The Electrodacus SBMS thread (SBMS0, DSSR50, etc)

[michael d]

not everyone wants this stuff on top of a 2 story house. so ground mount it is. besides easier to clean panels and check equipment with ground mount set up. My current project is 2 story house with the lowest roof edge probably 22 feet above ground and a steep roof. not enough good real estate up there for me.

 

[michael d]

Don't know what's he thinking? Ask him to join the discussion.

Back in the "old" pre mppt days, when pwm controllers were used for 12V LABs, it took some engineering effort to determine 36 cells was optimum for a 12V panel, powering a 12V battery. Nothing has changed. If you have 24V battery you need 72 cells when operating pwm.

A 60 cell panel doesn't have enough voltage headroom. In order to charge the battery, panel voltage needs to be greater than battery voltage. The 60 cell panel has Vmp = 30.3V. That's specified at room temperature. Since the panel is less than 20% efficient, about 80% of solar radiation goes to heat the panel. The temperature coefficient of panel voltage is about -0.34% per deg.C. If there's a modest rise of 25C, voltage drops by: 0.34 * 25 = 8.5%. Vmp drops to 30.3V * 91.5% = 27.7V

10 awg cable has 1 mOhm/ft resistance. 150 ft gives 150 mOhm resistance between panel and battery.

Charging current is dependent on panel voltage, battery voltage and line resistance:

I = (Vpanel - Vbattery) / Rcable

If the cells are at 3.2V then charging current is:

I = (27.7V - 8 * 3.2V) / .15 = 14A
The two panels in parallel have the capability of supplying 16A, but due to cable resistance and small voltage headroom, charging current is reduced to 14A.

If cells are at 3.3V charging current is 8.6A
If cells are at 3.4V charging current is 3.3A

I will check on this some more. My new insulated power solar shed could be moved as it is 8x8 but is getting heavier all the time. all off-grid. I may have to calculate more on wire voltage loss. there is a small 12x12 existing summer kitchen that I want to move that is part of the problem as it is in the way. so that dictated the longer wire runs also. Estimated 1840 to 1880 vintage farmhouse. thanks for ideas!

 

[Dzl]

Don't know what's he thinking? Ask him to join the discussion.

Back in the "old" pre mppt days, when pwm controllers were used for 12V LABs, it took some engineering effort to determine 36 cells was optimum for a 12V panel, powering a 12V battery. Nothing has changed. If you have 24V battery you need 72 cells when operating pwm.

A 60 cell panel doesn't have enough voltage headroom. In order to charge the battery, panel voltage needs to be greater than battery voltage. The 60 cell panel has Vmp = 30.3V. That's specified at room temperature. Since the panel is less than 20% efficient, about 80% of solar radiation goes to heat the panel. The temperature coefficient of panel voltage is about -0.34% per deg.C. If there's a modest rise of 25C, voltage drops by: 0.34 * 25 = 8.5%. Vmp drops to 30.3V * 91.5% = 27.7V

10 awg cable has 1 mOhm/ft resistance. 150 ft gives 150 mOhm resistance between panel and battery.

Charging current is dependent on panel voltage, battery voltage and line resistance:

I = (Vpanel - Vbattery) / Rcable

If the cells are at 3.2V then charging current is:

I = (27.7V - 8 * 3.2V) / .15 = 14A
The two panels in parallel have the capability of supplying 16A, but due to cable resistance and small voltage headroom, charging current is reduced to 14A.

If cells are at 3.3V charging current is 8.6A
If cells are at 3.4V charging current is 3.3A

Thanks for the explanation.

Regarding Dacian Joining the convo, I've made him aware of this post in the past, I think he has his hands full answering questions on his message board, through e-mail, and youtube comments.

I did start to do a bit of digging though, I haven't found a great explanation left (only been digging for 5 or s minutes) but this response to a question sheds a bit of light on his thought process:

Will a 60 cell panel allow you to get as much energy for a similarly rated panel as a 72 cell? It seems like the panel voltage is too low at times to fully charge the battery when it is near capacity. The 72 cell panels would have an additional 6 volts of headroom giving plenty of capacity to charge up to 28.8 volts. Thanks!

