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Electrodacus SBMS40 3D Brothers Edition Review Thread

I just bumped the battery shunt to .3600 milliohms. It corrected by about .25 of an amp. leaving it over reporting by about 2.4 amps. I will install a external shunt and see what that does.
 
@grizzzman did you make sure there was no current flowing on PV or battery line, last time you did a power cycle? I’ve been reading on Dacian’s google group that the zero offset calibration the device performs when it reboots can get thrown off track if the current is not zero, so maybe this is the source of some of the trouble?

I’m finding that with a PV shunt offset of 170mA and a PV shunt resistance of 0.36 mOhm, I’m getting fairly close results. Just still a little over the real current. I reckon I would need to program a shunt resistance of around 0.363 to get things spot on, but alas Dacian’s software will not currently allow that.
 
Yes I did, Sveirge. In fact I tried several times with the same results. However on the bright side, I installed a 300A 75mv shunt and was able to get the current spot on. ( I ended adding 101mv to the starting value of .2500 to get it dialed in.)
 
Yes I did, Sveirge. In fact I tried several times with the same results. However on the bright side, I installed a 300A 75mv shunt and was able to get the current spot on. ( I ended adding 101mv to the starting value of .2500 to get it dialed in.)
Good to know that with external shunts, accurate readings can be obtained. It’s a bit of a blow if the internal shunts can’t currently be calibrated properly in the software though. ?
 
I’ve been observing how the SOC meter behaves on my unit. It seems like it resets to 100% when the cell voltages rise above 3.55V and the “over voltage” flag lights on the status display monitor page, then the SOV percentage reduces in proportion to the accumulated load Ah count as measured within the SBMS40. This means the accuracy will be affected if the battery shunt resistance is programmed wrongly, or if the battery capacity is wrongly entered in parameter settings.

On initial connection of the BMS after a power cycle, 50% SOC is displayed, but this is arbitrary and not related to the real battery charge. Only once a full charge is put into the battery will it reset. Once the SOC meter reduces down to zero, it will stay there if the discharge continues.
 
Been running cycles and found that using an external shunt there is NO balancing. The only time it balanced was when it was on PV charging.
 
Been running cycles and found that using an external shunt there is NO balancing. The only time it balanced was when it was on PV charging.
I concur. Using charging direct to the battery terminal with iCharger I see no balancing occurring on the BMS, whatever I do with BMS settings. Even enabling “balance on discharge” doesn’t help, which seems odd to me.
 
Today we have that rarest of events during a Swedish winter - a sunny day!

I’m assuming I have something wrongly set within my advanced parameter settings, as I’ve yet to see the device do any balancing on the monitor screen, even towards the top of the charge when the cell voltages can differ up to 20mV. Can anyone advise on settings please?

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Hmm all I did was set to 1 from 0. Set charge only and it worked great for me.
Ok, and when it’s working, you see one of these V symbols (in the red rectangle) lit white, rather than greyed out as per my screenshot? Or are you seeing something else as evidence that the balancing is working?
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Yes. In fact the voltage notably drops during the balance timed event. (voltage drop)
 
I’ve been observing the behaviour of the BMS at the top of the charge today, which with my current settings is when one cell reaches 3.53V. Right on cue the BMS opens the charge FET so charging via PV ceases, then as my modest 0.96A load brought down the cell voltages to the “over Voltage recovery” set point of 3.4V, the charging FET closes again and charging resumes.

You end up with nice pulses of charging followed by no charging as the battery voltage safely “bounces“ within the limits the BMS is enforcing. Having seen this working reliably today, my confidence level has increased that the BMS will never allow overcharging of my battery.

Screenshots below of the figures on the battery monitor screen before and after the “end charge” voltage was reached. The PV current drops from around 2.5A to zero.

I‘m loving the graphs feature on the monitor menu. With switchable timescales 4mins, 4 hours or 24hours and graphs for battery, PV and load which can be switched between current or power, there’s some useful insights on offer and the user interface is pretty easily learned. The colour coding red for power drained from battery and green for charge into the battery makes sense too.

