Paralleling different panels with different electrical characteristics to one MPPT controller is not a good idea.Not sure why that would be always true. It's pretty simple to try it and see the amperage reading at the controller.
It is because the "knee" of the IV curve is different in the two different panels. That "knee" is where the MPPT controller observes the characteristics of the panel's output and determines how to sort voltage, amperage and resistance.
Think of it this way: The MPPT controller is lecherous. It likes to rub knees. If it has Charlise Theron in on one chair and Rosie O'donnell in another chair, it will get confused and start examining just Rosie's leg rather than Charlise's appendages. The result will not be pretty.
I can't erase that from my mind... I am feeling gravely ill after visualizing that nasty scenario.
I await mexicowanderer's input on this also.
So if you need 14.5ish-15.0V to gas, you need 29 or 30 solar cells at .5V each to get that? At that point, does a charge controller become optional?
The amps rating on this solar panel with PWM looks pretty darn good, if you could get the voltage to a usable level to recharge.
Surplus voltage or head room, unless under direct sun, no clouds, looks a bit thin.
So I came across this on EBay... and they are very local to me... but it sounds like a $100 experiment gone bad.
The specs on this thing are waaaaaaay different than any other 12V solar panel that I've ever seen.
Max V 15.03V?
Amps at short circuit 7.92?
Could someone with more brain power than me check the specs on this and tell me it would charge a Trojan T-1275 without even the need for a charge controller?
What about diodes and sucking juice out of the battery and back into the panel?
Funky Spec'd 100 watt panel with huge amps.
Do you run this with one of Mex's Voltage buck / boosters, then through a charge controller, so that there is enough V to charge a battery properly at bulk mode, 14.8V and give up a few amps in the process?
Need help, guys, but in layman's terms, EE's and above need to dumb it down to terms a Finance major can handle.
If you have two matching 120W panels, those are each close to 7 amps each charge rate. Why even bother screwing with the 50 watt solar panel and it's measly 2.5 addtional amps, when you already have 14 amps? Get another matching 120W panel if you can, and sell the 50 watt panel.
120W panels for 89 AH group 27's AGM's is plenty, for most applications.
Next time when your replace the Group 27's Trojans, consider 6V T105's instead. Much, much, much easier to keep charged, they don't have the crappy acid to lead ratios that car type sized batteries do, so that the damn battery can fit under the hood without shorting out at the terminals.
Trojan should make a T-105 AGM Side terminal batteries for cars already, for no shorts.
When you match batteries, you should match panels also... seems to me just to be common sense.
If I could get away with 200 volts 400 volts, 600 volts I would use that preferably. But that's dreaming. 80 at max will have to do and hopefully two or three Buckers connected in parallel to render 45 amperes max charge rate.
Now to go grab a hatchet and find the piggy bank. It's hiding.
Lin tells me China industry gossip has the country projecting the manufacture of eight million plus panels for the month of November 2014. Almost double that over 2013. Ships carrying raw material from Australia are lined up at ports, and railroad trains carry the material to manufacturing centers. African countries have been purchasing millions of panels. China is determined to sell more than ONE BILLION panels in 10-years. It is mind-boggling. He said automobile lithium batteries are in Beta testing phase. That country has big plans. I hope they don't turn it into a hazardous waste dump with toxic air. He said coal fired electrical plants have turned many regions into areas with perpetual brown sky and 1/2 km visibility. China to Mexico telephone call. I wonder how many NSA computers went whirring on that one? Thanks to a donated GALAXY 2 cellular and headphones I was able to understand Lin's heavily accented English very well. I look forward to lithium technology replacing lead acid.
Don't go blaming me for you getting investigated again by the NSA because I gave you a phone. You know, now my name is on a file or dossier at NSA just for donating you that phone. Don't screw it up for me!
Until the USA loosens their pollution standards to that of China, we will never be able to compete in manufacturing, globally. The clean up costs get added into the price of every widget. Clean air comes at a steep price. You should see what it costs to replace a Diesel Particulate Filter on my VW Touareg diesel. Outrageous!
Our 2008 Honda CRV AWD would get 26 MPG on freeway, the 2012 Touareg with 3.0 TDI and AWD and 5000#s gets 30 -32 mpg, all the time, when not towing a trailer, a bit less come the cold of winter, maybe 28 or 29.
