60 Cell Panel vs 24v Bank MPPT and PWM UPDATE

As a follow-up to the question whether the 60 cell panel could work with an MPPT controller (OP was with a PWM) on a 24v battery bank, I was able to run a test today on that using my Eco-Worthy MPPT controller.

Insolation not so good with some overcast and some sun through that, panel temp 33C and Isc around 5 amps

The bank was full, in Float at 14.4v as 12v bank, so knocked that down with microwave on inverter for three minutes, disconnected solar, put batts in 24v mode, connected solar controller but not array yet, and set Absorb to 31v (max setting) and Float to 29v (max setting) By now battery holding at 25.6v ready to start, so connected array

I measured Vmp at the controller array terminals and took battery voltage and amps from the controller's display. I did not note the times, but the whole thing took under an hour since the batts were near full going in. Controller was in Bulk and doing MPPT-- So here is how it went with Vmp, V batt, Amps, output watts

29.0, 26.3, 6.0
29.8, 27.4, 5.01, 138
30.1, 27.7, 3.52
30.4, 28.7, 4.64
30.4, 29.3, 4.81, 142
30.7, 29.9, 4.66
31.0, 30.2, 4.52
31.1, 30.3, 4.04, 137

It stayed at 30.3 saw 30.4 but fell back to 30.3 again so stuck there, still; showing Bulk but not yet to the 31v Vabs setting, so

I disconnected solar, to let battery voltage fall to 27v while I reset Vabs to twice 14.8 at 29.6v and left Float at 29v setting, and reconnected solar.

Saw Vmp 31, Vbatt 29.6 for the blink of an eye and it went to Float (so not in MPPT now) with panel voltage now 35v Vbatt 28.3 and 0.5 amps (panel was showing 5.57 Isc as indication of insolation at the time.)

So the story that a 60 cell panel cannot charge a 24v bank is not true, but we still need to try that at 50C panel as the reason for low watts and not just todays cool panel but poor insolation (if that matters)

The key seems to be the MPPT finds an ever higher Vmp as Vbatt gets higher, so the amps keep coming.

Found a few blurbs (Google) on this which all say a 60 cell can't get the 24v battery to its absorption stage in high temperatures, but as seen in the OP I had no trouble getting to 30v at 45C panel/20C ambient. I did not even try panel direct to see how high it would really go above 30.

Perhaps it depends on how high is "high" for temperature. Have to wait till panel temp is 50C and try again on 24v bank.

New vs old 60 watt panel solar cynergy, same watts, size, poly, 36 cell.

My old one should do 5%+ PWM based on specs, mppt would be the same!

Vmp 18.04 vs 17.2
Imp 3.33 vs 3.49
Isc 3.67 vs 3.86

Found this, which says a 60 cell on 24 can't get there at high panel temperatures

http://support.morningstarcorp.com/wp-content/uploads/2014/07/tech-tip-60-cell-PV-module-sizing.pdf

The question arose during a thread recently, whether a 60 cell panel could get a bank to 30v in the same way as a 36 cell panel could a 12v bank, where a 32 cell panel was proven inadequate with a 12v bank.

This test was to see if indeed a 60 cell panel would be able to recharge a 24v bank, and it turns out it can.

There may be issues at lower light, lower voltage where a 72 cell panel would "outshine" (ha! ) the 60 , but this is what happened today.

I need to see if there is any advantage in going PWM for high panel temps, but that is a different "issue" to be tested for in July.

Any time your convert something there is a loss to be dealt with. At least the loss is the same between my two controllers. It was pleasing to see the Eco-w could keep up with the MS. I still think it and a 24v panel make a quick, clean, inexpensive set up if it meets the need.

and the purpose of this test ?

to show that you can get a 24v bank to 30v for equalizing ?

you enjoy tinkering around with batteries .. way too much

there is a bit of the "Mad Scientist" in you

Jim, thanks for the tests you already did, showing the Eco-W gets as many amps out as the fancy controller. The fancy features are what is being paid extra for, not for more amps.

The controllers were at ambient 20C in a light breeze off the sea, so no overheating issues. The panel and controllers are performing to spec.

It does look like there is still a small penalty in the MPPT buck conversion, which the PWM doesn't have but it is tiny. So 24-24 if you already have a 12/24 controller, either type will do the job.

I've never done a 24v test with my Eco-w's. Also at 12v the much dryer air and altitude make for a lop sided test in my opinion. That said, my 250w panels easily hit 18.5a and 226w. In series they are a bit less impressive at 48a and 660w.

If BFL had a "respectable" controller he could run both of his panels in series against the two in parallel on the 30 to see if a higher voltage would give the MPPT something to work with. :P

It looks like I wont be getting any more comparison test in with the Eco-w and Schott 230w. I never updated the ad but someone wants to buy it this weekend and I wont have sun until Sunday. Oh well, I need batteries more than test. lol

Are the cc's overheating a little, perhaps? Are they well ventilated?

How do your solar30 and eco-w numbers compare to jimindenver's, and others'?