diy solar

diy solar

Finally, initial Electrocacus DSSR vs MPPT side-by-side/RW results ... and they're SHOCKING! lol

ADM said:
Just chiming in here with something that seems to not be discussed when deciding on charge controllers.
Built in bypass diodes in PV panels, not all of them have them but many do. These panels would really only properly work with mppt charge controllers as they will drop voltage during partial shading.
Yes they do confuse the MPPT charge controllers and I can attest to that. I recently swapped out my older Tracer mppt charge controller for a new MPPT to see if it would overcome the inconsistent voltages the controller would hold the panels at.
Will post my findings after a couple weeks testing.
Click to expand...

This is an interesting point, something that never crossed my mind, and afaik Dacian has never discussed. I would be curious to learn more about how this would play out in different scenarios.
 
I'm back to give you your "I told you so" moment. I was misinterpreting the point you were making throughout this thread re: efficiency of dssr vs mppt for 60 cell panels in parallel with a 24v system.

I have nothing to add other than that I understand the point you were/are making now, and agree that in this scenario there is little or no advantage to mppt.
 
Dhowman said:
There just isn't enough V difference between 60-cell/24V panels, especially when they're at STC or higher (which is most of the time and in most places?), and a 24V battery, so the MPPT is stuck with the power point the panel's already at or one that's not different enough from it to make up the overhead inherent in the MPPT itself. Intuitively this makes sense but it also seems to be borne out by the results above too, no?
Click to expand...
Precisely for this reason, we have partnered with Newpowa to design 30 cell "12V" 105 W panels for use on RV rooftops. These panels have an Isc of 7.5 Amps (vs 5.8 to 6.2 of other 100 W panels). When parallel connected, these panels and a PWM controller will deliver more current than the best MPPT.
 
Bogart Engineering said:
Precisely for this reason, we have partnered with Newpowa to design 30 cell "12V" 105 W panels for use on RV rooftops. These panels have an Isc of 7.5 Amps (vs 5.8 to 6.2 of other 100 W panels). When parallel connected, these panels and a PWM controller will deliver more current than the best MPPT.
Click to expand...

What is the Vmp?

Can you highlight the pros and cons of this approach?

What conditions will it do better in? What conditions will it do worse in?
 
Dzl said:
What is the Vmp?

Can you highlight the pros and cons of this approach?

What conditions will it do better in? What conditions will it do worse in?
Click to expand...
Vmp ~15V, Voc ~17.5V. For PWM controllers, Isc & Voc are the relevant parametrs.
As others have mentioned, PWM is as good as MPPT when the panels are at 40C or above. This is likely to be the case for most RV'ers (unless you're a ski bum boondocking in Aspen CO in January). We recommend the use of these high Isc panels for RV's where the panel to controller distance is less than 20 ft. We have tested these panels extensively with 25 ft 12AWG wires and have found them to be performing very well.

As to pros & cons, parallel connections are more reliable; if one of the MC4 connector fails, it wont take the entire string offline. If the controller fails, simply bypass the controller and charge the batteries until you have an opportunity to fix the controller. MPPT controllers do have a slight edge early morning when the panels are likely to be cooler. In relative terms, this advantage is likely to be 10-20% more current, but in absolute terms, it's likely to be be 0.5 to 1 Amp (for a typical 100 Watt panel). However, during the peak power production times (10 AM to 2 PM), the difference will be insignificant. The new panels & PWM will do better than most/all MPPT controllers & other panels.

Edited to fix a typo.
 
When you do the research on the MPPT algorithm, it really isn't on the solar panel side and more on the charging side. When it comes to efficiency, I do not believe anything can perform better than a buck converter at 98%, no matter what anyone says. My first solar charger was home made using a highly efficient buck inverter that was nearly 100% charging a LiFePo4 battery. I do not believe MPPT really does anything more than a buck converter when you are not charging Pb batteries.

There is a lot of 'Believable' videos on YouTube, I can find anything from perpetual engines that produce more energy than they use and other 'cosmic power generators' that require no motion. All I can say is "First law of thermal dynamics"
 
Bogart Engineering said:
Vmp ~15V, Voc ~17.5V. For PWM controllers, Isc & Voc are the relevant parametrs.
As others have mentioned, PWM is as good as MPPT when the panels are at 40C or above. This is likely to be the case for most RV'ers (unless you're a ski bum boondocking in Aspen CO in January). We recommend the use of these high Isc panels for RV's where the panel to controller distance is less than 20 ft. We have tested these panels extensively with 25 ft 12AWG wires and have found them to be performing very well.

