04 AM

Originally posted by Rainwulf

Yea, this system will work as long as you arent using a lot of power at all, so it really comes down to the question:

What kind of loads are you trying to power?

Pretty light.

2 laptops, an occasional desktop, 3 smartphones, a few LED lights, small thermoelectric cooler.
When power permits, we downgraded our 52" plasma for a 32" LED so we can catch a little television.

I also have 3 generators. One built in the RV, one small 700 watt one, and a 6000 watt larger genny so I can supplement during "less than favorable" conditions.

We'll be in the RV for 2-3 months before we get the mobile home towed and set up at which point we were already planning on upgrading to an 800 watt system.

What do you think? I felt pretty confident when I bought everything, we're set to take off and head that way before sunrise this Saturday. Finally doing it. Bye-bye city.

**lkruper** · 10-01-2015, 10:06 AM

Originally posted by Wooden Indian

Pretty light.

2 laptops, an occasional desktop, 3 smartphones, a few LED lights, small thermoelectric cooler.
When power permits, we downgraded our 52" plasma for a 32" LED so we can catch a little television.

I also have 3 generators. One built in the RV, one small 700 watt one, and a 6000 watt larger genny so I can supplement during "less than favorable" conditions.

We'll be in the RV for 2-3 months before we get the mobile home towed and set up at which point we were already planning on upgrading to an 800 watt system.

What do you think? I felt pretty confident when I bought everything, we're set to take off and head that way before sunrise this Saturday. Finally doing it. Bye-bye city.

I don't see any mention of a traditional grid-powered battery charger to use with your generators to charge your batteries, while you are setting up your panels and when you don't get enough sun to fully charge those batteries.

You need a charger that can supply at least 10% of your battery bank AH. I did not see you mention what kind of battery you have. Look at the user manual to fine tune the charge necessary. I presume you have Flooded Lead Acid batteries? Get a temperature compensated hydrometer and make sure you use it to ensure your batteries get fully charged.

**Wooden Indian** · 10-01-2015, 10:20 AM

Originally posted by lkruper

I don't see any mention of a traditional grid-powered battery charger to use with your generators to charge your batteries, while you are setting up your panels and when you don't get enough sun to fully charge those batteries.

You need a charger that can supply at least 10% of your battery bank AH. I did not see you mention what kind of battery you have. Look at the user manual to fine tune the charge necessary. I presume you have Flooded Lead Acid batteries? Get a temperature compensated hydrometer and make sure you use it to ensure your batteries get fully charged.

3 (soon to be 4) Flooded Lead Acid, currently 360 AH, 2/6A charger (harbor freight cheapie). No hydrometer and that was on my dang list too! Ugg. Ordering one as soon as I get up there.

I'm beginning to doubt what I thought I knew

I'm beginning to doubt what I thought I knew

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