Jk bms protecting

[torstein]

Sometimes this happening to my battery. Anyone know what could be the reason?

Battery size is 330a 52v

 

[RCinFLA]

Messages seem to indicate the BMS is passing too much load current.

There are ten parallel chip resistors of 1 milliohm each that are for current shunt sensor reading. If one or more of these goes open for any reason the result is higher net shunt resistance with microcontroller ADC reading a higher voltage drop across shunt and calculating a higher current than actual.

 

[torstein]

Messages seem to indicate the BMS is passing too much load current.

There are ten parallel chip resistors of 1 milliohm each that are for current shunt sensor reading. If one or more of these goes open for any reason the result is higher net shunt resistance with microcontroller ADC reading a higher voltage drop across shunt and calculating a higher current than actual.

Forgot to tell. This never happens White discharging. Only while charging.


Charging rate is limited to 80a

Is this something to be concerned about?

 

[Steve_S]

What model of the BMS do you have ?
What are your settings, including advanced ?
Clarify the Battery: 330A ? That is a peculiar value, indicate if cells are Paralleled and what the AH rating is on the cells.

I had a similar issue way back when. Solved with adjusting the settings as shown below.
NB I am running 150A BMS which can handle 75A charge. If you are running 200A BMS it can handle 100A Charge. You CANNOT exceed 0.5C charge rate on the cells, so for example a 280AH Cell can take a Max of 140A

 

[torstein]

Batteries are 3x https://www.secondlife-evbatteries.com/products/vw-egolf-15v-samsung-sdi + 1 module that is halv of this size. In series. Couldt find a picture of it right now

And I have 3 of these series in paralell. 326a

 

[torstein]

Forgot to say that I have B1A20S15P

 

[torstein]

Forgot to say that I have B1A20S15P

Thougt this could handle 150a charge?

 

[torstein]

Should i change to:
Chaege OTP from 70 to 60
Charge OTPR FROM 60 to 55
Discharge OTP from 70 to 60
Dischargd OTPR from 60 to 55
Charge UTP from -20 to 0
Charge UTPR -10 to 5
Private data?

 

[RCinFLA]

Thougt this could handle 150a charge?

Charging is rated at continuous current while discharge is rated for maximum (short term) current.

Continuous on both charging and discharging is 80 amps max. Short term (5-8 minutes) discharge is 150 amps max.

At 80 amp (charge or discharge) the BMS MOSFET's have a little over 8 watts of heating. At 150 amps the heating jumps up to 13 watts which will cause a thermal shutdown if sustained too long.

 

[Steve_S]

I had a Momentary Brain Fart.
Battery Cells cannot be charged higher than 0.5C, so 100AH Cell can only take 50A MAX. THIS IS FOR LFP / LiFePO4



Cat seem to find your battery easily. It appears they use 37AH Cells to make 108AH Packs.

 

[torstein]

I had a Momentary Brain Fart.
Battery Cells cannot be charged higher than 0.5C, so 100AH Cell can only take 50A MAX. THIS IS FOR LFP / LiFePO4

View attachment 113222

Cat seem to find your battery easily. It appears they use 37AH Cells to make 108AH Packs.

I had a Momentary Brain Fart.
Battery Cells cannot be charged higher than 0.5C, so 100AH Cell can only take 50A MAX. THIS IS FOR LFP / LiFePO4

View attachment 113222

Cat seem to find your battery easily. It appears they use 37AH Cells to make 108AH Packs.

But this is li ion batteries. 30% of capachy is reccomended charge rate. 330a can be charged with 100a.


Anyway I do it at 80. I can see that this is not the reason. This sometimes happening whit low charge rate also.

When I look at that chart it says max discharge 300a and continius 150a.. do noy understand this if it is 75a then?


Yes that is the battery. But i only have 3 of them in series and a smeller one to get 52v

 

[torstein]

I can see that it has happend tonight also. While discharging at 1.6kw

 

[RCinFLA]

My experience is the JK BMS's rarely make their spec stated series resistance and the number only come close to spec stated number when it is cold. When MOSFET's heat up from load current the resistance rises 1.4-1.6x from 25 degs C.

Most Chinese BMS's highly over-exaggerate their current handling capability, and most don't state their series resistance. Most seem to base max current rating on about 20 watts of internal heating which, with their limited heat sinking capability, will quickly cause a thermal shutdown.

It is fairly common practice to substitute MOSFET part used on lot-to-lot builds based on what parts are available at the lowest cost.

