JK-BMS inducing noise to rail

[MrX]

I installed a brand new JK BMS (4s-8s) in my off grid system yesterday. It is to replace my Daly BMS. After turning on the system there’s noise coming from my Victron Smartshunt. It has been dead silent before. Noise got less when pulling the VE. Direct cable, but it is still present. The noise disappear when I disconnect the solar panels from my chargers (Victron). Seems not the be audible during discharge, only charge. The noise increase if I connect via Bluetooth to the smartshunt (VictronConnect). Also seems it modulates with the communication, I can clearly hear the “BT handshake” when connecting.

I realised also that there’s similar noise coming from my solar inverter.

Has anyone else encountered this?

 

[MrX]

In the recorded scenario the inverter is turned off. It starts with me switching on the circuit breakers for solar panels and when the charge is ramping up the noise appears. It looks like the amplitude is related to the amount of current. The audible noise is solely coming from the Victron smartshunt. The oscilloscope is connected to b-/b+

Also confirmed, this is only during charge. As soon as the current direction goes to discharge, the noise disappear. (Even when solar is connected).

JK BMS Rail Noise

 

[RCinFLA]

It is possible you have an actual defect but more likely you moved cables around when installing new BMS.

Any ripple current from inverter or charger on battery cables can create a vibration in any nearby ferro-magnetic metal close to the battery cables. Most common issue is a loosely fitting metal breaker box cover for DC breaker

Running battery pos and neg cables taped together in parallel as much as possible cancels out much of their magnetic fields. It also reduces their series inductance. Separated battery cables with greater series inductance creates more overshoot voltage ringing on inverter input.

 

[MrX]

Thanks for the reply. I find it very unlikely that this behaviour wouldn’t have shown itself earlier if the reason for it was disturbance from a device already in this system. I have changed this system a numerous times over the last two years and never encountered any noise like this coming out of the smartshunt (or inverter).

The installation of the JK BMS didn’t have any physical effect on the system north of the smartshunt. It was more or less a drop in replacement for the Daly part from the new balance harness.

I don’t think the BMS is faulty, it works fantastically well part from it seems to introduce noise on the rail.

I will reconnect the Daly to verify if the noise disappear.

 

[MrX]

Daly BMS connected again, no noise detected…
Here’s the comparison

 

[acdoctor]

Interesting, to bad change amperage is not equal in the testing.

 

[RCinFLA]

Check if noise stops when you shut off balancing on JK BMS.

 

[MrX]

Interesting, to bad change amperage is not equal in the testing.

The sun was not good enough today, but the Daly have never induced any noise before, I find it highly unlikely that it will suddenly begin at higher power.

In both cases the amps are ramped up from zero. The JK begin to make noise as soon as there’s amps, increasing with amount.

 

[MrX]

Check if noise stops when you shut off balancing on JK BMS.

I’ve not shut of the balancing function per se, but the noise is there even when it is not balancing. (Eg when cells are under 3.48v or completely balanced)

 

[RCinFLA]

The JK active balancer 16S BMS has a turn-on inverter cap surge current limiter that triggers about 2 msecs before main MOSFET's are switched on. It may not like having charge current pushed at it to start off.

The 4/8S version has the surge MOSFET not placed so it may sequence on the main MOSFET's.

I'm thinking, without it seeing some small amount of discharge current after it is first turned on, it is not fully turning on MOSFET switches. Check BMS input to output voltage drop between blue and black leads.
Try with inverter load connected before turning on BMS.

 

[MrX]

I'm thinking, without it seeing some small amount of discharge current after it is first turned on, it is not fully turning on MOSFET switches. Check BMS input to output voltage drop between blue and black leads.
Try with inverter load connected before turning on BMS.

Well, might be, but I’m thinking I shouldnt have to go through a work around to get a BMS to start up correctly. It’s obvious it is either inducing noise to the rail by itself or trigger some other part of the system to do it.

I’ll try to charge the system with a “normal” charger instead and see if it is the same. Quite a hassle off grid but ??‍

 

[weeman]

Did you ever resolve this issue?

