The Eco-w's new VOC limit

Thinking about it I can do one better with a bit of side by side comparison. I'll set up both 245w systems, run them both at peak while keeping one controller cool and letting the other one heat up until I see a difference.

I think it has to get pretty hot before it clips. The only time it has been obvious for me was when the controller was exposed to the sun and dropped from over 12a to under 6a quickly. I do know it would have shut down had I left it there.

I'll has to see if I can get the controller to warm up in the shade by pushing 16+ amps for a few hours and then see if cooling it has a affect. Not as hot as it got in the sun but still pretty warm. I'll keep track of the temps so that if it is changed, I'll know how hot it has to get before any clipping happens. I suspect it wont happen unless I don't allow the back side to get ventilation. I've seen 15-17a for hours at a time and haven't had it overheat yet.

BTW no response yet but it is the weekend, even in China.

JiminDenver wrote:
My understanding of temperature compensation is that it changes the voltages depending on conditions. Higher voltage for cold, lower for hot. The Eco-W clips amps when it is hot, not voltage. It's too bad too because looking at the one I have opened up on my desk, the sensor is on two small wires and could easily be extended to the batteries.

Any info on how much it clips (reduces would be a better word?) the amps vs the ambient temp where the controller is mounted? I hope it doesn't do that in the shade where it is 25C in the compartment like mine has often been this past summer.

I thought my loss of amps was all about panel temperature and the voltage coefficient. If it is (also) the controller, then what to do? Maybe it needs a thermostat controlled fan like a converter has?

My understanding of temperature compensation is that it changes the voltages depending on conditions. Higher voltage for cold, lower for hot. The Eco-W clips amps when it is hot, not voltage. It's too bad too because looking at the one I have opened up on my desk, the sensor is on two small wires and could easily be extended to the batteries.

Ambient temp change does not correspond well with the panel temp change, using my IR gun gizmo aimed at the back of the panel (the IR gizmo calibration seems ok as the ambient in the shade cross-checks with a regular thermometer)

I got panel 44C with 16C ambient and panel 51C with 25C ambient and amps were approx. 15.5 vs 13.5 ( PWM would have given me 14.5 with 230w in both those temperatures)

It seems that the sun heats the panel to whatever it does regardless of ambient because they are affected by the sun to different scales. I think I am confusing how the sun heats the panel more in the summer by being higher with the change in ambient for cause and effect.

The change in amps is about right for panel at 50C so that ought to mean the controller has nothing to do with it. It is the controller in the shade that is getting the change in ambient while the panel is getting the change in its temperature from sun exposure diff seasonally plus ambient diff.

Anyway it is what it is and you cannot tweak Mother Nature to get more.

On the Eco-W, ISTR there was a video of the insides showing the temp sensor, so how can they say there is no temp comp? You said maybe it is just for its own temp protection. We do know you shouldn't leave it out in the sun or else it goes wonky (same as other controllers will---keep them in the shade.)

I have to agree with you on the temperature differences, I was disappointed when I didn't see 17a readings in July when it was 24-27C/75-80F. Saturday morning everything was frosted and it took a while to warm up. Had I thought to wipe down the panels after the frost melted I probably would have seen more. We never saw frost again or 17a. High 16's though.

As for the Eco-w being affected by temperature. I've seen asked if it has TC on you tube and the person that responds as Eco-worthy said no. I've seen it respond to high heat by clipping amps and I get higher readings when it's cold out. Yet you didn't change it with a Ice pack, so the difference has to be the panel unless the controller gets really warm. It's possible it clips amps then as a self preservation act to keep from burning up.

Those controllers do have amps clipped to their amps rating so they cannot overheat. They advise that over-panelling wattage will do you good when the sun is lower, since then the amps will still be under the rated max. Gosh, who knew? :) More panel wattage gets you more amps! :) For the brief time at mid-day the over-panelling gets clipped it doesn't hurt the controller.

As I posted elsewhere in Heat 1, MPPT 0 this summer I had "issues" with panel heat reducing my amps to the battery.

