Jk discharge short circuit help please

[6yolithium]

Hi, I have two 24v 280 amp batteries made up of 8 lifepo4 EVE cells each.
A JK BMS for each one. They have been running flawlessly for 73 and 85 days respectively.

They are paralleled to a Magnum 4024 PAE inverter and charge from two Midnite Classic 150s. A system that's been fine for over 10 years. Just these batteries and BMSs are new.

We've had some weather, and the batteries were low enough that with another cloudy day today I turned off the discharge on each bms since we were going to be gone a few hours.
I have turned off discharge on them before for just a few minutes out of curiosity before and they turned right back on when asked.

It ended up I was gone over 12 hours with my hubby in the hospital being checked for a stroke...
When I got home tonight I tried to turn the BMSs back on and got "Protection(Discharge Short Circuit)" on the app and they count down from 60 seconds to 0 then the countdown starts again...

Is there something I'm supposed to do during that countdown to get them to turn on again?? I'm sitting here with a lantern posting from my phone...
I did go out to the power shed and turned them both off with the button that powers them on and off. Turned them back on, but no joy. The message on the app remains. Discharge remains off on the app. and batteries.

 

[Crowz]

It sounds like its overloading trying to charge the inverter back up. You need to use a resistor to apply power back to the inverter to get it charged up so it won't overload the batteries bms when you turn the battery on. A pencil can be used to do that by disconnecting the positive lead on the battery cable that goes to the inverter and putting the pencil (with both ends shaved to allow access to the core of the pencil of course) between the cable and the post on the battery after turning the bms back on first. This will make a small spark and not overload the bms.

After this is done reconnect the battery cable back to the battery fairly fast. It would also be a good idea to turn off the inverter before doing any of this to keep it from adding load to the problem.

 

[6yolithium]

Thanks for your reply.
The batteries are at about 37% and the inverter had shut itself off because it was so cloudy all day. No incoming current.
So they weren't trying to start it up...

The inverter has never needed a "precharge" before, even the first time it was commissioned.

This morning I have turned off the solar panel breakers so there is zero power coming in. It's a nice sunny day, with lots of cloudy days ahead of us.

If I can't get the BMSs to work I'll have to disconnect them soon and let the batteries charge up without them...

 

[6yolithium]

Ok, back to the hospital, it's 70 miles away, so this will have to wait... until I get back.
Crowd, I appreciate your reply. I will try it later, BUT the inverter was off so i'm not sure it's applicable.

 

[Brucey]

Good luck with the hubby.

 

[Crowz]

Ok, back to the hospital, it's 70 miles away, so this will have to wait... until I get back.
Crowd, I appreciate your reply. I will try it later, BUT the inverter was off so i'm not sure it's applicable.

Even with it running it doesn't keep it charged on the battery side and since its a low frequency inverter there is a heck of a large draw when the battery is connected to it after battery power hasn't been sent to it in a long time. If you had lead acid batteries before the lifepo4 batteries you have now they would of fed it fine to get it going and you probably switched out the lead to lifepo4 fast enough to keep the inverter from completely discharging. By turning off the batteries like you did it had time to completely discharge before you turned them back on.

This is all guesswork without being there but its completely possible under those conditions.

 

[SparkyJJO]

I'm thinking it is inrush current too.

 

[6yolithium]

Even with it running it doesn't keep it charged on the battery side and since its a low frequency inverter there is a heck of a large draw when the battery is connected to it after battery power hasn't been sent to it in a long time. If you had lead acid batteries before the lifepo4 batteries you have now they would of fed it fine to get it going and you probably switched out the lead to lifepo4 fast enough to keep the inverter from completely discharging. By turning off the batteries like you did it had time to completely discharge before you turned them back on.

This is all guesswork without being there but its completely possible under those conditions.

Ok Crowz, I'm eating crow!
You were right.
Yesterday morning, I still had my older lifepo4 battery in the power shed so hooked it up to the 4 prong battery busbar after making sure the BMSs were off, and started up the inverter. Then I turned on the BMSs and viola! The short circuit messages were "poof!".
Except for massively cloudy weather, everything is back to normal, in clouding hubby back from the hospital.

Thank you very much!

 

[Crowz]

Ok Crowz, I'm eating crow!
You were right.
Yesterday morning, I still had my older lifepo4 battery in the power shed so hooked it up to the 4 prong battery busbar after making sure the BMSs were off, and started up the inverter. Then I turned on the BMSs and viola! The short circuit messages were "poof!".
Except for massively cloudy weather, everything is back to normal, in clouding hubby back from the hospital.

Thank you very much!

Your welcome and soooo happy its back working for you !

 

[OffGridIdaho]

My fix.........

Shut down for 30 minutes to clean the inside of the inverter (dust)
Turned JK BMS back on and instantly get the short circuit protection fault.
Went into advanced password settings and turned off discharge slider in the bms.
SCP counts down from 60 seconds and doesnt blow another error.
Turned on discharge slider and BAM SCP blows again.
OK I think I have this figured out.

30 minutes down time was enough to drain the caps on the inverter (see where Im going?)
Turned slider for discharge off again. BMS reset to GTG at T MINUS 60 seconds and its happy.
Flipped main breaker to inverter OFF, turned slider inside jk bms to on or discharge again, no error.
Sooooo I took a small wire and ran it from the neg side of the battery (not other side of neg bms) to the neg terminal of inverter. FLASH-SPARK it starts charging caps slowly. Slow enough not to have a huge in-rush and trip SCP in the jk bms.
I wait 60 seconds and remove wire and re-touch, no spark. I quickly flip the breaker back on ito the inverter
AND HOLY FLEEPIN BATMAN it doesnt blow the SCP error.

It was the massive in-rush to the inverter caps blowing the SCP fuse inside the jk bms.

 

[Brucey]

I was reading where some use solar to precharge the capacitors before connecting the batteries. Assuming it's daylight and producing of course.