From what I'm reading this would only be true with 72 cell panels not with 60 cell panels.
Actually MPPT was designed decades ago for AGM and FLA chemistries not LiFePO4! As LiFePO4 will take every bit of energy you offer it there is no need for MPPT to "optimize" the charge for this chemistry. I live in Canada and will have these mounted at least 4" above my roof, so heat is not much of an issue...when in the US, it would be over the winter months so once again, extreme heat conditions will simply not exist.True, but 60 cell panels are notorious for being marginal for charging 24V systems especially when they get warm and their voltage drops even further.
The following is a discussion on the best practices of 60-Cell Photovoltaic modules in off-grid applications using batteries.www.sunwize.com
Is less cost the potential advantage to use 72-cell solar modules? Reveal the pros and cons of 60-cell & 72-cell modules in different systems.couleenergy.com
Electrodacus is a nifty little piece of hardware, but it is 30 year old solar charging technology.
Actually MPPT was designed decades ago for AGM and FLA chemistries
As LiFePO4 will take every bit of energy you offer it there is no need for MPPT to "optimize" the charge for this chemistry.
I live in Canada and will have these mounted at least 4" above my roof, so heat is not much of an issue...when in the US, it would be over the winter months so once again, extreme heat conditions will simply not exist.
Are you comfortable with getting no more then 80% of the panels rated performance under any circumstances?
@snoobler Here is a video of a side by side test that seems to go against your theory of NEVER getting more than 80% with the DSSR20...in fact it is actually out performing the MPPT in some cases.For a small system where efficiency is not that important, the basic switch charge controller does work, but it is never going to be the best solution. All the talk of it being reliable is one thing, but quality MPPT controllers are very reliable, and far more efficient. Lets take a sample system with 6 typical 60 cell 300 watt panels.
A typical 300 watt panel is 33 volts at 9 amps per panel. With the switch type charge control, you parallel all 6 panels, you get 54 amps of charge current, to your 28 volt bank. This actually looks pretty good. Hitting 1,512 watts of charge power under a perfect full sun solar noon. But how far do you have to run that 54 amps? What gauge wire do you need to make that work? Clicking 54 amps on and off is pretty touch on a relay contact as well.
Now wire those panels as 2 parallel banks of 3 in series. Now we have 99 volts at 18 amps. Just 18 amps can run a decent distance over just #10 wires. Any volt lost is also a much smaller percentage. The charge controller uses DC-DC conversion to regulate that into the battery. Now we have 1,800 watts, let's say 97% efficiency on the MPPT conversion, that is typical. 1,746 watts / 28 volts = 62.36 amps. Does not seem like a huge difference in the full sun conditions, but that is still 1,512/1,746=87% with the relay vs the MPPT
And for the rest of the day, any drop in panel voltage and current directly drops the current very quickly on the switch charge controller. If the panel falls below 28 volts, you get no charge current. You may only be able to charge for 4 hours on a good day. With MPPT the voltage can fall a fair bit and the controller can still track the power curve and find the optimum power point and convert it all to the battery voltage. Even at very low light levels, it can pull good power from the panels. The area under the curve will be much higher.
Also when the battery comes close to fully charged, the switch type can only shut off, and kick back on to full current again if the voltage falls. The MPPT can smoothly roll off the current as the battery reaches full, and even keep powering the load while the battery is just kept in the CV area. This can be a huge advantage, and also much easier on the cells. You can completely run the loads off of solar while the battery waits until the sun goes down. Rather than charge, run on battery, charge, run on battery, repeat. More modern PWM controllers are between the old relay switch and an MPPT. Most of the cheap ones are no more efficient, and still just switch on and off, but there is not contact arcing in a mosfet, and they can react faster. Some of the better ones may even have a coil and give some current boost while it is dropping voltage from the solar panel, but this seems to have gone away as the cost of MPPT has come down, the coil in a PWM would wipe out the cost savings of a cheap MPPT.
@snoobler Here is a video of a side by side test that seems to go against your theory of NEVER getting more than 80% with the DSSR20...in fact it is actually out performing the MPPT in some cases.
@GXMnow This video shows how the SBMS0 combined with the DSSR20 can also feed loads directly from solar and not necessitate draining the battery and then needing to re-charge once the loads are gone.
