diy solar

diy solar

Adding solar to a motorhome, any conflicts?

I realize that the batteries are the weak link in the system right now. I have plans to upgrade them in the future, but right now I have what I have. As to running the Air Conditioner from batteries, that's never going to be in the cards. It would take a system of some 43,200 plus watt hours (2 15 amp 120 V air conditioners running 12 hours a day) thus the reason I have a 6KW genny. The reason I'm looking at solar is to keep from running the genny when I'm not hooked to shore power and I'm just using everyday things like the lights, maybe a little TV, the control voltage for the propane refrigerator, and other normal things, no heavy loads for long periods of time. With all of that said, all I'm really concerned about right now is not catching something on fire and not ruining any of the equipment I already have. From what I have gathered on this and other places the batteries will take what they need and if I have too much current available it won't be an issue.
 
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The charging source controls voltage, usually fixed by some regulator. Higher voltage at the charger equals higher amperes through the circuit limited by the maximum size of the charger.. However the battery voltage rises while being charged resulting in higher resistance. As the battery voltage (resistance) rises to the level of the chargers' voltage, the amperes are reduced. All batteries, of any chemistry, have a certain voltage they should be charged. If you stay at this voltage you will not push too many amperes into the battery. If you exceed this voltage you will overcharge your battery. It don't matter how many chargers are connected. It matters what voltage they are regulated. Except always unplug the shore powered charger while driving.
 
Not unplugging the shore power is a self-correcting issue, but costly. No I've never done it and I hope I never do.
 
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I have a small class C, 28-foot, 1988, and I put a new 15k BTU rooftop on her because I got a deal, $625, with the thermostat kit. Overkill for 160 sq ft, yeah, but once I get her reinsulated, it will only kick on every now and then unless we're in June through sept down here on the Texas Gulf Coast, but doable on my batteries and solar. I have a friend who has a 30-foot table with the 13.5k BTU unit, and he does in on 200ah, and I'll have 400ah. This is at 24-volt btw. The original unit still works but is only 9k BTU but pulls half again the amps. A super C, two rooftops, yeah, that puppy needs juice. It can be done; I know some folks with a new Newmar with like 30kw of solar and batteries, but they're swimming in money.
 
Ya, I'm not poor but I'm not swimming in money either. The payback for putting in that much solar would be would be sometime into the next decade and I couldn't fit it on my roof. All I'm really looking for is enough solar and batteries to run the normal stuff in an RV (no A/C) without having to run my genny unless I get a few days with no sunshine. I know I have to upgrade my batteries at some point but I've got to make a believer out of my wife first. She's OK with some solar so I'll get more panels and charge controller than I need right now so I can expand later. It's got to be a process to keep my wife on board.
 
Simple counterpoint.
I don't know how you camp, but since you are talking solar, I'm assuming you are boondocking. Depending on the campsite, your solar may or may not be useful given the location, tree coverage, etc.
If you are looking for runtime, you should spend your dollars on batteries, then add solar when you figure out exactly how much you need.

The existing battery bank appears to be 12V with (2) 100ah AGM's, so you only have 100ah available at 50% DoD. That's not much runtime, and your charging profile is going to take a couple of hours on generator for the AGM bank.
I assume you would be running the genny during the day since that's when you need the AC, and your max solar output is going to be at the same time the generator is running. So you aren't offsetting many, if any, generator hours with Solar and such a small battery bank. You will still exhaust the pack, probably before you can run the genny again (assuming quiet hours or similar).

Instead, let's assume you spent $1500 on one of these prebuilt server rack batteries, 12V 400ah.
You could completely discharge the pack for 400ah, which is a huge runtime improvement, and you can use that extended runtime regardless of the campsite. It's got huge charge acceptance rate, so it will charge very quickly and not need the genny as long or as often since the pack can discharge much deeper.
Your idea of adding solar isn't a bad one, but it's like trying to take a long trip with a tiny fuel tank.
 
