30v Panels for off grid set up

chal

So, this is what I've got and am planning to install.

12x270w (30v) panels (each wired separately instead of series parallel to keep voltage & amps low)
Combiner box with 12x15a beakers
Midnite controller 250
8x100ah deep cycle batteries (might need more) 12v array
12v 5000w inverter (I should have gone with a 24 or 48 but too late now)
60a manual disconnect switch with breakers (to switch from grid power to the battery bank)

Is there anything I'm missing?
Any glaring mistakes?

Also, how high can you kick up your pv array voltage before it becomes unsafe. 60v? 90v?

westbranch

Re: 30v Panels for off grid set up

please tell us what your loads are. A good system design is based on the loads.

That 5000W 12 V inverter is not going to work well for you!

Cariboocoot

Re: 30v Panels for off grid set up

chal wrote: »

So, this is what I've got and am planning to install.

12x270w (30v) panels (each wired separately instead of series parallel to keep voltage & amps low)
Combiner box with 12x15a beakers
Midnite controller 250
8x100ah deep cycle batteries (might need more) 12v array
12v 5000w inverter (I should have gone with a 24 or 48 but too late now)
60a manual disconnect switch with breakers (to switch from grid power to the battery bank)

Is there anything I'm missing?
Any glaring mistakes?

Also, how high can you kick up your pv array voltage before it becomes unsafe. 60v? 90v?

How did you pick that equipment? Looks like random chance.
For example you say you have the panels all "wired separately" which sounds like all in parallel (the 12 breaker combiner box confirms this) and then you have a charge controller capable of 250 Volts input. Why did you not buy a Classic 150?
And while we're at the array you could have wired it for 60 Volts even though that's 5X the system nominal.

Eight 100 Amp hour batteries at 12 Volts? Again a mistake as that's eight parallel battery connections which is more likely to cause trouble with keeping current even for all batteries.

5kW 12 Volt inverter: I sure hope you do not intend to use it anywhere near its rated maximum capacity, as that would be over 400 Amps current draw. Sounds like one of those lousy AIMS inverters.

In short it sounds like one of the systems I get called to fix.

Missing: fuse/breaker on charge controller output and inverter input?
Wire sizes? With all panels in parallel you will be feeding a max current of 100+ Amps from the array combiner to the charge controller. That's fairly outrageous as it would require at least 4 AWG and probably larger if any distance is involved.

Your array is twelve 270 Watt panels or 3240 Watts total. On 12 Volts that's 270 Amps, way beyond what the Classic or any other single controller can handle. That's a huge waste of panels. The largest array you could have for one controller would be about 1250 Watts.

Your 800 Amp hours of battery bank would only need that much, btw: 80 Amps @ 12 Volts.

Are you sure you haven't written something wrong?

zoneblue

Re: 30v Panels for off grid set up

Sounds like your post is precisely the exact amount of days since you bought that stuff too late. Its suprisingly common though, enthusiasm gets the better of us sometimes.

Ok, remedial time. Your priority right now is to return the inverter. Do it asap. That thing is no (or negative) use.

As this is a "bigger" system (3kWp+), you need a 48v system. You can rejuggle the batterys into 48v, 2 strings of 4, assuming your batts are 12volts. Charge rate is then about, 70amps total.

The controller, well youve bought it now. (250 volt version is a specialist controller designed for problematic installations where the array is a long way from the controller). Classics will only take about a kilowatt or so at 12 volts, so you need to go higher anyway to cope with the load. PV, would be something like 4 strings of 3.

Youll need more battery, as 70amps into a 200amp hr bank is too much. You could current limit for a while, but you need closer to 600 Ah for that 3kW array.

But before you do anything else, go back to basics, and do your load analysis as others said.

Cariboocoot

Re: 30v Panels for off grid set up

Yes; upping to 48 Volts is the solution that will fix the most problems with the least effort/expense. And the MidNite can be programmed to limit maximum current until/if you get a battery bank.

chal

Re: 30v Panels for off grid set up

These solar panels aren't 12 volt. They're vmp 31.5 voc 38.5 each.

chal

Re: 30v Panels for off grid set up

The 12 volt inverter is a problem and I'm looking into a 24 or 48v. I'm also adding a fuse to the charge controller output and inverter input.

I suppose my main worry in putting the pv array in series parallel is fire safety on my roof. At 3 X 4, that would put the voltage up to 94.5 voc 115.5vmp

Cariboocoot

Re: 30v Panels for off grid set up

chal wrote: »

These solar panels aren't 12 volt. They're vmp 31.5 voc 38.5 each.

The panel Voltage isn't the problem; the system Voltage is.

niel

Re: 30v Panels for off grid set up

chal,
they are talking about the nominal battery voltage as a 12v nominal battery setup will not work out well for you. contact the place you bought the inverter from and ask if you can return it to get preferably a 48v inverter, but at least a 24v inverter.

if you did not intend to put pvs in series for voltages over 200v then you wasted your $ going with a classic 250 as a 150 would've done.

chal

Re: 30v Panels for off grid set up

Yes, I know they're talking about the battery voltage and that 12v is an issue, but it's a Chinese manufacturer and they don't make anything but 12v. I'm working on selling it and buying something else.

As to the controller, I found a classic 250 for cheap. It was about $10 more than the 150 elsewhere and I wasn't sure how I was going to set up the pv at the time or how much I'd need for the wind turbine I'll be adding onto it.

At the end of the day my biggest worry is that 100v pv is safe when most arrays you see don't go above 48v.

Thanks for all the advice.

Cariboocoot

Re: 30v Panels for off grid set up

Be advised that a wind turbine will need its own controller; you can't connect it in parallel with the PV input of the Classic. They require dump loads too, so that there is always some place for the power to go if the batteries are charged and the regular loads supplied. On the whole they're a pain.

A 48 Volt system will actually have an array Vmp of 70 or more. Anything over 60 is considered 'dangerous', and the danger increases as the Voltage does. But most central grid-tie inverter use arrays that have a Vmp of over 300, and it is still possible to handle them safely.

Any electricity handled unsafely can be a problem, as you can start a fire with a couple of 'D' cells and some steel wool.

zoneblue

Re: 30v Panels for off grid set up

No matter how you do this, this is a serious ssystem you are installing. If you arent confident, or dont have a good grounding in electrical safety, then get help.

In order to run 3kw of panel into a single classic you need to get the string voltage up. Have a play with the string configurator on the midnite website, and see what your options are.

chal wrote: »

Yes, I know they're talking about the battery voltage and that 12v is an issue, but it's a Chinese manufacturer and they don't make anything but 12v. I'm working on selling it and buying something else.

As to the controller, I found a classic 250 for cheap. It was about $10 more than the 150 elsewhere and I wasn't sure how I was going to set up the pv at the time or how much I'd need for the wind turbine I'll be adding onto it.

At the end of the day my biggest worry is that 100v pv is safe when most arrays you see don't go above 48v.

Thanks for all the advice.