diy solar

diy solar

The Electrodacus SBMS thread (SBMS0, DSSR50, etc)

The fact he uses wrong numbers to support his argument that MPPT are useless and dismissed the question 3 times when I asked him about it.

The fact that wires losses and costs are not taken into account. And to make this problem even worse you can't go past 24 V.

The fact that it has no way to interrupt current itself and relies on other devices to act correctly.
You are mistaken again. The sbms0 turns off the dssr20 to prevent overcharging. You have no direct knowledge of this product. When the battery is fully charged the sbms0 turns off the charging from the dssr20.

there is very little wire loss with the standard 10awg wire. it is minimal at best. I use 50-60 feet runs and have no problems what so-ever charging the 2p8S lishen 544amp battery. the 30 foot runs have even less voltage drop when calculated and also is not an issue.

the SBMS0 can also control MPPT's if you go that route.

the SBMS0 is the BMS and it turns off the solar charge controllers so i would say it definitely stops the flow of current by using the control circuits using small sense /control wires (24 AWG cat 5 or cat 6 wires). there is no large current going through the SBMS0. it does not have the problems of getting rid of excess heat that some of the other BMS's do. there is nothing heating up and causing any problems in the SBMS0.

I have 2 SBMS0's functioning on 2 separate 24-volt redundant systems. they work like a finely tuned clock. and are very accurate to 3 decimal places and balance the LiFePO4 cells in the batteries very well. each one controls the DSSR20's. I do not have them controlling the inverter but that can be done also.
I fail to see where you say they do not control the current. they definitely control the current from the DSSR20's and can also work with the MPPT type solar charge controllers if that is what you choose.

when the individual cell voltage reaches 3.55 volts for too long of a pre-set time the SBMS0 turns off the DSSR20's (the solar charge controllers)
the inverter uses the load from the batteries or directly from the charge coming into the batteries from the solar panels through the DSSR20's.
when the sun is shining you can use as much of the incoming solar as you can through the inverter.
i have a 6000 watt inverter hooked up but have only used 1500- 2000 watts through it at this time.
 
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Say the battery is fully charged. I have a 400 watt load on the 12v common bus bar. Is the BMS going turn off the power from the solar, forcing the 400 watt load to come from the battery?
 
2. Not sure what you mean by wire losses. Losses during cell equalization? One of the advantages of his approach (as I see it) is that to high currents go through the bms. I like that. There are no huge wire losses.

I'm talking about the wires between the panels and the battery. For example 10 kW of panels @ 24 V is 400 A... good luck sending that to the battery with reasonable losses, cost, etc. if you have more than a few feet of cables.


3. Perhaps that's what you mean by a cult (a misplaced or excessive admiration for a particular person or thing) following?

No, I was talking about dismissing the data you don't like (like wire losses just above for example) because it goes against what you want. That's not how engineering works.


I wouldn't call off-loading current interruption (due to fault conditions) to other devices a bad move.

I don't too, of course, but only as a convenience in normal operation, not as the last resort solution. Remember we're talking about a non-normal event that shouldn't happen in normal operation. Saving the battery becomes the priority in non-normal conditions so things like inductive spikes (that wouldl actually not damage anything but the switch used to interrupt the current) becomes less important in that case.


I feel that's sound engineering. Disrupting high currents within the bms will generate inductive spikes. Why subject electronics to those spikes? An elegant way to disable current is for the bms to signal the charging sources to shut down. No high current fets are involved. The design becomes a lot cheaper and robust.

What happens if a MOSFET shorts in the SCC (and that includes the MOSFETs in the DSSR20 which are the SCC in that case) for example?


You are mistaken again. The sbms0 turns off the dssr20 to prevent overcharging. You have no direct knowledge of this product. When the battery is fully charged the sbms0 turns off the charging from the dssr20.

