Like everything sold by the lying, untrustworthy, and morally bankrupt Chinese, ( sold or manufactured) there are loads of Controllers labeled MPPT which are not.
Simple ways to get started telling one from the other are a proper MPPT will always have a screen as one needs to do the settings, they will always have a coil inside as needed by the electronic Function of the MPPT circuit and they will cost $50-70 Au as a minimum. Anything cheaper than that is a 99% change it's actually PWM.
I have been playing with a lot of solar over the last couple of years both Low voltage and gird connect and am also of the belief MPPT is over rated in the low voltage application. In a nut shell it IS more efficient but I believe one has to look at the margins between what one would get with PWM and MPPT. And that is the key, it's the MARGINS between the 2, not the output per se.
I have a bunch of PWM controllers and the difference in them is Vast. I have one which is brilliant and does a great Job. It has a screen and I can set Multiple Parameters with the thing the most important being cut off voltage. It also has a " Dump" feature where once the battery is charged the load can be diverted to something else so the power is not wasted. I have a couple of others with screens and ajustments as well but they just don't work anywhere as good. The lesser ones I have all interestingly have a USB outlet. I do have a couple I bought as stand by battery chargers for Mowers etc which are also OK. I don't know about the efficency and don't really care. they are on a modified household panel and keep the batteries they are hooked to without cooking them, job done. Bought them a few years ago for around $8 ea as I recall.
The good ones I looked for a couple of months ago were no longer being sold. Typical. They were Under $20 delivered. I have had one of them on a setup that ran for over a year and never falted.... unlike a number of other components on the same setup that just fell over for no apparent reason.
A meter I had monitoring the batteries just happened to burst into flames in from of my eyes when I went out to check it one day without touching a thing.
At least the timing was good if not the quality!
MPPT is better under non ideal conditions but what you gain in the question. Given the low power one is looking at to start with in a camping situation where you are playing with 100W rather than 5Kw like a house system, To me the margins are going to be too small to worry about.
I can well see where one might get say 1 Kw with a GOOD PWM ( and there are differences between the same type) and one may get say 1100 Wh with a MPPT.
The question I'd ask is if that extra 100WH makes a real Difference? I would suggest not.
It's impossible to put a real world figure on the gains but practicaly I'd be thinking about 10%, Maybe at a big stretch 20% would be about right. I also know that if I was really chasing every watt, re orienting the panel every 30 min would give me a better output with PWM than an MPPT could do ajusted 2-3 times a day.
It's also going to be rare that someone puts the panel at the correct tilt for that time of the year which would also make more of a difference, small as it may be, to the power generated against an MPPT controller.
Pulling an extra 10% out of a 5 Kw system over the course of a day at say Sydney latitude on average for the year would be around 2 Kwh. That's a useful amount of energy that could run a TV or a fridge or cover the needs of a Kettle being boiled Multiple times. If we have a 125W folding panel going at name plate generation which will NEVER happen, that same 10% Difference is going to run a camping Fridge for Minutes or a decent LED lighting setup for an hour. For mine it's well and truly far too little energy to be concerned about.
To break it down into my cost analogy, one would be paying minimum $30 Difference between a decent PWM and MPPT and that $30 will buy a LOT of KW in just Kicking the Vehicle over and letting it run a while. In the case of the 50 Wh gain with an MPPT in the example, It would take seconds Literally to put that extra energy into a battery when you have a potential of 80A and an output of 20+ at Idle.
Crunching the Numbers ( which I am hopeless at, ) one would expect a 125W panel to produce about 500 Wh in a day. A car alt that put a conservative 20A into a battery would take 15 Min. On my 4L Diesel, that's about 250Ml of fuel or not even .50c worth. Running the vehicle requires only a cable to charge a battery, no extra cost, weight or space.
Hence the question of the value of spending $150 Plus on a solar panel when you could spend less than even $1 a day on fuel and have a lot more power for anything you wanted.
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