2nd Battery Bank for XW???

John XW NY
John XW NY Solar Expert Posts: 50 ✭✭✭✭
Hi Guys,

I would like some opinions about adding a second bank 4 my XW system with the 4024 inverter. I have been having a problem with voltage drops.
I read about this guy who live on Mead mt. in Woodstock Ny and he has a similar system except he has 40 L-16 batteries with 3.7 kw panels and he produces 20 kwh per day!!! I am producing about 7 kwh right now but I am realizing a second bank would mean i could run my system continuously instead of shutting it off in the early evening. I definitely think 12 S 530 batteries is not enough and i need to double up to really benefit from my system, Any Ideas? Thanks JOHN


Also it makes sense that my battery bank at 1/3 the size is producing 1/3 the energy and that my PV panels can put out more power than they are.

Here is a link to the Mead Mt guy...http://onmeadmountain.livejournal.com/

I live in the same area so it is logical that i could produce similar results.

Does anyone have experience with 2 banks systems and the XW system??

Comments

  • RCinFLA
    RCinFLA Solar Expert Posts: 1,484 ✭✭✭✭
    Re: 2nd Battery Bank for XW???

    When you say low battery voltage I assume you mean you are unable to supply your loads with given available solar recharging.

    If your batteries are getting recharged quickly and are sitting in float condition for most of the day you may benefit by more battery capacity.

    Both battery types are about 400 A-hr capacity. With 12 batteries, you have three series strings yielding 1200 A-hrs at 24 vdc. At max of 50% discharge this will give you about 14 kWh's of power.

    XW4024 at max power load draws about 196 amps so a 1200 A-hr battery should not have a problem. (16% of A-Hr in current demand)

    For 3.7 kW of panels you will be getting about 1.85 kW's per hour of insolation. Assume you are getting at least 4 hours of insolation per day, that would be 7.4 kWh's per day on average.

    You have enough batteries for your panel wattage. Your friend is pulling your leg on his 20 kWh's per day for his 3.7 kWh's panels. Maybe if he lives in Arizona with a sun tracking mount.

    If you are discharging batteries too much you either have to cut your consumption or add more panels.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: 2nd Battery Bank for XW???

    John,

    I guess I am getting lost... Are you running your system Grid Tied, Off-Grid, or some hybrid mode?

    Before I layout any more money on a battery bank (or whatever)--I would want to ensure that Xantrex/Schneider understands the fault, your system, and that this would be the correct fix.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • John XW NY
    John XW NY Solar Expert Posts: 50 ✭✭✭✭
    Re: 2nd Battery Bank for XW???

    Ok I think I explained that I have been running the system and shutting it down in the evening around 9 pm. The system is grid tied. I do have a lot of loads hooked up to it. I have an old refrigerator which is about 10 years old which may need to be replaced/updated for a more efficient model, any recommendations?

    The guy at Mead Mt has a website where he logs his energy production. The website I listed in the link above. Are you saying he is lying about it? Maybe but why would he be doing that??

    I would like to be able to leave my system running without shutting it down.
    I am still very new to this whole solar experience but what is annoying is that I have to manually clear the faults b4 the XW runs the loads again.
    It may be I will need to take off some loads including the kitchen Microwave, Toaster etc.
    My original plan was backup power for emergencies etc. I am not unimpressed that the Solar Produces but probably the system needs to be fine tuned.

    It seems to make sense that a bigger bank means more storage/power.
    The guy at Mead Mt has 40 batteries in his bank so it makes sense that it runs better. I suggest you look at the link and check out what this guy is saying and then comment to me about it.

    I appreciate any positive thoughts. John XW


    Jah Guide.:D8)
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: 2nd Battery Bank for XW???

    John,

    OK, my confusion is the amount of power you are "collecting"... Normally, a grid tied inverter will ship ~95% of the power so the grid during the day and just sit idle at night waiting for a power failure (Hybrid mode like XW inverter).