You are the one mistaken. I know you can use the DSSR20 and I know they're basically SSRs (and yes, I read the schematics, don't tell me I have no knowledge about the product... I wouldn't give my opinion otherwise, that would be stupid). Again, what will happen if one of the MOSFETs shorts?
 
Say the battery is fully charged. I have a 400 watt load on the 12v common bus bar. Is the BMS going turn off the power from the solar, forcing the 400 watt load to come from the battery?
Let’s say you have 1000 watts of solar, a full battery, and a 400 watt load. In this example the pulse width modulator in your MPPT charge controller will be running at a 40% duty cycle to keep the battery voltage constant with a net zero amp battery draw.

The SBMS will do the same thing (operate at a 40% duty cycle and zero net battery draw) except that instead of cycling thousands of times per second, it will be cycling on the order of 10s of seconds.

Continuing the example, a 400 watt load will deplete a 1000Ah 24v battery by about 0.01% in 30 seconds where as a PWM charge controller will deplete the same battery by 0.00000001% during a 5000th of a second discharge.

There is no practical difference for cell life between discharging the battery 0.01% 500 times in 8 hours vs discharging the battery 0.00000001% 2.5 million times in 8 hours.

The chart below shows how cycle life approaches infinity as depth of discharge approaches zero. This chart has a logarithmic scale so the vast majority of the battery’s useful life will still be consumed during the deep discharges (and general battery age).
dod.gif
 
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I'm talking about the wires between the panels and the battery. For example 10 kW of panels @ 24 V is 400 A... good luck sending that to the battery with reasonable losses, cost, etc. if you have more than a few feet of cables.

No, I was talking about dismissing the data you don't like (like wire losses just above for example) because it goes against what you want. That's not how engineering works.

I don't see any problem other than his SCC is rated for only (I believe) 20A. If you want to switch 400A then 20 of his SCC are required. If you have 10 kW of panels then a more suitable CC needs to be chosen. You don't have to use his SCC. Use a mppt controller and connect panels in series to reduce current and wire losses. The charge controller requires hardware to accept a shutdown signal from the bms.


I don't too, of course, but only as a convenience in normal operation, not as the last resort solution. Remember we're talking about a non-normal event that shouldn't happen in normal operation. Saving the battery becomes the priority in non-normal conditions so things like inductive spikes (that wouldl actually not damage anything but the switch used to interrupt the current) becomes less important in that case.

Not necessarily, it all depends how the system is setup. The bms can be the first (primary) disconnect or the last resort disconnect. It it's used as the first disconnect then there will be lots of spikes. My system uses the bms as the primary disconnect. Should the bms fail to do its job then the mppt cc will limit charging voltage to a safe level.

What happens if a MOSFET shorts in the SCC (and that includes the MOSFETs in the DSSR20 which are the SCC in that case) for example?

That would be a problem. Perhaps with my mppt cc also. There is no backup plan when using his SCC.
 
If you have 10 kW of panels then a more suitable CC needs to be chosen. You don't have to use his SCC. Use a mppt controller and connect panels in series to reduce current and wire losses. The charge controller requires hardware to accept a shutdown signal from the bms.

That's my point. Yet, @michael d has 10 kW of panels and says 18 kW will not be a problem... Also: "I have not run all the numbers yet but it works great." is exactly what I was saying when talking about cult, "works great" means nothing. Of course it works, but if you have 5 or even 10 % losses in the wires alone I wouldn't say it works great :rolleyes: of course you can avoid most of the losses but that means wires as thick as my thumb, or loooots of smaller wires which will be a nightmare to manage (and both solutions will cost a lot).


My system uses the bms as the primary disconnect.

That's a very weird way of using a BMS. Why did you chose this way?


Should the bms fail to do its job then the mppt cc will limit charging voltage to a safe level.

Safe level for the battery as a whole but not for each cell. For example stopping charge at 29.2 V (3.65 V/cell) you can have 7 cells at 3.6 V and one at 4.0 V, that's far from ideal (and that's a pretty conservative example...).
 
