12v MPPT and 24v MPPT vs 24v PWM Test

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EDIT saw the above-- note the current on the panel to controller path is the same either way. Panel is rated at 8.3 amps Isc and the PWM will do that with high sun etc. The MPPT runs at Imp of about 7.7 amps, so there is no difference in line loss due to current on that path.

Meanwhile the controller to battery path is the same too at battery voltage so same line loss if any. I can't measure any loss there on mine.

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There is nothing wrong with the MPPT controller. Get over it :( I did the efficiency thing and there it is, same as a Morningstar's.

Amps to the battery are lost with MPPT because of panel heating killing its watts. PWM does not lose amps from panel heating and it doesn't use watts anyway, just amps. At some point you get more amps with the PWM just from that.

You have to compare 24-24v or 12-12s to be fair, because there is a loss going from 24-12 and the PWM can't do 24-12.

We will see this summer how the numbers come out compared with last summer, now I know I can run my 230w panel with the Solar30 as long as the battery bank is 24v too.

Last year in the Spring it was MPPT 15.5 amps (like today) vs 14.5 amps with PWM using 12-12 for the same 230w. By mid-Summer, hot panel, MPPT was 13.5 amps while PWM would still be 14.5. ( I know all the bumph says this is impossible--so measure your own and see what you get! )

My aim here is to see if I can replace that lousy 13.5 amps from the MPPT with more amps using the Solar30 and 24-24. Since the panel rated amps is 8.3, I hope to see 8.3 on the 24 from the PWM which would be like 16.6 amps instead of that 13.5. Based on today's test, it looks possible :)

16.6 is higher than the 14.5 because the ratio of Isc to wattage is higher with the 230w panel than it was with the 130w panel at 8.2.

Using the 130w's ratio to get expected amps from 230w you would see 230/130 x 8.2 = 14.5 amps

BUT the 230w rated Isc is 8.3 which would be 16.6 as a "12v"

So it seems you could get more amps with a single 240w panel in PWM with 24 batts, than with two 120s in series for 24 and the same PWM!
Somebody with a pair of 12v panels can test that out and report back here :)

EDIT: In that case, never mind. :)

Ahh.. insolation. Good word.

BFL13 wrote:
Got a chance to try out comparing amps to the battery using MPPT vs PWM on a 24v battery bank and comparing those with the usual MPPT on 12v with my 230w panel.

The bank is four 6s, so it was easy to change from 12v to 24v and back.

(Was able to swap them all around with insolation etc as near the same over the time it took as you can do in these tests, so the results are useful but not lab perfect of course. )

(The actual amps are not necessarily the max amps for the day with the sun higher later on, but the amps can be compared with each other within the time frame of the tests.)

MPPT controller is the 20a Eco-Worthy and the PWM is the Solar30. Battery bank "resting" voltage before the tests was 12.4 volts, low enough to accept all the amps.

Voltage and amps results as shown on the controller's display, confirmed with multi-meter.

12v MPPT- 12.7v/14.97 amps (190w)
24v MPPT- 25.4v/7.95 amps (203w) so that would be 15.9a at 12v
24v PWM- 25.5v/7.99 amps (204w) (15.98a at 12v)

The MPPT buck converter is more efficient doing 24-24 than 24-12 as we know, and this test seems to show that.

I expected the PWM on 24v to do about the same as it would with 12v for getting amps, which it did here.

The ambient and panel temps are moderate today, so the MPPT was not suffering from high panel temperature so much like it does in July/August here. I wanted to see this summer if I could beat that problem by using the Solar30 with the battery bank in 24v mode.

I have a spare 12v battery to leave the rig on during the day while the main bank is disconnected at 24v. However the mechanics of swapping things around may make it all too annoying.

The lower amps of the MPPT in July are still plenty for our needs, so there is not much reason to do all that work. I just hate not getting "all my amps" so we'll see if it looks worth it this summer when I do another set of tests with the panel being hot.

With the hot panel I expect the 24v MPPT to not do as many amps as the PWM at 24v, which just uses panel amps and they are not reduced by the panel getting hot. We'll see in July!

About a 7% difference between 12 and 24 mppts; it appears the system was in bulk mode so that difference may be volt drop?

So the pwm performed better than the mppt?

MPPT should be at least 5% better. Seems the controller has issues.

BFL13 wrote:

24v MPPT- 25.4v/7.95 amps (203w) so that would be 15.9a at 12v
24v PWM- 25.5v/7.99 amps (204w) (15.98a at 12v)

pigman1 wrote:
What was your wire size and length, panels to controller and controller to battery?

It was the same for all the tests. My regular set-up stayed the same for the tests with the 230w panel out on its contraption ( twirls and tilts) about 40 ft (one way) of various wires mostly jumper cables #2 cu-al and some #8 cu to controller. I have measured 29.3 at panel (rated 30Vmp) and 29 at controller, so it has about 1% loss when amps on that path are near rated Imp of 7.7

Controller to battery is about two foot each of #8, same in both controller cases above.

I posted a test of the efficiency of the Eco-Worthy MPPT recently doing the 230w panel on 12v batts. It came out in the mid-high 90s same as other MPPT controllers like Morningstar in 24-12 mode. (see the graphs on the Morningstar site)

I have not measured the efficiency of the Solar30, but it can't be bad the way it gets the amps out doing 12-12 or 24-24 as seen here.

What was your wire size and length, panels to controller and controller to battery?

jrnymn7 wrote:
To be clear, the "12v MPPT- 12.7v/14.97 amps (190w)" was done just before you switched to a 24v bank?

Yes. I tried to do the swaps quickly so the insolation would not change during the three tests. Once I got back to 12v and hooked the MPPT back up, it was 13.0/14.47 (188w) so it all went fairly well.

The controllers were on wire nuts and alligator clamps for quick connecting, but it still takes time to swap and get the controller going.

To be clear, the "12v MPPT- 12.7v/14.97 amps (190w)" was done just before you switched to a 24v bank?