Active balancer, make it smart!?

[CrossStreet]

I had good success with controlling the Run switch on my balancer via that A30 controller. Extra difficulty for me is that the battery is made of two halves connected by a ~1 mOhm cable. If a large current is flowing the cable biases the voltages that the blancer sees and the balancing turns out to be somewhat wrong. Thus it's best for me to try balancing when the current is not high.
With that A30 controller, I managed to pick a start balancing voltage when the inverter is in the saturation phase and the charge current keeps dropping. Then the inverter stops charging and the battery starts relaxing. I've set the lower threshold to be the voltage when the battery has settled. As a result my balancing takes place during the 2-3 hours from the point when the charging is almost complete to the point when the battery has reached the settled state, when the current is not big, which I think is ideal.

 

[Hans Kroeger]

Does anyone have experience with using a transistor or FET instead of a relay to switch the run port on the balancer? I'm thinking of a small board with e.g. ESP8266 that reads all cell voltages from my BMS via RS485 and switches the balancer on or off depending on the load current and cell voltage.
It is therefore necessary to know the electrical characteristics of the balancer's running connection.

View attachment 131350

I guess you are looking for a circuit like this one:

 

[Vi s]

I guess you are looking for a circuit like this one:

Hans, did you also look into and could you figure out how to use an optocoupler to switch the active balancer on and off? That would be probably the most neat, efficient, cheap, precise, convenient smart solution of all or?

 

[Hans Kroeger]

Hans, did you also look into and could you figure out how to use an optocoupler to switch the active balancer on and off? That would be probably the most neat, efficient, cheap, precise, convenient smart solution of all or?

Yes, you can also use an optocoppler, preferably with a FET output.
However, it is more expensive and requires more power.....
I used both types of circuit. I ended up with the simple P-Channel MOS FET transistor in the diagram above, rather than an optocoppler.

 

[Vi s]

Yes, you can also use an optocoppler, preferably with a FET output.
However, it is more expensive and requires more power.....
I used both types of circuit. I ended up with the simple P-Channel MOS FET transistor in the diagram above, rather than an optocoppler.

Many thanks for sharing the diagram!
Do i understand correctly that your diagram describes how mueller energy modified (active balancer is switched on and off whenever passive balancer is switched on and off) their custom bms? Is the mosfet in your diagram one of the mosfets in the passive balancing circuit?

 

[Vi s]

The idea i got from picturing what mueller energy did was

Optocoupler is connected to some point in the passive balancer circuit and the relay of the optocoupler gets closed whenever energy flow in the point where the optocoupler is connected to is detected.



I have no idea where to connect the optocoupler, what kind of optocoupler can be used (the ones i saw online cost only a few cents and since these are smd components i guessed they draw close to no energy) and if they even work the way i understood from a quick research!?

 

[Hans Kroeger]

The Optocoupler can be connected as shown below. I used an optocoupler with a MOS-Fet output.
The G3VM is available with a normal DIP case......

 

[Vi s]

The Optocoupler can be connected as shown below. I used an optocoupler with a MOS-Fet output.
The G3VM is available with a normal DIP case......

...but to what is your optocoupler connected to, what controls it? To the passive balancer circuit of the bms so that the active balancer can be controlled together with the passive one via the bms app etc or to a separate sensing and controlling circuit?

 

[Hans Kroeger]

...but to what is your optocoupler connected to, what controls it? To the passive balancer circuit of the bms so that the active balancer can be controlled together with the passive one via the bms app etc or to a separate sensing and controlling circuit?

Sorry, but my original message was to answer Gerhards question:

"I'm thinking of a small board with e.g. ESP8266 that reads all cell voltages from my BMS via RS485 and switches the balancer on or off depending on the load current and cell voltage.
It is therefore necessary to know the electrical characteristics of the balancer's running connection."

My circuit diagram shows only how to connect a normal OPAMP or similar circuit to the active Balancer. I am not familiar with the particular bms circuit you are looking for.

