How to wire to batteries and inverter

Tim D · April 2015

Thanks for looking.
I will be adding 4 grape160 panels to my 5th wheeler. Mppt controller, which one not sure at this point.
So for the best results do I wire the panels all in series. What if one is shaded?
Also do I just go from the controller to the batteries? What happens when the Magnasign inverter is charging the batteries? Do they both just add to the batteries. Yea not to much up on the sparkly stuff.
I have 4 6volt agms, new.
I have not purchased anything yet, but the inverter.

BB. · April 2015

In general, you don't want to shade your solar electric panels--If you do, a little bit of shade can dramatically reduce the total output of the panel/array (depending on how they are wired, etc.).

So--Like to start from the beginning. You have what AH 6 volt AGM batteries--And is this 2x in series and 2x parallel strings for a 12 volt battery bank? Or for a 24 volt battery bank?

Also, what Grape model number panels? Something like these?

http://www.homedepot.com/p/Grape-Solar-160-Watt-Monocrystalline-PV-Solar-Panel-for-Cabins-RV-s-and-Back-Up-Power-Systems-GS-S-160-Fab8/202959994

With Vmp~18.5 volts and Imp~8.65 amps?

Any specific location for camping? Winter in the south, summer in the north? Snow Camping in Wyoming? etc....

-Bill

Tim D · April 2015

Bill, Agm's are wired for 12 volts. 190 Ah. And yes those similar to the panels I was looking at, seems like a nice price. Unless they are not recommended.
I only camp late spring, summer and early fall. I live on the east coast. Outer banks camping this summer. And mostly state parks. Also run a Honda eu3000 for ac

scrubjaysnest · April 2015

If yours is typical 5ver battery location, curb side front you can mount the controller, CC, and breakers there. I would suggest series parallel for the panels if they are 18.5 volt Vmp. This will reduce wire size needed from the roof. Say 10 awg marine grade from panels a roof mounted combiner. Use 8 awg from the combiner to the CC input if you can keep it to 10 feet. Something like a Morningstar Pro 30 mppt CC is reasonable in price and leaves room for expansion. Usually the 5ver battery compartment is well ventilated so you could mount the inverter in the center compartment. Wire runs from the CC to batteries need to be short and maybe 2 or 4 awg, 2 is larger and may be better. Inverter wiring to the batteries needs to be short as possible. You didn't say what size inverter and that will determine wire size and fuse/breaker size. Breakers are better then fuses. For the CC to batteries size the breaker per CC instructions.

I'm sure BB or others will chime in on this.

Tim D · April 2015

I have a Magnasine Ms2012, 2/0 welding cable to the batteries, max length 30"
Me-Rc remote panel with shunt.
200amp fuse and an on/off battery disconnect.
All this is accessible from the front panel of the camper.
All running great for the last month.

BB. · April 2015

You are at the point where MPPT controller can make solar array wiring easier (2 panels in series, 2 strings in parallel, or other possible configurations, but you need to respect the maximum input voltage from the solar array to MPPT charge controller). However, MPPT controllers (at least those US designed) are way more expensive than PWM.

The size of MPPT controller you would need is:

160 Watt panels * 4 panels * 0.77 panel+controller derating * 1/14.4 volts charging = 34.2 amps minimum MPPT controller rating

So, larger than the cheaper 30 Amp MPPT controllers--So you are looking at 40 amp or larger. A Morning Star 45 amp TS MPPT controller would cost about:

Morningstar TriStar 45 amp MPPT Solar Charge Controller $410

And larger controllers will run:

MidNite Solar Classic 150 MPPT Charge Controller $610

Or a pair of 30 amp MPPT controllers:

MidNite Solar The Kid MPPT Solar Charge Controller $315 each

The MorningStar and "The Kid" don't have fans for cooling--A significant reduction in noise... All solar charge controllers need good air flow for cooling.

PWM controllers can work just fine for smaller installations... But most PWM controllers are "simpler" types and can work OK with the four panels in parallel (Vmp~18 volts)--You should have a "fused/breaker based combiner box" (one fuse/breaker per parallel connected panels when you have 3 or more panels in parallel to protect against short circuits in the solar array).

Another type of solar panel to look at are the >~200 Watt solar panels intended for Grid Tied Solar... Can be less expensive for the solar panels (Vmp~30 volts typical), but you need a MPPT controller to efficiently charge a 12 volt battery bank (and Vmp~30 volt panels cannot reliably recharge a 24 volt battery bank with a PWM controller).

Sorry, PWM/MPPT charge controllers and the mix of solar panels available is a complex subject--And you usually have to do several paper designs to see which is most cost effective for you.

Another question, are you planning on adding more solar panels in the future?

-Bill

Tim D · May 2015

Looks like the Morningstar is the inverter, no fan means no noise. I have 6' x 7' of space in front of the AC. 30" x 48", 40" x 48" and 30" x 72" below and to the side of the AC. So can a go with a mix of units?

