The Electrodacus SBMS thread (SBMS0, DSSR50, etc)

[childcarepro]

I believe you have found the wrong product. Heltec makes active balancers, as well as an active balancing BMS (balancer vs BMS is another often misunderstood topic). The balancer is just a single purpose tool, not a replacement for a BMS. The BMS is more expensive than the balancer and obviously more fully featured. Search for the BMS @upnorthandpersonal is using, IIRC, it is in the ballpark of ~$200.

edit: I believe this is the correct link and this is a relevant thread (if you get past the first page or two where the conversation is a bit muddled).

Rookie mistake. Looks like I got a little too excited at finding an active balancing [not] BMS for so cheap and from a US seller. Let me look at the active balancing BMS instead of the active balancer. Thanks! Looks like the link you gave is for an 8S-24S passive balancing BMS w/ 200 mA balance current. This one appears to be an active balancing BMS that supports 1.5A balance current: https://www.aliexpress.com/item/1005001412712740.html?spm=2114.12010612.8148356.16.628c4df41Hrmw8

I'm still waiting to hear back from 123electric.de about pricing on their 123\SmartBMS gen3. They did confirm their BMS can activate the SmartBattery Protects and turn off the MultiPlus and SmartSolar, but no pricing was offered.

Back in the day, Bell motorcycle helmets had an ad:

If you got a $10 head, wear a $10 helmet.

I agree that you often get what you pay for, which is why I have a 90% Victron setup. But don't worry, I was not going with Heltec just to save money! I just want a simple, plug-and-play, capable solution. I was really excited about true active balancing, though it turns out I was barking up the wrong tree anyway.

 

[Dzl]

While I agree more research is a good idea-- particularly for a BMS that is rather new here, I think you also may need to do more research before forming or stating an opinion.

Sorry dude, opinions require no research.

My intention was not to offend, only clarify. Setting aside opinions on the validity of the statement above-- in this instance you are drawing inaccurate conclusions based on the wrong product (beyond that, its not even for the right battery chemistry), so in this instance I don't think its a stretch to conclude a bit more investigation wouldn't hurt, and I think we have an obligation to make an effort to give correct info or state our uncertainty. Happens to all of us from time to time, I feel like I misspeak or misread, or misunderstand something almost daily, its no biggie (I have interacted with you enough to know you share some great info), I only wish to clarify.

Rookie mistake. Looks like I got a little too excited at finding an active balancing [not] BMS for so cheap and from a US seller. Let me look at the active balancing BMS instead of the active balancer. Thanks! Looks like the link you gave is for an 8S-24S passive balancing BMS w/ 200 mA balance current. This one appears to be an active balancing BMS that supports 1.5A balance current: https://diysolarforum.com/threads/the-solar-bms-thread-sbms0-sbms40-sbms120-dssr20-and-so-on.4194/

I'm not sure this is the correct link. When I click it, it just takes me to the first post in this thread.

I'm still waiting to hear back from 123electric.de about pricing on their 123\SmartBMS gen3. They did confirm their BMS can activate the SmartBattery Protects and turn off the MultiPlus and SmartSolar, but no pricing was offered.

If you want ballpark pricing, here is an EU distributor with a-la-carte prices given in USD. They may ship to the US, not sure.

 

[childcarepro]

I'm not sure this is the correct link. When I click it, it just takes me to the first post in this thread.

If you want ballpark pricing, here is an EU distributor with a-la-carte prices given in USD. They may ship to the US, not sure.

Oops, I've edited my post with the correct link.

Thanks for the link; the prices seem reasonable.

Wondering if 123Smart may not be ideal. It seems like a monitoring and safety shut-off system with top balancing feature rather than continuous cell balancing? I watched their intro video and read their manual. I've reached out to them for confirmation.

In 123electric's intro video their app shows voltages for 16 cells, between 3.225V and 3.335V, a 0.10V delta, and they say they're "within safe limit." This delta seems a lot higher than inter-cell differentials with other BMS’s which shoot for 10-20 mV. The manual states: “V balance: This is the balancing voltage where you want all the cells to end up. Above this voltage the cell modules start to dissipate 1 ampere to balance the cells.”

The video also mentions your relays either shut off charging or discharging when any cell falls outside the voltage range. So it appears balancing only happens at the top, at low voltage if any cell falls below Vmin, it shuts off the loads rather than attempting to bypass the low cell.

Am I making a mountain out of a molehill?

