JK 4S 200A BMS Electrical Noise

[weeman]

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 shunt, but bypassing the BMS fixes the issue.

The problem only occurs while charging through the BMS and it causes the BMV-712 current reading to fluctuate with current readings from -20a to +20-30 amps all while charging with a constant 50a. I can also hear coil whine or similar coming from the BMS when this happens. I have replaced all the BMS cables and this happens on both my JK 4S BMS's.

When discharging through the BMS there are no issues at all and it works perfectly. I also have a modified PSU which I use as a charger and when connected through these BMSs the current output jumps all over the place, whereas when connected to other battery banks with JBD BMS the charger output to rock stable.

Anyone else having similar issues while charing with the new 4S JK BMS?

@Nami - was there an issue with the charging circuit mosfets on the early model JK-B2A8S20P units?

 

[koobs]

I've just replaced a 100amp overkill solar bms with a 200amp 4s-8s JK BMS that I bought in mid June. Put it on a 4s 280Ah battery.
Same issue when charging with a 30v10a variable PSU. Hissing noise comes from the PSU that gets louder with higher amperage. Two different brand PSUs, same hissing noise.

Think I almost friend the first PSU as the noise got louder and louder with time, I thought maybe the fan was breaking. Second PSU has same noise!

Never heard such a noise before when using these PSUs got charge literally everything else.
No issues from my 16s JK BMS either.

Checked all wiring, everything is correct. Noise goes away when I bypass the bms and charge directly at the cell terminals....
I've bought a 2nd JK BMS unit at the same time to build a 2nd camping battery, so will replace it next week and see if noise still exists.
It sure doesn't sound healthy and I feel the PSUs are going to blow up if I keep it on!
I'd love to understand what the electronics and physics source of the noise is.

 

[gregcope]

Ah. Really interesting. I get the same issue on a BMV-700 shunt. Wild variations in Amps.

I have “early” JDB 4S 200A BMS. The ones where the lugs are proud of the rest of the BMS.

 

[koobs]

Bump, any technical heads have any idea why this would be happening?

 

[ocular]

About to buy a JKBMS for a 4S build, this issue of interference with shunts and electrical noise has now popped up with a number of users here. Is this a function of the early releases of these versions of the 4S JKBMS and the problem is now rectified? @Nami comment please.

 

[koobs]

Yes would like @Nami to comment if this is the case and if there is a fix

 

[koobs]

Woops double post

 

[Bari Rosch]

I would hold off and wait for an answer. I would be interested to hear if there is a fix as well. Reached out to Hankzor/JK via Aliexpress and got a response that the engineer is looking into it. I'm wondering if its an "early release" problem, or a general problem. Anyone that has a 4S JK BMS working properly with Victron equipment? The functions (low/high voltage) on the BMS itself work fine, however the BMS causes problems to surrounding equipment like a BMV and/or battery chargers.

I've been doing some tests over the last couple of days, but they are not very promising. Im testing it in combination with a Victron BMV-712 and Multiplus 800VA. If you place the BMV between the battery and the BMS I manage to register proper discharge and charge currents on the BMV, however while charging the battery from the Multiplus the sound coming from the multiplus is terrible. I now removed the BMS and stopped testing as I'm afraid to damage the Multiplus. I recorded sounds from the Multiplus while charging the battery with 25A. Without the BMS there is a constant "healthy" hummm/buzz, while if the BMS is installed it sounds like arcing and has a really weird rhythm. I'll see if I can upload/add it tommorow. Placing The BMS between the battery and the BMV creates misreadings on the BMV so is also not an option.

 

[koobs]

Did you get an answer from Hankzor? I also messaged them on their Aliexpress store, and sent them a video of the electrical noise that my charger makes when attempting to charge via the BMS. They quickly instructed me to send it back to them for a replacement, and they are paying for freight too.

 

[Bari Rosch]

Did you get an answer from Hankzor? I also messaged them on their Aliexpress store, and sent them a video of the electrical noise that my charger makes when attempting to charge via the BMS. They quickly instructed me to send it back to them for a replacement, and they are paying for freight too.

Yeah, got a reply earlier this week that I can return the unit and they will ship a new one. Hopefully this resolves the issue.

 

[SvenT]

Are there any news on this ?
I use a 4-8S JK BMS together with a BMV712 and a SmartSolar MPPT 100/30.
Was the issue solved by he new BMS?

 

[koobs]

Are there any news on this ?
I use a 4-8S JK BMS together with a BMV712 and a SmartSolar MPPT 100/30.
Was the issue solved by he new BMS?

I bought two of the 4s BMS when they first came out. One had the issue and the other didn't.
The faulty one I'm about to send back.
The working bms did have an odd error once, but hasn't happened since then.

 

[ocular]

There is a statement on the forum @Nami that there were about 20 units initially JKBMS 4s-8s that had a DC DC converter ( because the basic circuitry of the JKBMS needs >25V) that consumed current and become hot and unstable. This DC DC converter chip has been replaced to a more efficient one. I am not sure if this relates to the noise problem. Apparently the faulty JKBMS 4s-8s units drew 1600mW. The newer fixed ones draw 800mW and the JK BMS7s-20s draw 560mW. For those that may still have these faulty ones in use, would be keen to know what the resting current draw is.
see https://diysolarforum.com/posts/610374/

 

[SvenT]

Hey thanks for the information.
How can I measure the drawn power?
Simply a clamp amperemeter that measures the current in the B+ wire?

 

[koobs]

Hey thanks for the information.
How can I measure the drawn power?
Simply a clamp amperemeter that measures the current in the B+ wire?

Since its such a small draw, might not get much with the clampmeter.
I'll try run the b+ wire thru a Multimeter today and see what I get

 

[SvenT]

My DMM shows 65..70mA DC if the BMS is on.

With the small display ~130mA

If it is powered off 0

 

[ocular]

My DMM shows 65..70mA DC if the BMS is on.

With the small display ~130mA

If it is powered off 0

That's about 850mW so that suggests the 4-8s JK BMS with the latest DC DC converter chips. I notice you have a BMV-712 shunt. Do you have any electrical noise problem with this combo like others have noted?

 

[SvenT]

Hey,
Up to now I have not recognized any noise issues.
But to be honest: the sun is rather weak the last days so the max charge current was 15Amps and I did not hear any humming or buzzing up to now.
Which current flew in the devices that made the sound?

S.

 

[SvenT]

Oh I forgot: my solar charger is a SmartSolar MPPT100/30 and NOT a Multiplus.

 

[SvenT]

Oh man, my brain: I also shortened the RJ11 (6p6c) connection between the Shunt and the BMV to a length of 1m.