Reddit mentions of EPEVER MPPT Solar Charge Controller 40A MaxInput Voltage100V Negative Grounded Tracer 4210AN + Remote Meter MT-50 with Backlight LCD Display for Gel Sealed Flooded Lithium Solar Battery Charger

So, I had the panels working for over a year with no problems, so I doubt it was the controller.

But there were 6 Renogy flexible solar panels 100W each, nominal voltage of 18.5 I believe, with this charge controller. Two parallel sets of 3 panels in series wired to the controller, wired to the battery.

I think the main thing though was I drained the batteries and had them connect to a 24V/12V step down with no low voltage shutoff. Maybe we just haven't been getting enough sun to power it, and it killed it.

Like others have said, it's a mistake to run any sort of electrical heating device off of a solar power system. This includes, kettles, electric blankets, hair dryers, etc. They simply require too much power unless you have a huge battery bank and a very large inverter.

For charging phones, you could just wire up your own cigarette lighter port. You can buy a combo cigarette lighter port and 2 USB ports for like $7 at Walmart. You just have to wire it into your car's 12V system and stick it to your dashboard or something. You can use a cigarette lighter inverter in it for small devices. It might be enough to run a laptop charger. You'd have to check the amperage limits. (I use a cigarette lighter inverter for my phone's special AC Adapter which has quick charge. I don't get quick charge just using a USB port.)

Have you considered buying a "solar generator"? They're all-in-one solutions for moderate power needs. It's basically a box that contains battery, inverter, and charge controller. All you need to do is add solar panels. The portable folding ones might be good, or you can get traditional ones and mount them on your roof. Here's an article about them that links to other comparisons between them. He even built his own using relatively inexpensive batteries (with an added battery management system), and a normal charge controller and inverter.

That site is run by William Prowse who has a ton of useful videos and tutorials on solar power, including several plans.

Of course, you can always build a full solar power system by buying all the separate parts and wiring them together. I'm not going to lie, it's not easy. The best thing to do is watch hours of YouTube videos and read tons of forums posts and articles to learn about all the parts, what they do, and which ones work with each other. You gotta watch out for misinformation, though. There are some... "older people" who are set in their ways and will tell you all you need are lead acid batteries and a PWM charge controller instead of an MPPT one. What those mean is a topic for a different day. Or you can follow a plan online and buy the exact parts they do, but then you wouldn't know how to adjust it for your own needs.

Here are some of the questions you need to be able to answer in order to design a solar power system:

• How many watts of power do each of your devices use, and how many hours a day do you plan on using them?
  
  • You can buy a Kill-A-Watt to accurately measure the wattage your AC devices use.
    
• How many rainy days in a row do you need to survive before you have to either stop using power or charge your battery through other means? (Alternator, generator, wall charger.)
  
  • 2-3 days is the most you can really hope for in a van. You simply don't have enough space for panels.
    
• How much sun (insolation) do you get, on average, in the locations you will be at the times you plan to be there?
  
  • Are you going to live year-round in one place, or travel all over?
    
  • Do you plan on spending any time in Winter in Northern locations with less sun?
    
    You buy large enough batteries so that you can get those 2 days of usage, and you buy enough solar panels so that you can get back those two days of usage with one day of sun. For the most part, the number of solar panels you can fit on your van is the limiting factor. You can buy a ton of batteries which will last you a week, but there's no point if you can't charge them back to full in one day.
    
    Regarding batteries, you also have to account for the fact that traditional lead acid batteries take a long time to charge because of their high internal resistance. With too large of batteries, if you discharge them too deeply, no amount of solar panels will help. The batteries can only take so much current at once, and there simply aren't enough hours of sun in a day to provide it, no matter how many panels you have. If you don't charge the batteries to full regularly, you will literally destroy them. (None of this applies to lithium ion batteries, which are so much better for solar, but they cost a lot more up front, but last much longer.)
    
    It's a balancing act between battery size, solar panel wattage, and amount of sun.
    
