Using JK-BMS. Do I need a smart shunt?

[kolek]

My unfinished system:
Inverter: Deye 8K
BMS: old JK (not the "inverter" version)
Battery: 16S2P (32 280AH cells)

The JK BMS suck at monitoring battery SoC. Some say use a Victron Smart Shunt to monitor SoC. I'm unclear on how important it is to have a smart shunt monitoring SoC. Say, on a scale of 1 to 10, where 1 is not important at all, and 10 is absolutely mandatory.

And if I buy the Victron Smart Shunt, do I need 1 or 2, and where in my wiring diagram are they installed? I've assigned green letters to the various points they could be installed to make it easier to respond to this question. THANKS!!

 

[kolek]

I was doing further research about where to locate the shunt. @rmaddy wrote:

battery negative terminal -> shunt -> negative bus bar

which would be location "E" on my wiring diagram and would imply I need 2 shunts, one per battery. Is this correct?

Placement of battery disconnect and Victron shunt

Where should I place the battery disconnect and the Victron shunt relative to the class t 200 amp fuse? Please tell me the correct order to wire them in the circuit.

diysolarforum.com

 

[shavermcspud]

Point F would be the most logical place, as its the combined end point for both negative leads from both battery packs.

 

[kolek]

@shavermcspud
Thanks a lot for your response.
That would save me $100+ if I only need 1.
I would then just be concerned that if there's a problem with either battery, and the SoC are wildly different between the 2 batteries, you won't discover it with just 1 shunt? That's not a potential concern?

 

[bolowo]

Point F would be the most logical place, as its the combined end point for both negative leads from both battery packs.

point F is the best location if he is only connecting one inverter to the bus. otherwise if you plan to connect other components such as CC, inverters etc then the shunt should come just before your distribution busbar

 

[bolowo]

@shavermcspud
Thanks a lot for your response.
That would save me $100+ if I only need 1.
I would then just be concerned that if there's a problem with either battery, and the SoC are wildly different between the 2 batteries, you won't discover it with just 1 shunt? That's not a potential concern?

i gues you have a bms + fuse on each bank which should keep you calm. for as long as your cells are healthy, and bms balancing them well, the two banks connected in parallel will always have matching SOC

 

[kolek]

How important is having a smart shunt when using JK-BMS?

 

[timselectric]

Shunt at location F.
My Smart Shunt is my "one truth" accurate SOC.

How important is having a smart shunt when using JK-BMS?

That depends on how important (to you) it is to know what your actual SOC is.

 

[shopman]

Smart shunt is accurate down to milliamps and i use it as the main window into the six batteries at my location. I get the data from the BMS's as well and they're close but diverge at different levels of SOC. So, for a true representation of the overall state of the six batteries in parallel, nothing beats the accuracy of the smart shunt. Get one. You'll love it.

 

[kolek]

Get one. You'll love it.

If it was a Lambo, maybe. Love a smart shunt? That's a stretch. lol

 

[kolek]

Shunt at location F.
My Smart Shunt is my "one truth" accurate SOC.

That depends on how important (to you) it is to know what your actual SOC is.

I thought what's more important than me knowing the SoC is that my inverter knows the SoC, and this isn't going to solve that problem since the shunt can't talk to my Deye AFAIK.

 

[timselectric]

I thought what's more important than me knowing the SoC is that my inverter knows the SoC,

If that's what you think.

and this isn't going to solve that problem since the shunt can't talk to my Deye AFAIK.

Correct, if that's the problem you have.

 

[volomoto]

since the shunt can't talk to my Deye AFAIK

That's true if we are talking about some direct communication, but there's a workaround - https://github.com/sijones/VE.DirectMQTTCANBUS
I installed it and it works perfectly.

 

[shopman]

I thought what's more important than me knowing the SoC is that my inverter knows the SoC, and this isn't going to solve that problem since the shunt can't talk to my Deye AFAIK.