Pros:
- 1 amp balancing current
- clean look w/o spaghetti wires everywhere
- integration with Victron ecosystem
- reasonably priced for an elegant system

Cons:
- no continuous intercell balancing, only top balancing
- appears to require soldering
- possible to damage the modules when working with the bank/cells?

 

[childcarepro]

I was looking at the specs of the Heltec active balancer w/ BMS for <16S (I'm shopping for one 4S and one 8S). I was going to oversize it, so the 360A for my 8S even though I never anticipate more than 125A so I get beefier components.

Am I reading this correctly? The photo is labeled, "50 mA passive balance, single string voltage reaches 3.65V to turn on" AND "1.5A active balance, single string pressure difference 0.1V open equalization." Does this mean it top balances at 3.65V using 50 mA resistance on the fully charged cells, vs up to 1.5A to actively balance between cells when >0.1V differential?

 

[childcarepro]

Or... what if I used the 123SmartBMS as my monitoring/top balancing/Victron connected system (1A is better than 50 mA for top balance) AND used the Heltec 5A active balancer (not BMS) to keep the cells in balance during charge/discharge? It seems to me they wouldn't interfere with each other, since the 123Smart only turns on its 1A resistor at the high voltage limit, while the active balancer only kicks on when cell voltage differential goes over 0.1V.

The other question is whether the active balancer would interfere with charge/discharge from the battery.

 

[Dzl]

I was looking at the specs of the Heltec active balancer w/ BMS for <16S (I'm shopping for one 4S and one 8S). I was going to oversize it, so the 360A for my 8S even though I never anticipate more than 125A so I get beefier components.

Am I reading this correctly? The photo is labeled, "50 mA passive balance, single string voltage reaches 3.65V to turn on" AND "1.5A active balance, single string pressure difference 0.1V open equalization." Does this mean it top balances at 3.65V using 50 mA resistance on the fully charged cells, vs up to 1.5A to actively balance between cells when >0.1V differential?

I think parts of this conversation would be better moved over to the Heltec BMS thread, or start a new topic with your questions, we are taking this conversation pretty far off topic in the SBMS thread.

 

[Cal]

I think we have an obligation to make an effort to give correct info or state our uncertainty. Happens to all of us from time to time, I feel like I misspeak or misread, or misunderstand something almost daily, its no biggie (I have interacted with you enough to know you share some great info), I only wish to clarify.

My research lead me to the official Heltec website. There was no listing of an active balancing BMS at that site.

I stand by by research.

 

[Dzl]

My research lead me to the official Heltec website. There was no listing of an active balancing BMS at that site.

I stand by by research.

That's understandable, their website is pretty shitty and feels like an afterthought. But the post directly above yours had the correct, direct link to the Active Balancing BMS. Hopefully that helps clear up any confusion.

Here are links to the Active Balancing BMS:
Heltec Store on Aliexpress
Heltec Store on Alibaba

 

[Dzl]

Back to the topic of the SBMS0 I recently learned became aware that while the SBMS0 has low temperature protection, charging and discharging cannot be set or controlled separately which significantly limits its utility.

In his usual style, Dacian has a well reasoned but narrow and rigid argument as to why low temp disconnect is not the proper way to solve the predicament of LFP in low temps (he feels avoiding low temps, insulating, and/or heating are better solutions). While I don't disagree with his logic (actually I was fairly swayed by it), I don't think his argument eliminates the usefulness of low temp disconnect as a safety measure, and protection layer. This will not be a problem for many people, but I do hope this is addressed in future iterations of the SBMS0.

Some relevant info here and also in this thread (read the second link if you want to here Dacian's reasoning).

 

[sremick]

Back to the topic of the SBMS0 I recently learned became aware that while the SBMS0 has low temperature protection, charging and discharging cannot be set or controlled separately which significantly limits its utility.

In his usual style, Dacian has a well reasoned but narrow and rigid argument as to why low temp disconnect is not the proper way to solve the predicament of LFP in low temps (he feels avoiding low temps, insulating, and/or heating are better solutions). While I don't disagree with his logic (actually I was fairly swayed by it), I don't think his argument eliminates the usefulness of low temp disconnect as a safety measure, and protection layer. This will not be a problem for many people, but I do hope this is addressed in future iterations of the SBMS0.

I'm planning on incorporating heating system in my kit to address this. While I don't ever expect to have the kit exposed to conditions that would require it, I like the failsafe of having it there just in case. I have a number of thin-film 12V heating elements that will go in-between the cells, which will be controlled by PID code on the Arduino along with separate temperature sensors (although the Arduino will also be getting temp info from the SBMS itself to do with however I see fit).