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There was a person in the ElectroDacus forums that wanted Dacian to increase the shunt offset due to his amps readings being to high on his "green" SBMS40. This does look like a flaw in at least the prototype units.The second time I emailed Alex about the problem, I never heard back from him.
I can not in good conscience recommend this unit at this time. The lack of accuracy with respect to amps reading errors and lackluster support.
 
There was a person in the ElectroDacus forums that wanted Dacian to increase the shunt offset due to his amps readings being to high on his "green" SBMS40. This does look like a flaw in at least the prototype units.The second time I emailed Alex about the problem, I never heard back from him.
I can not in good conscience recommend this unit at this time. The lack of accuracy with respect to amps reading errors and lackluster support.
That was me enquiring on Dacian’s forum. I was mainly asking about the automation functionality as I would like to do a little more, or at least have the flexibility to do more than the existing type 1- type 6 automation outputs allow.

An interesting detail which emerged from the subsequent discussion was that even if Dacian releases a new version of his software, it cannot be loaded direct onto the green 3D Brothers edition devices due to the use of a different wifi module on these units (ESP8266 vs ESP32 in Dacian’s original design). This means that any further software upgrades would need to be recompiled and rereleased by Alex / 3D Brothers following Dacian’s release of a new version.

This also brings me back to the issue of the PV shunt accuracy, as based on above I believe it would actually be Alex who would need to modify Dacian’s source code to increase the shunt resistance range, then compile and release this with user instructions on how to upgrade devices. This assumes that this will not be done “in house“ prior to shipping the production versions of these units, which is of course far preferable.

Unless Alex wants to help out, those of us with prototype units may well not get that software update although I suppose we could get a copy of Dacian’s source code and figure out the intricacies of correctly bundling it with the right ESP8266 drivers and settings, etc. That’s beyond my capabilities, but someone with a software background who is au fait with ESP8266 might well be willing to take it on.

I will send over to Alex my thoughts on this and emphasise the importance of modifying that software before shipping his production batch to indiegogo backers, to avoid his users being disappointed.
 
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That was me enquiring on Dacian’s forum. I was mainly asking about the automation functionality as I would like to do a little more, or at least have the flexibility to do more than the existing type 1- type 6 automation outputs allow.

An interesting detail which emerged from the subsequent discussion was that even if Dacian releases a new version of his software, it cannot be loaded direct onto the green 3D Brothers edition devices due to the use of a different wifi module on these units (ESP8266 vs ESP32 in Dacian’s original design). This means that any further software upgrades would need to be recompiled and rereleased by Alex / 3D Brothers following Dacian’s release of a new version.

This also brings me back to the issue of the PV shunt accuracy, as based on above I believe it would actually be Alex who would need to modify Dacian’s source code to increase the shunt resistance range, then compile and release this with user instructions on how to upgrade devices. This assumes that this will not be done “in house“ prior to shipping the production versions of these units, which is of course far preferable.

Unless Alex wants to help out, those of us with prototype units may well not get that software update although I suppose we could get a copy of Dacian’s source code and figure out the intricacies of correctly bundling it with the right ESP8266 drivers and settings, etc. That’s beyond my capabilities, but someone with a software background who is au fait with ESP8266 might well be willing to take it on.

I will send over to Alex my thoughts on this and emphasise the importance of modifying that software before shipping his production batch to indiegogo backers, to avoid his users being disappointed.
Did you provide pics around the shunts like Dacian asked?
 
Some positive news to report is that I’ve found a way to get remote monitoring working on my iPad, with iOS13.7. I’d previously believed the rumours that after iOS 13, local files could not be opened on iPhone / iPad, but it seems there is a way.

Using the app “File Explorer” by developer Skyjos co ltd I can open Dacian’s HTML file having downloaded it onto the iPad within Safari browser, then exported into “File Explorer” app using the iOS native file manager app “Files”.

With the HTML saved into File Explorer app and the iPad joined to the wifi hotpot the SBMS40 creates, all works as it should. You can even choose whether to open the file in web browser or file editor mode, so changing some of the HTML labels to make the text more meaningful to yourself is easy, as is changing the page refresh rate (I changed from default 3s to 10s so the page jumps less frequently).

