Quick Test of Eco-Worthy MPPT Controller

[BFL13]

Ordered it on 3 Oct arrived at the door 23 Oct free shipping.

Controller rated to 42V so watch that. EG I have it on one 230w panel, Voc 37v at 25C, so would be more Voc at cold temps.

Not able to do proper testing with Trimetric to measure, but rigged up a yard test to see if the thing worked at all 🙂

Used one full SOC 12v battery with a 400w inverter clamped on and two 100w lamps for an estimated 20a draw. Got battery to 12.5v connected controller and 230w panel (Voc 36.8, Vmp 30 , Isc, 8.34, Imp 7.67 )

The displayed voltage was confirmed with another voltmeter. Before starting, checked disconnected panel aimed at sun, got:

34.7Voc and 8.06 Isc. (Rated 36.8 and 8.34) so expected less than max amps.

Best amps on controller when aiming panel was 14.99a Didn't note battery voltage

Lost the window--sun behind trees. It works (assuming its amps read-out is to be believed) and might even get my hoped for 16 to 17 amps on a better day. So far so good. Be a while before I can do any real testing and comparisons with PWM.

Just wanted to report the controller seems ok as was posted by JiminDenver. Jim, thanks for the good steer to this controller for $102

http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/26464298/srt/pa/pging/1/page/1.cfm

http://www.eco-worthy.com/catalog/mppt-solar-charge-controller-free-shipping-p-182.html

[JiminDenver]

The MPPT vs PMW debate will rage on just as the FLA vs AGM will. BFL is doing all of us a great service with his comparisons and testing, those designing a system should pay attention.

Cost is a easy basic comparison but should be on the whole, not just the controller. 12v panels cost more per watt, have a larger footprint per watt, need heavier wiring all so you can save a few bucks on the controller.

Look at the controllers being compared too. The ultra cheap PWM controllers have few if any features. The one from Solarblvd has many returns too. Are you saving money if you have to replace the controller or decide you want one with features like a display, the ability to set charge values or in some cases even a float? What does a nice PWM controller cost and how does that system on a whole compare price wise?

I was hoping the $12 RJ special MPPT controller was real and would give a apples to apples comparison for price. Then we found it didn't do MPPT at all and a 24v panel would only be good on a 24v bank. Too bad too because that would have really dropped a 24v system in price.

12v has always had the edge in price while the 24v system has it in footprint. Cheaper 24v panels and controllers like the Eco-W brought them closer until I saw the 200w 12v system shipped and ready to go for $300. That's going to be hard to beat unless you can find your panels cheap like I did.

[NinerBikes]

ktmrfs wrote:
BFL

At least I think it was you. Asked about temp effects and what temp panels are referenced to.

well, I just got a 100 W portable panel from solar world. And looked at the panel spec's. Nominal panel temp for rated spec's for Imp and Isc and Vmp is 47C.

Which works out to pretty close to the panel temps I was seeing in my report on MPPT controllers for panel temp at a 70F ambient.

Link to 100w portable panel from solar world? My Googler is having a hard time finding that product.

[NinerBikes]

As I see it, with today's prices in panels good for portable situations... $195 complete for a folding 120 watt panel suitcase set works out to about $30 an amp. Some of that is all the hardware installed on the panels, and some of that is the cheap PWM 10 amp controller and cables and battery clamps, but raw, about $20 per charging amp is what I'm guessing the panels are worth or about a dollar a watt.

You can buy a panel that will give you 7 or more Amps for $140. Or you can buy a MPPT for $120 and get one or two more amps. If real estate space is not critical, it seems a no brainer to me. However, if you have a bit of Mr. Gadgetry in you and have money to burn for a little bit of gain, and you like to fiddle and be the captain of your ship, then perhaps the MPPT will serve you better. It's fun to monitor what the sun is giving you for free.

In the future, all my solar needs are going to be priced out at $ per amp... after all, battery chargers are measured in amp capacity to recharge also.

[JiminDenver]

Now wait a minute. You are critical if heat causes a minor loss on a high voltage panel, but not if the controller clips a amp or so?

I haven't really seen many 12v panels that would work with the low VOC of the Eco-W. I think it's a great match for a single 24v panel though, maybe as high as 270w at lower altitudes.

