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The Electrodacus SBMS thread (SBMS0, DSSR50, etc)

FilterGuy said:
I don't have experience with electrodacus but it does intrigue me.

* what kind of voltage can it handle coming off the PV array? Does it force relatively low voltage high current coming from the roof to the rest of the system?

* Where do the DSSR20 modules get installed? At the panels or with the rest of the system?
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I'm not positive but I believe so (maybe I'm showing my ignorance of PWM here, but isn't this the way PWM works?).

With the caveat that I know almost nothing about the DSSR20 or PWM, and that I also would like to hear more about how these units are meant to be installed/used, I have some guesses.

From the schematic and the spec sheets (post 3 of this thread or pg 3 and 4 of the manual), it looks like:
  1. each DSSR20 is optimized for 2 x 60 cell panels in parallel. (max 49V @ 20A).
  2. DSSR20's are meant to be connected in parallel up to 30 units
  3. The schematic makes it look like they get installed near the panels but this may not be accurate (but they don't look weatherproof so I suspect they aren't meant to be installed outside)
I hope someone more knowledgable than me might shed some light on here.
 
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Dzl said:
I'm not positive but I believe so (maybe I'm showing my ignorance of PWN here, but isn't this the way PWN works?).
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In general, PWM has much lower voltage limits on the solar. However, the electrodacus equipment is enough different than other systems that I don't want to make assumptions.... that is why I asked.

Dzl said:
  1. The schematic makes it look like they get installed near the panels but this may not be accurate (but they don't look weatherproof so I suspect they aren't meant to be installed outside)
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I went through the same thought process.... and then decided to ask.

With large arrays, running lots lines down to the 'battery room' is a PITA and running a single low voltage-high amperage line can be a pain too. One of the advantages of MPPT is that they tend to accept higher voltages. This allows for higher voltage, lower amp (easier) wiring.

As with everything else, in some cases the wiring constraints will not matter and in others it might be a show-stopper.
 
I guess I am in a "Trust but verify" position.
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I tend to be the same. Its a good default position to take, especially if its something important, but its also impossible to do so for everything, and that's where our judgement comes in. If I were seriously considering using the DSSR20 I would definitely run the numbers based on my actual equipment, as I'm not seriously considering that, the information I have is enough for me to place reasonable trust in his numbers (though I'm still curious how partial shade, overcast, etc effect his model).

But I highly recommend you watch the video(s) if you are of the trust but verify mindset. He spends a lot of time going over the numbers and the math and the different variables and explaining his logic and the concepts behind it, and he tends to report not just the data that supports his conclusions.

FilterGuy said:
In general, PWM has much lower voltage limits on the solar. However, the electrodacus equipment is enough different than other systems that I don't want to make assumptions.... that is why I asked.


I went through the same thought process.... and then decided to ask.
Click to expand...

A wise approach to take


With large arrays, running lots lines down to the 'battery room' is a PITA and running a single low voltage-high amperage line can be a pain too. One of the advantages of MPPT is that they tend to accept higher voltages. This allows for higher voltage, lower amp (easier) wiring.

As with everything else, in some cases the wiring constraints will not matter and in others it might be a show-stopper.
Click to expand...

Yeah, I would like to hear more about this too. It seems like one of the bigger shortcomings in the design (considering that it's designed to handle up to 14kw of PV). 14kw @ 24v is some serious amperage and some seriously thick wires. I think this is definitely a point he needs to address.

On the other hand, its a one time expense, and a one-and-done PITA

One of the things that helps understand a lot of Dacian's design decisions is he is very concerned with cost over time. He would seems to analyze most everything through that lens (solar vs lpg heating, solar vs traditional grid tie, off grid vs on grid, battery capacity vs pv array size, alternator charging vs solar charging, mppt vs PWM, thermal storage vs battery storage). Its no the only lens he views things through, but it seems like a central consideration for him, maybe more so than for many of us.
 
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FilterGuy said:
With large arrays, running lots lines down to the 'battery room' is a PITA and running a single low voltage-high amperage line can be a pain too. One of the advantages of MPPT is that they tend to accept higher voltages. This allows for higher voltage, lower amp (easier) wiring.

As with everything else, in some cases the wiring constraints will not matter and in others it might be a show-stopper.
Click to expand...
Click to expand...