    Where is the 7kW being measured? Output from the solar charge controllers, Total Net Power output from the inverter, GT meter/billing or what?

    Roughly, cycling your battery bank can give you 20-30% or more losses just for the "privilege" of running your home at night (for every 1kWH you use at night, you will needs ~120-130%, roughly, to refill the battery bank).

    I guess the other guy is averaging around 16 kWH per day in Grid Tied operation during sunny weather--seems very reasonable. My 3.5 kW of solar panels on a pure GT inverter run around 19-20 kWH per day in very good conditions and averages about 13 kWH per day over the year (my panels do not point south, and I have a bit of tree shading issues).

    Regarding your battery bank--I personally don't really like to parallel more than two or three strings maximum of battery banks. More strings than that become very expensive (wiring, fusing per string, etc.) and requires a lot of ongoing maintenance (checking / filling a whole bunch of cells, monitoring current flow through each string to ensure cabling and cells are are performing properly, etc.).

    You may be left with adding parallel strings to your existing battery bank... But in the future I would recommend looking at large capacity cells (even large 2 or 4 volt cells to keep them movable by one or two people if you don't have room for a crane/engine hoist) so that you can keep parallel strings to a minimum.

    So, I am trying to understand what the 7 kWH per day means... If this is GT operation during the day--then this sounds way low. But if this number does not include energy needed to recharge the battery bank--and you are consuming something like 5kWH every night--then I would understand a "net" 7kWH to the grid very easily.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • John XW NY
    John XW NY Solar Expert Posts: 50 ✭✭✭✭
    Re: 2nd Battery Bank for XW???

    Dear Bill,

    The guy at Mead Mt is offgrid, again if you checked the link you would have known that already. He is not grid tied. The 7 kwh is mostly during the daytime and early evening.
    I need to figure out how to operate in hybrid mode that will probably alleviate some of the issues i am having. I will go over the manual and try to sort it out.

    Do you think a new fridge will help out a lot?

    It seems that the well uses a lot of juice when it kicks on 2.

    I think i should be producing at least 10 kwh per day.



    John
  • mikeo
    mikeo Solar Expert Posts: 386 ✭✭✭
    Re: 2nd Battery Bank for XW???
    I think i should be producing at least 10 kwh per day.
    On average in your location, 7KW a day is reasonable. On peak days you should probably double that on perfect sunny days. I don't under stand yet what mode you are running in. If a pure grid tied mode, you shouldn't be using your batteries at all. It is likely the batteries are using about 4 amps for float while the sun is shining. That could be as much as 40 amps hours during long summer days. A larger battery bank will consume even more power just to float them. I run a similar system with older technology (see my sig) but with half the panels. I have a basic stamp computer that shuts my inverter off based on the charge controller output, so I don't have to manually turn it off when the sun goes down to save idle losses. I would think you could pick a mode with the XW inverter that would do virtually the same thing so your batteries wouldn't have to power any loads at all. Only during a power failure would the battery provide power to any loads connected to a separate panel that you would consider to be critical loads.
  • RCinFLA
    RCinFLA Solar Expert Posts: 1,484 ✭✭✭✭
    Re: 2nd Battery Bank for XW???

    From their March results:

    "Peak daily production: 21.68 kWh, a new record! (We had also set a new record the day prior to that -- 21.61 kWh -- and keep in mind that the record prior to that -- 21.49 kWh -- had only been set in February. It's looking like Don's plan to maximize spring and fall production is working very well.)
    Peak instantaneous production: 3660 watts (92 better than February)"

    Peak Instantaneous production of 3.66 kW's, this would be close to noon, with most direct sun facing panels. 21.68 kWh's / 3.66 kW's would be nearly 6 hours of peak production insolation. This is a bit hard for me to believe for March.

    Anyway, I replaced my 10 year old refrig last year. The old one, a 26 cu ft side by side, drew 4.2 kWh's per day. The new 26 cu ft side by side draws about 2.1 kWh's per day.

