Solar gurus please comment on my shopping list!

[ski2live]

Again thanks everyone for your input.

Originally Posted by BatteryPro

I often hear people say things like “I would run X size here and Y size there”. That might work or it might not. The size of the wire for a PV solar system should always be a calculation, not guessed at, unless you can afford to waste money or power...

Larry

Larry: I am definitely not using the prewire I'm just glad its there so that I can pull it out a bit... Wrap some electric tape around the existing wires to the new #4 (i think) and hopefully pull it down into the panel area. I have my lengths of #10 pre cut and ready for panel install tomorrow. I am hoping to at least get the panels on and combiner box installed. The rest can happen over the next couple weeks after I wrap my head around all my needs.

Regarding the series wiring, I think I follow what your saying.. Though my panels are wired in parallel the circuit to the controller is in series?

I have looked at some voltage drop calculators and I'm not having any luck with them. Theres a lot of questions I don't know. ie:

Distance or Conductor Size:
Single or Three Phase
Conductor Type:
Installation:
Voltage:
Maximum voltage drop:
Conductor Size:
Current:

Although I agree with many of the comments above, I strongly suggest you read the specs of your PWM controller VERY CLOSELY....

Pigman: I've read the specs very closely. If I achieve full harvest which is unlikely I could pull up to 32amps. My controller is designed to handle up to 31amps and will not exceed that. I believe they engineered it that way. If I do find I need to add more panels I will get a bigger controller.


There's a lot of information that is overwhelming for a first time installer.

I'm going to try and draw a wiring diagram for you folks to pick apart and hopefully I can develop something that makes sense over the next week or so.

[Old Scout]

OK--I read all the posts here and now feel like a total dummy. Not to hi-jack the thread but if I might--could I get a clarification on the 12v vs 24 volt panels. Right now, my coach is equipped with a minimal 100watts [2 panels], a controller sized for that wattage, a 2000 watt [12v] inverter, and six 6-volt batteries. I once heard a "rule of thumb" that matches panel watts to battery storage--so with approx. 660 amp/hrs of battery storage and a relatively new 2000 watt 12v inverter, what would make sense for me to buy/build? I am not a big boon-docker but would like to reduce my genset time when we do go off grid. Again, sorry to have diverted from the OPs original question.....

[ski2live]

I posted this in another thread so apologies if you have seen it but here is my wiring diagram so far. I get confused when the inverter comes into play. I think I've got it right so far though.

[JFNM]

If asking about how to wire the inverter - the inverter positive to the battery positive (or "insulated positive lug", in your case) and inverter negative to shunt (opposite side as the battery). In both cases, with BIG cables (#4 or #6), depending on length. You mentioned cable sizing in the other thread. Here is the calculator I use. If not at my computer, I just use the basic printed charts that seem to be in about every manual every printed.

[twinboat]

Originally Posted by ski2live

I posted this in another thread so apologies if you have seen it but here is my wiring diagram so far. I get confused when the inverter comes into play. I think I've got it right so far though.

Magnum recommends 2/0 battery cable for your inverter up to 5 foot distance, one way.

The neg of the inverter goes to the left side of the shunt, in your picture. You also need 2/0 from the right side of the shunt to the battery bank. Keep the total length under 5 foot, otherwise you may need to use larger cable.

The pos of the inverter can go to either the power post or directly to the battery bank. Again keep all of the wires 2/0 gauge and under 5 foot.

[twinboat]

Originally Posted by twinboat

Magnum recommends 2/0 battery cable for your inverter up to 5 foot distance, one way.

The neg of the inverter goes to the left side of the shunt, in your picture. You also need 2/0 from the right side of the shunt to the battery bank. Keep the total length under 5 foot, otherwise you may need to use larger cable.

The pos of the inverter can go to either the power post or directly to the battery bank. Again keep all of the wires 2/0 gauge and under 5 foot.

Update, Magnum says up to 3 feet with 2/0. More then that 4/0.

[Reed Cundiff]

Originally Posted by BatteryPro

Don't try this. You won't be able to operate your 12 volt, 2000VA Magnum inverter from a DC converter. The inverter can draw up to 190 amps (2280 W).

Larry

Apparently there was some confusion on the part of the reader. Our Magnum 4 kW PSWI runs directly off our 48 V(nominal) 9.6 kW-hr LFP battery suite. The 508 W Meanwell 48 V to 12 V power supply is only to supply power to the 12 V internal system of the 5th wheel.

We have trialed the battery-inverter to around 3.5 kW by running the micro-wave and air-conditioner simultaneously.
Reed and Elaine

[BatteryPro]

Originally Posted by Reed Cundiff

Apparently there was some confusion on the part of the reader....
Reed and Elaine

Hi Reed,

I understand your system. I was tellling the OP to not try making a high voltage battery system because he already bought a 12 volt Magnum inverter. If he tried that, he would need a massive DC converter to run his inverter.

Thanks, Larry

[Luv2go]

Originally Posted by ski2live

I posted this in another thread so apologies if you have seen it but here is my wiring diagram so far. I get confused when the inverter comes into play. I think I've got it right so far though.

This is probably obvious but you have the connections on the top of your SC2030 reversed, I'm sure you meant to tie the battery positive to the + bat side of the SC2030 and the positive wire coming out of your solar panel breaker to the + solar side of the SC2030.

