Oh No ! I bought a Mppt Solar Controller

Thanks for experimenting, BFL. I'm guessing that you'll be reaching some conclusions about the MPPT function in the future?

UPDATE--hooked up, some first results below:

I won't be able to test it as hooked up till later on, but looking inside, the circuit board (both sides) has no inductor coil at all. The unit is very light-weight and has smaller hole wire terminals than the LS2024. Not sure yet what gauge (it took #10), but the LS2024 can take #8.

There is no battery type selection as with the LS2024, and mine did not come with the promised instructions. Those are on-line with the ebay ad, though. I have no info on its Voc rating limit, so I will not try it on a couple of 12s in series, which would be approx. 44v.

I don't think this will do for a real 24v panel like a 230w. No idea. You need the Voc limit.

I should be able to tell what sort of charging profile it has once I get a chance to play with it. I don't even know yet if it is series or shunt as a PWM.

UPDATE #1: #2 below that.

OK, hooked up, no smoke. Got 7.8a showing (panel rated at 8.2a but some cloud /haze going on.) Solar spotty right now, need clear sky steady state to compare amps Isc at panel vs Trimetric to battery amps from the controller.

Meanwhile, I did note the voltages at the controller's terminals while it was hooked up and operating. Array side 13.02v, Batt side-12.81v

That's it until I can get steady blue sky and also must wait to find out what sort of charging profile it has and its high set-point.

UPDATE#2

Got some clear blue steady so new set of readings, for whatever they might mean:

Bank is 490AH approx at about 83% SOC. Controller model is 20 amp CMTP02. Panel is 130w Sharp 12v rated 8.2a Isc

Panel Isc 8.23a, Amps to battery from Trimetric 7.8 plus add .3 for standing load at the time, = 8.1a

Panel Voc 20.2v, (measured close to controller with controller array side disconnected) Controller array side 13.16v, Batt side 12.92v, Trimetric 12.9v

It was having someone open up the Eco-worthy and I could see the inducoer that made me think it was at least functional.

There is another el cheapo with the inductor that I've seen. I'll find it and some reviews.

That round thing with wires is called an "inductor" (a torroid high efficient inductor to be specific) it is a device that stores energy and then releases it - current flowing in the wires creates a magnetic flux - when the current stops flowing the magnetic flux decays and produces a current flow in the wires. Yes there are other ways to get the buck conversion accomplished say a traditional less efficient transformer, buck conversion requires some form of inductor. Take a look at the Rouge controller guts that big nice Induuctor is the heart of the buck conversion stage. That thing costs money and when higher current is needed the price rises for that part - a good reason for multi phase controllers using many smaller inductors in parallel

Ok, now I get it. The dispute whether this is a fake MPPT vs a real one AFAIK from that video guy linked earlier in the thread, was that these cheapo so-called MPPTs did not have the whatever part on the circuit board when he opened it up.

IIRC, the real ones have a sort of doughnut with wire coiled around it and the fake ones didn't? And he said the fake ones used some other thing instead that didn't do anything "air--something" Not clear to me what he was saying.

Is that round thing with the wire the buck converter? Is there a different way to do that which could still be "real?" If I take it apart and don't see the round thing, is it game over and it is just an ordinary PWM?

Thanks.

You will see higher amps going into the battery than coming out of the panel. It may not be double but it will be higher.

I'll have to find it again but I've read that these have a issue with something over heating and failing.

Sorry could have made it a be clearer

The BUCK conversion within an MPPT controller drops the array voltage to the battery voltage - the controller then charges the battery with a PWM charging alogrythm. YES MPPT controller use a PWM charging scheme. So if you measure the array voltage at the controller inputs and then measure the battery voltage at the controller and find they are different the MPPT BUCK converter is doing its job. However it does not mean the controller has a proper tracking alogrythm just that the buck conversion is working.

PWM controllers connect the array directly to the battery - so if you measure at the controller and see both array and battery exactly the same voltage (assuming the battery is taking a good charge) there is no buck conversion or it is not working as it should.

The buck conversion stage can be though of as a voltage to current changer - it drops the array voltage to the needed batery voltage if 100% efficient Power in = Power out - a lower output voltage translates to a higher current - nothing magic at alll with a buck converter. The magic is in the MPPT tracking alogrythm

To directly answer your question "YES" It is expected to have the array voltage different from the battery voltage - My array voltage is typically 40 Vdc (the Vmp chages from the low 30's to the high 30's depending on the light / heat conditions) while the battery voltage is 14.4 or there abouts - the buck conversion does that.

MEX - you are living the life of Riley until the next hurricane comes thru in the next two months. I watched you make several trips to San Diego on the last wipeout you had. You have already spent all of the Insurance money hehe... Enjoy while you can hehe...

Roy Ken

Thanks. Not clear to me though. How is that different from PWM? I thought when connected, that the array voltage was the same as battery voltage, which is how the IV curve operates where you get a drop in Isc as battery voltage gets up past mid-13s. Panel Voc is 21v.

I can measure panel voltage at its junction box with panel connected I think, but not Isc. With MPPT controllers, can you get 40v or whatever at the array with it connected and 14v at the battery? How do you know the controller is doing MPPT unless the charging amps are higher than panel Isc?

A quick simple test would be to measure the array voltage and the battery voltage while in operation. I assume your 130watt panel has about 17Voc and maybe 15Vmp depending on the light/heat conditions. If you measure the array voltage it should be close to 15 volt mark while the battery should be charging at a lower voltage. If there is no difference then ...... after all it was only $20.00