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I don't see any problem other than his SCC is rated for only (I believe) 20A. If you want to switch 400A then 20 of his SCC are required. If you have 10 kW of panels then a more suitable CC needs to be chosen. You don't have to use his SCC. Use a mppt controller and connect panels in series to reduce current and wire losses. The charge controller requires hardware to accept a shutdown signal from the bms.




Not necessarily, it all depends how the system is setup. The bms can be the first (primary) disconnect or the last resort disconnect. It it's used as the first disconnect then there will be lots of spikes. My system uses the bms as the primary disconnect. Should the bms fail to do its job then the mppt cc will limit charging voltage to a safe level.



That would be a problem. Perhaps with my mppt cc also. There is no backup plan when using his SCC.
the DSSR20's with diversion can also be used to heat water and to heat in-floor so then the excess solar-PV generated electricity can be used to heat the home or shop. I bought 4 24-volt water heater elements to try that out on 4 of the dssr20's with diversion.
the battery storage capacity will be 4 24-volt batteries 2P8S per battery using 16 272Ah Lishen cells in this part of my off-grid build. it will have redundant 24-volt batteries.
i directly observe up to 51-60 amps of charging using 6 250-watt used polycrystalline PV panels wire in parallel. the voltage drop is not an issue. it charges the batteries quite readily on the 50-60 foot runs of 10 AWG PV wire.

Dacian the engineer/designer of the SBMS0 has always been prompt to answer any questions I asked him.

voltage drop with 10 AWG PV wire:
example55 ft of 10 AWG PV wire will have a 2.13% voltage drop at 7 amps 36 volts
55 ft of 10 AWG PV wire will have 2.41086 percent voltage drop at 8.27 amps 37.6 volts
55 ft of 10 AWG PV wire will have 4.82173 percent voltage drop at 16.54 amps 37.6 volts2 250 watt 60 cell panels in parallel - the amperage doubles to 16.54 amps
4.821% voltage drop
so 37.6 volts - (.04821 x 37.6) = 35.787 volts
60 ft5.25% voltage drop
so 37.6 volts - (.0525 x 37.6) = 35.626 volts
30 ft2.63% voltage drop
so 37.6 volts - (.0263 x 37.6) = 36.61112 volts
the 2.62 percent voltage drop is nothing. the 5.25 percent voltage drop is still nothing on a 60-foot run. it still pushes up to 16 amps or more at 30 plus volts and charges the battery using standard PV wire which is only 25 cents per foot. for those using it in RV applications, the wire runs could/would be even shorter. if I put it on top of the roof I could make shorter wire runs but I am not going to climb on top of the steep roof of the 2 story house to do that. I use a ground mount for this part of the off-grid solar.
it is difficult enough mounting the solar panels at a 45-degree angle. 6 solar panels are about 10 foot by 12 foot at a 45-degree angle.

I use 4/0 wire between the battery and the inverter. that wire is about 18 inches long so no problems there.
a dozen ways to do the same things. solar panels were quite inexpensive in the year 2020 at about 58 dollars each including delivery for the used 250-watt 60 cell polycrystalline PV panels.

as you know, the SBMS0 (the BMS) does not charge the batteries... the solar charge controllers do this part.
 
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if you have any real numbers to report on the SBMS0, show them. but I would like to see real user data. show a video.
the SBMS0 does not charge the batteries the DSSR20's do this part quite readily at 16 to 20 amps each although they are rated for up to 24 amps each.
as far as some number of Dacian you disagree with --- you would have to take that question up with Dacian. he is the electrical engineer designer of the SBMS0 and DSSR20 and dect16's.
again if you have no real numbers to report --- real data using this equipment, it is impossible to evaluate them.
today the 3 DSSR20's charged the LiFepo4 batteries up from 76 percent to 100 percent and I have been running a small constant 260-watt load through the inverter all day. the sun is down and it is at 99 percent SOC.
6 250-watt used panels into 3 DSSR20's. the DSSR20 is a digital solid-state relay, it is not a PWM and it is not a MPPT.
if you can do more accurate measurements that would be great to see. ?

