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BFL13's avatar
BFL13
Explorer II
Apr 22, 2014

PWM vs MPPT Test Results

Today (blue sky, not quite to STC at this date at this latitude 49.3N but almost according to the calculator on that) I was able to run a test on my 230w panel and Eco-Worthy 20a MPPT controller.

I could at last compare the amps I got with an equivalent 230w on PWM. Result was a slight MPPT advantage in amps. EG 9.2/10.07, 11.85/12.74, 13.44/15.32, and 14.50/16.65 going from am-high noon.

Comparison was with a 130w panel proportioned up to 230w which I have found to be valid in previous tests using eg, 200w (two 100w) in same location. I won't repeat all that proof here, so if you haven't seen that stuff before, just have to trust me on the PWM amps used to compare. :)

So--- just taking the MPPT performance at high noon with some measurements that may be of interest to MPPT experts (or not!)

230w Hanwha panel- specs Vmp-30, Imp-7.7, Voc- 37.0, Isc- 8.3

Conditions at test: Voc 35.0, Isc 8.92 Ambient temp 16C/60F Temp at back of panel (aimed at sun at high noon) 44C (using infrared therm.)

Array to controller voltage drop not connected-Voc only, 0.3v
Voltage drop array to controller with 16a to battery 0.4v

So actual measurements at high noon were:
- array voltage at controller 29.2,
-batt voltage 12.3, amps into battery 16.65,
-Eco-W watts reading 205w, so it uses batt v and the amps.

The Eco-W has a little fun program to compare MPPT with PWM at any time. It said MPPT 17.00, PWM 8.92, Efficiency 91%. Note that 8.92a is the same as the Isc I took at the panel when disconnected.

So bottom line is I got slightly more amps than with PWM. Whether that is "worth it" is very situational and not the topic, but these results might help individuals evaluate that for their own situations.

PS. For the geeks, with the battery voltage climbing and about an hour before high noon I got:
-batt v 13.4 and 15.32a , 205w, array v at controller-29.3

I then turned on a bunch of 12v stuff to lower the batt v to see if that made any difference. Got:
-batt v 12.7, 16.48a, 210w, array v at controller-29.0

While fiddling with the panel and changing batt loading, I saw the Eco-W readings get a little unstable-- one time saw 17.13a unfortunately it all settled quickly to the mid-16s for amps :)

Perhaps in two months when solar conditions peak for the solstice, I will see more amps at high noon. I don't know if the test today shows there is "room to grow" for that or not, but maybe some experts could tell that from the above measurements.

19 Replies

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  • BFL13's avatar
    BFL13
    Explorer II
    Apr 23, 2014
    I did a test last month with the EcoW on the 12v 130w panel. I got 9a MPPT vs 8a PWM. There is no doubt that the MPPT gets slightly higher amps, similar to what Salvo got on his test.

    It is true that you can change the results more in favour of MPPT by comparing them at low battery SOC. In real life, by the time the sun gets up high enough you are already climbing in batt v so may never see max amps even at high noon. Another "situational" thing, "depending"

    You can't fine tune your solar. You will have too much or too little each day but at least you can calculate what your set up could do and then after that you can see if it is still working about right.
  • pianotuna's avatar
    pianotuna
    Nomad III
    Apr 23, 2014
    Hi,

    It would be interesting to see how a top of the line mppt unit fared against a top of the line pwm.

    For example a Tristar 45 amp mppt vs a Tristar 45 amp pwm.
  • BFL13's avatar
    BFL13
    Explorer II
    Apr 23, 2014
    I would make the price comparison between the 20a PWM controller for $20 and the Eco-W 20a MPPT for $102.

    There is nothing wrong with those $20 PWM controllers either. They do Series, three stage charging profile exactly like the MorningStar's profile. In fact they have the exact same charging profile diagrams in their owner's manuals. ( I have tested those and so have other forum members.)