    Then you have to answer these other questions:
    
    
• What's the peak amperage my panels will provide based on location, time of year, angle of tilt (or not), and coldest ambient temperature?
  
• How large of a solar charge controller do I need to support the above?
  
• How many continuous amps can my battery bank provide?
  
• How many continuous amps do I need to support an AC inverter of a given size?
  
• Do I need a pure sine wave inverter, or can I get away with a cheaper modified sine wave one?
  
• How large do the wires need to be that go from my battery to inverter, or charge controller to battery, or the battery to fuse box and then to my 12V devices? (fans, fridge, lights, etc.)
  
• What size fuses do I need for all these connections?
  
• And much more...
  
  You can forget about all that and just follow someone's plan online. Well, except the fuses and wires for each 12V device. You'll still need to figure that out. Will Prowse has this "Classic 400W solar package" that you can follow to the T and get by just fine, but you won't know if that's even good enough for you until you figure out your power usage. But if it is, then the article and video are great.
  
  There's even a link to everything on Amazon, although the last time I checked, the specific charge controller he links is no longer available except from random sellers. There's a newer model instead. Oh, wait, he links to eBay now, but it's $51 more expensive than the new model on Amazon ($209 vs $158). I would just buy the new model. It's what I did. But the rest of the advice, plans, etc, is pretty good. Except all inverters suck if you read the negative reviews, even the one he links. They often can't really handle the wattage they claim. (I personally went with a Samlex brand inverter, which was nearly the same price, but less than half the wattage rating, which is much more realistic.)
  
  I used his videos a bit in helping design my system, but I have 600W of panels to suit my higher needs, so I had to scale some things up. I run two strings of 3 panels in series (2x3). This gives me a good balance of voltage and current.
  
  I don't have a battery that can support a 2000W inverter, so I bought a 600W one. I bought a 170 Ah Renogy lithium ion battery. Renogy suggests no more than 100A of continuous draw (more than 150A, and it will turn itself off). 100A is less then gentle to the battery, though. You can multiply the DC amperage by 10 to get an estimate of the wattage of an inverter it can run. So 100A could run a 1000W inverter. If I bought a second battery and wired it in parallel with my current one, I could get 200A continuous, but this battery was $1300. I'm going to live with what I got for a while. (In retrospect, I should have bought 2 100Ah batteries instead, but supply was very limited, and they cost more per amp-hour, $950 each.)
  
  After my (literal) months of researching and teaching myself about batteries, solar power, and all that, I have come to the conclusion that buying lead acid batteries is a mistake. This includes traditional flooded lead acid, sealed AGM, deep cycle marine, etc. Unless you treat them super gently, charge them to nearly full every day, never discharge them lower then 50%, equalize the cells on a schedule, etc., then they will only last a couple of years before you end up buying new ones. In the long run, lithium ion is cheaper.
  
  Good lithium ion batteries can be discharged "100%", be left for long term as low as 20-30%, don't need special equalization, weigh half as much, and have almost zero internal resistance so they charge faster. And they will last 10 years, easy. Even longer if you treat them extra gentle. The only problem is the upfront cost. I could have purchased 4 Trojan T-105 6V deep cycle golf cart batteries for 1/3 the cost of my one battery, and I would have had even more capacity, but the size, weight, fragility, and the whole spewing acidic vapor was a turn off. In 10 years, I'd probably replace them 3 times, at least, making them cost the same or more. I've read many experienced solar power users say you should expect to replace them in 1 year because you're going to do something wrong in your first year and ruin them.
  
  (There is one downside to lithium ion batteries I should mention. You can't charge them directly from a van's alternator. They draw too much current and will fry it! You instead would need to use a battery-to-battery charger. A found a good one for about $200, though I didn't buy it and I don't have a link handy. Just something to consider.)
  
  (Continued in reply)

true looks like almost a $120 difference.. damn

PWM

vs.

MPPT

edit: any thoughts on this one? sounds pretty great for a 200W setup.