XW6848 charge rate apparent failure

[MarkNiwot]

My Schneider XW6848 has started to fail to charge the batteries other than at VERY low (and perhaps dropping) charge rate/current. It t has been in place for over a year, all seasons, with no configuration or hardware changes - until the last few days of debug.

Generator (8kW Generac) output, frequency, voltage all look fine. (I don't have a scope on it, but my older Trace inverter works as always from the same source.)

I've watched the sequence dozens of times by now, at different states of charge. It sees AC input when I start the generator, does AC qualification, then flags it as OK, and switches to Bulk mode. The main display goes briefly to '----' and the charge relay picks, after which the generator starts to load up, and the display ramps up the charge current - until it drops the relay. No indication of why on anything I can see (we are VERY 'off-grid; there is no web GUI connection.) Then the cycle repeats.

If I drop the max charge rate low enough (now down to abut 10%, of 400 Ah; house load varies, but is less than 1 kW most of the time I've done the testing) I can keep it on-line and charging - very slowly. Any attempt to ramp it up above that level, 1% at a time, will trip the failure.Initially, I suspected a software issue, but I am beginning to think a hardware failure occurred.

The primary indication I have there is the main display battery 'SOC' indicator - which never shows below 3/4 - even when I see the individual LiFePO4 battery displays show levels below 50% (and much lower than I want to normally allow.)

Is it likely (since I don't know the software internals) that the charger is trying to avoid charging batteries that it mistakenly thinks don't need it? (There is no external shunt, battery voltages on the displays are all consistent, and track the apparently correct SOC.)

Any ideas appreciated. I'm not anxious to pull that thing down. (But I can pull the cables and do some probing, if appropriate.)

 

[BentleyJ]

Do you have System Control Panel or ComBox so the AC2 settings and Gen Support Amps can be reviewed? Web access is not necessary as you can login to the ComBox directly on a home network.

 

[hwy17]

The main display goes briefly to '----' and the charge relay picks, after which the generator starts to load up, and the display ramps up the charge current - until it drops the relay. No indication of why on anything I can see (we are VERY 'off-grid; there is no web GUI connection.) Then the cycle repeats.

This symptom description would imply that the inverter is disqualifying the AC generator input for some reason.

I do wonder from your other descriptions what your charge settings are. But the cyclical problem there does sound like disqualification as the main suspect.

Disqualification can be caused by voltage or frequency issues.

 

[MarkNiwot]

Do you have System Control Panel or ComBox so the AC2 settings and Gen Support Amps can be reviewed? Web access is not necessary as you can login to the ComBox directly on a home network.

No - this unit was part of a warranty replacement (used equipment) - so I don't have the com box, but I do have the small SCP and have used that for what metering it will do.

 

[MarkNiwot]

This symptom description would imply that the inverter is disqualifying the AC generator input for some reason.

I do wonder from your other descriptions what your charge settings are. But the cyclical problem there does sound like disqualification as the main suspect.

Disqualification can be caused by voltage or frequency issues.

That was what I thought at first, and for several days of debug. But I don't see either, even when I pre-load the generator (with another charge load.) It does happen only under load, as the unit ramps up, and the suspicious indicator is that the battery SOC indicator (on the main unit) is WAY (reading very high) off. And when it DOES drop out, the load just isn't that great. I wish I could set a 'ramp up' parameter to allow it to load up the generator more gently so I could watch what happens.

 

[hwy17]

Can you get some screenshots of settings? Do you use the SCP, or Combox, or Insight controller?

AC settings, charger configuration settings, and a live view of the XW status page while the generator is running would be helpful.

Like the screenshots in this thread for a similar issue: https://forum.solar-electric.com/di...-xw6848-inverter-wont-qualify-generator-input

 

[MarkNiwot]

The GUI output is definitely nicer than what I have available; I can't see some of the internal settings (and have to trust the manual for the defaults; min and max freq limits, for example, which are WAY wider than anything I've seen - 59 Hz to 62.1 Hz is the most I've seen under under any conditions. But it won't show me transients.)

It's AC2 only (way off-grid here) and again, the default limits have worked fine until recently. I'll have to copy some of the other items manually, or just take a photo of the SCP (which has a small display, and will only meter a few at a time.)

PS> I don't see any warnings or errors ever during the cycling. I wish it would say WHY it DQs!

 

[dougbert]

What is the Total Harmonic Distortion of that genny? Bad THD can hurt these newer inverters, including the XW

I use older gennys but through a Chargeverter. Once I learned about THD I decided NOT to use my XW Pro's charger. Rather I charge either from grid or genny through the CV

just a thought for you

THD Meters are $500

 

[hwy17]

You only have the SCP? Might be worth it to upgrade to the Insight now. Signature solar has the best price on it.

 

[MarkNiwot]

What is the Total Harmonic Distortion of that genny? Bad THD can hurt these newer inverters, including the XW

I use older gennys but through a Chargeverter. Once I learned about THD I decided NOT to use my XW Pro's charge. Rather I charge either from grid or genny through the CV

just a thought for you

THD Meters are $500

It's an 8 kW General PowerPact, about 2 years old - but other than what is claimed, I don't know, and can't measure.

I did consider the EG4 Chargeverter, though, and had just decided to order one of those. It will make a nice backup either way, and I intend to install a spare LP generator before fall. Thanks.