Likewise, a PWM fan will also be controlled by the Arduino to handle cooling if things get too hot inside the kit, with the speed ramping up proportional to how hot it is (preferably not running at all under normal conditions). Both the battery temps and the SBMS temp will be taken into account with this.

 

[childcarepro]

Back to the topic of the SBMS0 I recently learned became aware that while the SBMS0 has low temperature protection, charging and discharging cannot be set or controlled separately which significantly limits its utility.

In his usual style, Dacian has a well reasoned but narrow and rigid argument as to why low temp disconnect is not the proper way to solve the predicament of LFP in low temps (he feels avoiding low temps, insulating, and/or heating are better solutions). While I don't disagree with his logic (actually I was fairly swayed by it), I don't think his argument eliminates the usefulness of low temp disconnect as a safety measure, and protection layer. This will not be a problem for many people, but I do hope this is addressed in future iterations of the SBMS0.

Some relevant info here and also in this thread (read the second link if you want to here Dacian's reasoning).

Yes, let's get back to the topic, people! ?

I agree with you, while it is clearly better not to freeze your cells, it's even better-er to be sure that if you DO freeze your cells, you don't permanently damage them by charging them while frozen.

I also agree that SBMS0 (123SmartBMS has this limitation too, I learned) should only disable charging, not discharging, while below 0 Celsius, since only charging is harmful to the battery while below 0. [Well, much more harmful than discharging.]

 

[michael d]

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.

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.

yes. I am in process of assembling the Electrodacus SBMS0 system. I will be using a pair of 10 gauge wires from each set of 2 60cell 250watt panels to the Electrodacus SBMS0, 20 of the Electrodacus DSSR20 via the Electrodacus (2x) Electrodacus DECT16. the 10 gauge PV wire is going to cost a lot. For 40 panels(2 panels in parallel) 75 feet each run that is 20 runs of 10 gauge wire to the DECT16 which means (20x2x75=3000feet) 3000feet of PV wire for the 40-panel array. this part cost $1249 shipped but I bought 2000 feet red 10 gauge PV wire and 2000 feet black 10 gauge PV wire, 200 feet bare copper#6 wire, plus a 250-foot roll of thermostat wire. PV wire is expensive. could save a lot of the PV array is closer to the Electrodacus components and battery bank. I chose not to put the array closer to keep away from children (or other people) and safety issues and the view was also an issue for my location! 40 panels x250watt = 10,000 watt array. more later

 

[BiduleOhm]

Thanks for telling us the cost of the wires in a real world example

What's the cost for the SBMS0, DSSR20's and DETC16's?

 

[Cal]

I will be using a pair of 10 gauge wires from each set of 2 60cell 250watt panels to the Electrodacus SBMS0, 20 of the Electrodacus DSSR20 via the Electrodacus (2x) Electrodacus DECT16.

Trying to understand your system. Do you have a link or spec for the 60 cell, 250W panels?
In another thread you mentioned 327W panels.

 

[michael d]

Trying to understand your system. Do you have a link or spec for the 60 cell, 250W panels?
In another thread you mentioned 327W panels.

i have both size panels. i will send link or more details on 60 cell panels shortly

 

[michael d]

Thanks for telling us the cost of the wires in a real world example

What's the cost for the SBMS0, DSSR20's and DETC16's?

1 sbms0, 2 dect16's, 20 dssr20's cost $877.06 including shipping.

 

[michael d]

Trying to understand your system. Do you have a link or spec for the 60 cell, 250W panels?
In another thread you mentioned 327W panels.

the 250 watts 60 cell panels are: polycrystalline VOC37.6V, VMP30.3V, ISC8.85A,max power current 8.27A

 

[michael d]

the 250 watts 60 cell panels are: polycrystalline VOC37.6V, VMP30.3V, ISC8.85A,max power current 8.27A

(40) 250watt 60cell panels shipped to me cost $2340.80 these are used w/o defects.

 

[michael d]

Anyone using the DSSR20 controllers with 'diversion' capability? These are the controllers that take over the role of the older DMPPT diverting excess PV power to be used for heating water or a radiant floor, or stored in thermal mass.

Lately I've been thinking about trying to figure out how to utilize excess PV for water heating purposes, the DSSR20 with diversion seems like a practical way to accomplish this, but I can't find any info on it.

i ordered 4 of the dssr20 with diversion but have not tried this yet. i also want to use them for heating. that is the plan.

 

[michael d]

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.