Dzl said:
Yeah, I would like to hear more about this too. It seems like one of the bigger shortcomings in the design (considering that it's designed to handle up to 14kw of PV). 14kw @ 24v is some serious amperage and some seriously thick wires. I think this is definitely a point he needs to address.
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random youtube commenter said:
The wirings cost ! especially when there is long distance between the solar array and the technical room, for example if you have 2000Wc with x8 250 Wc in parallel it make something like 60amps (25/35 mm2 copper wire for a low drop voltage). With some solar mppt like the MidNite CLASSIC 250 you can put 4, 5 or 6 solar panels in series in our case you will have only 15 amps at ~150VDC (4 mm2 copper wire). You can consider 0,4cts/m/mm2. Big thumbs up for you project. Regards
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Dacian said:
PWM will do the same as the Solar BMS since in the bulk part there is no PWM used the PWM is used only in the constant current part of charging on Lead Acid and at that point MPPT is also useless there no gain there anymore. As for wire cost. I will have a large 7 to 9kWh array for heating and I made calculation for wire cost. The array will be relatively far about 20m (70ft) Normally with individual wires for each 8A (250W) panel you will need #10 AWG for that distance to be under 3% voltage drop. Thing is that you do not need to be at 3% and you can use #14 AWG for about 8% V drop so 5% more at full sun but average loss will be less. #14 can easily handle 8A even in a conduit with many other wires bundled. Thing is all this loss even 5% mean one additional PV panel at each 20 panels and that may be less than the extra cable. For sure less than an 5000W (250W x 20) MPPT just for that savings on cable. The #14 here in Canada can be had for about 300 to 350$/km so for each panel two wires 20m total 40m is about 14$ so not that much even for my 36 panels 9kW array at 20m total will be 36 x 14$ about 500$. For just a 3kW array what SBMS supports is about 170$ total for cable and for 2kW that MPPT in the example supported is even less so the savings can not be that large you still need cable anyway.
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Dzl said:
I believe that was me who posted that (maybe others elsewhere too). I was quite impressed and surprised by his line of reasoning. It was the first time I had heard anyone knowledgeable make a well reasoned argument in favor of PWN.
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SBMS line, apparently, is not actually PWM (though, of course, not MPPT either). Per this reply from Dacian to someone in the comments section of the video linked in my last post:

[SBMS] is not a PWM controller as PWM is not needed for Lithium charging (it is actually detrimental). PWM is used for constant voltage charging (absorption and float) with Lead Acid that require this sort of charging. Yes, if panels match battery they can work very close to max power point so much so that it will be in average more efficient than using an MPPT. If you have the space and add more panels that will be cost equivalent with the MPPT then that is a way better financial investment.
...
A Lithium battery say a LiFePO4 that is ideal for solar as it is the most cost effective is very simple to charge and almost like a capacitor so you can connect a solar PV panel to it "directly" as solar PV panel is a constant current source and that PV panel will push current in to the battery (current will depend on amount of light) and when that LiFePO4 cell gets to 3.6V charging should immediately stop as cell is 100% charged. What a PWM will do is turn the panel ON/OFF to maintain say that 3.6V and that will have detrimental effect on a Lithium battery as the LiFePO4 is already fully charge and charging should be completely stopped. So PWM is used for constant voltage charging (absorbiton) and only constant current charging (bulk) is needed for LiFePO4. With other type of Lithium cells say LiCoO2 or NMC used in portable electronics or EV's constant voltage (absorbtion) charging can be used to get some extra storage capacity but to the detriment of battery life. In those applications the extra 15 or 20% capacity you get using constant voltage charging (absorption) is more important than battery cycle life but that is not the case with solar energy storage where cost amortization is more important than energy density. In any case LiCoO2 and NMC are not cost effective when compared to LiFePO4 and with LiFePO4 there is no extra 15 to 20% from constant voltage charging possible as this cells will be fully charged already after the constant current charge phase and there is not even 1% extra left to gain by CV charging.

Granted, I've never been clear on the subtleties of meaning when folks refer to something being a "constant current" vs "constant voltage." Seems you can't take these at face value without context. Current from PV panels change constantly (depending on sun exposure) but their voltage doesn't (correct?) so you'd think it would be the other way 'round, though I think I get what he's saying when he refers to PV panels as "constant current" per this IV curve for a typical PV cell that I found here (Alternative Energy Tutorials):

1581548026593.png

Can someone else who understands this explain it a little better?

BiduleOhm said:
Hmm... there's a problem with these numbers: 239 + (239 * (25.6 / 100)) = 300.2. Well, obviously 300.2 is not 321 so that's not a 25.6 % gain... it's actually a 34.3 % gain (100 * (321 - 239) / 239). I didn't run the numbers for the other ones but I bet they are off too.
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Yeah, think I have half the discrepancy figured out but wrote Dacian to confirm what I think these #s actually represent. Really want to understand the details of how SBMS vs PWM vs MPPT work. May just wind up borrowing someones MPPT charger and do a side-by-side controlled experiment (vs the DSSRs) once I set this thing up (e.g. replace that 3rd DSSR in my schematic w an MPPT and simply toggle my breakers to measure current coming in from each, running the experiment over the course of a month or so to cover wide variation in sun and temp conditions. Think I could have done that multiple times already for the amount of time I've spent trying to sort out the theory.
 