 

[Vi s]

Sorry, but my original message was to answer Gerhards question:

"I'm thinking of a small board with e.g. ESP8266 that reads all cell voltages from my BMS via RS485 and switches the balancer on or off depending on the load current and cell voltage.
It is therefore necessary to know the electrical characteristics of the balancer's running connection."

My circuit diagram shows only how to connect a normal OPAMP or similar circuit to the active Balancer. I am not familiar with the particular bms circuit you are looking for.

I see, thank you for clarifying.

Did you see their post and smart active balancer solution? What are your thoughts about their solution?

New 250A Smart BMS with 5A Active Balancer

I hope this is okay, given that there is no longer a commercial corner on here. But I just wanted to share our new 250A JBD Smart BMS that has a built-in optocoupler that outputs a signal to a supplied 5A Heltec active balancer, so it turns on and off when the on-board passive balancer does...

diysolarforum.com

 

[Hans Kroeger]

Did you see their post and smart active balancer solution? What are your thoughts about their solution?

New 250A Smart BMS with 5A Active Balancer

I hope this is okay, given that there is no longer a commercial corner on here. But I just wanted to share our new 250A JBD Smart BMS that has a built-in optocoupler that outputs a signal to a supplied 5A Heltec active balancer, so it turns on and off when the on-board passive balancer does...

diysolarforum.com

Yes I have seen the video. I guess it is a good system, but it is available only for 4S batteries. I have compared (tested) the Heltec 5 A active Balancer being added to the JBD module versus the 2 A active balancer of the JK BMS. The 2 A JK active balancer is more efficient (faster) than the so called 5 A Balancer.
I haven't checked the price for shipment to USA or EU.
Due to the fact, that the support of Jikong for the JK BMS seems to become worse, the Muller Version of the JBD BMS may become a good alternative.

 

[MrM1]

Yes I have seen the video. I guess it is a good system, but it is available only for 4S batteries. I have compared (tested) the Heltec 5 A active Balancer being added to the JBD module versus the 2 A active balancer of the JK BMS. The 2 A JK active balancer is more efficient (faster) than the so called 5 A Balancer.
I haven't checked the price for shipment to USA or EU.
Due to the fact, that the support of Jikong for the JK BMS seems to become worse, the Muller Version of the JBD BMS may become a good alternative.

Has it been produced in a 24 and / or 48v version yet?

 

[Hans Kroeger]

Has it been produced in a 24 and / or 48v version yet?

No, as far as I know 4S (12 Volts) only.

 

[Vi s]

Yes I have seen the video. I guess it is a good system, but it is available only for 4S batteries. I have compared (tested) the Heltec 5 A active Balancer being added to the JBD module versus the 2 A active balancer of the JK BMS. The 2 A JK active balancer is more efficient (faster) than the so called 5 A Balancer.
I haven't checked the price for shipment to USA or EU.
Due to the fact, that the support of Jikong for the JK BMS seems to become worse, the Muller Version of the JBD BMS may become a good alternative.

Thank you. Very interesting to hear that the 2A JK balancer is faster than the jbd + 5A combo (in most real life scenarios). On the other hand all those unfortunate quality and service issues one hears and reads more and more recently are indeed a bummer.

Seems we have to wait until a kind and knowledgeable person has figured out and shares with us how muller attached the 5a active balancer to the passive balancer circuit in order to complement out little collection of smart solutions here. So far mullers solution seems to me to be the easiest (only one small component added), cheapest (a few cents), smartest (can be conveniently controlled via app) and most cost effective one.

 

[octal_ip]

I've taken a bit of a different approach to this issue and addressed most of it in software. I have a JK BMS, and have been using the amazing esphome-jk-bms software by syssi to monitor and send all the BMS statistics to MQTT. With a small modification, I've configured this to switch a relay on once any cell voltage is above 3.4v, then off again as the highest cell drops below 3.35v (to provide some hysteresis). The relay is connected across the "run" pads on a 5A Hankzor active balancer. This minor modification cost me $2 and provides the ideal "smart" balancer to compliment the JK BMS.