The heat sinking is based on ease of manufacturing and cost. Thermal pads heat conduction from epoxy top side of MOSFET's has very poor heat transfer capability.

 

[torstein]

What is recoomended way to fix this? I have tried to tough parts and everything is ice cold. And this happens also with small loads.
Did not have this problem when I was only running 1 series. Seems like the problem came when adding 2 more i paralell.

Beleave there is an setting in the bms that can fix this?

 

[torstein]

Tonight the fuse between the inverter and the bms was down. Logged into the inverter and found this. Was not able to get rid of this without power off the bms. Then everything works again as normal. But there is something strange going on here.

 

[torstein]

Came accross this thread:

JK BMS owners, have you had this error yet? Heat pump electrical feedback???

I noticed this morning my JK BMS is throwing a "Protection current sensor anomaly". Unsure what this meant or how to remedy I contacted the seller on Aliexpress and I am being told this is a known issue and through some translation my understanding is that the BMS is picking up feedback from the...

diysolarforum.com

Can it be as simple that its caused by something in the inverter? I have a deye hybrid inverter.

 

[RCinFLA]

A grid connected hybrid inverter is running in parallel with grid.

If there is a grid glitch, like a momentary dropout or voltage dip due to heavy grid load, like wind pushing tree branch into HV line, or lightning hit on grid, the inverter will go up to its overload surge limit before opening its pass-through relay connecting to grid.

This creates momentary high battery current.

BMS's have some delay on a max current overload to allow a short overcurrent but they also have an absolute 'short circuit' current level they will trip in a very short time to prevent BMS damage.

There are some BMS settings for how it handles max current surges that may help.

- max discharge current
- max discharge current trip delay
- short circuit protection trip delay

Actual short circuit current limit is firmware fixed and if it is too low, only way to avoid grid glitch shutdowns would be with max short circuit delay setting. That could be risky if you actually have a short circuit with a long recognition delay. Maybe that is the firmware bug talked about in other post. Grid glitches usually are less than 8 msecs. I think JK BMS defaults "SCP delay" user setting to 1.5 msecs.

 

[torstein]

A grid connected hybrid inverter is running in parallel with grid.

If there is a grid glitch, like a momentary dropout or voltage dip due to heavy grid load, like wind pushing tree branch into HV line, or lightning hit on grid, the inverter will go up to its overload surge limit before opening its pass-through relay connecting to grid.

This creates momentary high battery current.

BMS's have some delay on a max current overload to allow a short overcurrent but they also have an absolute 'short circuit' current level they will trip in a very short time to prevent BMS damage.

There are some BMS settings for how it handles max current surges that may help.

- max discharge current
- max discharge current trip delay
- short circuit protection trip delay

Actual short circuit current limit is firmware fixed and if it is too low, only way to avoid grid glitch shutdowns would be with max short circuit delay setting. That could be risky if you actually have a short circuit with a long recognition delay. Maybe that is the firmware bug talked about in other post. Grid glitches usually are less than 8 msecs. I think JK BMS defaults "SCP delay" user setting to 1.5 msecs.

Thanks again. Yes i could try changing the settins. What are you renommending setting this to?

 

[torstein]

Thanks again. Yes i could try changing the settins. What are you renommending setting this to?

Or should I try contacting jk bms and ask?

 

[RCinFLA]

Thanks again. Yes i could try changing the settins. What are you renommending setting this to?

I would try increasing the 1.5 msecs short circuit delay in 0.5 msecs increments until you don't have the issue anymore. I don't think I would go over 5 to 8 msecs in short circuit trip delay though.

You could also try increasing the maximum discharge current limit setting and shortening its trip time but that would provide less protection for inverter if one of its MOSFET's goes bad. Having a maximum discharge current a little higher than maximum inverter surge load battery current with a trip delay a little longer than inverter surge time limit would be a logical setting.

I sent an email to JK yesterday asking what short circuit current setting is in firmware and what criteria is used to reset SOC indicator to 100%.

My guess is they will waffle on stating a short circuit current limit value as the ADC reading the voltage across shunt resistors likely hits max dynamic range rails during very high current and likely they just pull the plug when it rails for more than a given time length so they don't actually have a short circuit current amperage number limit. This time may be the SCP delay setting and the effective short circuit current limit would be the point where the ADC reading clips at its dynamic range rail which has some variability tolerance from unit to unit.

Don't know when or if I will get a reply but will report on any response from them.