Lame - Xantrex XW 6048 won't load shave and sell at the same time

YehoshuaAgapao
YehoshuaAgapao Solar Expert Posts: 280 ✭✭
in Off Grid Solar & Battery Systems #1
Load shaving doesn't kick in until the charge controllers go into night sleep mode.

I wish during the waning sun hours that the inverter will readily switch between sell and battery drawing when sell and load shave overlap instead of it just switching betweeen sell and passthrough. It will probably not sell at all for the last hour of sun, but that don't matter. Starting at 5PM until 6:30PM the solar still produces, but not enough to meet subpanel demand. The inverter remains in 'Sell' mode without selling anything (it sells a 100-200W on demand dips occasionally)

Load shave amps also seems to be being applied with the leg with the lowest load, with the heavier leg pulling its difference from the grid (the attic insulation and attic ventilation upgrades and elastomeric coated, solar shaded patio, has enabled the house to be comfortably cooled with just one of the swamp coolers; the subpanel has been balanced for both of the swamp coolers running, leaving a long term 3-4A imbalance between L1/L2).

XW-Config screenshots (sceened captured from work over an Remote desktop connection).
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  • YehoshuaAgapao
    YehoshuaAgapao Solar Expert Posts: 280 ✭✭
    #2
    Re: Lame - Xantrex XW 6048 won't load shave and sell at the same time

    Looks like it worked correctly today. It probably didn't like me changing load shave settings during the load shave window yesterday. Solar panels got shaded by a cloud for about 20-30 minutes and the inverter entered load shave mode and then came out of it when the sun came out again. Dusk load shave started about 5:15PM with solar assistance. Yesterday load shave wasn't activated until the charge controllers went to sleep.

    Leg imbalance is still being drawn from the grid though (L1 500W L2 800W - 300W is drawn from grid on L2). Have load shave set at 0 amps.

    XW-Config screenshots (taken over remote desktop connection from work)

    5:37PM
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    6:10PM
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    Charge controller #1 - 3 panels, 25 degree tilt, top of south roof (not shown)
    Charge controller #2 - 6 panels, 25 degree tilt, top of south roof
    Charge controller #3 - 6 panels, flat mount, east/west on south side secondary gable
    Charge controller #4 - 12 panels, 20 degree tilt, patio roof facing south
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  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    #3
    Re: Lame - Xantrex XW 6048 won't load shave and sell at the same time
    YehoshuaAgapao wrote: »
    Leg imbalance is still being drawn from the grid though (L1 500W L2 800W - 300W is drawn from grid on L2). Have load shave set at 0 amps.

    Looks like it doesn't have any control on which leg the power is going. Probably because of a single transformer. If it increased the output, it would be selling on L1 and feeding on L2.
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  • YehoshuaAgapao
    YehoshuaAgapao Solar Expert Posts: 280 ✭✭
    #4
    Re: Lame - Xantrex XW 6048 won't load shave and sell at the same time
    NorthGuy wrote: »
    Looks like it doesn't have any control on which leg the power is going. Probably because of a single transformer. If it increased the output, it would be selling on L1 and feeding on L2.

    Looks like it is doing just that. XW-Config is not displaying it properly. But I got home 15 min before 8pm (the end of the load shave window) and the system control panel showed it selling on the less loaded leg and drawing on the heavier loaded leg. They weren't even though - it was drawing 3.5 amps on L2 and selling 2.5 amps on L1 for a net draw of 1 amp.

    Also the inverter did not enter load shave mode automatically today. It might be advanced interactive mode making it unreliable because I manually set grid support to close to the battery voltage and it kicked into load shave mode. I think advanced interactive mode would be desirable for proper absorption charge though.
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  • YehoshuaAgapao
    YehoshuaAgapao Solar Expert Posts: 280 ✭✭
    #5
    Re: Lame - Xantrex XW 6048 won't load shave and sell at the same time

    Load shave has only worked properly on Tuesday, which was a partly cloudy day.

    Wed-Thur I had to prod the settings of the inverter to get it to load shave. Solar production drops below subpanel demand at 5-5:30PM.

    I found these have to be simultaneously true to get the inverter to load shave
    *Charge controllers have to be bulk charging or not charging. Load shave doesn't work when the charge controllers are float charging. Not sure about absorption.
    *Battery voltage has to be above grid support by around half a volt
    *If has not been a cloudy day, sell has to be disabled.

