Schneider xw pro 6848 not powering up with eg4 lithium battery
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robby
Photon Vampire
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I think Precharge resistors are fine but I just don't like the way it was implemented in the EG4. I appreciate the fact that they were trying to make something that was more automated but it just seems like it did not work out.
If you have not watched the new video that Will posted on the SOK 48v battery you might want to. The way they implemented it is so much better, it is unobtrusive to the operation of the Inverter. You have to press a button if you want it to start charging, if not just throw the switch and done you got full power.
I could kick myself for not waiting on that battery as it is much better build quality than the EG4 and a bonus is the fact that you can remove and replace individual cells and replace them easily. The kicker is that it cost the same price as what I paid for the EG4LL and it has basically the same display.
Hedges: Would a heavier gauge of wire be better in this situation? Like 10g? Just asking out of curiosity.
I'm repeating myself here, but in my opinion, the capacitor pre-charge should be part of the inverter design. In the same way you don't put a soft-starter for the motor you're running on the inverter, but on the actual motor. The device that can cause the issue should do the mitigation of said issue. You can run a motor without soft-starter, just like you can an inverter without pre-charge if you take the precautions you would in either case, but I think this would be a good time for inverter manufacturers to start offering inverters with 'soft-start' capability built in. Doing it on the battery can lead to all kinds of weird compatibility issues and edge cases that cause the pre-charge to be completely ineffective.
Mr-Sandman
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@upnorthandpersonal that makes sense, except in most cases with Lithum batteries with BMS, the Battery is what can't handle the inrush and is damaged if the inverter isn't pre-charged. So they are putting pre-chargers in them to try to protect their BMS and battery, not for the inverter necessarily.
Yes, just like the inverter that won't be able to handle a motor with large inrush. The soft start goes on the motor even tough the motor won't break. Except in this case, it's a far more clear-cut and common problem.
Nope, they don't make these, or even assemble them. They just unload containers of them, shipped from China.
Hedges
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Sure, you could use any gauge, even 4/0 if long enough to provide the desired resistance.
All we need from the inverter is to not turn on immediately. Either manual precharge or BMS doing it, we want capacitors to reach near full voltage and then switch closed for low resistance before inverter starts sucking multiple amps.
The reason inverter can't easily do this is it doesn't have a controlled switch between DC input and capacitors. Some have a breaker built in, some do not.
BMS has FET or relay between cells and battery cables. Simply turning on FETs gradually so they present high resistance (limiting current) and burn off some heat due to voltage drop (as high as 48V or so) times current. Given enough time, that fully charges capacitors in inverter. Trouble is, inverter will likely draw some current for its internal circuitry, so FET (or separately switched precharge resistor) needs to handle that current. Definitely can't have inverter start producing AC until precharge complete and FET on hard or relay closed.
Best design would be BMS performs precharge and communicates to inverter saying when it is OK to turn on.
Specs for Sunny Island are 4W standby, 25W idle. (Of course, if AC loads present and motors being started, could be 11kW)
4W/48V = 83 mA. Sunny Island powers up in Standby, until you press and hold button to start.
25W/48V = 0.52A, this is what it would draw if AC loads were disconnected and inverter started the moment voltage appeared.
(Problem with other inverters is likely that they power up when DC appears.)
For this inverter, need to design for 83 mA.
Using a wire for precharge resistor, could be a length of telephone or LAN wire, enough for a few ohms or a fraction of an ohm.
That wouldn't be able to power inverter if it turned on before you closed the switch.
Using 12 awg or something larger, enough for about 0.5 ohms, could power inverter up to a few amps (couple hundred watts) with a few volts drop. If switch closed with a few amps and a few volts across it, small inrush. Best to close before that happens.
Don't use a coil of single wire, that is inductance. A coil of 2-wire cable is fine, with the two wires joined at end; current flows out one way through coil and back the other way, cancelling magnetic field and inductance.
Mr-Sandman
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None of us knows how the EG4 battery pre-charge works exactly.
Signature Solar told us early in this thread it's timer based, but we don't know how long, how much pre-charge current is supplied, when it activates "breaker on?" etc.. The manual makes me scratch my head even more, as it's startup procedure for them says to turn all your batteries on one by one, THEN turn your inverter on.. That seems like it would defeat the pre-charge timer completely turning the batteries on first then closing a breaker on your inverter.
For my EG4LL batteries with my Schneider XW Pro 6848, I powered the battery BMS up with the small switch, then closed the breaker on the battery. The inverter instantly jumped to life and worked. Did it pre-charge it any or just give her full power? Who knows, but it worked that one time....
Signature Solar isn't doing themselves or us any favors by not publishing detailed information on how their pre-charge circuit works. It should be documented in the manuals.
Signature Solar told us early in this thread it's timer based, but we don't know how long, how much pre-charge current is supplied, when it activates "breaker on?" etc.. The manual makes me scratch my head even more, as it's startup procedure for them says to turn all your batteries on one by one, THEN turn your inverter on.. That seems like it would defeat the pre-charge timer completely turning the batteries on first then closing a breaker on your inverter.