8x3.2=25.6; 25.6x280ah =7168; each 280ah cell wired in parallel 1st so you get 7168x2=14336 capacity on 8s 24 volt sbms0.

 

[Cal]

This is getting a bit off topic, but have you done an analysis if the 60-cell panels with Vmp = 30V will work with a 26 to 28V battery?

I have some doubts it will work at elevated temps (50C panel temperature). The operating voltage of the panel when in pwm mode is a tad below Vmp. The 30V is reduced by temperature and the long cable drop.

You really need a Vmp of 34V

 

[Dzl]

This is getting a bit off topic, but have you done an analysis if the 60-cell panels with Vmp = 30V will work with a 26 to 28V battery?

I have some doubts it will work at elevated temps (50C panel temperature). The operating voltage of the panel when in pwm mode is a tad below Vmp. The 30V is reduced by temperature and the long cable drop.

You really need a Vmp of 34V

60 Cell panels are what Dacian Recommends for his DSSR's

I have been curious about this for a while but never looked into it. I had always heard 60 cell panels were never popular pre MPPT as 36 cell or 72 cell panels were considered optimal for 12 or 24 volt systems with PWM type controllers. But Dacian seems to feel that 60 cell panels are optimal for his system (is this a difference in his design, a difference in battery chemistry that affects voltage, or maybe just a different design theory).

Can anyone shed any light on this? Why does Dacian consider 60 cells optimal for 24v when the rest of the industry considers 60 cells too small (or have I misunderstood something).

 

[BiduleOhm]

For 40 panels(2 panels in parallel) 75 feet each run that is 20 runs of 10 gauge wire to the DECT16 which means (20x2x75=3000feet) 3000feet of PV wire for the 40-panel array. this part cost $1249 shipped but I bought 2000 feet red 10 gauge PV wire and 2000 feet black 10 gauge PV wire, 200 feet bare copper#6 wire, plus a 250-foot roll of thermostat wire.

the 250 watts 60 cell panels are: polycrystalline VOC37.6V, VMP30.3V, ISC8.85A,max power current 8.27A

I have some doubts it will work at elevated temps (50C panel temperature). The operating voltage of the panel when in pwm mode is a tad below Vmp. The 30V is reduced by temperature and the long cable drop.

Well, 2x75' of 10 AWG will drop 2.47 V @ 16.54 A which is 8.2 % of 30.3 V.

Can someone tell me how spending 1000+$ on wires and almost as much for the DSSR20's + SBMS0 + DECT16 (and we still need to add 20 breakers/fuses + all the things you need to manage and connect 40 wires...) to end up with more than 8 % losses in the wires only is a superior solution to having fewer and thinner wires with a MPPT SCC which will be as or more efficient, harvest more power on cloudy days, be easier to install (40x 10 AGW wires doesn't sound fun to manage...), and be cheaper? did I miss something?

 

[michael d]

I am hoping to go to 60 feet long runs. but time will tell. the 72cell panels would have been better for the distance in all reality(i already caught that in my research).
I might be able to move a few components to shorten my length. I do not always make the best 1st choices, but I do not claim to be an expert in electricity either but have primarily worked with 120 240 house wiring. the bms monitoring/management is new to me but the Chinese bms's that I reviewed had many problems with little to no support. I am using 16 of 32 280ah lifepo4 cells for this with 24-volt components. the voltage drop on the wire was an issue potentially but I am working to remedy that issue. I do not have any real data at this time.
I do believe the Electrodacus SBMS0 without the mppt is the way to go; though. time will tell with more data. just sharing what I am doing. helpful critique is always welcomed. thanks all. snow in melting so outside I go to work. bye
each run is 75 feet of red positive and 75 feet black negative wiring. I never calculated the voltage drop exactly yet but did know 60 feet or less was better. there are a few components I could move a bit. I am using a ground mount so don't want to ruin all my view. already cut down trees for better solar siting.

 

[Cal]

60 Cell panels are what Dacian Recommends for his DSSR's

I have been curious about this for a while but never looked into it. I had always heard 60 cell panels were never popular pre MPPT as 36 cell or 72 cell panels were considered optimal for 12 or 24 volt systems with PWM type controllers. But Dacian seems to feel that 60 cell panels are optimal for his system (is this a difference in his design, a difference in battery chemistry that affects voltage, or maybe just a different design theory).

Can anyone shed any light on this? Why does Dacian consider 60 cells optimal for 24v when the rest of the industry considers 60 cells too small (or have I misunderstood something).

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