Overkill BMS trips with 2 inverters

[Flip]

Hey y'all. So I'm attempting to wire a second inverter to my system (24v, 300ah, Lifepo4 Fortune cells, Overkill 24V 100A BMS). When I hook both inverters to the bus bars and flip the breaker back on the BMS discharge protection trips and reads short circuit. If I hook the inverters up individually and flip the breaker, it's fine. If I hook one inverter up with the breaker off and hook the other inverter up after I flip the breaker back on, it's fine, however, if I flip the breaker off and on again it trips short circuit again. I have to believe it's a setting in the BMS that's causing this, but I don't know which one or why.
Does anyone have any experience with this issue? Is there something I'm doing wrong? Thanks in advance!

 

[Supervstech]

Odd indeed.
What size inverters?
How long does the pair need to be connected with the breaker off before tripping when resetting?
Likely has to do with capacitor discharge.
Inverters have HUGE momentary draw when first hooked up.

 

[grizzzman]

Hey y'all. So I'm attempting to wire a second inverter to my system (24v, 300ah, Lifepo4 Fortune cells, Overkill 24V 100A BMS). When I hook both inverters to the bus bars and flip the breaker back on the BMS discharge protection trips and reads short circuit. If I hook the inverters up individually and flip the breaker, it's fine. If I hook one inverter up with the breaker off and hook the other inverter up after I flip the breaker back on, it's fine, however, if I flip the breaker off and on again it trips short circuit again. I have to believe it's a setting in the BMS that's causing this, but I don't know which one or why.
Does anyone have any experience with this issue? Is there something I'm doing wrong? Thanks in advance!

Have you tried to precharge the capacitors in the inverters first?

 

[Flip]

Odd indeed.
What size inverters?
How long does the pair need to be connected with the breaker off before tripping when resetting?
Likely has to do with capacitor discharge.
Inverters have HUGE momentary draw when first hooked up.

2000W and 3000W. The BMS trips instantly when I flip the breaker.

Have you tried to precharge the capacitors in the inverters first?

I did hook each inverter up individually and leave it sit for a few thinking what you're thinking. I made sure to reconnect without shorting/discharging the capacitors and still had the same result.

 

[Flip]

The reason for the second inverter is when the solar fully charges the batteries, the BMS shuts down both charge and discharge hence turning off power to my house as long as the sun stays out. The second inverter will be wired to a relay driver and dump the excess power into ceiling fans or an ac unit or something that consumes a good bit of juice.

 

[Flip]

I'm starting to think this BMS isn't all its cracked up to be. It shuts down both charge and discharge when undervoltage is tripped so I have to change the settings in the app in order to charge them. It shuts down both charge and discharge when overvoltage is tripped which shuts off my house power. I figured as expensive and highly rated as this BMS is that it would be smart enough to let it charge in an undervoltage situation and let it discharge in an overvoltage situation. Or, maybe it does all those things and I'm the not so smart one.

 

[Bud Martin]

So when the BMS tripped, are the power switches on the inverter are set to ON? What happen if they are set to off?

 

[Flip]

So when the BMS tripped, are the power switches on the inverter are set to ON? What happen if they are set to off?

Both inverters are off with no loads connected when I flip the main breaker back on. The BMS still reads short circuit instantly.

 

[John Frum]

Does the bms trip on the 3000 watt inverter by itself?

 

[John Frum]

supposedly you can prime the caps with an old style incandescent light bulb.

 

[squowse]

I'm starting to think this BMS isn't all its cracked up to be. It shuts down both charge and discharge when undervoltage is tripped so I have to change the settings in the app in order to charge them. It shuts down both charge and discharge when overvoltage is tripped which shuts off my house power. I figured as expensive and highly rated as this BMS is that it would be smart enough to let it charge in an undervoltage situation and let it discharge in an overvoltage situation. Or, maybe it does all those things and I'm the not so smart one.

When you apply voltage from a charger it should release the under voltage cut out?

 

[grizzzman]

The reason for the second inverter is when the solar fully charges the batteries, the BMS shuts down both charge and discharge hence turning off power to my house as long as the sun stays out. The second inverter will be wired to a relay driver and dump the excess power into ceiling fans or an ac unit or something that consumes a good bit of juice.

So your saying that when the battery is full Discharge is disabled?

 

[Flip]

Does the bms trip on the 3000 watt inverter by itself?

No it doesn't. I can connect either one by itself fine. I can connect them both as long as the breaker is on first. I get a little spark like hooking up a car battery, but then it pushes both inverters just fine. But the fact that the breaker won't turn them both back on makes me think something isn't right/safe.

 

[Flip]

supposedly you can prime the caps with an old style incandescent light bulb.

So the caps won't prime by simply being connected to power? I need to run load through it first? I did not try that.

 

[Flip]

When you apply voltage from a charger it should release the under voltage cut out?

You would think, but it doesn't. I have to turn on the generator, plug in the charger, turn it on then go in the app and lower the undervoltage setting before it will let the charger work.

 

[Flip]

So your saying that when the battery is full Discharge is disabled?

That's correct. Overvoltage and undervoltage protection cut the batteries off completely.

 

[Flip]

Here's my parameters in case anyone can spot an obvious issue.

 

[grizzzman]

Here's my parameters in case anyone can spot an obvious issue.
View attachment 40863

to blurry for me to read.

 

[grizzzman]

So why is the BMS going over voltage. It should just shut down charging while allowing discharge otherwise there is no point to a seperate port for charge and discharge.

 

[John Frum]

So the caps won't prime by simply being connected to power? I need to run load through it first? I did not try that.

The caps will prime as long as the bms doesn't trip.
Caps draw a huge current for a small amount of time.
This looks like a short circuit to the bms.