Xantrex XW6048 - fault F49 - DC over voltage

pcguy2u

Well my system has been up and running for 10 months now, off and on. Periodically, the inverter and both MPPT-60 charge controllers sense that there is a problem and go into an infinite 6 minute cycle of Fault F49 (DC over voltage).

The immediate cure is to turn off Sell to Grid - Grid Support left on is ok. Of course, this situation defeats the grid tie benefits.

The days on which this occurs (here in foggy Bodega Bay, CA) have been non-descript - meaning, it could be foggy or it could be sunny.

This has happened three times now and a temp fix may be to turn off the AC input to the inverter for a brief moment - much like a power outage. That seems to have brought the system back on line 3 times now.

However, the question remains, what is the underlying cause. I have tested the batteries individually and in series and they constantly test at about 54 volts total. I have also tested the voltage at the batteries at the moment the fault occurs and the voltage indeed increases above the 70V threshold. Immediately following the fault, the voltage drops into the 54V+- range.

To me, this suggests that batteries are the recipients of the high voltage and not the source???

A Xantrex tech has stated that the battery pack (four Concorde 258A 12V AGM's in series) is too small. If that was the cause, wouldn't this problem have occurrred from the very beginning and why would turning off the power, fix the problem, however temporarily? Also, what does turning off the Sell function have to do with batteries that are not in use, with no load and in a float state???

Appreciate any insights...........
Many thanks, Nick

BB.

Re: Xantrex XW6048 - fault F49 - DC over voltage

A couple of thoughts...

400 AH at 48 VDC has been recommended as the minimum battery bank to support the 6kW XW inverter (as I recall).

If your batteries are reaching 70 volts--you have a problem. It could be a bad cable/electrical connection (may only show up when heavy current is flowing).

Or, via some setup problem (sell voltage too high?)--you may have "baked" your batteries and now their capacity is even less--causing the voltage to spike.

Or--you have an electical problem. The XW sell voltage is not working correctly (set at 52 VDC, as voltage rises, the inverter draws more power to sell--from my little understanding of this complex piece of gear). Or, you have another battery charger (the solar charger, or even the internal XW AC charger) is set wrong/functioning incorrectly and overcharging the batteries.

If the batteries are still working correctly (not boiled dry, or sulfated)--70 VDC on the battery bank takes a lot of current (on of the battery "chargers" is not working correctly at all). Or--you have an intermittent cable/connection (measure the voltage of each battery, on its post, and see if they are correct--or if one or more batteries has high voltage).

You could also have an "open cell" in one of the batteries--which could give similar results.

I would focus on the batteries (make sure each battery is carrying exactly 1/n of its share of voltage), and check each cable physically (see if loose), and when there is current flowing into/out of the battery (charge, or load) measure the voltage drop of each cable/cable connection. It will probably be obvious if there is a failed cell or connection (failed connection or battery may get hot too).

-Bill

pcguy2u

Re: Xantrex XW6048 - fault F49 - DC over voltage

Hi Bill, I have checked/disassembled the batteries and cable connections very early on. Would I be wise in turning off the power and checking each battery under an invert load? If there was a bad cell, wouldn't it be there all the time?

The problem only appears when the batteries are in a float state and Sell is on???

Thanks, Nick

BB.

Re: Xantrex XW6048 - fault F49 - DC over voltage

Yes, the problem (bad cell, cabling issue) should show up whether under charge (high voltage) or under load (low voltage)...

Turn off the power and put a 1 kWatt or so load on the inverter (electric heater, microwave a large bowl of water, etc.) and do some accurate measurements.

It may take a few minutes for problems to appear (surface charge is dissipated). Take the battery bank down 10% and see what happens:

0.10 * 258 AH * 48 Volts = 1,238 Watt*Hours (1,000 watt heater for 1.2 hours)

If the battery bank is bad--either you will find one weak battery/cell, or you will find the whole string starts to die.

That fact that you see 70 VDC on the battery bank is really strange. If the batteries are good (we hope), then that is a huge amount of current. If the battery bank is bad (or bad wiring) it should be very obvious where the unequal voltage drop is (54/4=13.5volts per battery; vs three batteries at 13.5 volts, and one at 29.5 volts because of an open cell--while charging).

-Bill

RCinFLA

Re: Xantrex XW6048 - fault F49 - DC over voltage

A clip on d.c. amp meter and measuring individual batteries would help diagnose the issue.

I doubt the solar charge controller could drag the battery that high even if not in sell mode. The XW should suck up all the solar controller excess, but if you can catch it in the fault, with the clip on ampmeter check solar controller line and main inverter lines to see who is sourcing the current and how much current.

You could have an intermittant high resistance on one of the battery cells. You did not say how long the batteries were subjected to 70 vdc. They will be damaged if subjected too long to this level, unless one of the cell is high resistance.

