JK-PB2A16S-20P BMS overloading at inverter startup

[PeteDD]

New 320Ah Yixiang battery system with JK-PB2A16S-20P BMS "Inverter BMS"
Sometimes when starting the inverter, I get an immediate short circuit protection cut out. This is with no load connected to the inverter so I can only conclude that this must be caused by an inrush current to charge the inverter's capacitors. (The inverter has no difficulty starting up using AC instead of the battery). The battery is well-charged. My understanding is that the JK Inverter BMS should be able to detect the difference between a true short circuit and charging the capacitors (reference a video about all the settings of the JK Inverter BMS where that is mentioned). Here are some of the key settings of the inverter:

SCP Delay: 1500 us
SCPR Time: 5 seconds NOTE: Discharge Connect is staying disconnected
Continued Discharge Current: 200.0 amp
Discharge OCP Delay: 300 s
Discharge OCPR Time 60s
Cell UVP 2.580 V

Anyone seen this issue. Any suggestions on how to eliminate this problem?

Thanks! Appreciate your experience.

​

 

[agtcovert]

Hi,

Yes I've seen this before. How many batteries do you have? Just a single one?

On the rare occasions I need to shut down for some maintenance, my startup process is along the lines of:

• Close breaker between battery bus bars and device bus bars (I have Victron Lynx power ins + and Lynx Distributors with a 400A breaker on the positive.
• Start inverters with AC power first
• Close PV circuit breakers (this is how mine's set up, each string has a breaker on it for easy disconnect inside my house)
• If BMSes have been turned off, turn on BMS
• Close each battery's breaker
• Wait for inverters to sync / switch into inverting mode
• Switch manual transfer switch into inverter/solar mode
• Profit

I've still had a couple cases where the main system breaker (400A) will trip with the inrush. Likely could be avoided by putting a precharge resistor in place, but resetting the breaker is all that's necessary. With a single battery's breaker closed, I've also had the BMS temporarily go into OCP. Turning on the additional batteries (I have 5 total) clears the BMS OCP.

There's probably a better way to do it, but it does happen, especially with only 1-2 batteries. It's a lot of current in a short time period. It's so rare I need to do this, for me, finding a solution isn't worth it.

 

[1234enough]

How about trying a pre-charge circuit, easy to implement with resistor and push button switch. Simply push button in to precharge inverter before main battery isolator is closed.

 

[Sleeper85]

New 320Ah Yixiang battery system with JK-PB2A16S-20P BMS "Inverter BMS"
Sometimes when starting the inverter, I get an immediate short circuit protection cut out. This is with no load connected to the inverter so I can only conclude that this must be caused by an inrush current to charge the inverter's capacitors. (The inverter has no difficulty starting up using AC instead of the battery). The battery is well-charged. My understanding is that the JK Inverter BMS should be able to detect the difference between a true short circuit and charging the capacitors (reference a video about all the settings of the JK Inverter BMS where that is mentioned). Here are some of the key settings of the inverter:

SCP Delay: 1500 us
SCPR Time: 5 seconds NOTE: Discharge Connect is staying disconnected
Continued Discharge Current: 200.0 amp
Discharge OCP Delay: 300 s
Discharge OCPR Time 60s
Cell UVP 2.580 V

Anyone seen this issue. Any suggestions on how to eliminate this problem?

Thanks! Appreciate your experience.

​

Increase SCP delay value to 3000us.

 

[HRTKD]

I have a Quattro 48/3000 and the JK-PB2A16S-20P. My inverter will start from compete DC disconnect, but I can hear the BMS complaining. It also blew the fuse the first time I tried it.

I installed a pre-charge circuit to handle inverter startup from complete DC disconnect. It's an extra step, but it works and my BMS doesn't complain.

 

[Aussie]

Could you explain how you designed and installed your pre-charge circuit. Thanks

 

[HRTKD]

Could you explain how you designed and installed your pre-charge circuit. Thanks

48 volt fork lift bulb in a 48 volt fork lift bulb socket. Insert the bulb until it mostly goes out and the inverter capacitors are charged, then pull the bulb out.

I really don't like inserting the bulb, nor having to store the damn thing. So eventually I'll put a switch into that circuit and leave the bulb permanently in the socket.

 

[pete75]

What kind of precharge switches do you have? I have resistor,but i need push button that will handle over 58v. Pics of your systems?

 

[mikeenea]

No trying to hijack the post but have a pre-charge question.

If I take a small power supply connected to my battery buss bar and go through the whole start up procedure of turn on the inverter battery breaker then turn on the power supply say set for 5 amps at the same nominal voltage of my batteries -- after a couple of minutes of the power supply at 5 amps would that suffice to pre-charge the inverters capacitors. Could I then proceed with turning on each battery without causing a SCP fault?

Thanks

 

[HRTKD]

What kind of precharge switches do you have? I have resistor,but i need push button that will handle over 58v. Pics of your systems?

No switch yet. I plug the bulb into the socket when I need the pre-charge. Remove the bulb when the pre-charge is complete.

If I take a small power supply connected to my battery buss bar and go through the whole start up procedure of turn on the inverter battery breaker then turn on the power supply say set for 5 amps at the same nominal voltage of my batteries -- after a couple of minutes of the power supply at 5 amps would that suffice to pre-charge the inverters capacitors. Could I then proceed with turning on each battery without causing a SCP fault?

That should work. My pre-charge takes seconds, not minutes.