Can someone explain how the SBMS balances the cells, vs a active/passive BMS?

As for SBMS, PWM, MPPT goes. Only MPPT allows me to use 24V panels with a mobile 12V system. Higher voltage, lower current, = smaller wires.
With a DC-DC charger w/MPPT I have two ways to charge my batteries and if I'm already driving, the alternator charging is free energy.
 
Sgt Raven said:
As for SBMS, PWM, MPPT goes. Only MPPT allows me to use 24V panels with a mobile 12V system. Higher voltage, lower current, = smaller wires.
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Well, more precisely MPPT allows you to use '24v' panels efficiently with a 12v system battery. To take full advantage of "higher voltage, lower current = smaller wires" running a 24v system and stepping down to 12v where necessary would be ideal. Alternator charging is still possible Victron and Sterling both make high quality DC-DC chargers that can do 12v to 24v (and no more difficult or expensive than 12v to 12v). Not trying to steer you away from MPPT (its what I plan to use), just thought it was worth pointing out that a 24v battery could coexist quite well with your 12v vehicle electrical system and 12v appliances.

With a DC-DC charger w/MPPT I have two ways to charge my batteries and if I'm already driving, the alternator charging is free energy.
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Well subsidized might be a better way to think of it. As I understand it, all other things being equal you will consume more fuel with a high load on your alternator. Depending on the load, and your normal fuel economy you may not notice though.
 
Dzl said:
Well, more precisely MPPT allows you to use '24v' panels efficiently with a 12v system battery. To take full advantage of "higher voltage, lower current = smaller wires" running a 24v system and stepping down to 12v where necessary would be ideal. Alternator charging is still possible Victron and Sterling both make high quality DC-DC chargers that can do 12v to 24v (and no more difficult or expensive than 12v to 12v). Not trying to steer you away from MPPT (its what I plan to use), just thought it was worth pointing out that a 24v battery could coexist quite well with your 12v vehicle electrical system and 12v appliances.



Well subsidized might be a better way to think of it. As I understand it, all other things being equal you will consume more fuel with a high load on your alternator. Depending on the load, and your normal fuel economy you may not notice though.
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I have a low mileage 2005 Ram 2500 4x4 CTD. I doubt pulling an extra 50 amps from the alternator will change the MPG much. I do wish Dodge put dual alternators on it like my friends F350 diesel has. At some point I'm going to do the Big 3 upgrade and get a mean green drop in 220A alternator to replace 136A stock one.
 
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Sgt Raven said:
I have a low mileage 2005 Ram 2500 4x4 CTD. I doubt pulling an extra 50 amps from the alternator will change the MPG much.
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Yeah I doubt it will be very noticeable, if noticeable at all. At worst it would probably be on the scale of the difference between driving with or without your AC on.
 
Dzl said:
Thanks that makes sense. I'm pretty clear on how the SBMS0 communicates with individual components, but I'm less clear on whether the SBMS0 only communicates with individual components or if it has any ability to completely cut charging/discharging to the battery (like most BMS' do-- either as a built in function or via Relays) and if there is a maximum current the BMS is rated for, or if it only depends on what you external components can handle.
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i have my SBMS0 controling my Victron Mutiplus to shut down charging in an over charge event and shut down inverting in a under voltage event. The SBMS0 is connected to the Multiplus Temp sense port and AUX IO port 1. You must set up the two signal bms assistant using the Victron Connect software.
 
Can someone explain how the SBMS balances the cells, vs a active/passive BMS? I think I have an understanding how a regular BMS does this, but not sure how the SBMS does it...
 
Sgt Raven said:
Can someone explain how the SBMS balances the cells, vs a active/passive BMS? I think I have an understanding how a regular BMS does this, but not sure how the SBMS does it...
Click to expand...