How much current is going into the battery at the 70 volt fault point? If it is low current, say less then two or three amps, then one cell is high resistance. I assume you have access to the individual batteries so check how the 70 vdc is distributed across the batteries. Make sure you check at battery post terminals, not the cable terminals. If one is showing high voltage, it is the bad battery. If voltage is equally distributed and current is higher then a few amps then I would suspect the XW.

I would be hesitant to put any replacement batteries on the system until the problem source is identified.

pcguy2u

Re: Xantrex XW6048 - fault F49 - DC over voltage

BB. wrote: »

Yes, the problem (bad cell, cabling issue) should show up whether under charge (high voltage) or under load (low voltage)...

Turn off the power and put a 1 kWatt or so load on the inverter (electric heater, microwave a large bowl of water, etc.) and do some accurate measurements.

It may take a few minutes for problems to appear (surface charge is dissipated). Take the battery bank down 10% and see what happens:

0.10 * 258 AH * 48 Volts = 1,238 Watt*Hours (1,000 watt heater for 1.2 hours)

If the battery bank is bad--either you will find one weak battery/cell, or you will find the whole string starts to die.

That fact that you see 70 VDC on the battery bank is really strange. If the batteries are good (we hope), then that is a huge amount of current. If the battery bank is bad (or bad wiring) it should be very obvious where the unequal voltage drop is (54/4=13.5volts per battery; vs three batteries at 13.5 volts, and one at 29.5 volts because of an open cell--while charging).

-Bill

Bill, the 70V is apparently only on the batteries for milliseconds - my test of the problem was simple and occurred when the problem was cyclic (every 5-6 minutes while Sell was on). I actually had two multimeters on the battery circuit, one on the battery side of the 250AMP DC breaker and one on the controller combiner plate side. The two meters progressed upward together indicating that the problem was likely not the circuit breaker. Immediately upon faulting, the meters both read 54+volts.

At the moment, the system is functioning normally and I hope to get out there and place a load on the batteries soon - just need to sort out this info. May ask the Concorde engineer to comment on this thread.

In your test hypothesis, it appears that about 6-7 minutes of a 1000 watt load should show something about the batteries/cabling - is that correct?

If the voltage for each battery remains equal to the others and falls off slowly, as one would expect, what does that point to in your mind? Remember, that both charge controller's connections are tied onto the 250AMP DC breaker on the combiner plate (separate lugs) and both experience an undocumented F70 (no answer forthcoming from Xantrex) fault just before the 6048 faults with F49.

pcguy2u

Re: Xantrex XW6048 - fault F49 - DC over voltage

RCinFLA wrote: »

A clip on d.c. amp meter and measuring individual batteries would help diagnose the issue.

I doubt the solar charge controller could drag the battery that high even if not in sell mode. The XW should suck up all the solar controller excess, but if you can catch it in the fault, with the clip on ampmeter check solar controller line and main inverter lines to see who is sourcing the current and how much current.

You could have an intermittant high resistance on one of the battery cells. You did not say how long the batteries were subjected to 70 vdc. They will be damaged if subjected too long to this level, unless one of the cell is high resistance.

How much current is going into the battery at the 70 volt fault point? If it is low current, say less then two or three amps, then one cell is high resistance. I assume you have access to the individual batteries so check how the 70 vdc is distributed across the batteries. Make sure you check at battery post terminals, not the cable terminals. If one is showing high voltage, it is the bad battery. If voltage is equally distributed and current is higher then a few amps then I would suspect the XW.

I would be hesitant to put any replacement batteries on the system until the problem source is identified.

Hi RC, don't have much of the sophisticated equipment you specifiy above - in any case, the 70V is not on the batteries for very long (millisecond). Moreso, the 70V is very transient - when this problem begins to occur again, it just occurred to me that I could trap the battery voltage at the moment of the fault. Through 4 cycles of the problem, I could use my Fluke 115 to trap the high limit of each battery.

That gives me something to go on.................

BB.

Re: Xantrex XW6048 - fault F49 - DC over voltage

The load allows you to "see" any weaknesses in the wiring or batteries. You could even run the 1kW load for an hour--the batteries would only be 10% discharged in that length of time (if I understand your setup).

Otherwise, I don't know where the 70 VDC is comming from unless it is inductive feedback (inverter under load "selling" and stop selling for whatever reason (instant stop in current can cause an inductive kick that could be caught with an instant reading meter / o'scope / etc.).

If the batteries are sitting at ~54 VDC and only only see a msecond of >60 VDC of voltage--then I would suspect that there is an inverter/charger problem or you are seeing a secondary effect (inductive kick back) from some other primary cause.

-Bill

pcguy2u

Re: Xantrex XW6048 - fault F49 - DC over voltage

In reading through the posts about this problem again, it occurred to me that I may be misunderstanding how the Sell function works. When sell is on, is the current being sold inverted from the batteries or is it inverted from the source arrays via the Charge Controllers????