the west array had 34.24 volts after the 30 feet (or less) of 10 AWG PV wire--- this is the voltage the DSSR20 would push to the battery at as many amps as were available by the sun's power. the DSSR20 was off as the battery was at 99 percent soc and waiting for some of the stored electricity to be utilized. there are only 3 small dc direct-wired (24-volt 16 LEDs each) lights on that battery right now so they get to run 24/7 on 2 250-watt west-facing PV panels which hardly get any sun at all until later in the day. no inverter on those led lights as they are wired direct. voltage drop is not an issue at all (Minimal at best)
the 2P8S LiFePO4 battery will take all the DSSR20 is allowed to give until the SBMS0 turns them off (16cells x 272Ah x3.2v = 13,926.4 watt-hour potential capacity). the sbms0 turns them off at 3.55 volts when any cell goes over 3.55V for too long of a pre-set time to protect the battery. the job of the BMS!

if you sweat the small stuff you will never get anything done.
i break all big projects down into smaller projects.???
a million ways to do the same thing.
 
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inverter size --- 6000 watts /24 volts = 250 amps.
so the load through the inverter could max out at 250 amps.
has nothing at all to do with the SBMS0.
no large current goes through the SBMS0.

voltage drop is between 2.63% for a 30 foot run in the dc circuit to the DSSR20, up to 5.25% voltage drop on a 60 foot run using readily avaliable standard 10 AWG PV wire.
so if you are only looking at the 5.25% voltage drop to get the same voltage you would have to add another 250 watt PV panel for every 20 panels installed.
i bought used 250-watt polycrystalline panels for 58 dollars delivered. so 58 divide by 20 = less than 3 dollar efficiency loss on the 60 feet of PV wire run in the dc circuit. insignificant expense in the big picture. less if one uses shorter wire runs to the solar charge controller (DSSR20 is the solar charge controller I am using)
the wire cost is about 30 dollars for every 2 250-watt panels installed for the 10 AWG PV wire.
or 90 dollars for every 6 250-watt panels and 3 DSSR20's at less than 37 dollars each for every 6 panels (1.5Kw array).
no soldering - except I installed a 1-watt fuse inline on the positive side of the DSSR20 to the positive bussbar I think this is standard 20 AWG automotive wire and fuse. if you position it closer then no soldering would be needed at all. a person probably could use crimp connectors but I soldered because I think the wires were not exactly the same AWG that I used there.
I color code and use red PV wire for the positive side and black PV wire for the negative side on all DC wiring. less confusion and easily identify circuits. The Dymo label maker also helps to keep it organized.

Again this is an off-grid DIY solar build. easily done in small increments by almost any handyman or woman.
For me, the most difficult part is installing the 41 pound 250-watt panels onto the array support structures. wish I had a second person for that task.

the LIshen 272Ah cells cost 95.74 dollars per cell delivered. for the 1st 32 that I purchased;
and only cost 90.73 dollars delivered for the second 32 Lishen 272Ah cells I ordered in 2020.

the SBMS0 is the BMS I specifically chose for this 24-volt off-grid DIY build.

Dacian the engineer/designer has been helpful whenever I asked him any questions. so personally I like the service after the sale and the functionality of the SBMS0 and DSSR20's.

the solar panels easily charge the batteries by noon or before on any good sun day using the DSSR20's and are shut off by the SBMS0 when any cell reaches 3.55 volts for a preset time I did not change any of the preset values that Dacian already had input to the SBMS0. I put in 544Ah for 8 cells as each 2P acts and functions as one cell. 2P8S configuration....

