Need wiring advice on my 24 volt off grid system

[Alabamaoffgrid]

Hello,

I'm putting together an off grid genverter system with these components:

1

[Mike90250]

you have to use the Classic string calculator to figure if you can put all 4 panels in series (lowest losses) or if you have to go 2x2 array, the Open Circuit Voltage of the panels cannot exceed the max input of the classic, or you smoke it.

12 batteries ? Yikes, that's going to be a problem. 4 in series, 3 strings in parallel.

read up on connecting on the "diagonal"

Here's a great article about connecting batteries in parallel (on the diagonal)
http://www.smartgauge.co.uk/batt_con.html (connect batteries on diagonal )
and the book:
http://www.batteryfaq.org/ (very large)

MC connectors and cables are spec'd for 600V - BUT you cannot make/break with power/panels lit up. Got to cover them all with a tarp, or manually shut down the controller first, then open the breakers. or do it at night. A DC connection will try to ARC WELD when you make or break the circuit.

[Alabamaoffgrid]

Thanks Mike for the advice and the links. I will read up on them.

I have everything except the batteries, so I could do something else. Is there a better option for a $1200 battery budget? I would love an AGM battery bank, but I can't afford it now. I have limited options locally.
I really need about 550-600 ah battery bank.

The panel VOC is 35.4 The MPPT charge controller input voltage rating is 150 volts. It says that if you keep it on HyperVOC mode, it can take 150v+48v=198 volts without breaking, but I don't want to test it. I think I will do the 2 in series then parallel option.

[Naptown]

You might be able to do all panels in series
Check the Voc ratings on the panels, then do the temp corrections to your record coldest day where you live.
I have a feeling you will be under the 150V

[Sunking]

I have everything except the batteries, so I could do something else. Is there a better option for a $1200 battery budget? I really need about 550-600 ah battery bank.

Budgets and soar PV with batteries is an oxymoron statement. So you may be screwed.

Battery cost for a decent 3 to 5 year battery is $200/Kwh. A 5 to 8 year battery is $240/Kwh. To determine the Kwh is really easy multiply the battery voltage x Amp Hours = watt hours.

You mention 550 to 600 AH but that number is meaningless without a voltage. If this is going to be configured as 24 volts then 24 volts x 600 AH = 14,440 watt hour or 14.4 Kwh. There is no way on earth you can buy that for $1200. You are looking at $2800 to $3500. Well you might do it for $1200 if you go to Wally World or his Brother Sam and buy their cheap golf cart batteries, but you will be back there in a year buying replacements.

In addition you do not want to use 6 volt golf cart batteries as they are not made to do deep cycle applications. They are a hybrid battery and you will only get 2 maybe 3 years at most out of them. You want to find a 600 AH battery like Rolls 4-CS-17P, 6-CS-17P, or 8-CS-17P. These have a full 10 year warranty and is only discharged 20% daily and fully recharged will give you about 5000 cycles.

Another battery to look at is Crown

[Bala]

You mention 550 to 600 AH but that number is meaningless without a voltage

ummm, the title of the post is "Need wiring advice on my 24 volt off grid system" and he a has a 24V inverter.

ha ha

[Sunking]

ummm, the title of the post is "Need wiring advice on my 24 volt off grid system" and he a has a 24V inverter.

Yes I know. point is he cannot have 24 volt battery @ 600 AH with only $1200. He needs about 3 times that much money.

[Alabamaoffgrid]

OK, thanks for all the help. I've been reading this forum for a while and appreciate all comments.

I will look at the batteries Sunking suggest.

[Sunking]

OK, thanks for all the help. I will look at the batteries Sunking suggest.

You are welcome. The batteries will not be cheap, but if you take care of them they will last you up to 10 years.

With batteries you get exactly what you pay for. You can buy batteries for $100/Kwh and they will last a year or two, or you cany buy a Rolls for about $220 to $240/Kwh and they can last 10 years assuming you do not discharge more than 20% per day and take excellent care of them.

[Mike90250]

Another thing to keep in mind about batteries -

Many people kill their first set ! So sometimes, there is wisdom in getting a cheapo learning set, and then get the top of the line.

Also, getting a battery monitor could be a good investment, to monitor charge and discharge from the bank.

[Sunking]

Many people kill their first set ! So sometimes, there is wisdom in getting a cheapo learning set, and then get the top of the line.

Agreed but it is out of ignorance and typically on a very small scale of like a 50 to 100 AH 12 volt battery so they are only out $100 or so. 24 volt @ 600AH is not a toy, nor is it cheap with cheap batteries. True he could go the low ball rate for $1200 to $1500. You and I both know if he does that, takes good care of them, will only last 1 maybe 2 years tops.

So the options are spend $2500 today, learn how to maintain batteries from the strart, and be set for the next 5 to 10 years. Or spend $1200 now for low ball batteries, then in a year or two dump another $2500 for quality batteries.

I like paying once for quality and calling it done right the first time. But that is just me. That is why I hate battery systems. The expense never ends, and no way to ever get ahead. You end up paying 10 times more for electricity the rest of your life. It baffles my mind why anyone in their right mind would make that choice if they do not have to. I suspect those that do are in politics like POTUS now days.

[Saggys]

You end up paying 10 times more for electricity the rest of your life. It baffles my mind why anyone in their right mind would make that choice if they do not have to. I suspect those that do are in politics like POTUS now days. [/QUOTE]

I know why I am doing it, I just got the estimate to have grid power installed. I can buy alot of batteries for the cost and wait for the grid to get closer to me.

[russ]

I know why I am doing it, I just got the estimate to have grid power installed. I can buy alot of batteries for the cost and wait for the grid to get closer to me.

Same situation as Mike is in - might follow what he is up to for information.