It would seem that since the sell function is directly proportionate to the array output, that the batteries are not the source???

Need a little clarification here??

Nick

mike95490

Re: Xantrex XW6048 - fault F49 - DC over voltage

just in case a hefty load unveils a problem, I'd keep checking the battery termianls and cables every couple of minutes, if you have a high resistance, and walk away, you can melt terminals off the battery, my friend does it all the time in his EV. You may think 0.5ohm is not much, but with some big amps behind it .... At least he has a contact at a battery shop, where they just cast a new post onto the battery, and he's out the door in 10 minutes.

Solar Guppy

Re: Xantrex XW6048 - fault F49 - DC over voltage

Are your running 58V or higher sell voltage?, which will have the battery's more than 100% charged and they are not buffering enough and the chargers/inverters are not regulating in some transient condition, I ask as other have come to this forum saying that was recommend setting and its wrong.

For the XW and Sell mode, 100ah of battery's for every 1kwatt of PV your selling to grid is a minimum requirement for proper operation ... strange thing can happen with to small a battery bank, such as nuisance trips and at higher powers mppt tracking stalling on the charge controllers.


With such a small battery bank I would recommend you set the sell voltage to 50.8V, which is as close as one can get to be battery's fully charged ( 12.7V * 4 ) yet get some buffering by the battery's. Also, make sure the XW-6048's charger is turned off, its not needed as you have 5kw of PV to maintain a fully charged your AGM battery's.

This should offer some improvement and validate your need a bigger battery bank.

Its also important your using the Battery Temperature Sensors so the voltages are compenstated for. They come with the XW's, but you didn't mention if they were installed to the XW-6048 or XW-Mppt's

BB.

Re: Xantrex XW6048 - fault F49 - DC over voltage

You are correct... The GT XW Inverter acts like a diversion load based charge controller by removing any current that takes the battery above the "sell" voltage (around the long term float voltage or just above the 100% battery charge state).

Ideally, the MPPT Charge controller thinks it is working as hard as it can charging the battery bank (bulk charge mode with its cutoff point set >>sell voltage).

-Bill

pcguy2u

Re: Xantrex XW6048 - fault F49 - DC over voltage

Solar Guppy wrote: »

Are your running 58V or higher sell voltage?, which will have the battery's more than 100% charged and they are not buffering enough and the chargers/inverters are not regulating in some transient condition, I ask as other have come to this forum saying that was recommend setting and its wrong.

For the XW and Sell mode, 100ah of battery's for every 1kwatt of PV your selling to grid is a minimum requirement for proper operation ... strange thing can happen with to small a battery bank, such as nuisance trips and at higher powers mppt tracking stalling on the charge controllers.


With such a small battery bank I would recommend you set the sell voltage to 50.8V, which is as close as one can get to be battery's fully charged ( 12.7V * 4 ) yet get some buffering by the battery's. Also, make sure the XW-6048's charger is turned off, its not needed as you have 5kw of PV to maintain a fully charged your AGM battery's.

This should offer some improvement and validate your need a bigger battery bank.

Its also important your using the Battery Temperature Sensors so the voltages are compenstated for. They come with the XW's, but you didn't mention if they were installed to the XW-6048 or XW-Mppt's

Grid Support Voltage has been set to 57.0 and Max Sell Amps to 27.0 since day one. On each of the three failures and while talking with Xantrex tech, both these and other setting have been lowered with no effect on the then ongoing problem.

There is one BTS installed on only one of the controllers, but the batteries have never even felt warm to me. I do have the 2nd BTS here on my desk - the installion guys suggested only one was needed?? Should I install it and where?

Have turned off the XW-6048's charger - will report on the next event if any. Also will report on the batteries and cables under load as Bill suggested.

Many thanks............

pcguy2u

Re: Xantrex XW6048 - fault F49 - DC over voltage

BTW, I'm happy to make the changes to the Grid Support Voltage - this is somewhat counter intuitive to me and I would like to understand all the implications.

By setting the Grid Support Voltage to 50.8V does that mean the the grid output in terms of KWhrs is going to be greater as a result?

BB.

Re: Xantrex XW6048 - fault F49 - DC over voltage

By setting the Sell Voltage lower (as I understand the product--verify with the manual/Solar Guppy/etc.), you are just setting the charging voltage (and "trickle" charge current to the battery) to a lower value.

Ideally, the battery is at 12.7 vdc at 77F

The sell voltage has something like a 1 volt margin of error (you need to look up in manual):

4x12.7 + 1 volt error = 51.8 volt minimum sell voltage to keep batteries charged.

Or, 52 volt recommendation is close enough. That is how I understood the values to be derived.