All is working great --- ya ya ya - no number as that is an adjective.?

the SBMS0 turns off the charging with the DSSR20 via small sense wires I use 24 AWG solid strand cat 5 cable which is very inexpensive and readily available. the supplied ribbon cable that monitors the individual cells in the 24-volt battery is 28 AWG. there is no real amount of voltage going through the SBMS0.
I paralleled the DSSR20's with 20 AWG solid strand thermostat wire. only one wire is needed per DSSR20 for that part. again insignificant wire cost. I paralleled them into Dinkle terminal blocks with a cost of 50 cents per terminal block. this simplifies the wires some. I use a different color 20 AWG solid strand thermostat wire for each one (4 colors to choose from in my 20 AWG thermostat wire).

my understanding is the SBMS0 balances the cells with some small number like 300mA or something through the 28 AWG ribbon cable that is direct wired to each cell. the balancing works great as my cells run about 30 to 120 mA differences and often down to 8 mA (delta between cells).

I have 2 SBMS0 set up and functioning correctly they are the newest version 03d.
if any mistakes are made they are mine - ???
I purposely make a mistake everyday so I can learn from my errors.

I was a chemistry major chemist in the honors program and have extensive 10 years of college. 3 years undergrad college, and 7 more years graduate-level education at the state university but still learning. I graduated in 1987.
 
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February 21st, 2021: a cloudy day and snowing: 26.75 volts, 26.71 volts, and 26.74 volts at the breaker (about 55 to 60 feet of 10 AWG PV wire between breaker and solar panel) before the DSSR20 into the battery was producing 360 watts at 15 amps for the 6-panel south-facing array. panels mounted at a 45-degree angle for the south sun in winter. each measurement is a set of 2 250-watt PV panels wired in parallel right at the panel using a Temco branch connector (plug and play).
these 250-watt panels are 30.3 VMP and 37.6 VOC. according to the sale listing for these used 250-watt 60 cell used polycrystalline panels.
VOC is when nothing is hooked to them.
VMP is the maximum rated power output when connected. as I understand it.
hopefully, the sun will come out but still charging the 2P8S Lishen 272Ah cells in the 544Ah battery.
in good sun, I will get 1500 to 1600 watts at about 50 amps from the 6 250-watt used polycrystalline 60 cell PV panels. not too bad at 23 cents per watt delivered to my front door in a pallet of 20 panels.

the Electrodacus SBMS0 is controlling the Electrodcus DSSR20's and will turn them off if I get a full charge on the 544Ah LIshen 24-volt battery

I installed a breaker inside the solar power shed for each pair of panels, I breaker (32 amp dc breaker)both negative and positive using ferrules on the 10 AWG PV wire. basically, an on-off switch as the breaker is not needed at all. another point of resistance --- I know.
but makes it easy to turn them on-off during assembly without ever coming in contact with the live power from the solar PV panels.
I guarantee you that was quite useful.
about 390 watts right now. cheers all?
 
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C-rate for 544Ah 24volt battery LiFePO4 using 272Ah Lishen cells 2P8S configuration:
Optimum is around a 0.2C charge rate so if you have a 2p 272Ah so that will be 544Ah x 0.2 = 108.8A so that will be about 10 panels but 12 panels should also work if you prefer that.
The SBMS0 will not interfere in the charge current unless you use a dual PV array setup and that will allow you to have a PV array 3x larger made of two separate arrays say one with 10 panels and another one with 20 panels in total 30 panels and in that case the SBMS0 will control with array will be used for charging can be just the small 10 panels array if is sunny and you set limit to 100A or it can be the 20 panels array if amount of sun is about half and if is cloudy the SBMS0 will connect all 30 panels so you can still get a good charge even with bad weather.
my thanks and compliments to the electrical engineer DT

a few more answers for my off-grid DIY solar PV >>>> long-life span system!!!!!???

