XW6048 Charger Settings

OldSonne

I have a 200 Ah 48v battery backup system. I have Deka AGM 6v batteries. I prefer NOT to use the inverter's charger which draws power from the grid so I usually charge only from the PV array, but I do want to keep the batteries full enough to use when grid goes down or when I disconnect during lightning storms to protect my gear from surges through the grid. What would you suggest for these settings for the inverter and the XW SCCs?

Grid Support Voltage (54?)

Max Charge Rate (100%)
Charge Cycle (3 Stage or 2 Stage)
Recharge Volts
Absorb Time

The manual says the defaults for 3 Stage charging are 57.2 Bulk, 57.2 Absorb, 53.6 Float. My battery specs don't differentiate bulk and absorb, but they call for 57.6 charge and 54 float. Do I need to float? I want to maximize my sell back to grid but still need full batteries or manage to make last the longest.

Schneider wrote me to upgrade my firmware and use Enhanced Grid Support and set grid support voltage to 64. Wow. I guess it really never goes that high. I am a little scared to upgrade the firmware, but I guess I could manage. Schneider says I can borrow the config tool. Perhaps I need to enable the inverter charge to operate only in certain circumstances?

Any advice? Thanks.:D

BB.

Re: XW6048 Charger Settings

The numbers you are using should be OK... You can confirm the 57.2 volts with the Battery Mfg. (14.3volts at 12 volt bank--about what other AGM mfg. have recommended).

The "...use Enhanced Grid Support and set grid support voltage to 64 volts..." seems to be a new mode in the firmware... It actually does not go that high (another poster talked about Enhanced Grid Support too). Check around post #13 of this thread:

Xw Xantrex 4024

However, I am certainly no expert in XW setup--so I cannot give you a better answer.

-Bill

RCinFLA

Re: XW6048 Charger Settings

Whatever "Enhanced grid support" software is, it must significantly change the functionality. Setting grid support at 64 vdc would seem to effectively turn off grid support so they must have done something in software to interact with another setting. This is the thing I hate about XW, software run amuck so you have a hard time figuring out what it is actually doing.

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from other thread

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Enhanced interactive mode This mode is suitable for Xantrex XW Systems with
only Xantrex XW Solar Charge Controller(s) networked to Xantrex XW Series
Inverter/Charger(s) through Xanbus. In this mode, Grid Supp Volts is set as
the charge controller’s Bulk and Absorb voltages (for example, 32 volts on a
24 volt system and 64 volts on a 48 volt system).
In enhanced interactive mode the Xantrex XW Series Inverter/Charger
automatically tracks the Xantrex XW Solar Charge Controller voltage as it
transitions through all charge states (from bulk to absorption to float). This allows
the Xantrex XW System to execute a full battery charge cycle while still
converting excess DC power to AC power to support the loads or export to the
utility grid. In doing so, the Xantrex XW Series Inverter/Charger only uses what is
not accepted by the battery to support local loads and sell to the grid, thereby
maximizing the use of the array. Since this mode allows the battery bank voltage
to reach absorption levels (when PV harvest is adequate), the state of health of
the battery is improved. The sell entry and regulation voltage level is 1 V below
absorption and float of Xantrex XW Solar Charge Controller set points. The sell
exit from sell is 1.5 V below absorption and float of Xantrex XW Solar Charge
Controller set point

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So it appears to be taking Grid Enable voltage setting from the XW charge controller setting. This effectively means if Grid support sell is enabled and charge controller is pushing out power, and batteries are at float (or absorb if CC in that mode) then XW inverter will take off excess power. It will shut down grid support regardless of grid support voltage setting if CC is not producing excess power (beyond battery charging needs). It seems the main change is it allows battery to go to absorb level where prior software did not.

The way it used to seem to work was:

1) Grid Support Enabled, Sell disable, Load Shave disabled. - Inverter will push power to ACout node if battery voltage goes above Grid Support voltage setting. There are other interactive conditions to this. Obviously if battery is going through its first and second phase of charging it won't be pushing power out. Being that Sell is not enabled, any pushed power to ACout node must be consumed by ACout load. No power will be allowed to go back up AC1in port. If ACout load cannot consume the pushed power then the battery voltage will be allowed to rise. Presumably the PV controller will take over the regulation and prevent battery voltage from continue rising.

2) Grid Support Enabled, Sell disabled, Load Shave enabled. - Exactly like above with the difference being inverter will be allowed to push power at lower battery voltage, down to 2 volts above LBCO setting. It will push power to ACout as needed to suppliment need based on limit placed on ACin current (through breaker amps setting @ 80% setting level) to provide load shaving limiting current on ACin.