As part of my system I have the Victron shunt reporting to Home Assistant and I use that data to tell the inverter, which is also connected to Home Assistant, exactly how I want it to behave. I also have a Chargeverter that's remotely controlled via Home Assistant so on a stretch of cloudy days when the SOC drops below 25%, the Chargeverter kicks in automatically and charges to whatever SOC I desire. With Home Assistant and some programming knowledge, you can create your own closed-loop system and circumvent deficiencies in most of this equipment.

 

[SeaGal]

That's true if we are talking about some direct communication, but there's a workaround - https://github.com/sijones/VE.DirectMQTTCANBUS
I installed it and it works perfectly.

and also read this related thread from Simon.

DIY Battery via Smart shunt to inverter integration (Solis etc)

Hi All, I've taken some code that handles Victron's VE.Direct protocol (Smart Shunt) and added in CAN Bus / PylonTech protocol connections, this allows the State of Charge, Voltage, Amps etc all be sent to the inverter - any one that supports the PylonTech protocol. I have it connected to a...

diysolarforum.com

 

[kolek]

That's true if we are talking about some direct communication, but there's a workaround - https://github.com/sijones/VE.DirectMQTTCANBUS
I installed it and it works perfectly.

@volomoto
Thank you for that great information. Which inverter do you have it working with?
Are you using a Raspberry Pi or Cerbo GX? Any info about your setup would be much appreciated!

Are you also doing this integration:
https://github.com/Sleeper85/esphome-jk-bms-can ?

 

[kolek]

and also read this related thread from Simon.

DIY Battery via Smart shunt to inverter integration (Solis etc)

Hi All, I've taken some code that handles Victron's VE.Direct protocol (Smart Shunt) and added in CAN Bus / PylonTech protocol connections, this allows the State of Charge, Voltage, Amps etc all be sent to the inverter - any one that supports the PylonTech protocol. I have it connected to a...

diysolarforum.com

@SeaGal
It's amazing all the information you pack into that little bird brain of yours!
Thank you, I'll check that out!!

 

[ChrisG]

Are you also doing this integration:
https://github.com/Sleeper85/esphome-jk-bms-can ?

This only works if you have one battery with one JK BMS at the moment. As @SeaGal mentioned, the Victron smart shunt project is awesome. I’m using it with an EG4 inverter but it will work with anything that uses the Pylontech CAN protocol. Here is the link to my build of this project.

EG4 6000xp CANBUS Comms with Victron Smart Shunt w/DIY Battery

Just finished a small test project with a ESP32 Devkit and MCP2515 CANBUS module following the instructions at the below post on the forum. In short, YES!, the Victron Shunt is reporting SOC%, Voltage, Current, and other items to the EG4 6000xp and controlling charge/discharge/etc. Thanks to...

diysolarforum.com

 

[kolek]

This only works if you have one battery with one JK BMS at the moment. As @SeaGal mentioned, the Victron smart shunt project is awesome. I’m using it with an EG4 inverter but it will work with anything that uses the Pylontech CAN protocol. Here is the link to my build of this project.

EG4 6000xp CANBUS Comms with Victron Smart Shunt w/DIY Battery

Just finished a small test project with a ESP32 Devkit and MCP2515 CANBUS module following the instructions at the below post on the forum. In short, YES!, the Victron Shunt is reporting SOC%, Voltage, Current, and other items to the EG4 6000xp and controlling charge/discharge/etc. Thanks to...

diysolarforum.com

@ChrisG
Wow that is terrific to know about. Was totally unaware of that project.
Btw I believe @chaosnature is using the sleeper85 project with 2 JK BMS and has posted about it.

 

[ChrisG]

@ChrisG
Wow that is terrific to know about. Was totally unaware of that project.
Btw I believe @chaosnature is using the sleeper85 project with 2 JK BMS and has posted about it.

I believe he is pushing dual BMS with the project, which is in future project scope but full release is unknown. I’ve also tried this project but with one battery. They are going way above and beyond the Victron CAN project and very excited to see where they get to.

Currently, I just like the simplicity of the Victron project and this Saturday will be 4 weeks of it running without me touching it…actually can’t as I’m 3+ hours away from my cabin where the installation is. It’s truly been rock solid for just a few dollars.