All my panels are 60 cells as they are the best option in cold climates. If you have winters at your location and then is when you get the least amount of sun then 60 cells are ideal as you need to design your system to deal with worst month that is winter.
If you live in a hot location with no winter and about same amount of sun in all months or you have very long wires to your PV array over 30m (100ft) then you may benefit from the 72 cell panels.

The 72 cell PV panel will cost proportionally more than the 60 cell panel and in a cold day they will both output the same amount of current.
Also at around 27.2 your battery is basically fully charged as when all cells are around 3.4V you will see that cells will very fast get to 3.55V or 3.6V so there is maybe just 1% SOC left at that point and one of the cells will always get first to 3.55V (that is my default high limit).

In winter I get 8.5 to 10A from a single 60 cell panel depending on how cold it is while worst case in summer I may only get 6A if panels are very hot but in sunny summer days there is huge amount of excess energy battery is already full well before noon so it makes no difference that a 72 cell panel may put out 8A instead of just 6A with hot panel as in my case over 90% of available solar energy remains unused.

 

[michael d]

(maybe a test) I will set some up with short wire runs and some up with the longer wire runs and compare them to an MPPT SCC. somehow I do not believe there will be any problem whatsoever to get the LIFEpo4 batteries charged from the solar panels. but I may be wrong. I will post when I get some real results to compare. I can always change a bit. A good carpenter fixes his mistakes.
A few parts are still on the way.
you can put 13 Electrodacus DSSR20's on one Electrodacus DECT16 and 7 Electrodacus DSSR20's on the other Electrodacus DECT16 which is what I am going to do. later I will use some of the DSSR20's with diversion as thermal heaters. Both DECT16's will be controlled by the Electrodacus SBMS0.
I am sheetrocking the ceiling of the solar power shed tomorrow. got up to 51 degrees outside in the sun today --- a heatwave compared to the cold and wind after the snowstorm. how I hate the cold. but solar panels like the cold.
another expensive part is the parallel branch connectors. they were $6.50 shipped to me in quantity. I bought 50 of them. I only need 20. for the penny pinchers (including me).
Will Prowse never even tested or at least there is no youtube video of him using the DSSR20's. Very few youtube videos of this part; only 1 or 2 that I have found.
But no one has time to do it all. I know many of the Chinese BMS have had problems or have given the DIY community big problems. this SBMS0 is a possible solution for the lifepo4 batteries. I am optimistic all will work out. I break big problems down into small parts and get to the solution. sorry for the soapbox.

 

[Dzl]

(maybe a test) I will set some up with short wire runs and some up with the longer wire runs and compare them to an MPPT SCC. somehow I do not believe there will be any problem whatsoever to get the LIFEpo4 batteries charged from the solar panels. but I may be wrong. I will post when I get some real results to compare. I can always change a bit. A good carpenter fixes his mistakes.
A few parts are still on the way.
you can put 13 Electrodacus DSSR20's on one Electrodacus DECT16 and 7 Electrodacus DSSR20's on the other Electrodacus DECT16 which is what I am going to do. later I will use some of the DSSR20's with diversion as thermal heaters. Both DECT16's will be controlled by the Electrodacus SBMS0.
I am sheetrocking the ceiling of the solar power shed tomorrow. got up to 51 degrees outside in the sun today --- a heatwave compared to the cold and wind after the snowstorm. how I hate the cold. but solar panels like the cold.
another expensive part is the parallel branch connectors. they were $6.50 shipped to me in quantity. I bought 50 of them. I only need 20. for the penny pinchers (including me).
Will Prowse never even tested or at least there is no youtube video of him using the DSSR20's. Very few youtube videos of this part; only 1 or 2 that I have found.
But no one has time to do it all. I know many of the Chinese BMS have had problems or have given the DIY community big problems. this SBMS0 is a possible solution for the lifepo4 batteries. I am optimistic all will work out. I break big problems down into small parts and get to the solution. sorry for the soapbox.