Also the choice of panels is mind numbing. Guess I don't need a high efficiency panel. I will be looking at the 400 to 600 watt range of panels.

mike95490 · May 2015

Tim D wrote: »

Looks like the Morningstar is the inverter, no fan means no noise..........

There is sometimes a faint hum from it. But fanless, it's by far quieter than others.

Tim D · May 2015

Mike, followed your link, impressive.
Little hum is ok since it's under the bedroom. Looking at the larger panels with the MPPT controller. Less $ is better.
As alway's chime in to this nubee. 30 years camping, first year going solar.

Tim D · May 2015

Anyway, back to my original question. Any special way to connect the CC to the batteries, since I also have a charger when connected to street power?
If I run my generator to use my AC when camping.
My inverter charger will deliver 85amps to the batteries, now I add my solar CC of say 30 amps, what happens to my batteries, do they cook off and get destroyed? Do I need to shut down the solar when hooked to street power?

Imurphy · May 2015

When you run your generator or are plugged into shore power your converter will be powered. That is not an issue.

Depending on your converter, it alone may never fully charge your batteries due to lack of voltage. Most mobile converters are CV power supplies. they always put out a set voltage I.E 13.4V or so depending on the converter. This will not charge a battery to even 90% SOC. So lets not sweat over charging from this.

Your Solar CC will be programmed to charge your batteries to 100% SOC. So even with an external source your CC will carry on like its supposed to. In fact When you are in bulk mode charging at 14.6+VDC the solar system will not even "know" your charger is running, due to its lower voltage.

If your batteries are quite dead, the converter may help bulk charge until the battery voltage equals or exceeds the converters voltage, then it will be 100% solar.

If you have a "smart" charger, that will apply the appropriate voltage and charging profile, the two systems will work in tandem and not negatively affect each other in any way.

Now for connecting it all up. The best thing to do would be to put a shunt right at the battery - terminal, connected to a battery monitor such as a trimetic, this way you can know where they stand on charge, power used, power put in and load. Than connect the solar CC out leads to the battery with the "house" load connections. Ensure you have a fuse or other OCD in this line.

Tim D · May 2015

Imurphy, I have the Magnasign 2012 which will charge to 100% SOC. also have the Me meter to monitor it, it has a shunt. The charger will do 100 amps, I have it set to 85amps for my 380 ah batteries. So if I add solar to this, I am afraid it will over charge my AGM batteries.

You say they will work in tandem, I don't understand how each charger will know what is being supplied to the batteries.
I have a battery disconnect, then fuse on the positive batt, shunt on the neg side.

Imurphy · May 2015

When you start the generator and the charger kicks on. If the magnum sees over 13 volts it will not go into bulk mode. Your effective charging will be from solar. If the solar does not keep up and voltage drops below 13v(morning, evening or high power use) then the magnum will kick in on its regular charge cycle.

I would watch the current to the batteries for a while, but I do not suspect you will have an issue with overcharging current.

Tim D · May 2015

Sorry for so many questions.
So do I put the solar input, CC, on the inverter side of the shunt, to monitor how many amps is going into the batteries?
I'm also looking at putting 2 250 watt panels on the roof. Cheaper for grid tie panels. I was thinking of running them in parallel in case one gets shaded, good idea?
Or should I just get 4 smaller panels and hook them up series/parallel for higher voltage?
Not really understanding why the grid tie are half the price. Must be a catch.
I was planning on a mttp 45 amp CC.

BB. · May 2015

What solar charge controller do you have right for the installation.

GT panels have higher Vmp and need less copper per Watt of power (higher voltage, lower current).

Also, I am sure volume and commodity pricing plays a huge factor (plus one 250 panel vs 2 or 3 smaller panels].

Draw back is that MPPT charge controllers are much more expensive. The total system cost is what matters.

There is no good way to make shaded panels work better. In your case 12 volt battery with Vmp 30 volt array is best unless you have a very long wire run from array charge controller.

-Bill

Imurphy · May 2015

Keep your panels parallel if you can. And if able mount one towards the front, and one towards the back. That way depending on how/where you park 1 of them will be out of any shade. If you are lucky both will be in the sun. As much as I enjoy the shade, I drive my wife nuts finding the perfect spot where I can get the most sun for our panels.

You want nothing going direct to the battery except the shunt. Any supply or load needs to go thru it. This is the only way the meter will be able to track all the power in and out of the bank. If you connect the CC to the battery. The meter will see the voltage go up, but have no idea how many AH's are in the bank and not be able to tell you the SOC.

Gride ties like BB said are cheaper due to volume. Since the advent of grid tie, it has become the largest sector of the solar industry. Most everyone is on the grid, while there are not many of use off the grid. High voltage panels make everything associated with grid tie easier, and the volume of panels makes it cheaper.

I dont have a bunch of experience with MPPT controllers, but what I have found is that their sweet spot is ~2X bank voltage. So if you have a 12 volt system(15 volts to charge) you want 30 volts feed to the CC.

How to wire to batteries and inverter

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