Oh No ! I bought a Mppt Solar Controller

Old & Slow wrote:
RJ,

Just couldn't let you be by yourself on this one. Just got from EBay and already paid for, one 20a MPPT Solar controller @ $14.28 (new)with free shipping. So bingo for me. I now have three panels and three controllers. Not that I needed all three controllers.:B
I like to follow the leader.

Thanks ole fisherman.

O&S
Floyd

Old thread however,

I must report all 5 of the elcheapo PWM and MPPT controllers I have, proved out okay. So, what will you say?



Everyday, Older and Slower- what a blessing!

BFL13 wrote:
No more results for now. Only thing missing is what it does when the batt reaches full (which is kind of important! :) )

Never quite got there in my test. It should drop to Float or just quit charging until batt voltage falls to a low set point and then resume charging and keep doing that to maintain the battery.

The manual mentions a LED going to off when "charging stops" or some such wording, so suspect it will do it that way.

O&S, you could check that yourself easily enough if you have a full battery to put it on. I won't have full batts like that for another couple weeks at least.

BFL,

Some times I get tired of battery posts BUT then I just open and take a look see. I've used lot's of paper printing out your posts.

At this stage of he game, I'm not able to get around like a young buck in the woods after something. Sooo, these threads are a God send. I by-passed the LED stories for years. Now, Thanks to you guys all, I almost daily also visit EBay. ~~ First Gens,Solar, then batteries and on to controllers and now to LED's Perhaps I need to look for warehouse space.

Rich,

You started this thread. It just may last forever. Plenty of great stuff has come out of it.

Carry on folks,

O$S

No more results for now. Only thing missing is what it does when the batt reaches full (which is kind of important! :) )

Never quite got there in my test. It should drop to Float or just quit charging until batt voltage falls to a low set point and then resume charging and keep doing that to maintain the battery.

The manual mentions a LED going to off when "charging stops" or some such wording, so suspect it will do it that way.

O&S, you could check that yourself easily enough if you have a full battery to put it on. I won't have full batts like that for another couple weeks at least.

BFL,

I'm sitting here looking at the vary controller in testing. ~CMTP02~ 20a. Waiting more results.

Thanks,

O$S

Been running the new controller on just one battery (135AH approx. at 81% approx. at start) to see how it works.

Started at 9am, 13.0v getting max amps (around 8.2) on the 130w panel mounted on swivel tilted. Reached 14.3v by 1pm and hold ing there for three hours.

So, 14.3 is the high set point, and there is no two hour time limit like with the LS2024 at 14.6v.

Controller is PWM, not MPPT, in that charging amps never go over panel Isc. Also, once the set point is reached, it stays there, no up and down like with the Shunt type controller, so it acts like the Series type, and amps do taper while batt voltage is held.

However something interesting happens once you reach 14.3v. The spread between array voltage and batt voltage on the controller terminals changes drastically. On the way to 14.3, it stays at about 0.24v as reported earlier.

On first reaching 14.3 batt, array was going between 15.1 and 14.8 and the red "solar" lamp on the controller had started flickering.

30 min later, still at 14.3 batt, array 16.10 and jumping around down to 6.99, back to 16 etc.

30 min more (1 hour) now array is steady at 17.17v, batt 14.28, amps 3.1 (still tapering)

another 30 min and array is 18.13v batt is 14.37 and showing 14.4 Trimetric

another 30 min and now Tri is showing 14.3v and 1.3a. Controller has 16.45 up and down to 6.7 whatever, batt 14.27

Disconnected to check panel--Voc 19.7 Isc 8.09

Ok, what the heck? It looks like the controller is controlling that voltage to stay at 14.3 by playing with its "array" voltage.

The controller manual says when the solar lamp is flickering like it has been all this time since the batt voltage reached 14.3,

"When red LED is flickering, battery is MPPT charged up in constant voltage."

So we learned before that with MPPT, array voltage and batt voltage is quite different with MPPT and with PWM is is nearly the same (actually array is a tad higher but not a lot - under a volt let's say)

So instead of calling this a "fake MPPT", maybe we should be giving them some credit and just find some different terminology that does not deceive English speaking people as to just what this thing is?

Note--I am not sure if this test can run long enough to see what happens next as the battery gets to "full" It is still in "absorption at 14.3 , 1.1 charging amps three and a half hours since reaching 14.3.

Sun is getting lower. On controller, batt voltage, 14.28, array voltage 15.94 down to 3.9 etc back and forth.

Anyway, either this thing will drop to Float or not or else batt voltage will fall off anyway due to the sun going down. So I will report on that later.

--Add in, at four hours since reaching 14.3, batt voltage rose a bit about 20 min ago to 14.4 and is holding there! Trimetric shows 14.4v, 1.1a. Controller has batt voltage 14.37 and array voltage is 18.29 dropping to 6.x whatever off and on. ----Getting weirder folks! Meanwhile the sun keeps going down, so this story might not have an ending. :(

I have to hook up the other batteries and get back to what passes for normal around here.

Last little test--four and a half hours since 14.3, now 14.4 for an hour, went panel -direct (no controller). Tri jumped to 15.8v and 4.3a. Back to controller and back at 14.4, 0.9a.

Got to stop the test, sorry. Need all four batts!

So far,as battery voltage rises, so does the array voltage at the terminals with a 0.24v spread approx. being maintained.

The story was that these should be the same voltage, but looking at my notes on the ASC brand controller I had two years ago, there was also a small diff between batt and array voltage at the controller with array a bit higher.

So the diff here does not indicate MPPT IMO, just normal PWM controller behaviour.

I will do a test with the controller and panel on just one of my batteries with the Trimetric in the mix, so it will all get done in one day. That should reveal the high set-point and the charging profile I hope.

So, far no smoke, but it hasn't actually controlled anything either! Can't get batt voltage high enough today to reach any possible set-point. Stay tuned over the next couple of days for the big finale!

Looking at the Sec 5 PARAMETERS, this is the way I read it. But then I'm Old and Slow and slower. Input voltage range ~ 12v~20v/ 24v~40v/48v~80v All shown under the 12v/24v/48v rated voltage heading.

Search as I did, the best I could do was the manual in the ad, and unfortunately I think the answer is there.

In section 5 Parameters it list input voltage as 12-20v/ 24v.

I wouldn't be able to use it with my panels.

I have this same CMTP02 to be installed on my e/scooter. The one I'm using has a .1 amp per day draw down on the battery bank. I'm waiting an 30a MPPT @ $49.95 that shows to have a large heat sink on the bottom. Maybe coffee and 'donuts'. I'll work my way up the price range, until I'm satisfied. Here's hoping this CMTP02 has no draw down at night.

Someone soon should be able to give us ( a link) to the least costly controller to go with the one panel 120w starter kits. For my part, I didn't need the high priced wire cable @ $2.00 per foot. All I needed was the 24v/100w panel and the right cheapo controller. If making a roof installation, then perhaps the UV protected cable could be helpful in the long run.

Did RJ ever get a comparison test done?