Just to be clear...I'm simply doing my research and want to decide on the best "Value" for my situation, if I need to spend more to see significant gains...I will...but if spending less with marginal looses then the "value" is obvious. The cost difference between an expensive charge controller with cheaper wiring and expensive cabling with cheaper Controllers in the end will most likely be mute. I'm a guy that will question...in a way to learn not dispute...information I'm given with no real life documented examples. The two video's I linked here simply do not, at least in the test conditions documented, support parts of what I have read.
Thanks for this info...it helps a lot...like I said...just doing my research! Looks like I will stick with my original Victron Charge Controller but will use the SBMS0 for my battery management!"MPPT vs DSSR20, side by side challenge.
With my new batteries still a couple weeks away I want to expand on the brief solar charge testing I did earlie
Flat mounted panels, low winter sun, clouds and rain for 14 days while I test the relative
performance of my Epever MPPT Solar Charge Controller and my DSSR20s."
Not side-by-side except in the most literal sense - the panels were side by side. So many uncontrolled variables in horrible conditions.
At no time in his testing did he demonstrate the DSSR20 captured more than 80% the rated power of the panels, in fact, he demonstrated that in full sun, they performed notably worse than the MPPT.
He demonstrated that when in the rare full sun conditions, the MPPT substantially outperformed the DSSR20:
View attachment 44255
The magenta bars, which represents 2X panels in series on the MPPT, are substantially greater than 2X higher than the cyan bar of the single panel on the DSSR20 indicating that 2X panels produced substantially more than 2X the power of the 1 panel. Dacian even tried to explain that away because the panels got hot and reduced the performance on the DSSR20.
When conditions are bad for solar, solar sucks, regardless of charging technology. When conditions are favorable for solar, MPPT trounces everything else.
If you want the potential to get rated power out of your array, you want MPPT. If you're okay with only getting 80% of your array's rated power, then Electrodacus or PWM is fine. It's basically a $ decision. Do you want to buy more panels, or do you want to buy an MPPT?
The other day with mostly clear skies and intermittent clouds:
View attachment 44261
2930W out of 2970W rated (98.7%).
Had these been installed in a 24V configuration, my 9 24V panels in parallel would have an Imp of 8.76A * 9 = 78.84A working at a battery voltage of 26.69V.
26.69V * 78.84A = 2104W
2104/2970 = 71% rated.
Even using Isc, the best would be:
26.69V * 83.43A = 2227W
2227/2970 = 75% rated.
It's worth $500 (price difference between my MPPT and 10X DSSR20) to me to get 25-29% more power from my panels.
MPPT: 98.7% rated.
DSSR20: 71-75% rated.
I choose MPPT.
If you've determined that you're cool with only getting 800W for every 1000W installed, then that's awesome. It's about being aware of the limitations and making an informed decision.
Thanks for this info...it helps a lot...like I said...just doing my research! Looks like I will stick with my original Victron Charge Controller but will use the SBMS0 for my battery management!
Luckily 95% or my portfolio is in Tesla not Electrodocus so I don't have a horse in the race. Like I said previously, so much of what you read on line is complete BS, but folks come across as knowledgeable. I like to see facts...no opinions. I do agree that their SBMS0 is a really cool device...basically a mini-Batrium for a fraction of the cost and complexity.The Electrodacus works great with Victron hardware in signaling low and high voltage cut-offs.
I don't mean to come across as negative on the Electrodacus. It's a pretty awesome piece of hardware. It just has limitations like everything else, and folks that are sweet on Electrodacus can be irrationally fanatical about them in spite of its shortcomings. I'm just trying to temper that perspective.
https://www.energystar.gov/productfinder/product/certified-room-air-conditioners/results. List sorted by efficiency. Inverter technology window ACs at top down to 13.8 ceer, top 18 on list.For now, just remove the RV AC system, fill the hole and get a normal Mini-split. If you really want to use a roof mount, there are several options out there that use ceiling mounted "indoor units" but wold need some work to cover them on the roof. New Horizons RV have made a few 5th Wheels with ceiling mounted head units!
That list doesn't seem to have any Mini-Splits...I looked up LG and the best one listed had a CEER of 13, when all of their Mini-Splits are over 20!https://www.energystar.gov/productfinder/product/certified-room-air-conditioners/results. List sorted by efficiency. Inverter technology window ACs at top down to 13.8 ceer, top 18 on list.