Why is my LiFePO4 going into protect mode when I turn on the DC breaker?

[corn18]

I installed a SOK 206 Ah LiFePO4 (LFP) a while back and it worked great. I had used cheapo cutoff switches and circuit breakers, so I swapped those out for the good stuff. Specifically, I replaced the generic battery cutoff switch and 100A circuit breaker coming from the battery with a Blue Sea 3 pole 250A circuit breaker that I also use as a switch.

The issue since the upgrade is that my LFP goes into protect mode when I flip on the breaker (nothing is on but the propane detector). The power comes on for a moment, and then cuts off and the battery is in protect mode. The only way to get it out of protect mode is to unhook the negative terminal from the battery and hook it back up. That's a pain. Interestingly, once I do that, everything works fine. I can flip the master breaker as many times as I want and the power cycles fine without the BMS going into protect mode.

If I leave the system off for a while and turn it back on with the breaker, the same thing happens again.

If I leave the system off for a while but disconnect the converter before I turn the system on (via its circuit breaker), the BMS does not go into protect mode. All works fine. I can turn it off and on without issue. The converter is a Progressive Dynamics 9160ALV made specifically for LFP duty. If I turn the converter on after I turn the main 250A breaker on, all works fine. Hmmmmm....

I cannot figure out what is causing the BMS to go into protect mode if the converter is connected.

Any ideas?

Here's my wiring diagram:

[Argosy]

Still got the cheapo switch you took out laying around? Put it back in the circuit and see if it works OK again.

[Bobby F]

Are you plugged into shore power when this happens?

[corn18]

Originally Posted by Bobby F

Are you plugged into shore power when this happens?

Negative.

[corn18]

Originally Posted by Argosy

Still got the cheapo switch you took out laying around? Put it back in the circuit and see if it works OK again.

I may have to do that.

[Bobby F]

Originally Posted by corn18

Negative.

(Sorry, this probably isn't going to help you much, but it's for my own confusion):



Then what's powering the converter? (You said you turn it off and on, so I assume it has power.)

[corn18]

Originally Posted by Bobby F

(Sorry, this probably isn't going to help you much, but it's for my own confusion):



Then what's powering the converter? (You said you turn it off and on, so I assume it has power.)

I think the converter bit may be a red herring. I think the inverter caps inrush current is triggering the BMS. Apparently they suck a lot of power on initial power up. And I have 3000W of inverter hooked to a 100A max BMS.

Weird that it worked with the cheap CB and cutoff switch.

I think once I add the second LFP (on the way) and hook up the solar (in work), the inverter caps won't be an issue. I hope.

[Jon_C]

Originally Posted by corn18

I think the converter bit may be a red herring. I think the inverter caps inrush current is triggering the BMS. Apparently they suck a lot of power on initial power up. And I have 3000W of inverter hooked to a 100A max BMS.

Weird that it worked with the cheap CB and cutoff switch.

I think once I add the second LFP (on the way) and hook up the solar (in work), the inverter caps won't be an issue. I hope.

^^^^ I had same intermittent issue with a victron multiplus 3000 causng 2 Battleborns to go to protect - inrush current to caps, had to add a 3rd battery to make it work. Maybe the cheapo switch is not allowing enough current to get thru whereas the Blue sea is…

[corn18]

Originally Posted by Jon_C

^^^^ I had same intermittent issue with a victron multiplus 3000 causng 2 Battleborns to go to protect - inrush current to caps, had to add a 3rd battery to make it work. Maybe the cheapo switch is not allowing enough current to get thru whereas the Blue sea is…

I think that might be it.

[Bobby F]

I do know that I was told to charge the inverter capacitors through a resistor on initial startup for this same reason.


(Here it is:

https://www.youtube.com/watch?v=ZlrtmJRfSP8

)

[corn18]

@Bobby F, you called it.

I added a precharge circuit for the inverters. It's a 6 ohm 50W resistor wired to a momentary horn button between the + battery terminal and the + bus that feeds the inverters. Hooked it up. Pressed the horn button for 1 sec and flipped on the main breaker. Worked like a champ.

I'm sure there is a more elegant solution, but I need to go camping on Thurs. Looks silly having that 14ga wire running around all that 4/0 cable, doesn't it? I'll see what else is out there, but this works.

[Bobby F]

Good. It wasn't that big a deal on my AGM's, but it sounds damaging with a BMS.


(P.S. Silly? Rather elegant and simple.)

[JHinman]

Originally Posted by Jon_C

^^^^ I had same intermittent issue with a victron multiplus 3000 causng 2 Battleborns to go to protect - inrush current to caps, had to add a 3rd battery to make it work. Maybe the cheapo switch is not allowing enough current to get thru whereas the Blue sea is…

What wire size did you use when you had that issue?

I have a 3Kw Multiplus and two Battleborne 100Ah batteries. I was planning to use 4/0 wire, but the Battleborne rep recommended using smaller wire to minimize the inrush current. I wired it up with 1/0 and it works.

I’m giving some thought to adding a battery and upsizing to 4/0 wire. Maybe the system will charge faster - I get about 75 amps using a Honda 2000.

[Jon_C]

Originally Posted by JHinman

What wire size did you use when you had that issue?

I have a 3Kw Multiplus and two Battleborne 100Ah batteries. I was planning to use 4/0 wire, but the Battleborne rep recommended using smaller wire to minimize the inrush current. I wired it up with 1/0 and it works.

I’m giving some thought to adding a battery and upsizing to 4/0 wire. Maybe the system will charge faster - I get about 75 amps using a Honda 2000.

4/0 wire