[BFL13]

Actually, I'd sell the 130w and keep the single 230w except I bought the 130w when panels cost a bunch so I would take a huge bath selling it now. Couldn't bear that humiliation. 🙂

It looks like those who got a 230 and the 15L got a good match as was discussed last year in a thread about that choice. The clipping at 15a limit isn't losing them much at all, apparently. EcoW better price than 15L, not sure about voltage limit comparison for using 12s in series instead of a single 24

[JiminDenver]

OK I'm taking odds on which day BFL drives himself nuts before he can test the systems out in the real world. lol

Now if he wants to save his sanity I'd be perfectly willing to send him one of those 200w kits and he can send me his 24v set up and we will call it even. I'll give that 230w panel and MPPT controller a good home and it will love being at nose bleed altitudes.

[ken_white]

BFL13 wrote:
...Yes, I ignored the controller loss for MPPT that would have put PWM ahead. That saves Ken from counter-claiming MPPT works better on every foggy Friday the 13th in November...

:B

You're testing at the battery so it doesn't come into play...

[BFL13]

Not sure what "operating space" means. When I am on solar, morning voltage is say 12.5 but very quickly gets to 13 after sunrise. The battery voltage is mostly in the 13s during the day. Once it gets into the 14s, it shoots up very quickly to the mid 14s set point

So really, 13v to 14v is the "operating space" that matters.

It did hurt, but I used watts despite the pain in the interests of science.

Yes, I ignored the controller loss for MPPT that would have put PWM ahead. That saves Ken from counter-claiming MPPT works better on every foggy Friday the 13th in November.

Also ignored was the assumption that if the 130w panel was at 46.5C, then so would be the 230w panel. NOCT for the 130 is 47.5 but NOCT for the 230 is 45 plus or minus 2. But that may have nothing to do with their relative actual temps under the same sun.

[red31]

BFL13 wrote:

13v- 208.3/13 = 16.02a vs 14.68a diff of 1.34a
14v- 208.3/14 = 14.88 vs (230/130 x 😎 14.15 diff of 0.73a

ot oh, BFL is using watts!!!!

And what if the panel is making 208 watts and you loose 5% to the controller?

[ken_white]

BFL13 wrote:
...So I am not getting very excited here about how MPPT will be better than doing it with PWM...

LOL...

Then sell it!

:B

I see a substantial advantage, but I am looking at the whole operating space and not just one small area of the operating space.

😉

[BFL13]

Using the coefficients is an interesting approach, thanks.

Does that calculation using V take into account how the temperature coefficient for P is greater than for V? If PWM doesn't care much about P and MPPT is all about P, then is it valid to compare them using V?

Where PWM is all about I, which goes up with temperature, and MPPT uses V which goes down with temperature, can they be compared for amps to the battery if you know the temperature and the panel specs?

Let's see----

I often see the Sharp 130w panel when disconnected and aimed showing
Voc- 20.3 (rated 21.9) and Isc 8.3 (rated 8.2)

It should be possible to derive the panel temperature from that using the coefficients. Voc is -0.36%/C and Isc is + 0.053%/C on 25C

21.9-20.3= 1.6 and 1.6/21.9 is down 7.3% and 7.3/0.36 = 20.3 so panel temp was 45.3 (spec NOCT is 47.5 as it happens)

Using the amps side to confirm, we get:

8.3- 8.2 = 0.1 and 0.1/8.2 = up 1.22% and 1.22/0.053 = 23 so panel temp was 48

So that sort of works out. Now knowing that, what would we get for P using the 230w panel at 46.5C ?

Spec says coefficient for P is -0.45%/C on 25C we are up say 21C so P would be down 21 times 0.45 = 9.45% of 230w =21.7w so P is 208.3

If battery is 13.5 then 208.3/13.5 = 15.43 amps

So that ought to mean when I am getting 230/130 x 8.3 = 14.68a from PWM I will get 15.43a with MPPT. Hey, that's a whole entire 0.75 amp!

But with the PWM 12's IV curve that 8.3 will be down to say 8.1 at 13.5, so that means 230w would be 14.33a. diff is 1.1 amp

So what would it be at batt 13 and 14? where Isc on the 130 would be 8.3 and 8.0?