    So I had to:
    *Drop grid support below 50V (49.8V) to get the charge controllers bulk charging. Takes a few minutes to get them to respond to that.
    *Then raise grid support back to 51.5V (float-1V) and let the voltage come back up
    *Then drop grid support down to 50.5V and disable sell
    *Then the inverter will go into load shave.

    Seems tedious. Think I'll need to check with Xantrex why it won't go into load shave on its own. Maybe it is tracking what is being sold, averaging it out, and counting that against load shave amps?
    Load shaving lets me get my batteries cycled and build up on-peak net-metering credits for July/August air conditioning (when it is too hot/humid for swamp coolers). SRP net meters on-peak and off-peak separately and won't allow transfer of on-peak credits to off-peak. They cash out any and all credits at the end of april for 3.5c/KW-h (credits rollover all other months in their separate onpk/offpk bins). Off-peak is around 10c/KW-h and on-peak is 24c/KW-h Jul/Aug (adding-in surcharges and rounding; 10c/21c May,Jun,Sep,Cot). On non-airconditiing and non-heating months (Jul, Aug, Dec, Jan, Feb) rooftop solar (6.5KW fixed tilt mount) + community solar (4KW 1D tracking) generate more than what I use.

    I wish Load shave scheduling could be set for certain days of the week on top of a time window. So load shave would happen M-F (sat/sun are off-peak 24/7). 1 day per week load shaving also would be great to exercise the flooded batteries once a week during winter too as not cycling them really screws up their SGs and SG evenness (Winter pricing does not justify load shaving on-peak usage - 10c offpk / 13c onpk, adding-in surcharges and rounding). This would be espeacilly true for the 1 day per week load shaving if I switch to the basic plan as SRP is suggesting (all 1 rate, unified net metering). I'll wait and see after July/August. Those are $400/mo electric bill months with 3500KW-h consumed (around 2200 of it by the air conditioner). They have a 12-month switch-back lockout after switching price plans.
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  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    #6
    Re: Lame - Xantrex XW 6048 won't load shave and sell at the same time
    YehoshuaAgapao wrote: »
    Load shaving lets me get my batteries cycled and build up on-peak net-metering credits for July/August air conditioning (when it is too hot/humid for swamp coolers).

    It is probably a good idea to cycle batteries from time to time, but I don't think it's a good idea to cycle them for load shifting. Batteries are a limited resource. Every kWh stored detracts from their useful life a little bit, so the more you cycle, the sooner you will need a replacement. You can look at manufacturer's cycle life charts to figure out the cost. It's likely to be 20-30 cents per kWh stored. The difference between on-peak and off-peak rate is probably less than this.

    In addition you lose about 20% of the energy that you store, but if you use solar excess this probably doesn't matter.
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  • YehoshuaAgapao
    YehoshuaAgapao Solar Expert Posts: 280 ✭✭
    #7
    Re: Lame - Xantrex XW 6048 won't load shave and sell at the same time

    Looked up Surrete cycle chart - http://www.dcbattery.com/rollssurrettecyclegraph.pdf

    Looks like Surrette prefers 60-70% DOD going by the chart (multiplying the cycles by the DOD) to squeeze the most KW-h out of them.

    Load shaving 5 days per week for 4 months out of the year and excercising 1 day per week the other 8 months out of the year looks like will put 125 cycles on the batteries per year.

    The chart has series 4000 at 1493 cycles at 40% DOD so at 125 cycles per year its 11.9 years. But at AZ's temperatures, I just don't see batteries lasting 10 years even on permafloat. My batteries are running 30 celcius right now and is just the start of the heat.
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  • YehoshuaAgapao
    YehoshuaAgapao Solar Expert Posts: 280 ✭✭
    #8
    Re: Lame - Xantrex XW 6048 won't load shave and sell at the same time

    Load shaving worked correctly today. Didn't do any finicky settings. Loads were high today. Everybody is home and my Newphew is over and the high was 102 today. Battery voltage still drops quickly from 50V to 49V but much slower falling from there. The faster drop may be from the increasing load (loads wen up from 1700W to 2000W and solar went down from 1200W to 1000W. There is not a cloud in the sky. Current outside temp is 100 degrees (high was 102)

    L1 has the living room. The home theater (including loud stereo) and the video games are booming. Most of that stuff is my sister's (My stuff is the family room - 2 laptops, DVR receiver, 32" LED TV, 19" LED TV, WiFi router, cable modem, printer, sips 2-3 amps). They might also have the swamp cooler in the garage running (Patio swamp cooler is L2, garage swamp cooler is L1)

    5:15PM
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    5:43PM
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