how do I get the electricity into the trailer?

[cmell]

hi,
I just finished installing two 12V 120W Mitsubishi panels in series at 24V, an Outback MX60 MPPT charge controller, a TriMetric battery monitor, and six 6V batteries wired in series at 12V.

Now I'm wondering about the best way to get the electricity into the trailer. The simplest way seems to be to cut the huge lead terminals off the trailer's old battery cables and splice the wires with some 2 gauge wire connected to the positive and negative bus bars in my solar DC center. it almost seems too easy, but that should work, right? the trailer's old battery cables are 6 gauge so I figure with bigger wire we'll stay on the safe side.

I also still need to ground the whole system but I'm not sure how to do that. Do I need to ground each component separately, or can I just have one main system ground? And how big does the wire that I connect to the grounding rod need to be?

Thanks for any guidance.

[Inland RV Center, In]

Originally Posted by cmell

hi,
I just finished installing two 12V 120W Mitsubishi panels in series at 24V, an Outback MX60 MPPT charge controller, a TriMetric battery monitor, and six 6V batteries wired in series at 12V.

Now I'm wondering about the best way to get the electricity into the trailer. The simplest way seems to be to cut the huge lead terminals off the trailer's old battery cables and splice the wires with some 2 gauge wire connected to the positive and negative bus bars in my solar DC center. it almost seems too easy, but that should work, right? the trailer's old battery cables are 6 gauge so I figure with bigger wire we'll stay on the safe side.

I also still need to ground the whole system but I'm not sure how to do that. Do I need to ground each component separately, or can I just have one main system ground? And how big does the wire that I connect to the grounding rod need to be?

Thanks for any guidance.

Six 6 volt batteries in series will provide 36 volts, not 12.

I would suggest that you draw up a schematic and post it.

Trying to help someone especially with electrical needs, and not having "ALL" the specifics, is walking a huge liability sidewalk.

I doubt that you will get any answers until you can be "exactly" specific.

Andy

[SteveH]

I agree with Andy. It seems your own statements are conflicting. You first state two 12 volt pannels in series for 24 volts, and to my knowledge, all RVs built in this country have 12 volt systems....certainly all Airstream trailers. Then, like Andy says, 6 X 6 = 36, not even the 24 you previously state.

Please tell us why you want to go with something other than the standard 12 volts. And, are you aware if you do go to 24 volts, you will need to change all lights, fans, and appliances for ones designed to run on 24 volts?

If you just want more battery and charge power, it's a simple matter to connect your two pannels in parrallel, to get twice the charge power while staying at 12 volts. Then, you can also wire the six 6 volt batteries in series/parrallel to get more power, while staying at 12 volts.

[HowieE]

I think what you are trying to do is wire the 2 panels in parallel to produce 12 volts, higher wattage to the batteries off the panels, and wire the 6 volt batteries in series/parallel, 3 sets of 2 batteries each wired in series and then the 3 sets wired in parallel. This will give you the 12 volt output off the batteries to the trailer.

The wire size for the panels should be large enough to carry the combined current from 2 panels, 240 watts. #12 wire should be large enough.

When connecting to the batteries just make sure you have the polarity of the panels matched to the polarity of the batteries. Use a DC volt meter to check this out and connect directly to the batteries. I would connect at opposite ends of the parallel pattern. Positive to the positive connector of the first pair of batteries, not the positive terminal you have used to complete the series connection of those 2 batteries, and the negative terminal of the last pair of batteries, again not the terminal used to complete the series connection of those 2 batteries. This insures that charging current will not abnormally charge the first set of bateries.

[5cats]

Originally Posted by SteveH

[snip]
Please tell us why you want to go with something other than the standard 12 volts.

I looks like cmell is try to use the MX60's "Voltage Step-Down Capability" to reduce resistance-related loss on the conductors from the pv array to the charge controller.

The MX60's specs say it can "charge a 12 or 24 VDC battery from a 48V nominal PV array".
Question for cmell: can it charge a 12 VDC battery from a 24V nominal PV array?

HowieE seems to have covered the battery bank configuration nicely.
I think the solar pre-wire in my 2007 uses #10.

Cheers,
-jd.

[cmell]

Yeah, 5cats figured out that the MX60 charge controller steps the 24V nominal voltage from the panels down to 12V nominal for the batteries. This allows the panels to be located further away from the trailer. I have 100 feet of 6 gauge copper wire spanning the distance, and the voltage loss to resistance at full charge (6.8 amps, 35 volts) should be around 2%.

and HowieE figured out how the 6V batteries are wired in two sets of three. I guess I'll send a picture soon to allay the confusion.

any advice on the mystery of grounding?

[cmell]

howdy,

here are some pictures of the panel set up. they are shaded for the first little bit of eastern morning sun, but they get great southern and western exposure.

I've also attached a picture of the charge controller, which was receiving 87 watts at 8:30 this morning just after the frost started to melt off the panels.

I still don't have a picture of the battery bank... soon to come though.

chester

[Aage]

Hi there and welcome to AirForums!

From your photos, it appears to me that you have a more or less permanent berth for your AS. If this is the case, and if you intend to keep the distance from the panels to the TT as they are shown, I think the distance has something to do with the guage you see as desireable. AM I right?

Just curious: why are your panels so far from the trailer?

[53flyingcloud]

Looks to me like that's where the sunshine hits it the most..The Airstream looks to be buried in the trees..

[cmell]

yup, we chose the current spot for the airstream based mostly on the location of the ground-fed spring, which is right inside the edge of the trees you see in the picture. we were also hoping to receive more protection from "nor'easter" winds by being in a little pocket of trees.

the spot where the panels are now is the closest spot that gets sunshine all day long. that's why I stepped up the solar array voltage to 24V nominal, so that I could decrease the amperage and span the distance with a smaller wire.

the panels charged the batteries 300 watt*hours yesterday, even though it was overcast all afternoon. We spent a couple hours reading before bed, which probably amounted to a usage of about 50 watt*hours.

I've been having so much fun messing around with my trimetric battery monitor, getting an idea of how much everything uses. The furnace blower fan uses 7-8 amps, which is by far the biggest load. I'm interested to see how long we can get by with the propane furnace before our solar panels stop being able to catch up.

[53flyingcloud]

The only thing I can say about "trees" is this..The further away the better, IMHO..Too many ppl have proof of the crunching power of falling trees. If you need to winterize it, you'd be much better served by putting simple things like baled hay around the edges of the unit to stop the wind from blowing underneath, etc. There's several excellent threads on full-timing in A/S..Good Luck~