13v- 208.3/13 = 16.02a vs 14.68a diff of 1.34a
14v- 208.3/14 = 14.88 vs (230/130 x 😎 14.15 diff of 0.73a

So I am not getting very excited here about how MPPT will be better than doing it with PWM.

It would depend very much on relative costs and that could be anything where some places you can get 24v panels way cheaper than 12v panels/watt but the controller costs more, or where the panels are similar in cost/watt. Prices are all over the map.

[JiminDenver]

BFL

Between the low temp and the high temp there was only a half a volt difference in IMP, and less than a amp in MPPT. In the real world it isn't enough to make or break a system. Either you have enough solar or you don't.

Is MPPT worth it? Hard to tell with the prices like they are. The cost comparison was close until I saw a 200w kit selling for $300 shipped. I can't build a 24v system for that, it's at least $400. The extra $100 would get you a extra 30w if it was needed.

In a case where you had two 100w panels the money would be better spent on a third panel rather than a Eco-worthy controller. you would get more out of the investment.

Have a roof maxed out with panels and need a few extra amps, then a MPPT makes sense.

For a person setting up a mounted system, find the panels that fit the best and then figure out what controller to use.

[ken_white]

BFL13 wrote:
I have hopes of getting 16.5amps or so when panel is getting full Isc and temp is not so high that it kills the voltage the MPPT needs to feed itself.

What makes you think the MPPT quits operating before PWM?

Lets do a quick analysis of panel voltages and temperature.

A BP 350 panel has a Voc = 21.8V and temperature coefficient of -80mv/degree Celsius.

If we assume it fits the form of y = mx +b, then the panel voltage is predicted by Voc = -.08V/Celsius * T + 23.8V when referenced to 25 degrees Celsius.

If we use Voc = 14V as the cut-off voltage for both the PWM and MPPT, then this panel would reach that voltage at 122.5 degrees Celsius.

A BP 175 panel has a Voc = 44.2V and temperature coefficient of -160mv/degree Celsius.

If we assume it fits the form of y = mx +b, then the panel voltage is predicted by Voc = -.16V/Celsius * T + 48.2V when referenced to 25 degrees Celsius.

If we use 14V as the cut-off voltage for both the PWM and MPPT, then this panel would reach that voltage at 213.8 degrees Celsius, a much higher temperature.

If comparing side-by-side, the MPPT would still have 28.6V available to operate when the lower voltage PWM panel hit its 14V wall.

The MPPT wins...

[BFL13]

Too complicated. I already know if I use PWM on 230w worth of 12v panels in parallel I will get 14.5a as expected max amps. Fact, BTDT etc etc.

So all I want to see is more amps than that from my 24v 230w single panel and MPPT controller, or else I wasted my money. Simple!

To make it an even, fair fight, I compare what I am getting with MPPT when I know the panel is getting full Isc (as required for full PWM)in steady conditions of blue sky-- no clouds going by every minute screwing up the readings.

Don't care about battery SOC either, since I can just run some lights and fans and note the diff in amps on the Trimetric with and without solar..

Same jumper cable(s) out to the array but different array and different controller. Same battery bank but the connections are a little different as required

Ken's money is probably safe, since I already saw 14.99a (which is above 14.50) in my initial test when panel had less than rated Isc.

I have hopes of getting 16.5amps or so when panel is getting full Isc and temp is not so high that it kills the voltage the MPPT needs to feed itself.

[ken_white]

BFL13 wrote:
Are you saying it is ok to compare two 120s in parallel and PWM with a single 240w and MPPT, but not with two 120s in series and MPPT?

Nope, I'm just saying that the MPPT gets one of its advantage from having the ability to use the higher input voltages which allow for more daylight harvesting during low light conditions (dawn, dusk, overcast, etc...).

Comparing values at different times and days with different set-ups will not yield valid comparison results.

EDIT: The only way to truly compare performance specifications between 2 systems is to have them operate under exactly the same conditions.

This means you would need 4 identical panels, 2 identical battery banks, identical loading, a PWM and MPPT controller having the same output specifications, and identical setups as far recommended installation practices. Then you should test under various environmental conditions as well.

Just my $0.02...