All you are doing is dumping a bit less energy into the battery bank (where it can do harm by generating too much gas and heat, and cause pre-mature aging).

-Bill

Solar Guppy

Re: Xantrex XW6048 - fault F49 - DC over voltage

pcguy2u wrote: »

BTW, I'm happy to make the changes to the Grid Support Voltage - this is somewhat counter intuitive to me and I would like to understand all the implications.

By setting the Grid Support Voltage to 50.8V does that mean the the grid output in terms of KWhrs is going to be greater as a result?

Yes, instead of needlessly overcharging the batteries @ 57V, your selling all energy just over the fully charge rest voltage of the battery bank

On your BTS, make sure the two chargers and the XW-6048 are all networked together with the cat6 cables and can be seen by the SCP ( system control panel)

So set sell to 51.8V, verify network is working so BTS sharing is working and turn XW-6048 charger off ... let it run and see if you have improvements

pcguy2u

Re: Xantrex XW6048 - fault F49 - DC over voltage

Have done all as requested. I will also test the batteries under a load and report, and if the problem happens again, I will test each battery for a high voltage level.

Many thanks for the fine input,
Nick

dlenox

Re: Xantrex XW6048 - fault F49 - DC over voltage

pcguy,

I have a wind turbine and have experienced the situation that you mentioned. I have had conversations with tech support at Xantrex as well as sent them logging data to back it up. But have not heard of a solar system doing the same, but with the 57v sell limit it can make more sense.

It seems that the XW inverter has a 20 second 'stabilization' period that occurs, once the battery voltage goes above Grid Sup Volts +1, the inverter waits this 20 seconds before it goes into sell mode. With a wind turbine the battery voltage can increase very rapidly, and initially I was using a C40 as dump controller.

The C40 contributed to the problem by not being very 'responsive'.

With my sell volts set to 54v, the dump controller set at 58v, occasionally the battery volts would go to about 65v!! Dump controller and inverter were entirely too slow. Since that time I have changed to a Tristar TS60 as dump controller and it has not been an issue.

Tech support said that the next release of the XW software would eliminate the 20 second period, but I have not heard of the software being released as of yet, and it was last December that the conversation took place.

So as others have said, lowering your sell volts should help to keep this from happening.

Dan Lenox

Windsun

Re: Xantrex XW6048 - fault F49 - DC over voltage

dlenox wrote: »

pcguy,

Tech support said that the next release of the XW software would eliminate the 20 second period, but I have not heard of the software being released as of yet, and it was last December that the conversation took place.

Dan Lenox

Firmware notes, downloads, etc are here http://www.xantrex.com/support/web/type/21/docldoc_type.asp

pcguy2u

Re: Xantrex XW6048 - fault F49 - DC over voltage

One final thought on this..........

We never discussed how it is that once this occurs, and the problem begins it's infinite 6 minute loop, that there are two situations that cause it to cease.

In one case (we briefly touched on this part), disabling Sell, causes the problem to cease being present. However, the problem remains indefinitely and even after a few weeks of not selling, turning Sell on gets the same results. Perhaps an indication that the inverter has a stored memory setting that is at the root of the problem????

In the other case, simply turning off the main breaker at the meter panel and then turning it back on causes the system to function normally once again. This seems to coincide with the stored memory setting being at the root of the problem as stored memory could be lost depending??

I actually have not been able to prove the second case to myself conclusively because the problem only appears very intermittently. It was only this last instance where after almost four weeks of no Sell, we had a brief power outage and I decided to try selling again. In retrospect, it occurred to me that this is effectively the same fix that caused the system to function again subsequent to each of the first two (of three) failures.

If this problem should ever occur again, I will definitely immediately try to fix the problem by turning off the AC at the meter.

Thanks again, Nick

RCinFLA

Re: Xantrex XW6048 - fault F49 - DC over voltage

A minimum detectable event on XW is usually at least a half cycle to full cycle. Like when grid goes down or a spike on grid due to lightning hit.

If you are absolutely sure it only happens in sell mode, I wonder if there is a spike happening on the grid at the point of failure. Not high or long enough to trip the grid overvoltage detection but long enough to cause an short backwash overcharge to battery where the XW reaction time cannot compensate. The D.C. battery voltage detection maybe faster then the A.C. out of range detection.

There is a little push to grid / push to A.C. load that happens normally as the grid line voltage goes up and down slightly in normal operation (without actually sell activated) and the XW compensates for the variance with a little reaction time delay.

Wonder if anyone else has seen this fault show up.