Another thing which is probably obvious, for the shunt to work properly nothing but the battery should be connected to the right side of the shunt in your sketch. All wires to house lights, chassis ground, inverters, converters, etc must go to the connection in the left side of your sketch.

In response to your voltage drop calculator question (click on the picture to make it readable):



I used the Arizona Wind and Sun calculator. Adjust the Length of cable run and current to your values. Note that they always say "utilizing a xxx kcmils", it's safe to say that with results like 8 to 0 or 1/0 to 4/0 they mean AWG, kcmil wire size commonly starts at 250 and come in increments of 50.

Also as twinboat says, use the proper wire both to and from the inverter all the way to the battery. The run from the shunt to the battery takes the full inverter current. 2/0 and 4/0 wire is not cheap, so you'll want to minimize the length by mounting your inverter as close as possible. Again it may be obvious it needs to be installed in a weatherproof compartment, not in the vented area where the T105 vented batteries are.

[BatteryPro]

Originally Posted by Old Scout

OK--I read all the posts here and now feel like a total dummy. Not to hi-jack the thread but if I might--could I get a clarification on the 12v vs 24 volt panels. Right now, my coach is equipped with a minimal 100watts [2 panels], a controller sized for that wattage, a 2000 watt [12v] inverter, and six 6-volt batteries. I once heard a "rule of thumb" that matches panel watts to battery storage--so with approx. 660 amp/hrs of battery storage and a relatively new 2000 watt 12v inverter, what would make sense for me to buy/build? I am not a big boon-docker but would like to reduce my genset time when we do go off grid. Again, sorry to have diverted from the OPs original question.....

Hi Old Scout,

PV solar modules (aka panels) come in many different operating voltages. [moderator edit] modules that operate from 16.5 volts all the way up to 90 volts.There are some refered to as 12 or 24 volt but in reality they are much higher. A 12 volt nominal module is usually 16 to 20 volts. A 24 volt is usually 34 volts or higher.

If you use an older technology PWM type charge controller, you should use a lower voltage solar module. The reason is that you will be wasting much of the power you purchased because that type of controller can never use the full power of the module.

If you are using a modern MPPT type controller, then you can use higher voltage solar modules, up to 250 volts for a 12 volt system. It's not advisable to use over 50 volts for a few reasons that I won't explain here.

The rule of thumb is another myth or what I affectionatly call "campfire talk". The amount of PV solar you install, whether small or large, will contribute to your overall daily energy consumption. A small PV system like you have can not make the energy you consume each day. This means you must make additional power from some other source. You can't fully charge your 6 batteries either as the most power you can make is about 35AH in one very sunny, cold day. Most RV's have a parasitic loads of at least 20AH per day. That only leaves 15AH maximum to run everything else in the RV.

When you say buy or build, I never recommend that you try to build a PV module. There are so many factors that affect production it is a money looser. You can purchase PV solar modules at very low prices today. I always recommend to people that boondock to have at least 500 Watts of power. A system that size can be purchased for about $800 on the cheap side. If you rarely dry camp, it may not be worth the investment compared to more generator time. You can go for a couple weeks without fully charging your battery and you won’t harm it because when you plug in again you will get a full charge.

Larry

[Luv2go]

OBTW ski2live, where do you plan on getting your 2/0 or 4/0 wire? None of our local electrical supply houses or big box home centers had it, I ended up ordering it from a marine supply store. All these people had was THHN house wire, not suitable for RV use due to lack of flexibility. Be careful on eBay, many sell so-called power cable which is really aluminum or copper coated aluminum, you need real copper. A quick search on eBay showed the cheapest real copper wire was about $10 per foot plus shipping. Local marine suppliers such as West Marine may be better for you if you're close to one as you've mentioned you're in Canada.

Something thing missing from your sketch is the inverter catastrophe fuse, mine needed a 400A class T fuse or 250A DC rated circuit breaker. These should be available from the same source as your inverter. A fuse will need a fuse holder also.

Arguably, the wire interconnecting the batteries should be the same gauge as the wire going to your inverter. Some would say that half the current would go through each battery but I was not willing to bet my families safety on that, so I used full rated wiring for each interconnect, in your case it'll be 2/0 or 4/0.

You'll have to terminate each of these wires with lugs, I just called my nearby West Marine and they have a crimper they would let me use in their store. They also have wire at a reasonable price (about $13 / foot) and a selection of lugs.

Note the lugs may need different diameters on each end. Batteries, for example, have different diameter studs for positive and negative.

[BatteryPro]

I posted an answer for you about the inverter on the other thread you started. http://www.irv2.com/forums/f56/solar...ml#post2769428

[BatteryPro]

Originally Posted by Luv2go

...
I used the Arizona Wind and Sun calculator...

Wow, for 34 amps @ 13 volts running 30 feet their calculator recommends wire smaller than 16 AWG (2 kcmil). Thats odd. See conversion here: https://en.wikipedia.org/wiki/American_wire_gauge

Larry

[Reed Cundiff]

Originally Posted by BatteryPro

Hi Reed,

I understand your system. I was tellling the OP to not try making a high voltage battery system because he already bought a 12 volt Magnum inverter. If he tried that, he would need a massive DC converter to run his inverter.

Thanks, Larry

Sorry, my mistake. Magnums are expensive, as we well know.

Reed