3) Grid Support Enabled, Sell Enabled, Load Shave Disabled. - Just like like 1) with allowance of any excess pushed power (beyond consumed by ACout load) to exit out AC1in port to grid. Range of battery voltage is active at Grid Support voltage, deactivate at Grid Support voltage - 0.5 vdc.

There are voltage and current senses on AC1in, AC2in, Inverter out, and ACout to manage the power flow directions.

OldSonne

Re: XW6048 Charger Settings

I assume the new firmware would have desirable features. I read the documentation they sent, but it was lengthy and complex. I guess things are working without the upgrade, but would it be wise to make it a policy to upgrade the firmware on the XW just as you do with your computer, phone, etc.?

Joe_B

Re: XW6048 Charger Settings

Upgrading the firmware entails risk and should only be done to get a new needed feature or fix an old problem. I would not just do it because I could.

That being said, The enhanced interactive mode is the best way to run a grid tied system. I operate mine in Enhanced mode, sell disabled, load shave enabled while the sun is shining. This mode will always keep the batteries near 100% which is a good thing. At night it will go into AC passthrough and use the grid if available

During the day, when the SCC enters float mode, the XW inverter will suck only the excess power off to run the AC loads and throttle back the PV to maintain that load. Here is where a dump load comes in, By adding a dump load, the SCC will load the panels and put the excess into heat (for DHW). Without the dump load, you will be wasting PV watts in enhanced mode.

But if you choose to not use the enhance mode, then the grid support will be draining your batteries at night and recharging them during PV production. The cycling will use your batteries life up faster than keeping them at 100% so you have to make a decision on how you want to run your system.

OldSonne

Re: XW6048 Charger Settings

Joe,

You don't sell to the grid? Do your settings remain the same all the time?

RCinFLA

Re: XW6048 Charger Settings

You should probably upgrade the software since you are using an XW charger controller with Xbus link to XW inverter. If you where using a non-Xantrex charger controller then the upgrade would do nothing for you. I think without it the XW inverter will not let the PV charge controller take the battery above grid support voltage setting.

If you set grid support voltage to float level then batteries will never be allowed to go above float (unless grid goes down and XW inverter does full charge cycle when grid is restored).

If you set grid support voltage between float and absorb voltage then you will not havest PV power until PV charger gets the battery to the higher voltage level.

With the new software the XW inverter will takes its que to from charge controller. If charge controller is in bulk charge mode then XW inverter will not be allow to harvest until battery reaches 1v below absorb level. When PV charge controller drops to float voltage then XW inverter will harvest at 1 v below float level.

Question I have on this new software is will PV charge controller ever get out of bulk phase since XW inverter will cap battery voltage rise to absorb voltage -1 volt. You may have to set a timeout limit for PV charge controller to drop to float level. You don't want it to get hung up indefinately at bulk - 1v voltage on batteries.

Bulk phase used to mean constant current phase. There are chargers that allow a separate higher voltage limit trigger point during constant current bulk phase before the voltage is reduced to contant voltage absorb phase. This causes the constant bulk current to continue to run up to, say, an equilize voltage level before dropping back and entering the absorb constant voltage phase. It will shorten time spent in absorb phase.

AGM's absorbs charge pretty well so there is probably no reason to jack the final bulk phase voltage higher then 57.2 vdc normal absorb voltage. You also have to avoid too much gas creation at the higher voltage that can cause venting from the sealed battery.

Battery SOC will lag behind the cell voltage and this lag is greater the greater charging current. If your bulk current is 25% AH rating and absorb is set to terminate charge at 2% AH rating current then absorb phase contant voltage, tapering current , will last longer then if the battery was bulk current charged at 10% AH rating, which would spend more time in bulk phase.

The boosted Bulk voltage capability is good if you are charging from generator where you want to get the most SOC for the least amount of fuel and run time on generator. It is a little harder on the battery and probably should not be used for any sealed lead acid batteries which would include AGM's.

Joe_B

Re: XW6048 Charger Settings

OldSonne wrote: »

Joe,

You don't sell to the grid? Do your settings remain the same all the time?

No, I dont produce enough excess to sell.

RCinFLA wrote: »

Question I have on this new software is will PV charge controller ever get out of bulk phase since XW inverter will cap battery voltage rise to absorb voltage -1 volt. You may have to set a timeout limit for PV charge controller to drop to float level. You don't want it to get hung up indefinately at bulk - 1v voltage on batteries.