One other thing I noticed playing with AGM charging. It seems their impedance is a bit higher when floating above 13.5 vdc. I noticed I can throw 2 amps at a fully charged 100 A-H AGM that was just on 13.8 vdc float and immediately pull it over 14.5 vdc. This seemed faster rise then on a 100 A-H flooded battery I tested. There might be some truth to having too small a battery set on XW (outside of service discharge time), with maybe AGM's causing even more sensitivity to a short overcharge spike.

pcguy2u

Re: Xantrex XW6048 - fault F49 - DC over voltage

As for only in Sell mode - once the problem starts the SCP displays the infinite sequence of events, the fault, the bulk, the float, the sell, the gradual increase (over 10 or so seconds) on the DC meters on both controllers and the fault again. Turning off Sell, causes the inverter to go into AC Pass Thru. Minutes or Days or Weeks later, turning on Sell causes the same fault and infinite loop.

And as I said previously, I believe the bandaid cure is to turn of the power for a moment and the system works ok again for an iindeterminate period.

Solar Guppy

Re: Xantrex XW6048 - fault F49 - DC over voltage

pcguy2u wrote: »

And as I said previously, I believe the bandaid cure is to turn of the power for a moment and the system works ok again for an iindeterminate period.

Have you done all the suggestions and turn sell back on? What are the results?

pcguy2u

Re: Xantrex XW6048 - fault F49 - DC over voltage

Sell has been on since the beginning of this thread. The problem only happens every couple of/few months, so I can't see what's happening with the batteries at this time. I have turned off the Inverter Charger and changed the level of the Sell DC. BTW, with the Sell DC level set to 51.8, the system starts selling much earlier when the sun is coming up..............

pcguy2u

Re: Xantrex XW6048 - fault F49 - DC over voltage

As promised, I'm getting back to everyone on the battery test - still have the test to perform under the conditions of the fault. I may or may not (if the problem never happens again) be able to report on that part of the test.

Used this storm here in California (read that as a power outage) to check my batteries under an inverter load of 300-2500W for 2+ hours. During the outage and after the power came back on, the individual battery voltage levels were all within .01VDC with the first/lowest reading (1 hour) at 2500W being 12.12 and the second reading (2 hours) at 400W was 12.17. When the power came back on at just under 2.5 hours, the readings were 12.30.

Seems like the batteries are operating correctly.

And BTW, all readings were taken from the cable ends and not directly from the battery terminals/posts.


Nick

RCinFLA

Re: Xantrex XW6048 - fault F49 - DC over voltage

I think you have something that may be a combination of items unique to your setup and grid environment. If you have not seen the post I wrote a week or so ago take a look at the link below and the diagram at bottom. This may give you some understanding of how the inverter interacts with the grid for the XW series.

http://forum.solar-electric.com/showthread.php?t=5903

One of the challenges to the inverter/grid parallel syncronous design of the XW is the inverter is building a grid waveform match based on assumption it is dealing with a sinewave. The grid has numerous possible pertubations from a dip when a heavy load like central air conditioner compressor starts up to a sharp high voltage spike when a lightning bolt strikes the power lines in the area. The XW must put up with, and handle these pertibations.

A lightning strike to grid will likely fall outside acceptable parameters setup within the XW and cause it to release from grid for a small period of time (AC1 relay opens). A heavy load startup surge, like air conditioner compressor only causes a short small dip in grid voltage as seen by XW. It will stay grid engaged and adjust to follow this dip but there is some time lag in the tracking process.

This adjustment is continously happening while the inverter is on and grid locked (AC1 relay engaged, inverter active). The time it takes (10-30msecs) to recognize and make the adjustments results in some random 'pushing' and 'pulling' from battery as the 'gear ratio' of the inverter PWM is modified to track the new grid voltage. The result of D.C. current fluxuations going in to, or out of, the battery is kept track of by the XW monitoring the battery voltage and any charge overage due to a sudden AC voltage increases is made up by some discharging of battery pushing back to grid or load (and vice-versa for a sudden dip in grid voltage).

Understanding this, the only different between this fluxuation in power flow due to grid fluxuations and the 'sell mode' is sell mode is intentionally pushing to grid for longer period of time.

When you say you turned off the charger you are turning off the inverter and going to bypass mode where only AC1 relay is engaged but no interaction with battery is happening because inverter is off.

Now for some possible theories for your issue.

If your local grid has a lot of pertubations you could be subject to more overages to instantaneous charge current to battery, even though you are selling. The fact you have small A-hr batteries may aggrevate this. Do you see flicker in lights often? Does XW momentarily disconnect from grid often?

On the battery side, battery line inductance can create transients in DC voltage seen by XW. Are your battery lines long, at least 2/0 gauge? Are the positive and negative lines kept together as much as possible to reduce line inductance?

The A.C. side reaction time of the XW is limited by the 60 Hz waveform. The D.C. voltage measurement could be quite fast. It likely has to be slowed down by XW to better match the reaction time of the AC side. Maybe for your setup/situation the D.C. measurement in XW is still too fast.