Sorry, I'm not sure how the balancing works and the manual doesn't indicate anything other than the balancing current is 200ma. Maybe @Will Prowse or one of the forum members who owns the BMS will chime in. If not you could ask Dacian directly via e-mail, he is very responsive normally.

edit: I did find this on another forum:

I am looking to upgrade at a later date to use the Electrodacus SMBS0 as my BMS for the Tesla module as it offer full automation for low voltage cut of and over charge protection at the individual cell voltage for much better protection as well as active cell balancing during charging.
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edit 2: actually, as luck would have it, it looks like the person I quoted from the sprinter forum is a member here too! Sometimes the internet isn't such a big place.. @Geriakt can you tell us anything about the SBMS0's balance method
 
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Dzl said:
Sorry, I'm not sure how the balancing works and the manual doesn't indicate anything other than the balancing current is 200ma. Maybe @Will Prowse or one of the forum members who owns the BMS will chime in. If not you could ask Dacian directly via e-mail, he is very responsive normally.
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I figure this is the place, this thread, is where to put the answer. I'm sure I'm not the only one wondering about it.....
 
Sgt Raven said:
I figure this is the place, this thread, is where to put the answer. I'm sure I'm not the only one wondering about it.....
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Agreed, I hope someone can clarify.

Also, I edited my last comment to add a bit of vague info I found on another forum, you should check it again.
 
Sgt Raven said:
Can someone explain how the SBMS balances the cells, vs a active/passive BMS? I think I have an understanding how a regular BMS does this, but not sure how the SBMS does it...
Click to expand...
Found this comment on Will's SBMS video from someone who appears to know and it jibes with my more limited understanding:

"The SBMS0 is unique in that it balances when two criteria are met. 1. there has to be a cell difference of 0.01v or more, 2. there has to be a charge or discharge current occurring. This means a: you don't have to cram the batteries full to get balancing to start and b: then it only happens while the batts are at their peak voltage. This allows the SBMS0 to spend a fair amount of time balancing so the 200mA current is plenty and there is very little heat generated so no heat sink is required on the SBMS0. Seeing as balancing starts with a 0.01v (hundredth) difference the cells end up being balanced to within less than 1% of each other. The cell balancing activity is displayed on the screen as it is happening."

... only thing I'd add is that it does this all the time (whether charging or discharging) as long as criteria 1&2 are met.
 
Dzl said:
I am like the poster child for this. I have spent the last few weeks obsessing over to build my own USB power delivery chargers to power my laptop, phone, etc., to gain a few percentage points of efficiency by cutting the inverter and the ac adapters out of the equation. Now this isn't completely unreasonable as that conversion can be up to 20%. But what really shows how irrational a quest it has become for me, my initial inspiration to build my own came because I didnt want to buy an off the shelve 12v version for my 24v system since the conversion down to 12v and back up to 19-20v would cost me maybe 5%. To drive that point home.. I am considering building my own laptop charger, to gain maybe 5% efficiency, on a device that uses AT MOST 54 Whrs A DAY...

I dont know what I'd do if I couldn't laugh at myself.



But yes, what sounds like small numbers all add up. And a 5% efficiency gain is no small thing in some situations.



You should watch the video. Dacian's videos never feel like they are trying to 'push' anything or evangelize. One of the things that I've really come to like about him is his level headed, transparent, relatively impartial approach. It a rare thing nowadays but it feels like he is confident enough in his ideas and committed enough to the numbers that once he has convinced himself he does his best to explain his reasoning to others and share the data, but doesn't get preoccupied with trying to convince others and doesn't let his ego get wrapped up in his ideas. Maybe I'm reading too much into things, but on the internet where everyone (me included) is so quick to be defensive about our ideas and wanting others to agree with us I find his calm, transparent, data based approach refreshing and disarming. I mean heck, in the video where he is explaining his 100% solar off-grid system, he devotes about 15 minutes to explaining all the ways in which natural gas is a superior energy source in many contexts.
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He will tell you directly that a small propane container will hold 100kWh and it would be silly to not use where he is at.
 
Really feel Dacian is missing an increasing market, by not offering a 48v version. As things head to 'all electric' the world over, larger battery banks are going to be sought. :-(
 
kernel said:
He will tell you directly that a small propane container will hold 100kWh and it would be silly to not use where he is at.
Click to expand...

I found the segment where he compares different fuel sources and cost ammortization over time very interesting, and one of the clearest comparisons I have seen.

Obviously for many of us here, we have reasons and priorities we are drawn to solar beyond the pure economics of it, but a purely economic objective analysis is interesting and worthwhile.
 
Solarfun4jim said:
Really feel Dacian is missing an increasing market, by not offering a 48v version. As things head to 'all electric' the world over, larger battery banks are going to be sought. :-(
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Possibly. It does feel like 48v is or is becoming the standard for off-grid residential systems. Beyond the added cost of production/components, I don't see a major reason not to produce a 48v version, even if he doesn't think its necessary. But its worth noting, Dacian already has an all solar-electric household (even heating is electric), so he clearly didn't feel that 48v was necessary for an all-electric home. But I imagine his home is way more efficient and optimized than most North American homes (even off grid homes) would be.