Why do this when the JK BMS already has an active balancer?
I had the Hankzor balancer sitting on a shelf from a previous project, so no point having it just collect dust.
The Hankzor also uses a different cascading balancing method to the JK BMS, which just drains and charges the highest/lowest cells, so the two compliment each other quite well.

Happy to share my ESPHome YAML file for any JK BMS owners who might find it useful.

 

[Hans Kroeger]

I've taken a bit of a different approach to this issue and addressed most of it in software. I have a JK BMS, and have been using the amazing esphome-jk-bms software by syssi to monitor and send all the BMS statistics to MQTT. With a small modification, I've configured this to switch a relay .......

Happy to share my ESPHome YAML file for any JK BMS owners who might find it useful.

Hi there, very interesting your description. Unfortunately I am an "analog" engineer. Therefore I do not understand exactly your description. I assume you are connecting an ESP mycroprocessor to the RS485 Output of the JK BMS. Your processor reads all Data from the BMS and controls a small relay in order to turn On/Off the active balancer.
I have 2 questions:

1. Is your additional electronics connected upstream or downstream of the BMS power Mosfets.

2. If it IS connected upstream of the Mosfets (directly connected to the battery), how much power do your additional electronics dissipate when the relay ist Off and the JK-BMS goes to Power Off Mode?

looking forward to your reply! Cheers Hans

 

[octal_ip]

I assume you are connecting an ESP mycroprocessor to the RS485 Output of the JK BMS. Your processor reads all Data from the BMS and controls a small relay in order to turn On/Off the active balancer.

That's correct, however my ESP32 connects to the BMS using Bluetooth. This is preferred as it has complete electrical isolation.

1. Is your additional electronics connected upstream or downstream of the BMS power Mosfets.

The buck converter powering the ESP32 is currently downstream of the BMS power MOSFETs. This means monitoring will stop in the event of the BMS cutting off discharge, however it's the safest option for placement of the device.

how much power do your additional electronics dissipate when the relay ist Off and the JK-BMS goes to Power Off Mode?

The ESP32 uses very little power, combined with the buck converter it'd be about 1W. You've made me curious though, I'll get an exact measurement when I have a moment.


I also have a similar balancer relay control setup working for my JBD BMS, however it uses the serial interface. If there's interest I can clean up the code and release it for the community.

Update: the buck converter and ESP32 use 18mA, or 0.95W.

 

[Hans Kroeger]

That's correct, however my ESP32 connects to the BMS using Bluetooth. This is preferred as it has complete electrical isolation.


The buck converter powering the ESP32 is currently downstream of the BMS power MOSFETs. This means monitoring will stop in the event of the BMS cutting off discharge, however it's the safest option for placement of the device.

Sounds good to me. I guess the ESP32 restarts automatically as soon as power becomes available?

 

[octal_ip]

Sounds good to me. I guess the ESP32 restarts automatically as soon as power becomes available?

Yes, that's right.

 

[Vi s]

That's correct, however my ESP32 connects to the BMS using Bluetooth. This is preferred as it has complete electrical isolation.


The buck converter powering the ESP32 is currently downstream of the BMS power MOSFETs. This means monitoring will stop in the event of the BMS cutting off discharge, however it's the safest option for placement of the device.


The ESP32 uses very little power, combined with the buck converter it'd be about 1W. You've made me curious though, I'll get an exact measurement when I have a moment.


I also have a similar balancer relay control setup working for my JBD BMS, however it uses the serial interface. If there's interest I can clean up the code and release it for the community.

Update: the buck converter and ESP32 use 18mA, or 0.95W.

Hi! I am quite interested to hear more about your balancer relay control setup working for your jbd bms. Many talked about this potential solution but so far nobody actually shared how to do it. I am also using a jbd bms as well got an esp01, esp32 and relays for that very purpuse. Unfortunately i can't code so my esps are just collecting dust.
Am i guessing correct your solution works offline?
Also in order to make this work you had to sacrifice the serial port, means you have to switch the serial adapters in case you want to access the bms itself right!?