Hoping Dodge Perryboy gets his Eco broken in soon enough so we can see some towing numbers for mpg come next spring, when it warms up a bit.
4200# of 64ft square here behind a 3.0 TDI in a Touareg... 16.5 to 19 MPG, when towing at 58 MPH. Confirmed over about 16k miles of towing now in 2.5 years.
It helps that the tires are 14", inflated to 55 psi, and limited to 55 MPH MAX speed rating.
I appreciate the mostly constructive answers. Others shouldnt even post. We dry camp at the most 7 days at the moment, however that might change. We do not use the lights much the main draw in the summer is the water pump for dishes and showers. We do not use the bath houses.. In the spring and fall the heater blower would come on. Those are the main draws. From what I gather the more the merrier and certainly if it was just a weekend I would consider less.
I believe that i will be increasing the battery bank, undecided if Ill add two more T-125's or sell them and get a pair of L16's upfront. Space and adding hitch weight are something to think about. I will start with around 500 watts or so with two panels, leaving space for more to add of we need it. We want to downsize our generator as the Honda 3000 is 135lbs and humping that up and out is getting to be a bit much. I want to sell it and get a pair of 2000's. One would be plenty to run on cloudy shady days to bump the batts up. A 2000 only weighs just under 50 lbs.
Once I find a good sale and install I will post for others to learn fro as well. While there were alot of posts. I wanted to hear from real time issues.
Here's some free advice... Seek professional help. You can't believe what you read on the internet.
Or use the search function and help yourself, this has been covered over, and over and over.
You remind me of wives that hired a contractor for a remodel, that sign the contract, with a certain scope of work for a set price, then keep changing their mind wanting more and more expensive material, that didn't do their homework before signing the contract, yet they still somehow thing the price should be unchanged. Until you define and figure out your needs doing an energy audit, there is no right answer. You have to learn how to crawl, before you can walk.
So a person cannot exaggerate anymore. Does anybody believe this 170 amp alternator was installed because it needs to make 170 amps regularly and daily and for prolonged periods?
Didnt think so
Prolonged periods, no, but for up to 4 or 5 minutes for running glow plugs while the engine is running and warming up, for pollution control standards for diesels, Tier 2 Bin 5 ULEV standards for CARB 50 state approval, yes.
Let me put it this way... the AGM battery in my VW Touareg TDI diesel is a Group 48 I believe. Alternator has a 170 Amp rate output. No idea how fast that battery takes a charge. But an alternator that powerful, the goal appears to be to recharge that battery rather quickly.
A single T 1275, 150 AH rate, at 40% SOC 12.0V, will easily gobble 33 Amps at 14.8V from a Power Supply Unit for close to 2:00 before the amps drop to a 9 amp/hr charge rate to finish it off. What % SOC it is at after 2 hours is anyone's guess, but I'd say the battery is 40-50% bigger than a Group 29 or 31.
If you pop the covers, in the last 1/2 hour, you will see the absolute finest of tiny, tiny bubbles, barely visible to the naked eye. They usually stick to something instead of overcoming surface tension and floating to the surface, unless they get big enough to pop free and float up.
The above procedure is for dry camping purposes where running a generator and wasting gas charging inefficiently is a major consideration. Add in Solar panels for the slow amp take rates above 85% SOC to top things off fully.
In some dank garage in Sebastopol, I have a mint .600 nitro express up in the rafters. One trip to the rifle range, that's all it took. One round. One dislocated shoulder. Black and blue halfway down to my elbow. Chest and ribs hurt. The weapon was fired in August of 1977.
If you need it to impact a 100 pound generator and tumble it 100 feet I'll let you borrow it. I bought it it off a destitute gambler returning from Reno. I fired one of his hand loads. Cudda took down a B-52.
Anti-generator people can get irate, strike that - violent. I don't use a generator anymore. '88 was the last time when I ran away from huracan Gilberto.
I'm glad I ain't got no thermistors, twisted sisters, or crazy aunts locked up in the attic. When the weather cools, ten seconds with a instrument screwdriver is all it takes for me. If it gets too hot or too cold, don't stand in the driveway.