    It gets tricky when the 12v panels cost more than the 24v panels but the MPPT controllers cost so much more. You have to really sharpen your pencil and keep your eye on the expected amps for the whole set-up.
  • ktmrfs's avatar
    ktmrfs
    Explorer II
    Apr 23, 2014
    BFL13 wrote:
    The "mainstream " MorningStar 15L ($300 here) gets 15a with a 230w panel but of course it cuts off amps at 15a. As reported by several forum members who have that combo.

    You guys want a test with a 20a "mainstream" controller but don't expect more percentage gain than the ($102) Eco-Worthy got here, so what's the issue really? You guys are not being logical.

    There is nothing wrong with the Eco-Worthy except you can get one for one third what a "mainstream" controller costs. Get over it. :)


    X2!

    yup, your results are plenty close enough to the tests I did back last fall in testing my Morningstar MPPT and then comparing to Morningstar PWM controller.

    In bang for the buck, looks like you can't beat the Eco-worthy and like you point out, the Morningstar limits at 15A, about 5A less than I'd like.

    And the Eco worthy vs. a Morningstar PWM, the win clearly goes to the Eco worthy, since both are about the same price.
  • ktmrfs's avatar
    ktmrfs
    Explorer II
    Apr 23, 2014
    Shadow Catcher wrote:
    The comparison I would like to see is a more well known i.e. Morningstar MPPT vs Morningstar PMW solar controller. The price point on the Ecoworthy is more in line with a morningstar PMW controller and I am suspicious of their "simulated" reading.
    I would love to do a comparison showing how they work. I recently bought an Oscilloscope input to the lap top and want to check wave forms etc.


    months ago I did an extensive set of test using a morningstar MPPT controller, mostly looking at IR loss effects on long cable runs (100ft) for portable use with a MPPT controller and did some comparison with a PWM controller.

    In the tests I also compared results with a morningstar PWM controller.

    From what I recall, my results showed similar to BFL's % gain with MPPT controller each was configured with the controller at the battery.

    In "bang for the buck" BFL's MPPT controller appears to be doing a very good job. Double or triple the price of the controller to a Morningstar and maybe you will get another 1% gain. Hardly worth it. And as BFL points out, the Morningstar MPPT controller I have limits at 15A

    In a comparison of a morningstar PWM vs. BFl's MPPT (both about the same price) BFL's wins hands down.

    BTW, these % gains are in the ballpark for calculating the % gain expected with 12V panels in "good sun" commonly used by RV'rs knowing how a MPPT controller works vs. PWM if you know the panels Vmp, Imp, Isc, Vsc and typical conversion efficiency and derating panels for temperature effects.
  • BFL13's avatar
    BFL13
    Explorer II
    Apr 23, 2014
    Just attempted a comparison for "low light." Condition is time 1830, sun lower in behind grey cloud.

    Both the 130w and 230w battery banks are at 12.9v. Both panels pointing South tilted up.

    130w- 0.6a
    230w- 0.8a

    0.6 x 230/130 = 1.06 so that is more than 0.8 Means when things are this bad for solar, nothing times nothing is still nothing. :)
  • BFL13's avatar
    BFL13
    Explorer II
    Apr 23, 2014
    Salvo wrote:
    Run the test when it's 100 outside. That will be a whole different story. Did you record temperature during the test? That and battery voltage are the biggest factors in mppt performance.


    It might get to 90 or so here in July. I will take panel temps then too. Yes, read the OP for temps this time.
  • Salvo's avatar
    Salvo
    Explorer
    Apr 23, 2014
    Run the test when it's 100 outside. That will be a whole different story. Did you record temperature during the test? That and battery voltage are the biggest factors in mppt performance.
  • BFL13's avatar
    BFL13
    Explorer II
    Apr 23, 2014
    The "mainstream " MorningStar 15L ($300 here) gets 15a with a 230w panel but of course it cuts off amps at 15a. As reported by several forum members who have that combo.

    You guys want a test with a 20a "mainstream" controller but don't expect more percentage gain than the ($102) Eco-Worthy got here, so what's the issue really? You guys are not being logical.

    There is nothing wrong with the Eco-Worthy except you can get one for one third what a "mainstream" controller costs. Get over it. :)

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