60.99 amps 1674 watt from 6 250-watt used 60 cell polycrystalline panels charging right now through 3 DSSR20's. about 55 to 60 feet of 10 AWG PV wire. woohoo! ???
I can't wait until I can show ya all 12 panels charging at 120 amps!
 

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You can see the DSSR20 as an ideal diode plus a solid-state switch in series so there will be almost no voltage drop on the DSSR20 (just a few mV) The important part is your battery that is 25.6V nominal but most of the time it will be around 26.5 to 27V and so the panel when hot needs to have at least this 27V + depending on cables 2 or 3V drop on those so around 29 to 30V max power point voltage with a 60 to +70C panel. The max power point for 60 cell panels is around 32 to 33V at STC meaning panel at +25C but for the panel to be at +25C ambient needs to be around -10C.
But PV panels are constant current sources so the voltage of the panel if connected to the battery will be the same as battery voltage plus the voltage drops on the wires. So in most cases (mostly dependent on PV panel temperature) the 60 cell panels + DSSR20 + 8s LiFePO4 battery will result in a 90 to 100% efficiency so an average of around 95% and thus it is an ideal match.
If you go for a panel with exact same cells but 72 of them then those extra 12 cells will not contribute with anything but the open-circuit voltage of 72 cell panels is below 51V so it is not a problem for the DSSR20 is just that a 72 cell panel has 20% more cells and so 20% higher power rating than a 60 cell panel and also a 20% higher cost but charge current will be the same so will be the charge power thus there is no advantage other than aesthetics (in your case) to pay 20% extra.
So DSSR20 can handle 60 cell and 72 cell panels with no problem is just that there will be no difference in power provided to the battery.

more thanks to Dacian the Electrical Engineer and designer of the Electrodacus DSSR20 and Elecrodacus SBMS0 for all the information above.
???
 
Michael D- are you working up to doing all your electrical with solar, and natural gas/propane for heating? And how do you do wifi monitoring with your SBMSO? I’ve got an Apple phone and iOS updates keep messing with the interface.

+1 on Dacian. We have a 2 panel (280w 60 cell)/4s 200ah lifepo4 system we put in our Sprinter 2 years ago.

As others have mentioned, in 12v mobile applications with 60 cell 30v panels in parallel, MPPT might maximize efficiency (that’s what we do). But his SBMSO (ours is the 1st Gen) works great as a bms and does the lvd/hvd/ltcd switching just fine. With the falling prices on lifepo4, I’d love to go off grid with the Electrodacus system here in the city. But we’ve got a tiny lot and bad roof design for panel placement.

Dacian is the best vendor I’ve ever encountered for replying to questions. Don’t know how he gets anything done- he’s a one man army up there!
 
So DSSR20 can handle 60 cell and 72 cell panels with no problem is just that there will be no difference in power provided to the battery.

That is a false statement. There is no difference in power IF cell temperature is maintained at 25C.

Cells are only 20% efficient. If 1000W is radiating on a 1 m panel, then close to 800W goes to heating the panel. The panel will get hot, resulting in panel output voltage dropping. On hot days, the 60 cell panel voltage could drop below battery voltage, resulting in no charging.
 
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Michael D- are you working up to doing all your electrical with solar, and natural gas/propane for heating? And how do you do wifi monitoring with your SBMSO? I’ve got an Apple phone and iOS updates keep messing with the interface.

+1 on Dacian. We have a 2 panel (280w 60 cell)/4s 200ah lifepo4 system we put in our Sprinter 2 years ago.

As others have mentioned, in 12v mobile applications with 60 cell 30v panels in parallel, MPPT might maximize efficiency (that’s what we do). But his SBMSO (ours is the 1st Gen) works great as a bms and does the lvd/hvd/ltcd switching just fine. With the falling prices on lifepo4, I’d love to go off grid with the Electrodacus system here in the city. But we’ve got a tiny lot and bad roof design for panel placement.