I'm sure any testing you do or lessons you learn will be much appreciated by folks here, since as you mention, there is not a ton of info or data or experiences to go off of. Particularly when it comes to the DSSR component, and even more particularly DSSR with diversion. Keep us in the loop! Would love a bit more comparative data between MPPT and DSSR20 in various conditions.

 

[Dzl]

Anyone aware of any projects attempting to communicate between an SBMS0 and a Victron GX (Venus OS) device?

Both are open source and both have multiple comms options , so it seems like it should be doable, but I don't recall seeing anything yet.

On top of this, the SBMS0 is designed to be able to interface with a Raspberry Pi and the VenusOS is able to be run on a Raspberry Pi.

 

[BiduleOhm]

(maybe a test) I will set some up with short wire runs and some up with the longer wire runs and compare them to an MPPT SCC. somehow I do not believe there will be any problem whatsoever to get the LIFEpo4 batteries charged from the solar panels. but I may be wrong. I will post when I get some real results to compare.

That would be awesome

You'll not have a problem charging the battery in either case; the question is more on the total losses of the system.

Will Prowse never even tested or at least there is no youtube video of him using the DSSR20's. Very few youtube videos of this part; only 1 or 2 that I have found.

Well, they are very similar to SSRs so not much to test. You can always test the ON resistance to calculate the losses but that's about it.

I'm sure any testing you do or lessons you learn will be much appreciated by folks here, since as you mention, there is not a ton of info or data or experiences to go off of. Particularly when it comes to the DSSR component, and even more particularly DSSR with diversion. Keep us in the loop! Would love a bit more comparative data between MPPT and DSSR20 in various conditions.

Yes, absolutely

 

[michael d]

According to the feedback replies on this forum; the wire length of the proposed runs is going to be a big issue with my off-grid solar setup.
I will try both ways. short wire vs long wires.

the obstacles here are: I can cut down 2 big cedar trees that are keeping me from putting the array closer, or I can move the 8x8 insulated power shed and run longer wires from the inverter and the new separate ac load center.

(((Heavy - 8x8 insulated power shed is built with 2x6's 16"o.c. 5/8" plywood sheathing, 3/4plywood floor, I inch Celotex outside with tar paper vapor barrier, 6" fiberglass insulation and 1/2" sheetrock inside, white steel pro-panel siding on outside of all of it, also 2x4 purlins so all steel has excellent landing place for all the screws. the whole building is screwed together with construction screws, a 36-inch insulated steel entry door already installed(with locks) with a new storm door waiting to be installed also.)))

these 2 things would make runs shorter. the trees are the main obstacle or move the old summer kitchen( a 12x12 or 14x14 building - not sure on its exact size).
kind of want to cut the big cedar trees, but then have to hope I don't squash the fence and have to fix it also (6 hair sheep would love to eat all of the yard and camp on the front porch, especially the bottle baby(pet)). then the coyotes and foxes (predators) would have to get a little braver.
When you work by yourself all of these things can be a safety hazard. I have 2 MPPT's 80 amp I can play with a bit.

winter is closing in fast! where did the summer go? Raccoons and possums already rob the cat food so have to limit feed my cats to keep them varmints at bay. Artesian well and pond attract all the animals, deer, ducks, turtles, eagles, owls, all the birds, fish/frogs in a small pond, muskrat, love the wildlife here. saw the turtle laying eggs this spring - never saw that in person before (wow) how cool! down on the farm- yea ha!!

 

[Cal]

According to the feedback replies on this forum; the wire length of the proposed runs is going to be a big issue with my off-grid solar setup.
I will try both ways. short wire vs long wires.

I would say temperature is as big an issue. Panel temps can get up to 65C in summer. That's 40C above room temperature.

0.34%/C * 40C = 13.6% voltage drop

Panel voltage drops to about 26.2V.

Volts per cell = 26.2V/8 = 3.27 V

Even with no cable resistance, cells can only charge to 3.27V when panel temperature is 65C.

