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Author Topic: MPPT charge controller question  (Read 1194 times)
Iceni John
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« on: September 08, 2013, 02:37:41 PM »

I've bought my PV solar panels, so now I need to choose suitable MPPT charge controllers for them.   I'll need controllers in the 60 to 80 amp range, ideally using heatsinks/fins instead of cooling fans (that's one less thing to potentially fail), with a proven record of reliability and with high build quality.   My house system will be 12-volt, and I'll probably use regular golfcart batteries.   I've narrowed my choice down to one that seems best for what I need, but before I spend a big chunk of cash on them I want to be sure about what works well in a bus.

What MPPT controllers are folk here with higher-power PV systems using on their buses, and why?   What do you like or dislike about yours?

Thanks, John     
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1990 Crown 2R-40N-552:  6V92TAC, DDEC II, HT740, Jake.      Hecho en Chino.     
Behind the Orange Curtain, SoCal.
bobofthenorth
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« Reply #1 on: September 08, 2013, 03:04:41 PM »

I bought a brand-x direct from Taiwan John.  I put 690 watts of solar on our boat last fall and we used it until mid-July.  Then we came back to the prairies and the bus so I don't have a lot of experience but so far I'm very happy with it and it was a lot cheaper than any North American alternative.  I does have a fan and you are right, that is one more potential failure point.  I wasn't particularly impressed one way or another with the build quality.  It wasn't obviously cheaply built but I wouldn't say it was overbuilt either.  I'm not sure whether I am ever going to add more solar to the frenchy-bus but if I do I wouldn't hesitate to buy another.
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R.J.(Bob) Evans
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Jerry W Campbell
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« Reply #2 on: September 08, 2013, 09:38:49 PM »

Hi John,
   I have been using 2 70 Amp Outback MPPT Charge Controllers.
They are working strong after about 10 years of steady use. The fans have died several times and it's brain surgery to change them. I have a couple of the first ones they made. I'm sure they have taken care of that by now.
I would do it again in a heartbeat. As far as I'm concerned, Outback means quality and dependability.
Jerry
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sommersed
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« Reply #3 on: September 09, 2013, 08:53:35 AM »

I use Blue Sky controllers with my 1200 watts on the Bus roof.  I especially like their remote as it allows advance control of the unit, plus offers all the information on the controller/battery's/ charge rate and Ect.

Ed
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Iceni John
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« Reply #4 on: September 09, 2013, 12:44:29 PM »

Thanks for your helpful replies.   I had been thinking of the Morningstar TS-MPPT-60 as my possible first choice, with the Schneider Conext/Xantrex (or whatever it's called these days) XW 60 and the Outback Flexmax 80 as other possible contenders.   I like the features of the Morningstar, but like the similar-power Xantrex it is slightly under-rated for the amount of panels I have.   The 80 amp Outback can handle full output from my panels, but is not my first choice because of its cooling fan.   It looks like I'll have to talk with the technical boffins at Morningstar to see if it's an unsurmountable problem having 1020 watts of PV feeding into it when it's charging 12V batteries.   If my house system were 24V I could use the Morningstar without a problem, but I'm not doing 24V anywhere  -  at 12V it's rated for only 800W input.   It will shut down if the input overloads it, but I don't want to rely on that happening often, plus it will probably negate the warranty.   So saying, Lostranger (he's converting a Gillig transit bus on the Nomadicista forum) is running four 255W panels into a Morningstar 60 with no reported problems so far, but he's not been doing this for long.

Decisions, decisions.   Your real-world experiences are a big help for me, so now I need to do more research (lots more research!).   It's too bad I can't charge the batteries as a 24V series string, while still drawing 12V power off them in series/parallel  -  the connection between batteries 2 and 3 would preclude that.

Jerry, if you are ever in Southern California on a Memorial Day weekend, there is an informal get-together of Crown and Gillig afficionados at the high-desert home of a friend of mine, and we would all LOVE to see your bus, especially your solar setup.   Let me know if this is a possibility one year . . .   You are my inspiration.