Dacian is the best vendor I’ve ever encountered for replying to questions. Don’t know how he gets anything done- he’s a one man army up there!
yes, I am working up to doing all my electrical with off-grid PV, and then I am going to use the excess PV energy to heat the hot water and to heat the house in the winter and eliminate the Propane or at least get it down to not using so much propane. insulation in the house will also help as I increase the energy losses that way as well.
the intent is to get off the electric grid totally. I have the panels and the battery capacity and inverters etc. just need to store more energy for the heating side of things.
I am not keen on the expensive propane either. monopolies control that price also.

on 12-volt mobile applications, the wire run length should not be much of an issue as the runs are relatively short. the DSSR20's digital solar charge controllers are less than 37 dollars to control 2 60 cell panels or 2 72 cell panels wired in parallel. so very inexpensive and you can add more as you grow your system. I like that.

I am thinking of constructing a carport so the panels can act as a shelter for things also (double duty). this is a stationary off-grid build using LiFePO4 batteries on a country house built between 1850 to 1880.

yes, the MPPT can also work with the SBMS0 if that is what you prefer, I am going to use the diversion side of the DSSR20 for heating purposes. so it is not strictly used to charge the batteries and run things from the inverters or dc direct wired as I have some lights wired that way (no need for inverter).
 
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As about half of the discussion (but 90% of the heat! ;)) on this thread has been devoted to theoretical DSSR vs MPPT efficiency, thought I'd direct y'alls attention to some initial "just in" RW side-by-side results.

Turns out, Dacian was wrong. DSSRs don't do "as well" as MPPT in full sun under STC or hotter, THEY DO BETTER! And, granted, the vid on the post above is somewhat cryptic on the point of partial sun results, but he seems to imply that his testing under those conditions provided pretty much the same result. DSSRs are still marginally better. Only possible other variable is the particular MPPT charge controller he was using. Would be interesting to see this done with one of Victron's MPPT charge controllers (as well as at colder temps).
they should factor in the cost of a Victron MPPT vs the cost of a DSSR20. Victron is way overpriced but one spends their money any way they so choose. I have 5 DSSR20's running flawlessly on 2.5kw of solar panels (each is 250-watt 60 cell polycrystalline) controlled by the SBMS0. more later. each DSSR20 is charging with 2 250watt panels wired in parallel. ?

another disadvantage of MPPT >>> if you get into high voltage with an MPPT it is definitely more dangerous and requires an expensive arc fault breaker to be to code in the USA (price that one into their system).

no expensive combiner box needed either as all wires go directly to the DSSR20 from the solar panels ( I did install a 32 amp breaker between the solar panel pairs and the DSSR20 (use as an on/off switch)).

Each pair of 2 250-watt panels wired in parallel are inexpensively put through one 32Amp DC bipolar breaker for about $4.08 although not required in an off-grid system at 24-volts -- they are handy to turn on the PV panels during assembly (so I used 5 breakers for 2500 watts of PV panels at a total cost of $20.40 including delivery). inexpensive and very handy during assembly!

24-volt is considered safe and good for my stationary off-grid house build. less regulatory hoops to jump through. I have 2 2P8S 16 cell batteries in operation (2P is 544Ah) 3.2V x16 Lishen cells X 272Ah= 13926.4 potential Watt-hour capacity each. so 13,926.4 x 2 = 27,852.8 watt-hours in the 2 batteries.
 
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This thread has taken on a religious fervor which is why I avoided joining this site.

Dacian’s argument is based on economics for his use case. And he starts with the tenet that panels are now so cheep (under $0.65/watt) that maximum efficiency is no longer a primary design driver and that 60 cell panels, when paired with 8 cell LiFePO4 batteries, are very efficient (good enough) and if you need more power you can always add another panel.

This isn’t possible for RV users and he’s argued with me that using the alternator isn’t cost effective. True enough, but those of us with RVs don’t care about 30 year amortized costs or we wouldn’t own RVs. We just want full batteries when we reach our destination or after 3 days in the rain and alternators can charge my batteries faster than the sun ever could.

