Can I get a thumbs up?

[Mikevr007]

Have:
-Six 150w 12v PV panels.  Four of one brand, two of another.
-MNPV6 with 15a breakers
-Six 12v LiFePo4 100ah batteries (Renogy) wired parallel.
-4000w inverter
-10ga y-cables
-10ga tray cable
-MC4 connectors

Will be purchasing:
-Midnite Classic 150

My plan:
-Three strings of two panels in series.  Two strings will be 43.82 Voc and 9.23 Isc.  Third string will be 45 Voc and 8.58 Isc.
-Each string will connect to a 15a dc breaker, three breakers total using 10ga tray cable.
-Battery disconnect and fuse on positive side between battery bank and Classic 150.
-Battery/inverter side is already wired up using recommended gauge (amps+distance) welding cable.
-Off-grid

I think my reading and research, much of it here, is reflected above but because you don't know what you don't know...to those that know this stuff inside and out please offer opinions, suggestions, comments.
Thanks!
Mike

[ClassicCrazy]

The Midnite MiniDC box makes wiring up a lot easier - it has inverter breaker, and place for pv input breaker and controller breaker to battery. It also has place to mount the shunt which you will probably want for putting the Whizbang on for monitoring system ( and controller Classic Aux relays) .  The Classic mounts on top of Mini DC box with matching knockouts . That box is well worth the $$ - keeps wiring nice and neat and has a schematic on it how to wire it up ( look at manual online to see it ) .

Usually you use largest gauge wire from combiner to controller ( first breaker in mini dc box ) that you can - usually 6 gauge so you get low voltage drop and max amps Classic can handle so 60 or 63 amps I think it is. If you are using 12v you probably want to  put in 100amp breaker from classic to battery - use the midnite breakers that have the 1/4 stud mount . Three of those type breakers will fit in minidc box.

I think  your PV looks okay but if Vic sees this post he is a pro for advice on those. Did you use the Midnite string calculator ?
You didn't mention how far you are running from pv to controller.
Not sure what you are using the y cables for ?

Larry

[Mikevr007]

Hey Larry,
The distance from PV panels to combiner will be less than 20 feet.  Combiner to the 150...four feet(?)...not far.
The y-cables are for series'ing' two 12v panels (x3, 6 panels total) to feed 24v to the Classic 150.
Battery side of the Classic 150 is 12v.
I appreciate the info on the MiniDC and the Whizbang.  I'm trying to keep costs as low as possible by using what I have but I will look at those.  I have not sized the the fuse yet for between the 150 and the batteries but I could, and may very well, go with a din mount dc breaker if that makes sense.
I have not used the string calculator but I will look for it.
Thanks.
Mike

[ClassicCrazy]

If your PV have the wires with MC4 connectors on them - which most do - you don't use Y connectors for series. You just plug the positive of one pv into the negative of the other pv and then you wind up with one positive and one negative and make a wire with your mc4 ends which goes to the breaker in combiner box and the negative to the bar in there. From the combiner box you go right to your positive input breaker and that goes to the controller.  The negative from your combiner box goes right to your controller - though on the Classic you can bring one negative down from the Classic negative and tie both the PV input negative and the Battery negative together if you want. If you are putting in a whizbang and shunt all the negatives for everything in the system will be one side of the shunt and  on the other side of the shunt is only the negative cable going to the battery .

Larry

[Resthome]

Don’t use a DIN breaker for battery or control breakers.They a polarity sensitive and use a screw clamp for wire connections. Panel mount breakers are not polarity sensitive and as Larry mention have studs to crimp on lug terminals. Just my 2 cents.

[Vic]

Hi Mike,

Will add a bit of a snide comment:

If you really need anything close to  FOUR THOUSAND watts of inverter power,   then the system should NOT run on 12 volts.

4 KW at 11-ish volts is nearly 400 amps !   This is a huge amount,   and cannot be handled efficiently at 12 volts,   where voltage drop,  due to these huge currents has a large negative impact on system performance.

AND,   almost any 12 v inverter that claims to be able to output 4 KW,   is usually based upon lies IMO.

Furthermore,   be certain to look at the Tare,   or idle power consumed by the inverter,   at no load.   Usually  this idle power will probably result in a large power consumption,  if the inverter runs continuously.

Could you please let us know the brand and model number for that inverter?

Is there a compelling reason that your system needs run at 12?

Just a drive-by comment.     Vic

[Mikevr007]

Thank you Larry for the reminder.  BTW, tried out the Classic calculator and got a green for the 150.

Resthome, nah not going to.  I have a fuse I can use (need to double check the rating) and a spare battery disconnect that is rated for more capacity than needed.