I should have traded you a smart phone for that dumb gun!
25 to mph is a personal limit that I set. I am not a young spring chicken any more these days with my reaction times or eyesight. I like and enjoy uneventful drives to where I am going camping. I like taking my time. I like high MPG while towing. I'm Dutch, and I am almost as cheap as a Scotsman.
Just my belief that by driving slower and obeying the speed limit (oh and BTW, for all of you out of staters that visit here in CA, some folks need to read the speed limit road signs on Interstates, the speed limit is 55 for all trucks, including SUV's, with trailers, on Interstates, including I-10), it increases my reaction time.
While my Touareg is capable of such maneuvers, cones belong on a track or a race course, and are a poor substitution for the reality of trailering in a state like California, with 40 million people in the state, many of which don't read English, or perhaps don't belong here, or perhaps are stuck with double digit IQ's on our public roads, in uninsured vehicles with no drivers license. Trailering, so far, in the west, in any other state, is a cake walk, compared to trailering anywhere through Southern California's Metropolis mess. Sad that I live here, weather is great, the people, not so much anymore.
As to the sway, it is inconsistent, and in my mileage, seems to be a combination of factors, all at once. Big Buses, going very fast 80 to 85 mph, think Van Hool, with huge frontal areas and a big bow wave, in Utah, where the speed limit is 80 and folks do 10 to 15 over that, on a whim, with cross winds out of the NW, with the driver straying closer to the right of their lane, seem to be the worst. Big rig trucks that are sleepovers with sloped noses are a non issue.
I can tell you, professional big rig drivers are much better about staying left in their lane when passing travel trailers, part time motor home drivers seem to be clueless as to the affect of the bow of their wind waves on travel trailers, doubt they were schooled on driving them, or they are not very observant.
I have driven both with and without the WDH, if my front end didn't come up 1" and rear end sag 1 3/4", I'd do without the WDH, the Touareg drives for some reason, much better without it, the trailer is free to react to the cross winds without being all tightened up and pushing the front end into the Bots Dots.
The Touareg, from what I have been told, has all the fancy anti sway software, brain power, brakes, and X,Y,Z yaw sensors built in to it... it comes off the same production line as the Cayenne and Audi Q7... it's just shorted on all the deluxe bells and whistle features on the interior, in the Sport model. For $40,000 for a diesel, at year end sale prices, it was hard to say no.
Basically, I really just don't enjoy driving in stiff cross winds. I get conservative, and get off the road then, I've seen too many blown over big rigs, 5th wheels, TT's and motorhomes on highway 395 in Eastern California on my way from L.A. to Mammoth Mtn or Bridgeport... way, way, way too many.
As always... YMMV.... these are my observations.
PS, the aerodynamics of a box, and an AirStream, is not a fair comparison... the Airstream is 4x to 6x the price or more of what I paid for my Palomino. The cD of an Airstream is much lower, and has much less flat surface for a bow wave to have an effect. When I bought the 21 footer, for $13,000, brand new, near MI, I got what I paid for, I don't have the right to expect much more from it when towing. If it ever got broken in to, or stolen, I wouldn't worry too much about insurance or the loss. An Airstream is another story... for that kind of money, I'd be looking into a 5th wheel instead.
Mex, what do you do with a strong sister in the bunch?
My T-1275s' cells are all over the map, can't get them equalized with my equipment. Been like that for a year now and the batts work great despite the funny SGs.
Banking them with the four 6s over a long period on solar doesn't work though. The 6s get charged before the T-1275s do and then the 6s just sit there losing water. Another lesson learned. Anyway, two T-1275s from pos to neg posts best readings:
Batt 1- 12.75, 75, 95, 75, 75, 75
Batt 2- 12.80, 75, 70, 90, 85, 90
Doing attempted equalizings now and then, the same cells are always the ones stronger or weaker so it is consistent in that way.
I just keep using mine the way they are, and don't worry too much about it. I do like to do a 40% state of charge left in them, run kind of hard, leave the TV on and the lights so I lose at about 7 -9 amps an hour for a few hours before I top off charge them then equalize them. But like your T-1275's mine are all over the map, a 10 to 20 point spread on the weak sister and the Top Gun. They work fine, for camping, maybe not so much good for a golf cart.