He readily admits MPPT makes sense in residential grid tied systems where array size is limited and every watt equals $$$, thus the payback on the MPPT can be justified.

His more detailed argument is that off grid users aren’t generally array limited and the benefits of his system are in the reduced fusing costs, safety of lower voltages, and reliability of being able to stick with solid state controllers with life-spans >30 years. MPPT requires the use of electrolytic capacitors which crap out after about 10 years give or take based on thermal cycles etc.

It’s still possible to use MPPT chargers with the SBMS, so long as they have remote on off switches that can be controlled by his SBMS so if using MPPT is important to your use case, go for it. In thirty years if your amortized costs are lower than Dacian’s system, you can call him up and give him an I told you so. I doubt he will care.

That said, his ability to heat his Saskatchewan home using solar is impressive. I would love to do the same for an Atlantic property but the winter sky’s are almost always gray and I worry about trees falling on large arrays.
There are no big expensive wires being used so that in itself is false. I use 10 AWG PV (25 cents per foot) wire to the DSSR20's -- standard stuff.
the inverter to the battery is a short 18-inch piece of 4/0 cable in my off-grid setup >>>standard stuff whether you use expensive high-cost MPPT or inexpensive DSSR20's. (even smaller gauge (AWG) on the 1st LiFePO4 battery to inverter I installed) again standard stuff!!!
I bought used panels for 23 cents per watt from Santan solar on eBay in pallet quantity.
the people with small expensive panels pay more as they do not have space for a larger array (you have to utilize what fits your space -- no problem) Yes I know RV's have limited roof space. My wife hated living in ours. so now live on a acreage in an ancient 1850 to 1880 vintage house.

please believe me this is not meant to be a personal attack but it is hard to beat the economics of the new SBMS0 and DSSR20 combo for protecting and charging your expensive LiFePO4 battery. not to mention all of the other functionalities (like diversion for heating)
real information.
no grid-tie for me, there is no net metering in South Dakota so I would never do grid-tie.
 
Today March 3rd, 2021 --- the 6 south-facing 60 cell 250-watt used polycrystalline panels were putting out 1000 watts and the 2P8S 544Ah battery is back to 98 percent(1:30 p.m.) and soon will be fully charged from 69 percent this morning(8 a.m.) at which point the SBMS0 will turn off the charging from the DSSR20's. there is not much charging until about 10 a.m. when the sun gets around the old summer kitchen.

how the weather changed as it is now 61 degrees Fahrenheit outside. a beautiful day - like spring has sprung.
I will try to document more as the weather changes and time permits. time to go fix the fences to keep the animals in and predators out.

about 35 amps charging the battery from the 6 south-facing 250-watt used polycrystalline panels through 3 DSSR20's.
cheers, all, ?

27.48 Volts, 27.58 Volts, and 27.68 Volts coming out of the top of the bipolar 32 amp breakers. maybe the wire length slightly different but I estimate the wire from the 6 south-facing panels to the breaker IS 55 TO 60 feet. the battery is full so turning on more loads at 2:30 p.m.
 

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So actually using the product will change Ohm's law (and other related ones)? yeah... right... ?
i never said that anything about ohms law. but I am clearly getting anywhere from 35 to 60 amps charging the battery at 55 feet to 60 feet of 10 AWG wire with 6 250-watt used polycrystalline panels using the 3 DSSR20 digital solar charge controllers.
what i am documenting is the output using the 3 DSSR20's and the SBMS0 balancing which you do not use.

the voltage I just measured was 27.48, 27.58 and 27.68 so the 6 south-facing used 60 cell 250-watt polycrystalline panels are easily charging the 2P8S 16 cell 272Ah Lishen cells with no problem whatsoever. I have 2 of these 2P8S batteries being charged. waiting on a second inverter. it is now 63 degrees and partly cloudy here.?
 
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