As to pros & cons, parallel connections are more reliable; if one of the MC4 connector fails, it wont take the entire string offline. If the controller fails, simply bypass the controller and charge the batteries until you have an opportunity to fix the controller. MPPT controllers do have a slight edge early morning when the panels are likely to be cooler. In relative terms, this advantage is likely to be 10-20% more current, but in absolute terms, it's likely to be be 0.5 to 1 Amp (for a typical 100 Watt panel). However, during the peak power production times (10 AM to 2 PM), the difference will be insignificant. The new panels & PWM will do better than most/all MPPT controllers & other panels.

Edited to fix a typo.
Click to expand...

Thank you for the explanation, this is helpful but my question was more directed at the pros cons of higher Isc lower Voc 30 cell panels vs 36 cell panels (specifically regarding PWM)

it seems that these would be more efficient at STC-ish conditions, but be less tolerant of any conditions that would reduce operating voltage.

On a related note, I'm curious how a bypass diode being 'activated' would effect this arrangement (PWM + 30 cell panels in parallel). Would this effect current, voltage or both?
 
Last edited:
Controlled, side-by-side MPPT vs DSSR updated test results under poor solar conditions from Bused_As.

Bottom line? No difference between his EPEver MPPT and the DSSRs (except, of course, price, size, longevity, etc) though it was interesting (and perhaps not surprising) that DSSRs start cranking amps earlier in the a.m. than MPPT. The later will hit higher peaks once sun's higher in the sky.

Continues to look as though the ONLY advantage to MPPT is being able to get away with smaller cables if you have long runs.

 
I found this thread interesting although it is a little old. I put my first and only solar system together using 280ah cells, Electrodacus SBMS0, and two DSSR20s. Connected to four used 235w, 60 cell panels. It's a 24v system. Work great but never had another system with MPPT and etc. Always wondered if I could get better "performance" with MPPT.
 
wpns said:
Sure, but how much better, and if it’d be worth it are open questions. #IfItAin’tBrokeDon’tFixIt.
Click to expand...
That's my feeling. And I have yet to see anyone explain how an MPPT would be better if you design a system from the ground up-matching all components.
 
Check electrodacus's site as he just posted some info comparing 3 x 255w and 3 x 260w panels on a sbms0+dssr50 vs 6 x 260w panels on a sbms+Victron 50a mppt charger. It looks like on a sunny day the mppt was around 5-6% more efficient. It will be interesting to see his results on overcast days and with shadows. It looks like the dssr50 had a slight advantage for sunrise and as the sun was setting if I'm reading his graph correctly.

The Victron is double the cost (or triple for Dacian), looks significantly larger, and weighs 10x as much. Some may require it, but not everyone would pick 6% extra over these other factors. I certainly wouldn't pay 200-300% more to get 6% extra solar.
 
APhoton said:
I found this thread interesting although it is a little old. I put my first and only solar system together using 280ah cells, Electrodacus SBMS0, and two DSSR20s. Connected to four used 235w, 60 cell panels. It's a 24v system. Work great but never had another system with MPPT and etc. Always wondered if I could get better "performance" with MPPT.
Click to expand...

What types of numbers are you getting from these four panels?

I have ten 250w panels hooked to my sbms120 and it can produce over 1850w in full sun.
 
orangezero said:
Check electrodacus's site as he just posted some info comparing 3 x 255w and 3 x 260w panels on a sbms0+dssr50 vs 6 x 260w panels on a sbms+Victron 50a mppt charger. It looks like on a sunny day the mppt was around 5-6% more efficient. It will be interesting to see his results on overcast days and with shadows. It looks like the dssr50 had a slight advantage for sunrise and as the sun was setting if I'm reading his graph correctly.

The Victron is double the cost (or triple for Dacian), looks significantly larger, and weighs 10x as much. Some may require it, but not everyone would pick 6% extra over these other factors. I certainly wouldn't pay 200-300% more to get 6% extra solar.
Click to expand...
6% more money spent on panels will have the same effect, no?
 
wpns said:
6% more money spent on panels will have the same effect, no?
Click to expand...

I had a longwinded explanation typed out, but the short answer typically is, "get one more panel." I am aware this is often not available or affordable on other solar setups which have panels in series to get higher voltages. This flexibility is another advantage for the Electrodacus system, compared to an industry where entire solar setups can be scrapped because they need to replace a roof.

This may not be workable on a boat or rv where space is at a premium. Even then, I'd prefer to seek out newer, higher efficiency solar cells and get creative with placement/angles before I'd try something else.
 
You must log in or register to reply here.
Back
Top