At the same time I noticed that my cooler temp panel wattage would show as say 200ish (of 230) on the Eco-W, but when hot out the max watts showing was more like 180w.

Once the panel wattage was sort of fixed for the day, then as battery voltage rose, this reduced the amps. If you killed off some battery voltage you got a jump in amps (as you have seen where you get the best amps readings at low SOC or high load draw that reduces batt v ) because the wattage was sort of a fixed amount.

The usual references show that panel wattage is reduced by temperature along with the voltage component instead of staying with the amps component--go to the bottom of this page for the graphs on that.

http://www.windturbine.ca/sun_panels.html

You see how the wattage is down by about 10% when panel temp is 50C instead of 25C. I was measuring 51C at the back of the panel when getting 180w instead of 200ish as when panel was more like 44C. doesn't come to 10% by panel temp diff but it does by ambient where it was 16C at 200ish watts but 25C at 180w (of 230)

I cannot explain the great effect of ambient temp when it is supposed to be panel temp that matters. I thought maybe it was the Eco-W being affected by ambient, but that didn't check out when I did the freezer bag test to cool off the Eco-W--made no diff to the wattage readout. Mystery!

I can say that lately now that ambient and panel temps are coming back down from summer highs, that the wattage read -out numbers on the Eco-W are going back up and that amps to the battery are getting higher too. So it is about temperature and not from some deterioration of my set-up from Spring to Summer that happened or it would not be getting better again all by itself now that Spring temps are returning this month.

I have no idea why they made the changes. I follow two people on you tube that use the ECO-W. Both use 2 150w panels, one in series, the other in parallel. The person using them in parallel had over heating issue but not the other. He has had his Eco-W pass 20a at times.

I can say that I had already decided that 270w would have to be my limit due to the boost I get at altitude. I've seen over 17a off of the 245w panels and that was a clear sky too, no cloud effect. Another 30w should push it to 19a or so with just a bit of leeway.

Now here is a question. Is 275w a limit for the rating of the panel or actual production? The 245w panels are doing good to produce 220w each, the 230 212w. When I talked to Marc at Rogue he was fine with putting more than you would think would be ok because he didn't expect to see actual watts above the controllers limits. I would expect it would just shed excess amps if it did. MorningStar even promotes over paneling.

I'll add that question when they respond.

JiminDenver wrote:
I've sent the message about the change in the VOC limit but didn't think to ask if it applies to the older ones. I'll ask when they reply.

Another difference from the manual to the box is the watt rating has dropped from 300/600 to 275/550.

Using my extremely accurate magic secret formula, where 130w gets you 8.2a at Isc, then the limit for a 20a controller, with no allowance for panel exceeding ratings, is

20/8.2 x 130 = 317w. With MPPT getting you say another 10% in amps, then the 8.2 is now 9a, and

20/9 x 130 = 289w so 275 seems low unless they expect MPPT to do better than 10% "extra" above PWM.

EDIT something is screwy with that thinking but can't put my finger on it just now. Problem is that MPPT amps do not depend on panel Isc, but depend on panel wattage as affected by temperature of the panel.

so moving right along---- :) --

BTW, when using PWM 20a controllers that do not clip their amps and could overheat if above rating, you must allow a 20% margin for when amps are above panel Isc at times, so that means 16amps "expected" and allow another 3.2 =19.2

16/8.2 x 130 = 254w would be the limit for a PWM 20a controller. 275w for an MPPT 20amper that clips its amps (Assuming the Eco-W does that, can't say--never got that high even in cloud effect with my 230w) sort of fits in.

However the MPPT is not like the PWM in that the MPPT's own "efficiency" where it loses some of the panel watts on the way to making amps must come into play. (PWM just passes the panel Isc amps through) So maybe the ECo-W folks found out they had to reduce their idea of panel wattage from real life compared with design?

I've sent the message about the change in the VOC limit but didn't think to ask if it applies to the older ones. I'll ask when they reply.

Another difference from the manual to the box is the watt rating has dropped from 300/600 to 275/550.