MPPT V.S. PWM Solar Charge Controllers - Ultimate thread

[WillSharp]

Hello everyone,
After searching the forums for threads about solar charge controllers and not finding much, I decided its time to open it up and see what you people are using in your rigs.

What I am trying to determine is what is better MPPT or PWM style controllers in a small 12v solar system on a Vanagon?

After doing some research on the matter, MPPT controllers are obviously superior, especially if you have a big system running high voltage and amperage. What is harder to determine is if these same pros as significant on a small system with low voltage/amperage. Some people maintain that on a small system, PWM is the way to go.

For more info, here is a truck camper site page on the two types: http://www.truckcamperadventure.com/2016/02/pwm-or-mppt-which-solar-charge-controller-should-i-buy/

My current system in my 91 Westy is 60Watts of solar (3, 20W panels wired in parallel) going to a cheap PWM charge controller then to 150ah of house batteries. The whole thing is 12V and works reasonably well. I had the panels and charge controller left over from another project and threw them on semi-temporarily.

My goal setup is to do around 100-120W of solar charging the same 150Ah of batteries (all 12V). The missing link is the charge controller. I am debating about MPPT vs PWM.

What are you people using? What are the pros and cons of the two types used in small systems?
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1889 Syncro Adventure Wagon 3.3 SVX

[kamzcab86]

Link


My truly small system:

Panel: Suitcase 100W & flexi 120W (which is used depends on the trip)
Battery: 50Ah
Charge controller: 30A PWM
Power draws: ARB fridge, Dometic fridge low-draw cooling fans, LED lights, occasional USB charging, faucet pump

General rule when I was researching: Up to 100W, PWM; over 100W, MPPT.
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~Kamz
1986 Cabriolet: www.Cabby-Info.com
1990 Vanagon Westfalia: Old Blue's Blog
2016 Golf GTI S
"Real knowledge is to know the extent of one's ignorance." - 孔子

[tim_ha]

My general thought is that the added cost of MPPT controllers on small systems could be better spent elsewhere.

Although the Australian Direct video does a good job of explaining the differences between the two controller types, it fails to talk about the charge curves of the batteries. No battery takes a fixed voltage or current for their entire charge cycle. As the battery charges, it requires a higher charge voltage and will accept less current. This means that the advantage of MPPT over PWM is greatest when the battery is fully depleted and decreases as the battery charges. So, even though at peak, the MPPT may be 20% more efficient than PWM, as the battery charges, this percent difference becomes less and less.

Furthermore, a well designed system will generally not deplete the deep cycle battery more than 50% overnight (often much less than this). So, in actuality, the time spent charging the battery where MPPT and PWM have a big efficiency difference is small on the average day. It will likely mean that your battery reaches 100% charge one or two hours earlier, at most, with a MPPT than it will with PWM controller.

I have found Handy Bobs Solar (https://handybobsolar.wordpress.com/) to be a wealth of information, although it takes some serious reading to find what you want. He generally suggests MPPT if your system has one or more of the following: 600 watts or more, high voltage 44 cell solar panels, wires too small to run panels in parallel. Very few if any systems in a vanagon will meet any of these criteria.

I personally chose to spend my money on a nice, reputable PWM controller and have never regretted not going for MPPT.
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1986 Syncro Sunroof EJ22
www.subagonsouth.com

[shagginwagon83]

Yeah when I did my research it seemed like if you had multiple panels then the MPPT is the way to go.

But honestly what sold me on MPPT was a controller with Bluetooth.

_________________
Brandon
"Jo Ann" - '83.5 Westfalia EJ22e w/Peloquin
Instagram @joannthevan

[kbeefy]

I feel the cost difference between MPPT and PWM controllers is better spent on more panels at the size your talking about.

When I was shopping it was easily $100+ for a MPPT controller. For that price I bought an additional 100w Panel.

I have 300w on a $50 PWM controller and it is huge overkill. I can run ALOT of stuff, parked in the shade. Even in winter it easily keeps up with my 12v fridge and kerosene heater.
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86 syncro CHC, NorthWesty subbie 2.5, decoupler, locker, custom interior, 225/75r16 Duratrack's on CLK's, Toyo cabin heater, ARB fridge, 300w Zamp Solar, Gowesty bumpers/skid/rails, Fiama awning

'86 Syncro Westy. Stock for now.

2000 F350 7.3 CC LB 11' Northland Cabover

2006 Subbie OBXT

2002 Tacoma DoubleCab 4x4

1969 Mustang Basket Case 351c/FMX/9

http://kbeefy.blogspot.com/

[WillSharp]

Good points from everyone. Thanks for the replies.
Thanks to kamzcab86 for that video, that was helpful!

I am a bit conflicted at this point still because most of you are saying just add more panels for the cost of a MPPT. This make sense, but I am pretty limited on roof space (roof box, solar shower etc.) and I don't think Im going to be able to fit a whole lot more than 100w up there. Maybe 120w. This makes me think it might be worth getting a MPPT and maximize what I'm getting out of my limited number of panels. Thoughts?

I am running a ProPex HS2800(pulls 1.8amps when running), a bunch of LED lights inside, and in the future I would like to get one of the smaller powered coolers (ARB or Engle). Those pull about 2amp as I recall.
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1889 Syncro Adventure Wagon 3.3 SVX

[Tobias Duncan]

100 watts does not seem like much. What solar shower will you use?
Maybe fleixble panels that you could detach and set in the sun?
Will you be charging laptops and phones as well?
If you drive a lot and dont camp for more than a day or two at a time your alternator will do most of the work for you.

[ledogboy]

[WillSharp]

[ledogboy]

You should run some calculations to figure out how many amp hours you are going to be pulling. Laptops are pretty power hungry devices, and when you add lighting, a fridge, etc., I think you will likely find that you need more panels.
_________________
1986 Westy Weekender
Now a full camper
1.8t Syncro conversion
Some people call him Maurice...

[WillSharp]

[TommyBoyGomes]

With the small solar systems we're running on our vans, PWM is fine. You don't start seeing significant performance advantages per dollar until you get into larger systems with more than 2 panels.

Keep in mind that solar panel ratings are about double what you can expect to put into your batteries. For example, if you have a 100W panel in full sunshine, you'll probably only be putting 50W into the batteries. This means that your accessories can only consume 50W of power before drawing power from the batteries.
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1969 Squareback, 1776cc
1990 Vanagon Multivan

[r39o]

I have 3 smallish panels. I feed two golf cart batteries in series.

I choose my MPPT controller because I could watch what it was doing by a remote panel or a connection to the charger.

Look for features that you will actually use vice obsessing over the how the charger actually charges.

NOTE your charger may not actually last forever, as I found out when my system basically totally ate itself. Read I came to my van after it sitting many months to a blown up charger and two ruined batteries.....sigh..... It was just sitting idle, with no load. WTF? Now I get to start over again......
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1990 Multivan EJ 22, Rancho trans 0.82 4th, Small Car front AC, CLKs w/ 215/65-16, homemade big brakes 303mm, Konis, Recaros, etc....

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