Thanks, John
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1990 Crown 2R-40N-552:  6V92TAC, DDEC II, HT740, Jake.      Hecho en Chino.     
Behind the Orange Curtain, SoCal.
Ralph7
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« Reply #5 on: September 09, 2013, 01:21:19 PM »

     I use a Morningstar MPPT , controller and have 840watts .
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Jerry W Campbell
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« Reply #6 on: September 11, 2013, 09:50:12 PM »


Jerry, if you are ever in Southern California on a Memorial Day weekend, there is an informal get-together of Crown and Gillig afficionados at the high-desert home of a friend of mine, and we would all LOVE to see your bus, especially your solar setup.   Let me know if this is a possibility one year . . .   You are my inspiration.

Thanks, John
Hi John, Thank you
   Yes, I know about the gathering there and I would like to go except it's the wrong time for me.
One of these days we'll cross roads. I usually go by there in the first part of November headed south.
I get back from down south in April and hit the ground running.
I just put together an electric bicycle for this winter.
Good luck with your electrical system.
Jerry

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harleyman_1000
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« Reply #7 on: September 11, 2013, 10:16:00 PM »

 Can anyone help me get started with some solar? Can I start small and add as I go?
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Scott 
St.Louis Missouri

1958 GM 4104 Extended 2 feet, with a 6v92 and 5 speed automatic

http://s783.photobucket.com/user/harleyman_1000/library/Gm4104%20bus?sort=3&page=1
pvcces
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« Reply #8 on: September 11, 2013, 11:14:45 PM »

Sure, Harleyman.

Just realize that as you increase solar panels, the controller has to be replaced with a controller of more capacity. Also, planning your roof space so that you can still get on the roof without taking a chance of falling will affect the size of your panels.

Most installations do not provide enough power for all of the needs, so putting on too much solar panel is not likely to happen.

Heating and cooling are the largest users of power, so minimizing these loads will help.

For stored energy, 3 ounces of propane will release more energy than you can safely take out of a 65 lb. golf cart battery. This makes it very difficult for a house refrigerator to compete with an RV refrigerator when dry camping.

HTH.

Tom Caffrey
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Tom Caffrey PD4106-2576
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harleyman_1000
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« Reply #9 on: September 12, 2013, 09:14:03 AM »

http://www.modernoutpost.com/gear/details/ic_manual_21amp.pdf

 This is the link to charge controller that was wired into my bus? There was no other signs of solar on the bus, so Im guessing that it was used for some other reason with the batteries? Is this a decent charger to use with solar?

« Last Edit: September 12, 2013, 09:20:33 AM by harleyman_1000 » Logged

Scott 
St.Louis Missouri

1958 GM 4104 Extended 2 feet, with a 6v92 and 5 speed automatic

http://s783.photobucket.com/user/harleyman_1000/library/Gm4104%20bus?sort=3&page=1
Iceni John
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« Reply #10 on: September 12, 2013, 12:40:27 PM »

Tom and Harleyman:

Here's my plan:
1.   Paint the roof.   It's now stripped down to bare aluminum, so I'll be sanding each panel, wire-brushing around each rivet, priming, recaulking all seams, then painting two coats of Rustoleum gloss white mixed with the ceramic micro-sphere insulation.
2.   Install five weatherproof junction boxes on the roof for the PV panels' two 4AWG positive downfeed cables and each panel's individual 15A fuse, the panels' single 2AWG negative downfeed cable, the PEX water line to the panels' washdown water outlets, and the PEX hot and cold water lines for the eventual solar water panels.   All cables and PEX will run inside the hollow roof ribs that are spaced every 19".
3.   Make a 26'-long central walkway of diamond-plate 1/4" aluminum between the two opening roof hatches, four inches above the roof so it will cover the five junction boxes.   It will be bolted with two 3/8" stainless bolts through each rib, for a total of 36 bolts.
4.   Make eight frames for the PV panels, hinged to the walkway so each panel can be raised up to 50 degrees from horizontal.   Each frame will be 17.5 feet of 1.75" 6061 angle with stainless hinges.
5.   Make a folding ladder that will stow on the walkway, for easy access up to the roof from inside the bus.   Obviously I'm not going to have an outside ladder up to the roof!