Ok....and now for the rest of the story, well some of it anyway.  Thanks for your patience.

I am helping someone and this person tends to buy stuff with loose plans and...the target keeps moving.  I think the target is now nailed down meaning no new purchases that will cause a redesign.  The system components and overall design has changed four times.

I wholeheartedly agree with 12v on the battery/inverter side.  24v battery/inverter side was the plan.  However, Renogy says "DO NOT" wire their LiFePo4 batteries in series which was discovered after the batteries were purchased.  They don't explain why, I'm guessing their BMS(?).  At 8-900 each (and not my money) I wasn't going to go against their recommendation.

So, cables between the battery bank and the inverter have been sized according to recommendations for their 4kw model at 12v which their manual says is 150mm² (up to 5m).  We chose 4/0.  Cable length from the battery bank to the Sungold Power brand "Pure Sine Wave Combined Inverter Charger" inverter is less than 4 feet and will include a 400a fuse and battery disconnect rated at 600a on the positive cable.  They don't like model numbers so it's just a "SUNGOLDPOWER 4000W", which they claim has a surge rating of 12KW!  Anyway, The inverter will only be used for emergency power, manually, no auto transfer.  It will power less than 20 amps (AC) of lights(all LED), refrigeration, and well pump.  Its idle consumption is 45 watts or less so they say.

For the solar side, since each string will be less than 10 amps, I think the 10ga tray cable is overkill but it's what we have so will be using that.  From the combiner to the Classic 150 I'm thinking the 10ga will still be fine because the max current between the two will be less than 30a (?).  Distance between them will be less than 10 feet.
Cabling from the Classic to the batteries will be 2ga unless someone thinks otherwise.

I don't insult easily so snide, chide, deride away!

Thanks for your comments, much appreciated.

[Vic]

OK Mike,   Thanks for the context of this system.

Sounds like you ARE off to a good start.

Have fun,  Vic

[mike90045]

Explain to me, how much less than 30A, will the charge controller output be, to the batteries.

I ask for 2 reasons, Voltage drop and cable heating.   10ga is rated for 30A.  And since the Classic has no remote voltage sense, running undersize cable, can leave lead acid batteries undercharged.  Li batteries not so much, but -

cable and connection overheating is a distinct possibility, and making that run with #8 will improve things.

[Mikevr007]

Thank you Vic...I'll take your word for that!

mike90045, the charge controller output to the batteries according to the Classic calculator could be a bit over 60a (if I'm reading the results correctly) which is why we're going with 2ga to the batteries.

Which leads me to ask, based on the Classic Sizing Tool (aka Classic calculator), "Rated PV Array Power" is "25.41 Amps" and "Battery Charging Current @14.4V" is "62.5 Amps".  Is that the highest amperage the Classic will see from the combiner and send to the batteries respectively?  Those numbers are what I am gauging my wire gauge on between the combiner and the Classic and the Classic and the batteries.
Thanks,
Mike

[ClassicCrazy]

Thank you Vic...I'll take your word for that!

mike90045, the charge controller output to the batteries according to the Classic calculator could be a bit over 60a (if I'm reading the results correctly) which is why we're going with 2ga to the batteries.

Which leads me to ask, based on the Classic Sizing Tool (aka Classic calculator), "Rated PV Array Power" is "25.41 Amps" and "Battery Charging Current @14.4V" is "62.5 Amps".  Is that the highest amperage the Classic will see from the combiner and send to the batteries respectively?  Those numbers are what I am gauging my wire gauge on between the combiner and the Classic and the Classic and the batteries.
Thanks,
Mike

yes the Classic Sizing Tool should give you those correct numbers. Though around here in winter when it is very cold sometimes the PV can go over rated amperage though that is more rare, and usually you don't get the rated power.

What Mike was saying is from your combiner box to the Classic is to go larger size wire since it will have less voltage drop and won't be near it's max capacity won't heat up the wire .  So 12 or 10 gauge from PV to combiner box and he suggested 8 from combiner to Classic - or you could go up to 6 gauge which would be the maximum of the Classic input if you ever decide to put more PV on your system . Use appropriate breakers for your wire size.

You certainly want to use 100 amp breaker between Classic and battery charging wires and appropriate wire size for that part of circuit.

Larry

[mike90045]

yep, what ClassicCrazy said about my post.

[bee88man]

Need more specifics about well pump...start-up current surge, full load running amps and voltage...

[billmill]

THUMBS UP BRO!

[Mikevr007]

Been up to my armpits in auto repair.

Thanks all for your input.

bee88man, I'm not so concerned about this system beyond the inverter as that's all been figured out.  The solar/charge side was my main concern to complete the design and I'm glad I asked; got some good info and suggestions.

73