I've having pretty much the exact same issue with 2 different 4S JK BMS's. See here:

JK 4S 200A BMS Electrical Noise

I've got 2 early model (purchased in May) JK 4S BMS (JK-B2A8S20P) which are both creating electrical noise / interference only when charging. I first noticed this with erratic current readings on my Victron BMV-712 Shunt which only occurred while charging and initially thought it was a faulty...

diysolarforum.com

Its causing my BMV-712 to go crazy (swings in current measurement) when charging. I've temporarily replaced it with a spare JBD BMS and all the problems go away.

 

[MrX]

Did you ever resolve this issue?

I've having pretty much the exact same issue with 2 different 4S JK BMS's. See here:

JK 4S 200A BMS Electrical Noise

I've got 2 early model (purchased in May) JK 4S BMS (JK-B2A8S20P) which are both creating electrical noise / interference only when charging. I first noticed this with erratic current readings on my Victron BMV-712 Shunt which only occurred while charging and initially thought it was a faulty...

diysolarforum.com

Its causing my BMV-712 to go crazy (swings in current measurement) when charging. I've temporarily replaced it with a spare JBD BMS and all the problems go away.

No solution. I have removed it from the system. ??‍

 

[Horsefly]

I never saw this thread, but add me to the list of those with a rhythmic noise issue that seems to be caused by the JK B2A8S20P BMS.

I actually have two of these. I bought the first one early in the year, before they added the heat function. I put it on a small, mostly portable 8S 160Ah battery. I bought the second one after they restarted shipping with the heat function. This one was to replace the JBD BMS on the 8S 230Ah battery we have at our cabin in the mountains.

Due to other schedule issues I didn't get around to trying to install the second one at the cabin until this week. I took the smaller battery up there with me, and hooked the two batteries in parallel, so that I could shut down the cabin battery but keep everything powered up while I replaced the BMS. After replacing the JBD with the JK BMS, I started it up and all seemed fine. Then I started the solar charger and the charge current eventually went up to 40A. There was immediately a rhythmic hissing sound seeming to come from inside my Schneider SW4024 inverter. At that point there was only small loads on the inverter. I even put the inverter in standby, and the sounds continued. It seemed to be about 50% duty cycle, and each cycle was about one second.

At this initial test stage I still had both batteries in parallel, so to isolate the problem I tried turning off the cabin battery, leaving just the smaller 160A battery. The sound completely stopped. I then turned the main battery back on, and disconnected the smaller battery. The sound started again immediately. I tried forcing the charge controller into float, which reduced the charge current. This made the sound get much quieter, but it was still there.

To me the sound almost sounded like some small arcing going on, which obviously very concerning. It's strange that it is only present with one of the two JK B2A8S20P BMS's. The older one seems fine, but the newer one causes the sound. I swapped the two, so now the newer BMS is on my 160Ah Battery. I hooked it up to my Midnite Solar DIY 3kW AIO and started charging at 40A, and couldn't detect any odd sound. When I return to the cabin (it's a 6 hr drive each way, so I don't do it often), I'll try again to put the older JK BMS on the main battery.

 

[koobs]

Same issue here with noise coming from an adjustable bench top supply. Goes away when bypassing the bms. Hissing noise from the power supply makes it sound like it's going to pop. Two different PSUs and same noise. Posted more details in the thread linked above.

 

[MrX]

Might be the reason why my brand new PSU blow some days ago. Yes, it was on a test setup with 8s JK

 

[Horsefly]

Did anyone notice anything else when this was happening? I thought I briefly noticed that the current was varying wildly, but I turned it off before something bad happened, and didn't have any equipment to see fluctuations. From what I remember, the charge voltage looked fine.

 

[MWeiss]

Is this referring to audible humming noise coming from the BMS itself? I noticed that too when running two air conditioners and an electric dryer today. I was rather surprised to hear humming coming from the battery Bank but I think the ripple from the DC side of the inverter is being imposed on the BMS output.