It's very important to record panel temperature when conducting your tests.

Very nice place you got there!

 

[sremick]

Question: on the SBMS40, what area of the back gets the hottest?

My heatsink isn't quite big enough to cover the whole thing so I wanted to place it over the power MOSFETs or whatever. I remember once seeing a cut-away showing the internal design layer by layer but I can't find that again after a bunch of searching.

 

[TROLL]

Hey all, researching BMS systems to add to an already installed LiFePO4 setup in my RV.
*Balancing ability and individual cell voltage monitoring are priorities for me*

Quick stats on my current setup:
> 8x Sinopoly 200A 3.2v cells set up in 2P4S to make a 400A 12.8v setup
> 3 charging sources: Victron BlueSolar 100 | 50 solar cc, Nations Auto 280A alternator with Balmar MC-614 charge controller, Magnum 2012 Inverter/Charger
> 2 load types: DC all routed through Victron BP100, AC all routed through Magnum 2012 Interter/Charger
> Solar panels: 5 x 100w AM Solar Panels - 17.7v operating voltage set up in parallel with 4 awg cables (https://amsolar.com/rv-solar-panels/solar-sp100)
> Victron BMV-702 battery monitor with voltage/temp alarms

*I have not had a full BMS on this setup ever (roughly 7 years of use), but I have some basic low voltage protections in place and I monitor things and manually top balance from time to time. It has worked well, but without a BMS it is obviously not perfect or flawless. My batteries seem to be getting out of balance too quickly lately even after a top balance, and I've wanted to add a BMS anyway so here I am.


The Electrodacus seems really promising, but I have a few logistical questions I've come up with that I'm hoping someone can help clarify for me.

1) This BMS lists a .2A balancing rate -- on a 400A system this seems too low, doesn't it? Will this be capable of keeping up with my setup which seems to be getting out of balance quicker than I would think is normal? Just thinking out loud, if my cells are even 3% apart, that would be 1.2A and would take 6 hours of balancing time. I charge and discharge at up to 150A so it makes me wonder if a .2A balance rate could ever keep up.

2) If I do choose this BMS, would it make sense to just keep my Victron solar charge controller, or change over to the Electodacus units? I'm not sure if my panels are the correct voltage to charge my system on a PWM setup.

3) I'm trying to work through the logistics of signaling each of my charging sources / loads to turn off in the even of a fault
-Charging Sources:
--Victron BlueSolar 100 | 50 solar charge controller -- does this have remote switch capability?
--Magnum Inverter has a remote switch capability
--MC-614 alternator charge controller has a remote switch capability --- **BUT it is my only alternator so I can't shut it off or it won't power the vehicle and starting battery when engine is running (I could instead use a relay/contactor on my LiFePO4 main negative cable to remove the lithium cells from the system but leave the rest in tact (is there a suitable high amp relay/contactor for this?)
-Loads:
--Victron BP100 has a remote switch capability
--Magnum Inverter/Charger has a remote switch capability

4) Less important, but I just don't comprehend the 2 shut setup vs. a 1 shunt setup like what I have now, if anyone can explain it like you're talking to a 6 year old .


Much thanks to anyone who takes the time to help me start working through this. If this isn't the one for me, any other suggestions?

 

[Airtime]

Hey all, researching BMS systems to add to an already installed LiFePO4 setup in my RV.
*Balancing ability and individual cell voltage monitoring are priorities for me*

Quick stats on my current setup:
> 8x Sinopoly 200A 3.2v cells set up in 2P4S to make a 400A 12.8v setup
> 3 charging sources: Victron BlueSolar 100 | 50 solar cc, Nations Auto 280A alternator with Balmar MC-614 charge controller, Magnum 2012 Inverter/Charger
> 2 load types: DC all routed through Victron BP100, AC all routed through Magnum 2012 Interter/Charger
> Solar panels: 5 x 100w AM Solar Panels - 17.7v operating voltage set up in parallel with 4 awg cables (https://amsolar.com/rv-solar-panels/solar-sp100)
> Victron BMV-702 battery monitor with voltage/temp alarms

*I have not had a full BMS on this setup ever (roughly 7 years of use), but I have some basic low voltage protections in place and I monitor things and manually top balance from time to time. It has worked well, but without a BMS it is obviously not perfect or flawless. My batteries seem to be getting out of balance too quickly lately even after a top balance, and I've wanted to add a BMS anyway so here I am.