Ya, I'm not poor but I'm not swimming in money either. The payback for putting in that much solar would be would be sometime into the next decade and I couldn't fit it on my roof. All I'm really looking for is enough solar and batteries to run the normal stuff in an RV (no A/C) without having to run my genny unless I get a few days with no sunshine. I know I have to upgrade my batteries at some point but I've got to make a believer out of my wife first. She's OK with some solar so I'll get more panels and charge controller than I need right now so I can expand later. It's got to be a process to keep my wife on board.
Yeah, I was married a few times, LoL; I know how that game is played. Good luck. For what you're trying to do, that little kit with 100 watts worth of solar panels (4-25 watt) at Harbor Freight would more than do the job. When I bought my RV back in April, the previous owner had one already in one of the basement lockers, and a wore out 12-volt 100ah AGM Battery. I've been using it but had to buy another temporary battery, a Windy Nations, I think 100ah ($190), but that little Harbor Freight solar rig does the job. I have my LiFePO4 batteries so it will be used as an extra winch batter on my Jeep WJ tow behind. Seriously, that's your best bet for now. A 200ah Lead/Acid battery is only 100ah in reality.
 
I have a Magnum MM1212 inverter charger. It has a 70amp charger built in. I have 2 6v GC2 batteries for a total of 200ah. I have never seen the shunt monitor go over 50 amps even when batteries were low. The batteries determine how much they will take in. They taper off as they fill up. This is different than Lithium as they take everything you can give them (up to BMS limit).

Yes, the charger will flip from Bulk to Absorb as the voltage parameters get hit, so the charger is smart enough to keep the voltage at the proper level. The amps will taper off based on what the battery can absorb. So charging from multiple sources will not hurt.
 
Yep, I know that I only really have 100 AH of battery available. My goal is to probably get a 300 AH LiFePo battery with a waterproof case. My battery compartment is not enclosed so I may need to get a heater pad for it but I really don't plan on spending a lot of time in cold weather. I've got some money squirreled away that my wife doesn't know about so that my be the ticket for getting the battery. I don't know. Right now I'm just in the planning phase so we'll see what happens over the next few months.
 
My best advice is save and buy premium quality parts. Renogy panels are good but a tad over $1 per watt. I fit 400 watts on my van with no problem. A quality charge controller such as MorningStar costs money but will outlast all the other junk available. I bought one. My friend has 3 of the others over these same 4 years. Good wires with fuses is the same deal, except cheap wire and circuit protection can cause fire. invest in Walmart marine batteries. They hold up well and if you hurt them you can return under standard warranties at any Walmart. Your first battery is a learning battery. Once educated you will get better batteries. Prosperous New Year. I remember Wives.
 
Yep I'm hip to good equipment. There's an old saying, the bitterness of low quality lingers long after the sweetness of low price is gone. Right now I'm looking primarily at Victron control equipment. It's pricey but good stuff ain't cheap. I've already got an Onan genny and a Magnum MS2000 inverter/charger. There may be opinions about the Magnum but that's what I've got and it can be configured for LiFePo batteries as far as I know so until it takes a crap I'm going to stick with it.. For a batteries, I currently have 2 Universal UB121000 100 AH AGM batteries with a couple more, I think Trojans, for backup, but for now I have them slated for my trolling motor. When I have to or want to replace my batteries I'll likely look at whatever Will is recommending at the time. The price and quality are changing so fast I can't look too far ahead for them. It's probably going to be one 300 AH battery, but we'll see at the time.
 
I'd like to go with Victron too, but I'm on a budget so, I'm looking at "good stuff" in the 'Ford and Chevy" price range; not top tier, but reliable in a working-class price range. The Victron 150 | 70 or 250 | 70 would be sweet; we're talking $550 to $750 in real money. I need at least 2000 watts of solar panels to start, and a controller(s) who can handle the combined voltage/wattage within the temperature zones/seasons of my RV cruising range. I have a battery bank of 400ah at 24-volts; I'm looking for a total of 3000 watts, but half will have to be ground deployed when parked. While driving, I can maybe get 1500 watts on the roof with another 500 (250-watt panels) on top of my Jeep WJ, the tow vehicle, and I can store extra panels on the little back porch of the RV, which carries the generator and other sundries. I'm open to suggestions myself.
 
I'm not planning on running the genny all the time for A/C. If it's that hot I'm likely moving, but it will happen at times if I'm not plugged in. My plan so far is to get a Victron 100/50 charge controller and power that with 2 REC 350 panels or similar 350 watt panels so I don't have to run the genny for anything but A/C. The bigger batteries will be added later sooner if I need it. If I find I need more power generation I will simply do the Victron and the panels above again. That will give me redundancy and I don't forsee ever needing more than 1400 watts, I doubt I'll need that. I'm not going to spend several thousand dollars building out a big system and then finding out I don't need it. I'm pretty sure some solar will be nice, but I don't see needing a whole lot and if I do, I can always add it later. Thanks for everyone's advice.
 
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