 

[BentleyJ]

While its true the SCP is limited to displaying only one menu item at a time, it does have the ability to interact with most of the available settings. Its a "long shot" but I was thinking its possible some of the default settings may have changed. It wouldn't be the first time it happened. I recently had a situation where the password in the ComBox got corrupted or changed somehow but after a factory reset and re-entering the password the unit responded normally and was not damaged in any way yet the password just quit working.

Would recommend you work your way through the settings using the SCP and see what they are.

 

[MarkNiwot]

While its true the SCP is limited to displaying only one menu item at a time, it does have the ability to interact with most of the available settings. Its a "long shot" but I was thinking its possible some of the default settings may have changed. It wouldn't be the first time it happened. I recently had a situation where the password in the ComBox got corrupted or changed somehow but after a factory reset and re-entering the password the unit responded normally and was not damaged in any way yet the password just quit working.

Would recommend you work your way through the settings using the SCP and see what they are.

Thanks - I tried that, but have found that only SOME of them seem accesible that way; others I can't access or confirm. Any ideas?

 

[BentleyJ]

Thanks - I tried that, but have found that only SOME of them seem accesible that way; others I can't access or confirm. Any ideas?

Do you have the XW Pro, XW+ or older XW model? I have the XW+ and have found the SCP is fully compatible with all the set up menus (albeit, clumsy) but the XW Pro is only partially compatible. If you have the XW Pro, I would recommend getting the InsightHome or perhaps a used Gateway or InsightHome if you can find one on ebay for a good price.

There is also a Conext Configuration Tool that installers use but that costs even more than InsightHome.

 

[MarkNiwot]

Do you have the XW Pro, XW+ or older XW model?

It's the XW+.

 

[MarkNiwot]

This would have been SO much easier if the XW+ would just flag a warning when it disqualifies the input voltage as to WHY!!!

AC settings, charger configuration settings, and a live view of the XW status page while the generator is running would be helpful.

While I can't readily do that without a connection to the charger - did try to just take some pix while it cycled and tried to load up. EVENTUALLY I 'caught it in the act' - and was able to confirm what I at first did not believe:

The XW+ shows the generator output voltage INCREASING UNDER LOAD! And - while it never flagged an error, that seems to be why it drops.

Eventually, after changing screens more times than I can count, I saw this:
AC2 in L1 -5.5A 138V (!)
AC2 in L2 -9.9A 135V

That was at only a 7% charge rate on the generator (any higher charge, the voltage goes still higher - and it trips off.)

My immediate first thought was to blame the Generac (It's less than 2 yrs old, and has failed three expensive times in less than 150 hrs. I'll never buy another!!) But there's no mention in their "manual" about any adjustment of generator output.

But wait - I had already tested the generator with the old Trace 4024 system, and it qualified and charged fine.

So I loaded up the generator with about the same charge output to another system, and then checked what the XW+ thought of that:
(It consistently sees 120V on both legs, BTW, during AC qualification, and under 'no load'. And the input freq stays at 60 Hz +/- 1)
AC2 in L1 0.0A 117V
AC2 in L2 0.0A 123V
AC2 Freq 60.9 Hz

So there actually seems to be some kind of load interaction with the charger.

 

[hwy17]

I would next try to watch it with a multimeter while it's doing the overvoltage thing, to see if you can confirm what the XW is reporting.

On the gen AC terminals in the XW, or at the generator, or anywhere in between.

 

[hwy17]

This would have been SO much easier if the XW+ would just flag a warning when it disqualifies the input voltage as to WHY!!!

That may be the kind of history that an Insight controller would give you but idk, I've never used a generator input on mine.

 

[MarkNiwot]

PS> So I went to look for some kind of line, ground, or neutral fault to the inputs - but so far I don't see anything suspicious.

 

[hwy17]

PS> So I went to look for some kind of line, ground, or neutral fault to the inputs - but so far I don't see anything suspicious.

Yeah I thought of an open neutral but that would normally cause imbalance like 100/140v rather than over volt on both.

 

[MarkNiwot]

I would next try to watch it with a multimeter while it's doing the overvoltage thing, to see if you can confirm what the XW is reporting.

On the gen AC terminals in the XW, or at the generator, or anywhere in between.

Yes, I did exactly that (with my reliable ole Fluke 77, which has been trustworthy for decades) - and it confirms what the XW+ was reporting, at each stage. The high output from the generator is real, but only when the XW+ is trying to charge the LLiFePO4 batteries on that system.

Otherwise, it seems to behave (with the Trace) as it should.

 

[400bird]

Do you have a different generator to try?
Sure does seem like the generator doesn't like the XW.

 

[dougbert]

What is the Total Harmonic Distortion of that genny? Bad THD can hurt these newer inverters, including the XW

I use older gennys but through a Chargeverter. Once I learned about THD I decided NOT to use my XW Pro's charger. Rather I charge either from grid or genny through the CV

just a thought for you

THD Meters are $500

interesting portion of a generator and THD, at the end of the rebuild video

 

[MarkNiwot]

Do you have a different generator to try?
Sure does seem like the generator doesn't like the XW.

I have an old 5 kW diesel military MEP as a backup, which hadn't run for about two months. And I attempted that over the weekend, but found that it started readily (it always has) but simply would NOT continue running once I released the starter. So I couldn't confirm, but have something else to debug later on...