Schneider xw pro 6848 not powering up with eg4 lithium battery

[Mr-Sandman]

I know the directions say turn the batteries on one at a time, but turning on all batteries breakers at the same time would give you a lot more precharge current using all of the batteries resisters instead of just one. Just a thought.

 

[Horsefly]

The battery has a built in pre charge resistor

Yeah I know, but way back several pages in this thread @RCinFLA suggested that likely the battery's pre-charge only works if the power is enabled via the BMS. That would make sense. Otherwise, how would the battery know to use the pre-charge rather than just the direct connection?

 

[Mr-Sandman]

Yes, WE need to understand how the Pre-Charge works on these batteries. I believe that's what causing the issue while starting up the XW. The XW doesn't have a power switch to turn it on, so besides the initial cap charge like all inverters, it starts pulling power to boot up immediately when hooked up. More power than the pre charge resister in the battery is supplying it seems.

 

[MrM1]

Yeah I know, but way back several pages in this thread @RCinFLA suggested that likely the battery's pre-charge only works if the power is enabled via the BMS. That would make sense. Otherwise, how would the battery know to use the pre-charge rather than just the direct connection?

Exactly. I don't know how it knows and that is why some how in that system there seems to be a break down and the battery is not coming out of resistor mode

 

[Horsefly]

Yes, WE need to understand how the Pre-Charge works on these batteries. I believe that's what causing the issue while starting up the XW. The XW doesn't have a power switch to turn it on, so besides the initial cap charge like all inverters, it starts pulling power to boot up immediately when hooked up. More power than the pre charge resister in the inverter is supplying it seems.

Good point. My only experience is with the CSW4024, like @MrM1. Is it safe to assume that the XW also has a standby mode? In the case of the CSW, if you have it in stand-by mode when you turn off the power, when power is restored it will return to standby mode, which would be much less draw than if it was turned fully on. Maybe turning on the power when the Inverter was shut down in standby would work? I know I'm reachin' now.

 

[Koldsimer]

I know the directions say turn the batteries on one at a time, but turning on all batteries breakers at the same time would give you a lot more precharge current using all of the batteries resisters instead of just one. Just a thought.

Definitely tried that as well with no success

 

[Koldsimer]

Good point. My only experience is with the CSW4024, like @MrM1. Is it safe to assume that the XW also has a standby mode? In the case of the CSW, if you have it in stand-by mode when you turn off the power, when power is restored it will return to standby mode, which would be much less draw than if it was turned fully on. Maybe turning on the power when the Inverter was shut down in standby would work? I know I'm reachin' now.

Not a reach at all. Tried that multiple times in different ways. Tried placing system in standby via scp and standby button then restarting. Same issue- clicks and fan pulses. Tried disabling inverter and charger functions in advanced settings (effectively placing inverter in standby) same result.

 

[MrM1]

I just don't think you should have to jump through any hoops to start the XW. IMHO this is a breakdown between the built in BMS and the resistor system

 

[MrM1]

If you were to take battery cable directly off of the cells inside the case from the series end positive, and the series end negative, bypassing the BMS and the resistor I guarantee you the XW would start

 

[Koldsimer]

How does the batteries built in pre charge resistor even work? What makes voltage "decide" to stop flowing thru it. I bet if you opened up the battery and bypassed that resistor they would work

I'm thinking the same thing

 

[Mr-Sandman]

Well the reason the XW isn't starting is confirmed, the battery isn't supplying enough current during startup. The question is why the battery isn't supplying enough current "voltage drop". It's built in Pre-Charge is likely the culprit, we need to learn how it functions since the manual doesn't tell. I would call Signature Solar support in the morning and let them know what you are seeing "Voltage Drop" during startup from their battery and ask them for details on the Pre-Charge.

 

[Mr-Sandman]

I have never looked at the BMS software on these batteries. It's possible, I suppose, there could be a setting for pre-charge time? Lowering that would probably assist in your setup. No idea if that's an option or not, but would nice if it was. We don't even know what triggers it, I would assume breaker turn on with a countdown pre-charge timer, but again just guessing.