I’m pretty pleased with this development, as it unlocks a lot of functionality and makes monitoring my system far easier, even if there’s still the limitation of having to swap from my normal wifi router onto the SBMS40 hotspot each time I want to check.

I have to say, I really like the way Dacian has done the graphs with 1 minute, 1 hour and 12 hour timescales displayed alongside each other. With one look I can see not just what the system‘s doing now, but what it has been doing all day.

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So it’s a been a while since I posted to this thread, but I’ve continued to use the SBMS40 which was performing well, sitting between my 2 parallel connected 160W PV panels and 4S LiFePO4 battery. I say “was“, because today we had a major malfunction :cry:

I happened to pass through the room which houses the set up and noticed a bad smell. Glancing at the screen of the SBMS40 my eyes popped out of my head as I saw all four cells at 4.4V and rising....! I quickly tripped the breaker which connects the PV panels, so charging current reduced to zero, and went to add some load to the circuit to bring down the voltages. By the time I got my iPad connected for monitoring, to take the below screenshot, the cells were down to around 3.9V each. Note the SBMS temp reported on the screenshot is 23.2C and the battery temp is the room ambient, a very modest 15C.

On examination I see a blown component, presumably the charge FET, so I guess this has failed short circuit and no longer switches off when commanded by the software. I’ve checked and found that the EXTIO3, used to control external charging sources, does operate as normal, switching from closed circuit to open circuit when cell voltages rise above the “over voltage” set point which I have configured as 3.5V.

On the screenshot you see the PV 1 hour graph showing the charging current up to the over voltage event (when it drops to zero). Charging current was under 20A and had peaked at just over 20A about 20 mins before. I had been warned that this SBMS40 might be more properly named SBMS25 when used without a heatsink, but now I wonder if even that is correct. I’m quite mystified though, as the SBMS40 was reporting an internal temp of just 23C and Alex from 3D brothers tells me they have soak tested at 30A without heatsink.

I could go on using this device to control external charge controllers via EXTIO3, but if there’s no current via the PV port there is no cell balancing function, which makes it a not very useful BMS. I doubt I can replace the failed FET, it’s too tiny. A real shame.

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So it’s a been a while since I posted to this thread, but I’ve continued to use the SBMS40 which was performing well, sitting between my 2 parallel connected 160W PV panels and 4S LiFePO4 battery. I say “was“, because today we had a major malfunction :cry:

I happened to pass through the room which houses the set up and noticed a bad smell. Glancing at the screen of the SBMS40 my eyes popped out of my head as I saw all four cells at 4.4V and rising....! I quickly tripped the breaker which connects the PV panels, so charging current reduced to zero, and went to add some load to the circuit to bring down the voltages. By the time I got my iPad connected for monitoring, to take the below screenshot, the cells were down to around 3.9V each. Note the SBMS temp reported on the screenshot is 23.2C and the battery temp is the room ambient, a very modest 15C.

On examination I see a blown component, presumably the charge FET, so I guess this has failed short circuit and no longer switches off when commanded by the software. I’ve checked and found that the EXTIO3, used to control external charging sources, does operate as normal, switching from closed circuit to open circuit when cell voltages rise above the “over voltage” set point which I have configured as 3.5V.

On the screenshot you see the PV 1 hour graph showing the charging current up to the over voltage event (when it drops to zero). Charging current was under 20A and had peaked at just over 20A about 20 mins before. I had been warned that this SBMS40 might be more properly named SBMS25 when used without a heatsink, but now I wonder if even that is correct. I’m quite mystified though, as the SBMS40 was reporting an internal temp of just 23C and Alex from 3D brothers tells me they have soak tested at 30A without heatsink.

I could go on using this device to control external charge controllers via EXTIO3, but if there’s no current via the PV port there is no cell balancing function, which makes it a not very useful BMS. I doubt I can replace the failed FET, it’s too tiny. A real shame.

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Thanks for your honesty and for being the sad example of what I keep repeating (having redundancy on the battery charge/discharge control is a must).
 
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