One other thing I just remembered. The grid-tie regulations require the XW to be intelligent enough to quickly release from grid when grid goes down (or open). One thing that may only happen in sell mode is a periodic monitoring of grid impedance. One common method for doing this is intentionally, slightly off-phasing the grid pushed voltage to detect the extra current that should happen when grid is good. Not sure if this is a factor but it is something different about sell mode.

pcguy2u

Re: Xantrex XW6048 - fault F49 - DC over voltage

RCinFLA wrote: »

I think you have something that may be a combination of items unique to your setup and grid environment. If you have not seen the post I wrote a week or so ago take a look at the link below and the diagram at bottom. This may give you some understanding of how the inverter interacts with the grid for the XW series.

http://forum.solar-electric.com/showthread.php?t=5903

You really know this stuff.........

One of the challenges to the inverter/grid parallel syncronous design of the XW is the inverter is building a grid waveform match based on assumption it is dealing with a sinewave. The grid has numerous possible pertubations from a dip when a heavy load like central air conditioner compressor starts up to a sharp high voltage spike when a lightning bolt strikes the power lines in the area. The XW must put up with, and handle these pertibations.

Power here is pretty clean and our lights never flicker or dim. We have no air conditioner and the only motor is the fridge.

A lightning strike to grid will likely fall outside acceptable parameters setup within the XW and cause it to release from grid for a small period of time (AC1 relay opens). A heavy load startup surge, like air conditioner compressor only causes a short small dip in grid voltage as seen by XW. It will stay grid engaged and adjust to follow this dip but there is some time lag in the tracking process.

This adjustment is continously happening while the inverter is on and grid locked (AC1 relay engaged, inverter active). The time it takes (10-30msecs) to recognize and make the adjustments results in some random 'pushing' and 'pulling' from battery as the 'gear ratio' of the inverter PWM is modified to track the new grid voltage. The result of D.C. current fluxuations going in to, or out of, the battery is kept track of by the XW monitoring the battery voltage and any charge overage due to a sudden AC voltage increases is made up by some discharging of battery pushing back to grid or load (and vice-versa for a sudden dip in grid voltage).

Understanding this, the only different between this fluxuation in power flow due to grid fluxuations and the 'sell mode' is sell mode is intentionally pushing to grid for longer period of time.

When you say you turned off the charger you are turning off the inverter and going to bypass mode where only AC1 relay is engaged but no interaction with battery is happening because inverter is off.

Isn't there still interaction with the batteries from the charge controllers? And, if as you say, the inverter is in Bypass mode, it is still selling to the grid, so the published mode SellMode???

Now for some possible theories for your issue.

If your local grid has a lot of pertubations you could be subject to more overages to instantaneous charge current to battery, even though you are selling. The fact you have small A-hr batteries may aggrevate this. Do you see flicker in lights often? Does XW momentarily disconnect from grid often?

Aside from the fault 49 issue, and occasional power outages there are no other anomalies.

On the battery side, battery line inductance can create transients in DC voltage seen by XW. Are your battery lines long, at least 2/0 gauge? Are the positive and negative lines kept together as much as possible to reduce line inductance?

Battery cables are 8', half of which is in a 1.5" pvc conduit.

The A.C. side reaction time of the XW is limited by the 60 Hz waveform. The D.C. voltage measurement could be quite fast. It likely has to be slowed down by XW to better match the reaction time of the AC side. Maybe for your setup/situation the D.C. measurement in XW is still too fast.

One other thing I just remembered. The grid-tie regulations require the XW to be intelligent enough to quickly release from grid when grid goes down (or open). One thing that may only happen in sell mode is a periodic monitoring of grid impedance. One common method for doing this is intentionally, slightly off-phasing the grid pushed voltage to detect the extra current that should happen when grid is good. Not sure if this is a factor but it is something different about sell mode.

See responses in bold above.

One thing that the above doesn't really address is why the unit starts operating correctly again, only after disconnecting from the grid by opening the main breaker at the meter panel momentarily??? I believe that the XW inverter has a software or hardware glitch.


Many thanks, Nick

RCinFLA

Re: Xantrex XW6048 - fault F49 - DC over voltage

The XW plays some name games with basic functions. There is one spot in op's manual that says when charging is disabled the inverter is off. Also says in bypass mode inverter is off. Could just call it 'inverter off' like older SW series but they seem to want to tie it to a tangible use function. They even seem to use two different names for same thing (bypass and pass-thru) between op's and installation manuals. Inverter 'off' might be overrided if you also try to sell.

The solar charge controller is for the most part a totally separate circuit and yes it would still continue to charge battery if PV output is available. The two devices do talk together although I do not know exactly how much info is shared. For example, the XW inverter, through Xanbus, may automatically set its inverter charge points based on solar charge controllers setpoints so inverter is always lower charge float and bulk voltage points. This ensures when solar charge controller raises battery voltage above XW inverter charge set battery voltage the inverter will push to grid/load.

