New solar project

[daveyboy12]

I have a 30 foot travel trailer with plenty of space on the roof and I want to do some remote camping. I'd like to be able to run the refrigerator, watch TV through-out the day, and be able to use laptop, and some other small electrical items.

I was planning on getting two of the Grape 250 watt mono panels. I've heard others say the MC4 connectors don't work all that well so they cut the MC4 off and splice in 10 or 8 AWG. I know this likely voids the panel warranty. Either way, I would fish the two sets of wires down an existing vent (refrigerator vent likely). Down into the lower storage bay.
There I planned on buying a decent charge controller, something I could use on another project down the road, the midnite classic 150. I would likely install a breaker/shut off box (as smkettners install).

I am thinking I could get 8 six volt trojans (T-105) batteries with a 1500w or 2000w inverter.

I was even thinking about installing a 30 amp transfer switch, wiring the inverter into the 'generator input' and taking the existing 30 amp shore power plug, wiring that into the 'shore input'. Then wiring the transfer switch output to the existing shore power input. That should give me power to the entire trailer??? I don't think I could run the microwave and everything, but that would allow me to use any receptacle.

Does anyone have any suggestions?

[Almot]

With 1000W panel, 80A unit will do.

[time2roll]

Midnight Classic 150 is rated way more than needed for 500w. Good for at least 1300w. (95a x 13.5 volts)

[Almot]

daveyboy12 wrote:
I'd like to be able to run the refrigerator, watch TV through-out the day, and be able to use laptop, and some other small electrical items.

I was planning on getting two of the Grape 250 watt mono panels.

Some "small items" draw a lot more than big items, especially "small" 120V items. Microwave will draw more than DC circuit of LP fridge, coffee maker can draw more than MW, and the DW running her hair drier on Hi for half hour will draw more than MW for the day. With 500W solar you can have all these items, but some self-discipline is needed not to run them all at the same time and to restrict the use on some days. If you can make your meals and coffee on propane, your daily energy draw will be a lot smaller, and 500W will work fine. If you can't - then you will need either more solar or a generator because on some days 500W won't harvest enough.

daveyboy12 wrote:

I've heard others say the MC4 connectors don't work all that well so they cut the MC4 off and splice in 10 or 8 AWG.

MC4 connectors work perfect. The problem is that the panel has 3ft long MC4 cable, but controller takes a stripped wire and it is faar away from the panel, so you have to transition from the panel to controller. For that, you need one looong MC4 cable cut in half - MC4 ends connect to the 3ft MC4 panel cable, and stripped ends go to controller.

Yes, many people choose to run #8 or #6 or thicker cable to controller. For parallel wired panels and long wire run you might have to. MC4 comes in #12, #10 and #8. There is probably no MC4 in #6 gauge.

daveyboy12 wrote:
I know this likely voids the panel warranty.

I don't think it matters these days. Shipping cost is nearly as much as the panel itself. If it works when you pick it up or receive at home, it will work for many years. It's easy to test the panel right in the warehouse.

There I planned on buying a decent charge controller, something I could use on another project down the road, the midnite classic 150.

Way overkill. 500W panel needs 30-35A controller, and 45A would be a little overkill already. Unless you plan to upgrade to 2,000W in future, you don't need 150A controller.

daveyboy12 wrote:
Got it, I see the - from one panel goes directly to the + of the 2nd panel, and the two left run down to the charge controller.

SMK was talking about series connection. If you have to have a parallel for some reason, then you can still use MC4 connectors, but you will have to buy costly Y-splitters or whatever they are called, for parallel wiring of MC4.

[daveyboy12]

Got it, I see the - from one panel goes directly to the + of the 2nd panel, and the two left run down to the charge controller.

Thanks

[time2roll]

Except no combiner box. The panels will literally connect to each other directly. Just insert one male/female MC4 from each panel and you are done. The MC4 cable then snaps on direct to the two remaining connectors. If the panels are mounted too far apart you just get the extension cable needed and snap them together. Low tech, plug and play.

This exactly how a home system is wired except they have 12 or more panels all snapped together and a single pair of wires coming down to the grid tie inverter. These are often close to 600 volts.

[daveyboy12]

red31 wrote:

daveyboy12 wrote:
I've heard others say the MC4 connectors don't work all that well so they cut the MC4 off and splice in 10 or 8 AWG.

This seems odd, why not open the box on the back of the panel and wire directly or open the box and add short MC4 versus cutting.

I appreciate the input from everyone, I probably am overkill for what I want to do - but good advice, the fridge can run off propane, I was thinking worst case where I wanted to preserve the propane for cooking.

I was probably wrong about the MC4 guys cutting them off, it was probably more they were just taping into them from the back of the panel.

I've read about the combiner boxes. I assume that is really only necessary where you have multiple panels coming in and you want to wire them in series? Assuming I go with the midnite classic, I could do a homemade combiner box on the roof, uping the voltage to 48+ on the two panels, and one set of wires coming down to the charge controller? Would I just use 8 AWG or something like that coming from the combiner box down to the shut-off / fuse box, than onto the charge controller?
How much maintenance are we talking about with the batteries, typically? What is a good GEL battery for solar. Do they have a decent life?

[red31]

daveyboy12 wrote:
I've heard others say the MC4 connectors don't work all that well so they cut the MC4 off and splice in 10 or 8 AWG.

This seems odd, why not open the box on the back of the panel and wire directly or open the box and add short MC4 versus cutting.

[MrWizard]

RV absorption fridge ?
leave it on propane Not on electric
electric uses way to much power around 300 watts to power the heating element
thats 24 amps , the avg total output from your solar panels
'fridge control' uses very little power

[time2roll]

Standard RV fridge will mostly run on propane and is not a huge 12v draw.

The rest of the stuff can be run from a 300w inverter. Microwave needs 1800+ watts, electric coffee needs 800-1200 watts and other big stuff that can often be avoided.

MC4 is excellent IMO. They are specifically designed for all conditions up on a roof for 20+ years.

Midnight Classic 150 IIRC goes to 150v Voc so I have to recommend series panel connection with just two wires coming down. Due to the high voltage I do recommend an appropriate switch on the panel connection for ease of service and safety.

8x T105 is a lot of battery. With a small inverter and LED lights you may only need two T105s and four would get you through a period of clouds/rain. If you go 2000w inverter then you do need four but I would wait and see if you need the second set of four. Could about go to a 24v system at this level.

Whole house inverter connection is fine. I only recommend sine wave inverters.

[2oldman]

daveyboy12 wrote:
the midnite classic 150.

I am thinking I could get 8 six volt trojans (T-105) batteries with a 1500w or 2000w inverter.

That should give me power to the entire trailer???

Great controller..good choice.

8 wet batteries is very heavy and a lot of maintenance. If you can afford that controller, perhaps you'd prefer AGM batteries.

It will. That's what I do.

[westend]

renoman's compilation of Member's solar installations Thanks, Reno!

The 30 amp direct connection with transfer switch has some merit as all receptacles are then powered. You could also use individual, smaller transfer switches (ala smkettner) to power select circuits. If all you are going to need is screen, laptops, and installed circuit boards, there are lesser systems that will allow that, i.e. you won't need 8 Trojans and 500w of solar charging with 2000w inverter.

First step: Downloadable spreadsheet for use and solar calculations

BTW, MC4 connectors are purpose-built for solar application. They are available in 10AWG and you can't find much better.