 

[curiouscarbon]

Hi! I am quite interested to hear more about your balancer relay control setup working for your jbd bms. Many talked about this potential solution but so far nobody actually shared how to do it. I am also using a jbd bms as well got an esp01, esp32 and relays for that very purpuse. Unfortunately i can't code so my esps are just collecting dust.
Am i guessing correct your solution works offline?
Also in order to make this work you had to sacrifice the serial port, means you have to switch the serial adapters in case you want to access the bms itself right!?

hi; not using esp32 but have accessed JBD data over serial before, and yes. i needed to choose whether the bluetooth adapter or the microcontroller got to talk to the bms.

kind of a drag in the sense that a manual physical modification was needed to reprogram the parameters.

haven't really thought of a clever way to allow easier switching between bluetooth and microcontroller.

good luck with your project

 

[myles]

Love this thread, but would like to build an entire 64S smart balancer, has anyone here looked at other esp32 features, or if anyone hasn't checked out the particle library I highly advise it. I was able to build firmware on Particle with little coding experience to use a car backup sonar sensor as a water tank level sensor at my remote cabin. Now I always know where the water level is at (we rent the cabin out, this is important for guests to have water :D)

 

[octal_ip]

Hi! I am quite interested to hear more about your balancer relay control setup working for your jbd bms. Many talked about this potential solution but so far nobody actually shared how to do it. I am also using a jbd bms as well got an esp01, esp32 and relays for that very purpuse. Unfortunately i can't code so my esps are just collecting dust.
Am i guessing correct your solution works offline?
Also in order to make this work you had to sacrifice the serial port, means you have to switch the serial adapters in case you want to access the bms itself right!?

In my setup the ESP queries the BMS for all its running statistics every few seconds, and then uploads the data to InfluxDB. It also operates the balancer relay if the necessary cell voltage conditions are met.
While this was coded to work online/while connected to WiFi, it'd be trivial to modify the code to remove this function such that in runs in an offline mode. If this is all you needed you could get away using a cheaper and simpler microcontroller without the WiFi capability.

hi; not using esp32 but have accessed JBD data over serial before, and yes. i needed to choose whether the bluetooth adapter or the microcontroller got to talk to the bms.

kind of a drag in the sense that a manual physical modification was needed to reprogram the parameters.

haven't really thought of a clever way to allow easier switching between bluetooth and microcontroller.

good luck with your project

I built a very simple serial multiplexer using a separate STM32. It allowed both the bluetooth adapter and ESP to communicate with the BMS at the same time, with the bluetooth interface taking precedence if it is connected.

If I get a bit of time this weekend I'll upload my code and notes.

 

[curiouscarbon]

I built a very simple serial multiplexer using a separate STM32. It allowed both the bluetooth adapter and ESP to communicate with the BMS at the same time, with the bluetooth interface taking precedence if it is connected.

If I get a bit of time this weekend I'll upload my code and notes.

Nice. Thanks for mentioning this.

Great approach. Especially bluetooth precedence.

 

[octal_ip]

Here's the code, some documentation and photos of the ESP8266 JBD BMS monitor:

GitHub - octal-ip/ESP8266_JBD_BMS_Monitor: An ESP8266 based monitoring device for JBD BMS.

An ESP8266 based monitoring device for JBD BMS. . Contribute to octal-ip/ESP8266_JBD_BMS_Monitor development by creating an account on GitHub.

github.com

I nearly never used the BMS app after I added the TFT screen to this project, except for making the occasional configuration change.

And here's the STM32 UART multiplexer:

GitHub - octal-ip/STM32_JBD_UART_Mux: A UART multiplexer allowing a single JBD BMS to communicate with 2 other devices.

A UART multiplexer allowing a single JBD BMS to communicate with 2 other devices. - GitHub - octal-ip/STM32_JBD_UART_Mux: A UART multiplexer allowing a single JBD BMS to communicate with 2 other de...

github.com