It handles it nicely, the XW will not enter grid support mode until the batteries reach float. Then it begins to invert and holds the battery at float-1 volt by drawing energy from the batteries to support loads.

Battery SOC will lag behind the cell voltage and this lag is greater the greater charging current. If your bulk current is 25% AH rating and absorb is set to terminate charge at 2% AH rating current then absorb phase contant voltage, tapering current , will last longer then if the battery was bulk current charged at 10% AH rating, which would spend more time in bulk phase.

Yeah this is a big problem with the XW, no current shunt means that it is estimating S.O.C. from the voltage and the loads. I found that there is a slight stairstepping error that results in the system thinking that the battery is at 100% when in fact it is dangerously low. You need to really keep an eye on the S.G. and initiate a full charge cycle when it gets low. This essentially resysncs the battery monitoring software. I have to do this about once a month.

RCinFLA

Re: XW6048 Charger Settings

Joe_B wrote: »

It handles it nicely, the XW will not enter grid support mode until the batteries reach float. Then it begins to invert and holds the battery at float-1 volt by drawing energy from the batteries to support loads.

This does not jive with the description:
"The sell entry and regulation voltage level is 1 V below
absorption and float of Xantrex XW Solar Charge Controller set points. The sell
exit from sell is 1.5 V below absorption and float of Xantrex XW Solar Charge
Controller set point ."

I guess what you say is true if the the XW inverter does not initiate the pull until the charge controller reports that it is done with its cycle first. You need CC to execute its timeout on absorb cycle if PV power never can get the battery to absorb voltage level or XW inverter would never initiate sell even with battery voltage holding at 56 volts. Of course for this condition you may not have much power to sell anyway.

Joe_B wrote: »

Yeah this is a big problem with the XW, no current shunt means that it is estimating S.O.C. from the voltage and the loads. I found that there is a slight stairstepping error that results in the system thinking that the battery is at 100% when in fact it is dangerously low. You need to really keep an eye on the S.G. and initiate a full charge cycle when it gets low. This essentially resysncs the battery monitoring software. I have to do this about once a month.

It would be nice to have an actual DC current shunt input but "calculated" is a better description then "estimate". It does the calculation based on knowing the AC power coming and going through inverter, with inverter efficiency factored in. Every AH current tracking monitor accumulates errors over time if the batteries are not allowed to be taken through full absorb cycle to reset the 100% capacity reference point.

Additional error comes into play because the current contribution by the charge controller is out of the inverter power in/out loop. An external current shunt directly inline with battery could capture the combined XW and Charge controller currents coming and going from battery.

Joe_B

Re: XW6048 Charger Settings

RCinFLA wrote: »

This does not jive with the description:
"The sell entry and regulation voltage level is 1 V below
absorption and float of Xantrex XW Solar Charge Controller set points. The sell
exit from sell is 1.5 V below absorption and float of Xantrex XW Solar Charge
Controller set point ."

I guess what you say is true if the the XW inverter does not initiate the pull until the charge controller reports that it is done with its cycle first. You need CC to execute its timeout on absorb cycle if PV power never can get the battery to absorb voltage level or XW inverter would never initiate sell even with battery voltage holding at 56 volts. Of course for this condition you may not have much power to sell anyway.

The description in the latest manual appears to be wrong. My system will not enter grid support until the charger gets to float. Then the inverter will act as a shunt regulator. I will add that once the system thinks the battery is full, it will enter grid support mode and then pull the battery below 100% by a few percent. The battery runs at about 95% until the PV drops off and the inverter goes back into AC passthrough. At this time, the remaining PV is used to top off the battery. The problem comes in at this point. The system will think the battery is topped off and it is not. Several days of this and the battery S.G. will say 80% and the system will think it is at 100%. (not good at all).

It would be nice to have an actual DC current shunt input but "calculated" is a better description then "estimate". It does the calculation based on knowing the AC power coming and going through inverter, with inverter efficiency factored in. Every AH current tracking monitor accumulates errors over time if the batteries are not allowed to be taken through full absorb cycle to reset the 100% capacity reference point.

Additional error comes into play because the current contribution by the charge controller is out of the inverter power in/out loop. An external current shunt directly inline with battery could capture the combined XW and Charge controller currents coming and going from battery.

I have told the tech support guys that the next product S should develop is an XW current shunt that plugs into the Xbus and supplies current information to the system. This would give the system a much more accurate way to characterize the battery S.O.C.

Another thing I have told them is that the system is not consisitant now with some parameters being set in voltage ans some in AH, etc. If they had a current shunt, they could set things based on S.O.C. which would fix a lot of problems with the XW system.