 

[Koldsimer]

Well the reason the XW isn't starting is confirmed, the battery isn't supplying enough current during startup. The question is why the battery isn't supplying enough current "voltage drop". It's built in Pre-Charge is likely the culprit, we need to learn how it functions since the manual doesn't tell. I would call Signature Solar support in the morning and let them know what you are seeing "Voltage Drop" during startup from their battery and ask them for details on the Pre-Charge.

Here's my exact email to Signature last thursday. still no response.

�

Koldsimer​	Thu, Dec 30, 2021, 5:33 PM (5 days ago)
to Matt

A knowledgeable guy on diy solar suggested that the bms is sensing a short circuit as the capacitors are loading up on the inverter. Although it's a fraction of a second, the bms senses it and shuts down. That would explain my w48 warnings of low voltage, right?

Can the bms be adjusted to allow for a longer time duration before it shuts off due to a short? I would also think this would be logged in the bms if that's what is happening?

 

[Mr-Sandman]

A knowledgeable guy on diy solar suggested that the bms is sensing a short circuit as the capacitors are loading up on the inverter. Although it's a fraction of a second, the bms senses it and shuts down. That would explain my w48 warnings of low voltage, right?

Can the bms be adjusted to allow for a longer time duration before it shuts off due to a short? I would also think this would be logged in the bms if that's what is happening?

I don't think think it's detecting a short . If it was the battery would shut down. You never lost power, the voltage just dips down.
From the manual on overcurrent protection:

102.0A Trip
10s delay 60s Recover

150.0A Trip
3s delay 60s Recover

Short protection 200.0A Trip
1s delay Manual reset

 

[Hedges]

Ok, so i tried again this afternoon after the firmware update.

With everything off, i switched to the eg4's and still won't start.

With my dvm, i measured 52.8 at the dc breaker before connection. As breaker was switched on, voltage immediately dropped to 13v and slowly (over about 3 seconds) rose to 33-34v and hovered there. Inverter clicked and fan pulsed but nothing would turn on. I considered adjusted inverter minimum input voltage to say 30v but its minimum voltage input is 40v i believe.

System started right back up with fla.

How does the battery behave with a resistive load, no inrush to capacitors?

One or more space heaters in parallel. A 1200W heater at 120V would be 10A, 12 ohms. At 48V, about 4A. If you have several you can load it more heavily.

It is possible BMS is disconnecting due to 1000's of amps inrush. But also possible bad/damaged so can't supply current needed for inverter idle operation.

I earlier proposed that a 100' to 250' coil of romex would make a good precharge resistor. By using two wires white/black out & back, it will be low inductance.

 

[MrM1]

I'd try it

 

[GVSolar]

Late to the party, but afaik, I've seen no mention of using the reset "button" on the Eg4 batteries...

 

[Koldsimer]

Well that video Will just did added to my confusion. So the pre-charge resistor is built in and helps start big inverters huh? My wife started laughing because i was yelling at the computer.

Knowing it already has a resistor built in should i even try the resistor and button idea?

Just spoke with a knowledgeable guy at Schneider and he seemed to understand the issues i am having. He made some suggestions about the startup procedure that I'm going to try later this afternoon.

 

[Horsefly]

Well that video Will just did added to my confusion. So the pre-charge resistor is built in and helps start big inverters huh? My wife started laughing because i was yelling at the computer.

Knowing it already has a resistor built in should i even try the resistor and button idea?

Just spoke with a knowledgeable guy at Schneider and he seemed to understand the issues i am having. He made some suggestions about the startup procedure that I'm going to try later this afternoon.

Like I said yesterday (or was it day before yesterday?), but I'm not sure it got traction: @RCinFLA made a good point early on in this thread. If a battery has a pre-charge resistor, something needs to route the power through the pre-charge resistor before the regular power directly from the battery to the load. Just connecting it to the load (the inverter in this case) doesn't do it. How would the battery know to switch to the pre-charge.

Rather, it seems like the pre-charge must be enabled from the battery itself. That is, the BMS would have to route power through the pre-charge before attempting to connect directly to the load.

Have you tried to have the battery turned off, turn on the main breaker between the inverter and the battery, and THEN turn on the battery? Maybe that forces the connection through the pre-charge before connecting the battery directly to the inverter.

 

[Quattrohead]

So the pre-charge resistor is built in and helps start big inverters huh?

No, the resistor may protect the BMS/batteries from high discharge current when initially connected to an inverter.