The more I think about the anti-islanding sense function in sell mode the more I think it may be involved in your issue. When the XW swings the phase alignment offset periodically to do grid presence checking it will cause a current backwash through the inverter to the battery terminals. How great these spikes will be I do not know. If you have too much cable inductance or too high a battery impedance (too small a battery pack) these current spikes may 'twang' the battery lines causing a transient battery voltage response.

You could always try a big honking 75vdc electrolytic cap at the battery terminals on XW. (just half serious)

pcguy2u

Re: Xantrex XW6048 - fault F49 - DC over voltage

At the moment, I think I have this under control, at least to the extent that if it occurs again, I may be able to bring it back on line easily and very quickly as described in my last post. Should that not cure the problem the next time, I will be sure to report my findings.

And I will report back six months or so from now as to whether or not this problem has resurfaced.

In any case, Xantrex should be interested in this thread, there does appear to be a serious flaw in the way the XW is performing under these circumstances, whatever they really represent.

Thanks again, Nick

dlenox

Re: Xantrex XW6048 - fault F49 - DC over voltage

PcGuy,

I recently had a similar event happen, luckily I have my monitoring/logging software running and captured it, so I thought that I would share some graphs showing it.

I am running a Xantrex XW-6048, single XW-SCC charge controller with solar array of 720watts total. Currently my wind turbine is not running.

The following is a graph showing voltage levels over the period of time of 12:00:00PM to 12:20:00PM. During that period of time the grid dropped out at 12:00:19, back on after 1 second, off at 12:01:00, back on after 1 second, dropped out at 12:02:03, and again back on after 1 second.



Next is a graph showing the wattage, negative watts is when the inverter/charger is charging the batteries, and positive watts is when the batteries are being used to put out power.



Here is data from the log file:

Time,LogType,BatteryVolts,BatteryAmps,Watts,WattsAvg,WattsToday,WattsTotal,ChargeAmps,Efficiency,SolarAmps,SolarAmpsIn,SolarVoltsIn,WindSpeed,WindDirection,WindDegrees,Temperature
11:59:42,Data,53.83,,,212,32,54348,,,,,,9,NNE,14,0
11:59:53,Data,54.02,,,212,32,54348,,,,,,10,NNE,21,0
12:00:04,Data,54.19,,,212,32,54348,,,,,,12,N,8,0
12:00:15,Warning,High Inv Volts 60.4
12:00:15,Data,55.25,-1.7,-98,210,32,54347,,,,,,9,NNE,15,0
12:00:16,Warning,High Inv Volts 67.3
12:00:17,Warning,High Inv Volts 69.4
12:00:18,Warning,High Inv Volts 68.7
12:00:19,Warning,Grid Not Available
12:00:20,Warning,Grid Available
12:00:21,Warning,High Inv Volts 61.7
12:00:22,Warning,High Inv Volts 67.5
12:00:23,Warning,High Inv Volts 68.5
12:00:24,Warning,High Inv Volts 68.6
12:00:25,Warning,High Inv Volts 68.3
12:00:26,Warning,High Inv Volts 67.4
12:00:26,Data,66.03,-28.1,-1903,166,26,54341,,,,,,10,NNW,353,0
12:00:27,Warning,High Inv Volts 64.3
12:00:29,Warning,High Inv Amps 103
12:00:30,Warning,High Inv Amps 106
12:00:31,Warning,High Inv Amps 89
12:00:37,Data,54.54,18.8,899,179,29,54344,,,,,,10,NNE,28,0
12:00:48,Data,53.77,1.1,57,177,29,54344,,,,,,9,NNW,359,0
12:00:57,Warning,High Inv Volts 61.2
12:00:58,Warning,High Inv Volts 68.8
12:00:59,Warning,High Inv Volts 68.4
12:00:59,Data,57.47,-13.1,-865,157,26,54341,,,,,,8,NNE,12,0
12:01:00,Warning,Grid Not Available,High Inv Volts 60.6
12:01:01,Warning,Grid Available

You can see that what appeared to initially occur is the dreaded 20second 'stabilization period' that Xantrex programmed into the inverter before it begins to generate power. In that period of time at 12:00:04, the battery voltage was 54.19v. Eleven seconds later it reached 60.4v and still not generating power!

The voltage continues to climb until 12:00:19 when the grid dropped off, hitting nearly 70volts!

The grid comes back on but the volts stay high. To make matters worse the inverter wants to charge the batteries when ever the grid drops off - compounding the problem!!! (negative watts)

Two more series of things occur, and the inverter finally throws an F49 and goes offline...

I have discussed this 20 second 'stabilization period' with Xantrex in January of this year. They agreed that in the next release of software that they would eliminate it, but still waiting on their release of the firmware...

