My solar build

[johntaves]

Originally Posted by harryn

Your decision to go 24 volt instead of 12 is a very good one.

I am completely happy with it. I am going to adjust the voltage output of the DC/DC closer to 14v. It is set to 13.2v but I would rather hear the slide and lift motors with a little more spunk in them.

But, I am a little annoyed that I did not take as much advantage of this as I could have. I struggled with fat wires when I didn't really need to. I reused the 3/0 ground cable and the original 2/0 cables that ran the width of the coach. When I take photos, you'll see how I ran 3 of these fatties into one junction. They were a pain in the rear to route and attach even though they are multi-strand. They are overkill. I would have been just fine with 2ga.

Originally Posted by harryn

Wiring losses are lower, but the thing that many people miss is that since most solar controllers are "output current limited", a 24 volt system can use a controller with 1/2 the rating for the same power.

Right, I am putting 800watts of solar panels into a controller that outputs a max of 30amps.

Handy Bob praises the SC-2030, but says it is limited to small systems of 400 watts. I can put 1600 watts of solar on the roof and 2x of these sc-2030 will be able to handle all they can put out.

Bob's praise of this controller is largely why I went with 24v. I wanted this controller and I wanted more than 400watts.

Originally Posted by harryn

If you ever decide that you do in fact want to charge from the alternator, there are 12 v - 24 volt battery to battery chargers on the market.

Right, but there is no point to that. If the batteries need juice, and I am running the main engine, starting the generator adds no additional noise.

What is more interesting to me is having the 24v keep the 12v starter battery charged. This would allow me to do nothing with respect to either battery bank when I park it for long periods. The solar will keep the 24v topped up and the 24v will keep the 12v topped up.

My DC/DC converter says that it is OK to connect its output to a 12v battery to charge it. It will apply a constant voltage, of say 13.2 to the starter battery. However I am chicken to do this because I have not found something from Deka that says that the best way to store my new starter batteries is to put a constant voltage of X on them.

In addition, I am not sure if I would also need to put a disconnect when the alternator kicks in. If the alternator is producing say 13.7 and the DC/DC is producing 13.2, I need to read that the DC/DC will be OK. A minor issue is that I would the be using gas $ to run the coach electric stuff instead of solar when the alternator is running.

For now, I have a cheap smart charger that I can plug into the 110AC inverter output to charge the starter batteries every now and then if the RV is in storage.

[Searching_Ut]

Sounds like you have a system that should do you well, especially when it comes to battery charging and maintenance. The system I have on my 5er is very similar.

Unlike you, I kept my system at 12vdc as I didn't see any real need to spend the money to run 24vdc to meet my needs. I'm using 4 230ah 6 volt wet cell golf cart batteries, which are easy to get to and service. With the bogart SC2030 charger taking care of the batteries, my water use is predictable and easily manageable which makes wet cells a good fit for my needs. The trailer has a PD9280 DC converter. The Progressive Dynamics chargers are rated okay but it's actually a pretty crude and basic charger so the solar system really makes a difference even when I'm on trips with hookups available more often than not.

I initially started with 4 grape solar 100 watt panels and almost immediately upgrades to 5 flat mounted panels. Later in the year when the sun was getting lower on the horizon I added a 6th being the SC2030 is reputed to be able to handle higher currents and will just self limit. 600 watts definitely overloaded the controller to where it would cycle on and off rather than just reduce output to 30 amps or less so I went back to a max of 5 panels until I worked out how to further expand my system. I experimented with several different MPPT controllers, found none of them particularly good as battery maintenance devices, and that none of them handled shade issues well with parallel, or series parallel setups.

My final upgrade was to go with 2 SC2030 solar charge controllers controlling 2 banks of 5 100 watt solar panels for a 1kw system. The Trimetric controls them both, and easily handles shade issues.

The bogart battery monitioring/solar charging system is a true gem, that doesn't get anywhere near the attention it deserves in my opinion.

[johntaves]

Originally Posted by Searching_Ut

600 watts definitely overloaded the controller to where it would cycle on and off rather than just reduce output to 30 amps or less

That's not what I was expecting to hear, so I went back and reread bogart's SC-2030 technical manual. I found 2 statements that support your observation. "Max 31A for full efficiency. May be safely used with panels up to 45A, however charging current will be reduced to protect charger". I figure your 600watt setup could have potentially delivered 50A at 12v. You'd have to have some nice summer sun to get that.

The second is "Four 135 watt solar panels for 12V systems (eight at 24V) can be accommodated." 4x135 = 540, so your 600w setup was exceeding that.

I am using the same 100w Grape Solar panels. I was tempted to load on some more panels to extract more out of the Seattle winter overcast. Your findings tell me I can only add 2 more to get to 1000w, before I should add another SC-2030.

Thanks for the info.

[Searching_Ut]

Originally Posted by johntaves

..... I figure your 600watt setup could have potentially delivered 50A at 12v. You'd have to have some nice summer sun to get that....

Thanks for the info.