Maybe a dumb question but Is there an inherent advantage to higher voltages with larger battery banks? I understand the benefits of higher voltages for larger loads (higher voltage = less spent on wiring and components and less significant voltage drop), but what advantage is higher voltage in relation to battery bank size?

That said, I wouldn't be surprised if he eventually comes around ot the idea of a 48v model if enough people want it.
 
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Dzl said:
I found the segment where he compares different fuel sources and cost ammortization over time very interesting, and one of the clearest comparisons I have seen.

Obviously for many of us here, we have reasons and priorities we are drawn to solar beyond the pure economics of it, but a purely economic objective analysis is interesting and worthwhile.
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Something similar I have done comparing cars. Car A gets XXa mpg and uses regular. Car B gets XXb mpg but uses premium, figure the cost per mile..
 
Dzl said:
Maybe a dumb question but Is there an inherent advantage to higher voltages with larger battery banks? I understand the benefits of higher voltages for larger loads (higher voltage = less spent on wiring and components and less significant voltage drop), but what advantage is higher voltage in relation to battery bank size?

That said, I wouldn't be surprised if he eventually comes around ot the idea of a 48v model if enough people want it.
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He uses like 1-3 kWh per day last i knew...... that is without water or space heating. We use about the same. 24v works fine except that i could have 4kW on one FM80at 48V and not require a mate control and interconnecting cable, and............

With our largest overlapping loads being under 1800W 24V actually is not any kind of real detriment other than needing to parallel controls in order to get all 12 solarworlds feeding the system.
 
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Dzl said:
I found the segment where he compares different fuel sources and cost ammortization over time very interesting, and one of the clearest comparisons I have seen.

Obviously for many of us here, we have reasons and priorities we are drawn to solar beyond the pure economics of it, but a purely economic objective analysis is interesting and worthwhile.
Click to expand...
It has more to do with being in a very cold long dim winter. With propane as a heat and cooking fuel source, using it to run a generator for backup allows him to remain off grid. Its been some time since i had a chat on a forum with him, but last i knew this was his mode.

They guy is absolutely a sharp intellect. Very polite, to a fault. And an astute engineer....
 
kernel said:
They guy is absolutely a sharp intellect. Very polite, to a fault. And an astute engineer....
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This is the impression I've come away with as well.

It has more to do with being in a very cold long dim winter. With propane as a heat and cooking fuel source, using it to run a generator for backup allows him to remain off grid. Its been some time since i had a chat on a forum with him, but last i knew this was his mode.
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I was under the impression solar is his only energy source, no backup whatsoever, but I could be misremembering, or he could've changed his design. But I'm pretty sure in one of his videos he states that the solar heating would never be worth it financially if he had to spend money on a backup or supplemental conventional system. I believe he determined it made the most sense to go with a massively oversized PV array as the sole energy source that could supply all his electrical needs easily and redirect the excess to thermal storage for heating.

edit: I believe its in this video somewhere.
 
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Dzl said:
Possibly. It does feel like 48v is or is becoming the standard for off-grid residential systems. Beyond the added cost of production/components, I don't see a major reason not to produce a 48v version, even if he doesn't think its necessary.

Maybe a dumb question but Is there an inherent advantage to higher voltages with larger battery banks? I understand the benefits of higher voltages for larger loads (higher voltage = less spent on wiring and components and less significant voltage drop), but what advantage is higher voltage in relation to battery bank size?

That said, I wouldn't be surprised if he eventually comes around ot the idea of a 48v model if enough people want it.
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For me it is simply a case of wanting to monitor as few cells as possible for a given capacity. A 16S 280Ah cells gets me 13.44Kw capacity. How do you achieve this on a 24v system, monitoring 'every cell' with one 16S BMS....you cant. Yes you can monitor pairs, but that to me is no monitoring at all. I wish to see each individual cell. You can parallel up BMS's etc, but complexity/failure rate increases.

It is really no use folks saying, decrease loads, parallel up etc, since folks just want the simplist system with the maximum power. In Scotland, we are in the process of no longer getting coal for homes unless it is smokeless, no longer legal to burn 'wet' wood etc. Gas boilers being phased out....petrol and diesel cars being phased out at specific targets which keep being reduced. The days of RV's burning various gases for heating/cooking are numbered(ok it might be a decade away or so, but it is coming). As things are being driven constantly towards 'clean' electric, the demand on systems is simply going to keep increasing.
 
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