As you can see the voltage to the batteries is *not* milliseconds, but potentially quite a bit longer...

Had my wind turbine been operating this could have been a lot worse. Luckily for me it was mostly an overcast day, so PV array was not producing a lot of power.

This problem is clearly in Xantrex's court and I for one am still waiting on resolution.

Dan Lenox

pcguy2u

Re: Xantrex XW6048 - fault F49 - DC over voltage

Helo Dan and thanks for the relevant info. I have recently made contact with Xantrex again, wanting to pass on this thread to the product manager whose name was given to me in August. She is no longer the PM and I have yet to receive an email address and name for the current PM. The below is what I am planning to send to the PM.
_______________________________________________________________
Hi there, As you may have gathered from the previous case number (00132874), my 6048 has been experiencing Fault F49 (and once it starts, there has been no known fix or workaround) off an on for a year now, with no logical explanation. I have gone to great lengths outside of Xantrex support to find the cause of this problem and may have stumbled upon some relevant information.

As you know, your technical support staff are trained to analyze this kind of problem, in part, by determining what the battery pack looks like, ie, how large or small it is or isn't. Every time I have called for help, the stock response has been, "you need a larger battery pack" and of course, I have only spoken to Nick Klein. And while you folks may have found that in your experience, that solves the problem, in my experience (and I have been programming, repairing, trouble shooting and building computers since the 60's), the issue is related to an underlying glitch of some sort - either hardware, software or a combination of the two.

So, I posed this problem to a solar forum, whose collective wisdom appears to be very useful - in particular, especially in this case.

The basic problem is that, there is no common denominator that relates to the onset of the issue - it can happen on a warm day, on a cold day or on an overcast/foggy/rainy day and once it starts the only cure for the infinite loop has been to turn SELL off, which of course defeats the purpose of a Grid Tie. At no time have any of the batteries ever tested out of spec or even remotely felt warm (BTS is connected).

In the early stages of the incidents, beginning a year ago, there was no evident fix that would bring the system back on line and somehow, weeks/months later, the system miraculously would begin working again when I arbitrarily set it back to SELL. It was only when I tried to bring it back on line, after weeks of F49, F49 in an infinite loop whenever SELL was turned on, that I discovered that the resolution was to turn off the AC power source (Grid connection) at the main meter panel, similar to a brief power outage, that I determined that this may be a work around. That was the last time that I experienced the problem, which was in late September and at which time it had been out for five weeks, until that fateful day when the power went out briefly and I subsequently and coincidently decided to turn SELL on once again. It's been on ever since without any disruption.

The problem at that point was that there was no reason that it wouldn't happen again and there was no logic for it to have occurred in the first place, at least none that didn't point to hardware and/or software. If it was really an improperly sized battery bank, it would seem logical the problem would occur frequently and/or right off the bat when the system was first turned up.

I have attached a PDF file that details the back and forth conversation regarding this problem that occurred on the Solar Forum - this thread was started on the heels of my possible discovery of the work around. In a nutshell, here is what was suggested by those participating, all of which seems very logical to me, but obviously does not address the underlying problem.

Reset the battery charge level from the recommended 57.0VDC to 51.8VDC.
Turn off the 6048 AC charger option and rely solely on the charge controllers to float the batteries.

To date the problem has not recurred (and during this time the power was out for a day and the batteries performed perfectly), but the real question becomes, is the above the real long term fix for this problem - only time will tell for sure?

No matter, in view of the fact that the above changes were made subsequent to the "turn off the power" workaround, there remains a some very significant questions - in other words, we really don't know if the problem is just not happening, at the moment, as has been the case since day one, or, have the above changes contributed to the avoidance of the circumstances surrounding the event onset? Regardless, the following questions need answers:

Why does the 6048 not correct the F49 situation once whatever the underlying cause(s) disappear(s) - in other words, why the infinite loop and why not reset the conditions that caused the problem and to begin the test for the problem from the beginning?

What does disconnecting the AC/grid do to the internal workings of the 6048 that would allow it to once again begin selling to the grid successfully? My experience with this kind of workaround suggests a memory variable, one that contains residual/incorrect data and with which the 6048 determines an F49 condition exists, is being reset due to the loss of AC power (total supposition on my part about the inner workings of the 6048 ). However, by itself, this would account for how the workaround is successful.

The Xantrex recommended fix (more batteries) for this problem may have solved the issue for some case in the past, but that kind of fix may be masking the incorrect workings of the 6048. In other words, I believe that a larger battery pack (if that really has fixed this issue in the past) is merely hiding a problem in the system and is effectively doing your customers a disservice by causing them to redesign their systems and to find more space and money for more batteries that really aren't required.

Many thanks,

Nick

BTW, I expect to discuss this personally with your software/hardware engineer at some point after the above is given serious consideration and I am prepared to escalate the fix for this problem all the way to the top.