The Electrodacus seems really promising, but I have a few logistical questions I've come up with that I'm hoping someone can help clarify for me.

1) This BMS lists a .2A balancing rate -- on a 400A system this seems too low, doesn't it? Will this be capable of keeping up with my setup which seems to be getting out of balance quicker than I would think is normal? Just thinking out loud, if my cells are even 3% apart, that would be 1.2A and would take 6 hours of balancing time. I charge and discharge at up to 150A so it makes me wonder if a .2A balance rate could ever keep up.

2) If I do choose this BMS, would it make sense to just keep my Victron solar charge controller, or change over to the Electodacus units? I'm not sure if my panels are the correct voltage to charge my system on a PWM setup.

3) I'm trying to work through the logistics of signaling each of my charging sources / loads to turn off in the even of a fault
-Charging Sources:
--Victron BlueSolar 100 | 50 solar charge controller -- does this have remote switch capability?
--Magnum Inverter has a remote switch capability
--MC-614 alternator charge controller has a remote switch capability --- **BUT it is my only alternator so I can't shut it off or it won't power the vehicle and starting battery when engine is running (I could instead use a relay/contactor on my LiFePO4 main negative cable to remove the lithium cells from the system but leave the rest in tact (is there a suitable high amp relay/contactor for this?)
-Loads:
--Victron BP100 has a remote switch capability
--Magnum Inverter/Charger has a remote switch capability

4) Less important, but I just don't comprehend the 2 shut setup vs. a 1 shunt setup like what I have now, if anyone can explain it like you're talking to a 6 year old .


Much thanks to anyone who takes the time to help me start working through this. If this isn't the one for me, any other suggestions?

I can help on part of your questions... One observation though, when you say A I think in general you are meaning Ah, right? Amp-hours not amps. Also, check out the electrodacus forum, you can access it from the web page.

1) I'll defer to others here.

2) Whether to change your SCC is a completely separate and unrelated question. No need to change out your Victron if you don't want to.

3) No comment, haven't looked at these datasheets

4) It actually is pretty simple. But you do have to keep in mind that in Dacian's world view there is only solar charging, and loads. He does not really care about variations such as alternator charging in a vehicle, or an inverter/charger vs. separate inverter and charger. But he's really into measuring his solar input over time.

So in that worldview, two shunts give information about solar charging vs. loads. The first shunt measures total current into/out of the battery, as with most shunts you are used to. The second shunt measures just the current from solar charging. And with those two, you can calculate load current = main shunt current - solar shunt current. The BMS does some nice graphing of battery, solar charging, and load currents.

However, if you have an inverter/charger, then the graphs make less sense especially for loads, since the inverter/charger can source or sink current. But it still will show you info on solar.

In the end the second shunt is optional, only needed if you actually want to look at solar charge current seperate from total charge + discharge current. You can just go with the main shunt, ignore all the graphs on solar and load currents, and it will still offer the core BMS functions of indivitual cell monitoring, protections, and balancing.

Hope this helps...

 

[michael d]

That would be awesome

You'll not have a problem charging the battery in either case; the question is more on the total losses of the system.



Well, they are very similar to SSRs so not much to test. You can always test the ON resistance to calculate the losses but that's about it.