I have 2040 watts of PV, probably more than I need, but it neatly covers most of the roof while still allowing me safe access there.   There will still be space for about 30 sq.ft. of solar water panels, plus maybe a roof AC unit up front over the driver.   With half the panels raised to face the sun directly, and the other half laying down against the curved roof at about 20 degrees below horizontal, I will get pretty good solar coverage, not quite as good as having all the panels raised to face the sun, but having a walkway on the roof justifues that slight loss in PV efficiency.   My hope is that the worst-case scenario of an overcast or rainy winter day should still give me a few hundred watts, enough for careful use of power.   At other times of the year I should have more than enough for my needs, maybe even enough to run the rooftop AC while driving (now wouldn't that be cool?).   Another incidental benefit to covering the entire roof (except for the front and rear end caps) is that the roof is almost completely shaded, significantly reducing heat load on it in the summer.   I may even find that I've finished charging batteries by midday or so, in which case I could use the excess PV power to heat water by my water heater's electric element, ready for a nice hot shower that night.

Back to my original question.   If I am feeding more than the recommended 800 watts into each 60A charge controller I could easily just lower the panels to reduce their output, so maybe I'm worrying too much about using more than their rated array power.   After studying insolation charts I still don't know exactly how much power my panels will produce, but I'm guessing I'll get anything from a few hundred watts when it's overcast (maybe one or two kWh per day) to well over 2000W on a cold clear winter day, and maybe just under 2000W on a hot summer day (possibly 10 kWh per day, or more?).   Storing that much power in batteries is a separate matter, allowing for the typical 30% loss when charging and using batteries  -  I would like to use cheap and readily-available golfcart batteries, but L16s may be a better alternative.   I made two pull-out battery trays that can each hold four batteries, so I hope that eight batteries will be sufficient, especially that I don't want to discharge them more than 30 or 40% to help prolong their life.   

I'm excited to do all this, and I'm slowly getting closer to my goal of having a bus that should never require non-solar energy to live in.   Whether I can achieve that is up in the air (sorry, couldn't resist that one).

John      
« Last Edit: September 12, 2013, 01:10:56 PM by Iceni John » Logged

1990 Crown 2R-40N-552:  6V92TAC, DDEC II, HT740, Jake.      Hecho en Chino.     
Behind the Orange Curtain, SoCal.
bobofthenorth
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« Reply #11 on: September 12, 2013, 02:54:50 PM »

That's an impressive amount of solar John.  I think solar wattage is like sex - its hard to have too much - but unless you have an all-electric galley I'm thinking you won't burn a lot of diesel fuel to make electricity although I always forget about AC because we so rarely need it up here.  I thought I was doing something serious with 690 watts on the boat but I'm small beans c/w you guys.  With my 690 watts I have seen close to 40 amps into 12 volts in early July in BC.  That's roughly 70% of nominal with the panels laying flat on my bimini.  That degree of efficiency surprised me so with your ability to tilt the panels I would expect much higher output. 
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R.J.(Bob) Evans
1981 Prevost 8-92, 10 spd
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Jerry W Campbell
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« Reply #12 on: September 12, 2013, 09:08:59 PM »

I have seen over 1400 watts out of 1580 total. In the desert of AZ on a cold winter day with the panels tilted.
Most of the time they put out about 1000 watts.
If you go far enough south in the winter you don't need to tilt them.
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Jerry W Campbell
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« Reply #13 on: September 13, 2013, 07:32:48 AM »

"There will still be space for about 30 sq.ft. of solar water panels,"

I don't think you will have a big enough hot water tank unless you plan on staying in the north where there is a lot less sun..
I have a 10 gallon Propane/Electric with heat exchanger.
This is what I'm going to do. This is the panel but not this set because the cost is too high.

http://www.amazon.com/Complete-Panel-EZ-Connect-Hybrid-Heater/dp/B008KC7ZBM/ref=pd_sim_sbs_misc_15

When the sun comes the water circulates. This hot water panel is about the right size for a 10 gallon tank.
Jerry
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harleyman_1000
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« Reply #14 on: September 13, 2013, 11:20:39 AM »

John, can you post a picture of the top of your bus?
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Scott 
St.Louis Missouri

1958 GM 4104 Extended 2 feet, with a 6v92 and 5 speed automatic

http://s783.photobucket.com/user/harleyman_1000/library/Gm4104%20bus?sort=3&page=1
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