Schneider XW Pro with Load Shave enabled, starts charging too soon

aj164
aj164 Solar Expert Posts: 122 ✭✭✭
edited December 2021 in Off Grid Solar & Battery Systems #1
I'm trying to set up the XW Pro to load-shave at night.  Load-shave start is 9:00pm, and load-shave stop is 10:30am.  Load-shave amps is 10.   I'm expecting the system to use the battery for loads that would otherwise exceed 10A from the grid.  I expect it to stop using the battery when the battery voltage drops below a threshold (I believe is the Recharge V setpoint).  Since load-shave runs until 10:30am, I would expect the system not to charge the battery before 10:30.   Instead, it starts charging early in the morning.  This morning, it begain recharging at 4:30.  Yesterday, it began at 6:00. 
Do I need to also set the Charge Block to coincide with Load Shave?  Will the unit start to charge when Charge Block expires, or will it get "stuck" waiting for the Recharge Volts setpoint to be reached?  The charge mode is 3-stage w/ float, since the system is AC-coupled. 


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  • aj164
    aj164 Solar Expert Posts: 122 ✭✭✭
    #2
    I got an update from Schneider: 

    Load Shave uses the battery to 0.5V above the Recharge Volts setpoint.  It will start a new charge cycle (recharge) when that battery voltage threshold is reached.

    He did not comment on Charge Block, but I'm guessing that will prevent the new charge cycle until the block expires.  However, based on observation, it will not start a new charge cycle at the end of the charge block.  It also requires the Recharge Voltage to be reached before charging starts again.  

    We need something a little smarter than this for AC-coupled systems.  It can't be that hard to implement something in firmware to help out with this issue. 


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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #3
    Just out of curiosity, why load shaving a grid tied/hybrid battery based system?

    In general, if you run the numbers on off grid/hybrid solar power systems, a relatively optimized system will usually cost you around $1 to $2+ per kWH (all costs, initial hardware costs, electronics, batteries, batteries replacement ever 5-15 years, electronics every 10+ years, etc. divided by total kWH harvested/used over lifetime)... (if you are really careful, it is possible to get down to $0.50 per kWH per one poster here).

    Cost wise, if you can legally install a full Grid Tied/Utility Interactive solar power system (no batteries), that is pretty cheap (well under $0.15 per kWH lifetime costs)...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • aj164
    aj164 Solar Expert Posts: 122 ✭✭✭
    #4
    You're right, BB.  However, some of our customers have purchased battery-backup systems (to go with their existing grid-tie PV), and they want to "use" the battery rather than it sit idle.  It doesn't matter how much I tell them it isn't economically worthwhile to charge-discharge every day.  
    I think I have come up with a couple of requests for features in future XW firmware:
    #1 (simple) - Provide the option to trigger a new charge cycle or force a charge state (e.g. bulk, abs, float) upon exiting Charge Block.  Currently, when Charge Block ends, the inverter goes into NoFloat.  (By the way, this behavior doesn't make sense to me.  If your charge settings are "3-stage float", then why would it not at least go back into float when Charge Block ends?)

    #2 (wishful thinking) - Provide an option to charge from excess PV in grid-tied, AC-coupled systems.  Or, stated a different way, don't charge from the grid.  From my perspective, it seems like a straightforward request.  When there is current flowing back to the grid (export), ramp up charge current.  As grid current approaches zero, ramp charge current down to zero.  How hard could it be?  he-he

    -Adam
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    edited December 2021 #5
    Adam,

    Are your installations in a location where Grid Tied Solar is "legal" and cost effective?

    I guess you are in Texas--So GT Solar should be possible and you can run your hybrid inverter system in GT Mode--And get their money's worth that way...

    Although I understand there may be some co-op Utilities that do not allow GT Connections. (However, your customers may already have existing GT systems--So running the XW in GT mode should be fine???).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • GXMnow
    GXMnow Registered Users Posts: 2 ✭
    #6
    I have been asking Schneider for the same fixes for over a year, and they keep saying that no one else is asking for it. Now we both know that it false. The truly sad part is that the smaller SW inverter does have AC coupled "Smart Charge" that does EXACTLY what we want to do in the XW-Pro. It will start a bulk charge when it sees reverse current flow, and it will even ramp the charge rate to zero export as the AC coupled current varies. That has been in the SW since 2018, and they are bragging about having a patent for it. That would be a great addition for AC coupled XW systems. 

    I have a net energy metering agreement, and I do export during the day, and the battery inverter is mostly for backup power, but since they have messed with the "Time of Use" rates, I do run my house off the XW-Pro from 4 om to 9 pm when they jack up the rate to about double, $0.43 per kilowatt hour now. So currently, I have to remember to manually tell the XW to charge before I leave for work in the morning. It pulls about 9 KWHs from my 20 KWH of solar production to top up the batteries. Then I have t do "Grid Sell" of just 3 amps from 4 pm to 9 pm. The XW-Pro is actually very smart. In the summer, when my solar is cranking out quite a bit of power to about 5 pm, the XW does sit in pass through mode with the AC coupled solar providing as much as 8 amps of back feed "sell" to the grid, through the XW. As the sun falls, it it drops below my 3 amp setting, it will start to use battery power, ramping up until the solar quits, and the XW is providing the full 3 amps. It is not really going to the rid, but it is running my other loads back in the main panel. And when my Central AC kicks on, I am still buying that power as the 3 amps is just not enough. The system works great. The inverter is rock solid. I could not be more pleased with the hardware. But after running my loads for 9 KWHs, it goes back to pass through from either time block, or the battery dropping to 0.5 volts ABOVE the recharge volts. So the next morning, my stiff lithium battery bank is still at 0.5 volts ABOVE the recharge volts, so it just sits there. It is absolutely beyond stupid that it won't start a charge cycle without intervention.

    How can we put pressure on Schneider to dd the "Smart Charge" function to the XW-Pro?
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  • aj164
    aj164 Solar Expert Posts: 122 ✭✭✭
    #7
    Well, I'm not just "one" person asking for this feature.  I'm an installer with several customers who _expect_ their systems to be able to use the battery at night and recharge from AC-coupled solar.  So here are at least 20 "elses" asking for this, and counting...

    -Adam

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