Actually about the best you can hope to pull out of 6 of the grape 100 watt panels is 36amps with a PWM controller. They max out current wise somewhere between Impp current which is 5.56 amps and ISC which is 6.13 amps. With flat mounted panels, and the sort of less than optimal conditions I encounter most of the time you rarely max output. When I was exceeding what the controller could handle I was at approximately 9000 feet elevation, late may in Southern Utah with high scattered clouds that provided an effect where the panel output would vary widely, and go way up.

We were in your Pacific coast area most of September and part of October, and my solar harvest was noticeably less than what I get in the high desert. For instance, tucked deep in the trees in a dry spot in Cape disappointment the highest output I saw was 12amps. I was actually a little surprised it was that high given that none of the panels ever received as much as a sliver of direct sunlight. In other areas along the coast 30 or so amps was the most we saw on the cloudy days, with a peak of around 50 amps when the sun came completely out.

Good luck on finishing your system. You're probably already at the point where you have more than you need for your battery bank under good conditions, and there aren't possibly enough panels to get you there under terrible conditions.

[johntaves]

Originally Posted by Searching_Ut

\You're probably already at the point where you have more than you need for your battery bank under good conditions, and there aren't possibly enough panels to get you there under terrible conditions.

True.

[johntaves]

Here are some photos:

I ran the solar wires down through the back cap. I drilled 2 holes that went through the roof where it overhangs the rear wall and epoxied 2 3/4" pvc conduit in there and ran the + and - wires through them. There is a small electric pcv box above the holes with a pvc conduit fitting that fits into the 3/4" pvc. The idea is that the epoxy seals the pvc pipe to the roof so that water cannot get into the innards of the roof. Water can run down the tube and fall down the back cap area to the ground. However, not much can go that way because the box above the vertical tubes has the matching fitting and snugly fits into the 2 holes. Unfortunately I failed to notice the aluminum strut before I drilled and my bit hit half the strut and I didn't get nice straight holes. It's all sealed, but one of the tubes is slightly to the rear and that left the box slightly angled and you can see the conduit that runs forward to the other box was angled and is now bent to meet the front box. Its rather ugly.

The 6 panels up front all join at the big box up front. The 2 rear panels join in the smaller box in the rear.

The original batteries were arranged in a row. I realized I could arrange them like you see in the photo and make room for the inverter/charger. I since put the inverter/charger inside the coach, under the bed which is probably only 4 feet away. I left the batteries in this configuration because I can rotate the batteries by simply changing one of the interconnects and moving the negative and positive leads to the new end batteries. I don't have to physically move the batteries to rotate them electrically.

Instead of throwing out the huge run of 2/0 cable that I hauled out of the original setup, I reused it to connect the inverter/charger to the batteries. I also used it as the ground to the DC/DC. I don't like those big cables because it was such a pain to work with them. I would have been happier using 2ga cable. The voltage loss would have been irrelevant.

I have rearranged things in the battery compartment countless times. I bought a hydraulic wire crimp tool for around $40. It has been used a lot because I changed how I run the wires a few times. You can see the 2 big loops of 2/0 cable that I should have cut shorter. I was so tired of crimping, that I said the hell with it and just left the big loops.


The DC/DC converter is essentially in place of the original house battery disconnect switch.

The relay that used to connect the house and chassis batteries is no longer used, except I left the chassis battery wires still connected to it. The relay still clunked when I turned on the power, and it also emitted a high pitch whine. Just today, I finally removed the signal wire so it will no longer clunk and whine.

I just wired the remote on/off for the DC/DC converter. This means I can now shut off power from inside the RV. I don't have to lock/unlock the compartment door to trip the circuit breaker (CB) every time I take the RV in/out of storage.

The generator starter cables used to be connected to the house batteries. Now that I am 24v I moved them to the chassis battery.

I bought an inexpensive 12v smart charger that runs on 110v. If I leave the headlights on and drain the starter battery, my plan is to plug the charger into the inverter. The charger has a high amp mode to help start an engine. If I am not getting the main engine to crank, then I will start the generator to charge the house batteries and allow the starter battery more time to charge.

[johntaves]

The legs are 2x3" aluminum angle iron on the bottom and 2x2 on top. The single screw connecting them allow the roof to have slope to it. The panel screw hole is elongated so there's left to right slop there. The panel flange is also somewhat flexible so there's no problem getting the legs perpendicular to the roof.

Each panel is taped to the roof with 4 2"x3" 3M VHB tape. It seems very secure.

I put these over 3" off the roof to provide lots of air underneath to keep the panels cool. Also it brings them above the closed roof vent, fridge vent, and shower dome so that shadows won't happen from those sources. The panels were placed away from air conditioner so that only when the sun is very low will they throw a shadow across a panel.

I bought the 12v 100w Grape Solar panels for $100 ea. from Home Depot. There are bigger panels for $.70 per watt, but I figured that the larger size would be more difficult to place on the roof for shadows, walking around, and servicing the various roof thingies up there.

I used eternabond tape to tack down the solar wires.