Yes, absolutely

A little info from Dacian reply about DSSR20 quoted below:

"SBMS0 is just a BMS + advanced energy monitor and the DSSR20 has no MPPT functionality of any type.
The 60 cell panels will already work at the max power point when used with a DSSR20 and a 8s LiFePO4 battery without the need of an expensive and large DC-DC converter.
Seems like you will build a 8s2p that will be done by having first groups of two parallel cells (no different in any way from a single 560Ah cell) then 8 of those groups in series for 24V
Since the 40 panels can put out anything from 320 to 400A in a cold sunny day you will need to use dual PV array setup and you can use excess energy for heating.
Each two parallel PV panels will need a pair of 10AWG cables going into a DSSR20 with diversion (if you want to use excess energy for heating).
Heating can be done either with resistive heating elements best case sunny day 80% efficient or having a solar PV panel as heater or maybe diodes if you want to DIY something. Both PV panels and diodes will work at max power point so will be more efficient than resistive heating elements."

Me: I will strive to make my array wires to the SBMS0 and the DSSR20 via the DECT16's shorter in distance though to reduce the voltage drops on the 10AWG PV wire

 

[343]

Hello people!

This is my first post on this forum which I joined because I'm converting an old horsetruck into a "housetruck" at the moment and reached the point of installing a PV system.
I've been reading this whole thread and am really happy about all the great insight and expertise which has been shard here about the electrodacus products and some other BMS solutions.

I own an old Victron Phoenix Multiplus 12V 3000W 120A and a 12V 360AH diy battery pack consisting out of 36 GBS 3,2V LiFeMnPO4 40Ah cells.
I'm planning on buying a Victron SmartSolar 250/100 MPPT and around 1,5-2kW of PV panels.

So the big questions is: what's the nicest BMS for this kind of setup?
At the moment I'm undecided between the SBMS and the 123SmartBMS and i really can't really wrap my head around which option has advantages over the other. Especially in combination with the rest of my (partly planned) gear.

Thanks in advance for any kind of input to this topic!

Cheers,

Jan

 

[KohalaJim]

So the big questions is: what's the nicest BMS for this kind of setup?

"Nicest" is so subjective, so it's a difficult ask.
For me personally, nice is the SBMS0...

I'm all in with some older DSSR20's for the "dual PV array" operations, and I'll be integrating some new diversion capable DSSR20's for turbine management in a small off-grid 12V system. The latest incarnation of the SBMS0 addressed my biggest dislike of the hardware, which was the side-mounted 8+2 connector. It's also added enhanced WiFi operations and MQTT support so I'm looking forward to integration with my hassio Pi controller.

 

[Dzl]

What do you mean by enhanced WiFi operations?

 

[KohalaJim]

What do you mean by enhanced WiFi operations?

client and server capable now...

 

[USF_TIM]

Has anyone seen the new redesigned version?

Doesn't look like he is going to hit his goal. https://www.indiegogo.com/projects/electrodacus-sbms-ble-pack-monitor-ltp-reader--2#/
It would be nice if Will Prowse could give his opinion. I would much rather see a higher power 48V version.

 

[Dzl]

Has anyone seen the new redesigned version?

Doesn't look like he is going to hit his goal. https://www.indiegogo.com/projects/electrodacus-sbms-ble-pack-monitor-ltp-reader--2#/
It would be nice if Will Prowse could give his opinion. I would much rather see a higher power 48V version.

48V version is unlikely to happen, Dacian has his reasons, much to many peoples' disappointment.

Edit: I commented without watching the video. My comment relates to the new version of the actual SBMS0, not whatever that spinoff is.
As to the new version, yes, I am excited about the new version. It has a handful of improvements. What I am most excited about is that EXTIO3-6 will all be usable out of the box (the old version only exposed 3 and 4). The connectors have been improved (which was a common complaint with the old version), the monitoring screens have changed a bit I think. I'm not sure what else has been changed. There has been some recent discussion of the new version here and also a few threads on Dacian's message board.

 

[Dzl]

I'm all in with some older DSSR20's for the "dual PV array" operations, and I'll be integrating some new diversion capable DSSR20's for turbine management in a small off-grid 12V system.

Can you speak to the "Dual PV array" functionality. I have been curious about this feature but don't quite understand it and also was under the impression this was a feature from older versions that the SBMS0 didn't use.