For my EG4LL batteries with my Schneider XW Pro 6848, I powered the battery BMS up with the small switch, then closed the breaker on the battery. The inverter instantly jumped to life and worked. Did it pre-charge it any or just give her full power? Who knows, but it worked that one time....
Signature Solar isn't doing themselves or us any favors by not publishing detailed information on how their pre-charge circuit works. It should be documented in the manuals.
Quattrohead
Solar Wizard
My theory is 2 different types of inverter, 1 that will run without a battery and 1 that must have a battery.
Let's take our much talked about SPF 5000 ES. It can run without a battery so it must generate the 48V from the AC power. It can control how quick this power supply can ramp up from zero to 48V. All is well when you connect a battery as the capacitors are already charged.
Now looking at the SPF 6000T, it needs a battery connected before it will do anything. Capacitors need to charge from the battery and suck a huge amount of power to do so.
In either case, it does not matter if the inverter is producing output right away or not. In fact neither do but that is not part of the problem.
SpongeboB Sinewave
Solar Enthusiast
Well, at least they do have a real electronics engineer on staff. Hopefully he might be able to find something that can help. I know they really want to get this stuff to work well.
Evidently this problem is not a small one in the industry !
I have the xw6848 with LiFE batteries individually.
This allows me to up the system to 17 cells. Normally 57.0 vdc.
Never had a power up issue. My JKBMS does not have a contactor to break the circuit.
Automation read the JKBMS data about individual cell voltages. And when one cell goes above 3.65 volts it reduces the charge current from the XW6848. Using ModBus to achieve that control on port 502 on the XW gateway. Works like a charm.
This allows me to up the system to 17 cells. Normally 57.0 vdc.
Never had a power up issue. My JKBMS does not have a contactor to break the circuit.
Automation read the JKBMS data about individual cell voltages. And when one cell goes above 3.65 volts it reduces the charge current from the XW6848. Using ModBus to achieve that control on port 502 on the XW gateway. Works like a charm.
At 38 degrees and colder I reduce Charge Max to the XW6848 to limit to 50 watts. Normally charge max is 2500 watts for me. Batts are 280 ah Eve cells.
I'd simply put a voltmeter at the DC terminals on the inverter and SEE what happens at the instant of turn on.
My best suspect is the BMS relay at turn on.
I do the gateway from S/E and XanBus to xw6848. Modbus works thru port 502 on the LAN. My JKBMS is bluetooth, That reading comes from a raspberry pi zero to the wifi LAN.
Mr-Sandman
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I have the Schneider Gateway also, hooked to my XW Pro 6848 and MPPT 60 via Xanbus. That all communicates well. I know the gateway has RS485 and supports modbus, but my understanding is the EG4 batteries do not communicate with it for whatever reason. It would be great if they did or if there was way to facilitate that. Having SOC controls in the XW would help.
SpongeboB Sinewave
Solar Enthusiast
So, what "standard" are you guys using to talk with all of these lithium BMS's from invertter/chargers ?
MrM1
I'm Here, But I'm Not All There
English? I mean seriously, who needs their anything (mppt) to talk in French?
SpongeboB Sinewave
Solar Enthusiast
English? I mean seriously, who needs their anything (mppt) to talk in French?
Pardon my French, MrM1 ! ??
CANBUS or RS-485 most likely
Seriously, people ask about "closed-loop" charging from inverters and chargers etc...
I think that doing that is not as easy as it seems to do with all of the different systems out there.
Not yet at least ?
I'm sure S/E makes backroom deals with the battery system manuf. S/E won't step on their toes and vice-versa. So the customer is left without solutions without lots of $$$ spent
Mr-Sandman
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Unfortunately, looking at how the BMS communication is selected from a specific list of batteries in the XW Insight Home and not a more generic communication like used by other inverters, make me think you are right. I'm not going to hold my breath, but it would be in BOTH their best interest to be communicate with each other.
Hedges
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Beats me, but here's a list of some dozens of batteries that speak a common language:
Mr-Sandman
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In the AltE Schneider XW Webinar today I asked Schneider about support for more batteries in closed loop RS-485 or CanBus, such as the Signature Solar EG4 batteries and other with similar BMS. It was clear by his answer, they only plan on supporting batteries with "mutual interest". He said that they have a list of batteries they support and referred to a few brands that support closed loop communication currently. No real road map to others mentioned.
That's really too bad, the technology for this to work is in place in both the EG4 batteries and XW Pro inverters. It would probably take effort on Signature Solars part to get Schneider interested in supporting their batteries. Not holding my breath.
Really all we need from the EG4 batteries is SOC, everything else we already have or can manually plug in. So simple, yet so hard.
That's really too bad, the technology for this to work is in place in both the EG4 batteries and XW Pro inverters. It would probably take effort on Signature Solars part to get Schneider interested in supporting their batteries. Not holding my breath.
Really all we need from the EG4 batteries is SOC, everything else we already have or can manually plug in. So simple, yet so hard.
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MrM1
I'm Here, But I'm Not All There
I'd like to say I am shocked, but this is what I said early on in this thread.
That's Schneider for you. They really don't want to deal with DIY people if they don't have to.
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