    You are going to be better having XW sell any excess during the day. Doing a time shift transfer using lead-acid batteries for storage is not efficient.

    Path going to batteries and back to grid:

    Wiring from panels * chg controller efficiency (95%) * XW inverter/chgr (93%) * battery chg efficiency (85%) * XW inverter inverter to grid (93%)

    Path selling XW directly to grid:

    Wiring from panels * chg controller efficiency (95%) * XW inverter to grid (93%)

    The difference is battery chg efficiency (85%) * XW inverter inverter to grid (93%), or an additional 79% transfer factor, a 21% additional loss, not to mention the extra expense of batteries wear/replacement.
  • 885kcdtq
    885kcdtq Solar Expert Posts: 27
    Re: 2nd Battery Bank for XW???

    Just me looking at your system and what is happening, I would say you have to do some resetting of your XW parameters.
    It appears to me that you are trying to run it OFF GRID. ie panels charge batteries, inverter load from batteries with no grid interaction.
    If set up correctly, you will not run out of battery unless you have disabled AC1 input.
    Look over all of your current settings and post them. We could all be a lot more help.
    I'm going off the top of my head here:
    In my scenario with only a 160 watt Air breeze.
    Float voltage 27.1 Volt
    Grid support: 27.3 Volt <<<< just above float voltage
    Grid support: enabled
    Sell mode: disabled <<<<<You probably want this enabled with 3.7 KW solar
    AC 1 I have set @ 40 amps

    . Need to look again and be sure of my settings.
    With the set up I have, when the turbine is going it will "support" the household loads untill the batt V drops to below grid support voltage. It will sit there Idling until I am back above Support Voltage. No dead batteries here......
  • John XW NY
    John XW NY Solar Expert Posts: 50 ✭✭✭✭
    Re: 2nd Battery Bank for XW???

    Ok . The System I have is connected to the grid . I am not selling power yet. I am considering doing this . I am not sure Central Hudson will allow me to because i have used the system and they have may have an issue about that. It would be much better to sell all day and charge the batteries in case of power failure.
    It would be nice to hook up the net metering aspect and maximize the power production.

    I will have to look into adjusting the XW parameters as well. I do have a subpanel already with the critical loads hooked up. i may have to remove some of them.
    Either way I need to iron it all out.

    Some good ideas so far keep em coming. .... :-) John;)
  • 885kcdtq
    885kcdtq Solar Expert Posts: 27
    Re: 2nd Battery Bank for XW???

    OK here's where I'm set up
    Inverter - Enabled
    Search mode - Disabled
    Grid support - Enabled
    Charger - Enabled

    BASIC
    Battery type - Flooded
    Capacity - 510 ahr
    Max charge rate - 35%
    Charge cycle - 3 stage
    Recharge volts - 25 volts
    A/C priority - AC1
    AC 1 breaker - 50 Amp ( I did this for a reason. won't get into it right now)
    AC2 breaker - 60 amp (I have no genset)
    Grid support - 27.5 volts
    LBCO - 22 volts.

    ADVANCED:

    INVERTER
    LBCO- 22 Volt
    LBCO Delay - 240 sec. I set it high for bigger surges like microwave.
    High Batt Cut out -35 Volt
    Search - 50 W
    Search delay - 2 sec

    CHARGER
    Battery type - Flooded
    Batt Capacity- 510 Ahr
    Max charge rate - 35 % equals about 53 amps
    Recharge volts - 25.0
    Absorb time - 180 minutes(maximum)

    A/C
    UNMODIFIED All factory settings

    GRID SUPPORT
    Grid support volts - 27.5
    Sell - disabled
    Max sell- doesn't matter. it's disabled
    Load shave - Disabled

    Generator support - Disabled


    With grid support enabled and sell mode disabled all generated power above 27.5 volts goes to support loads on your "back-up" panel.

    I do not have any solar yet, but I beleive you can copy all these settings to your MPPT's
    Something else I thought about is your LBCO set @ 24 volts. This might be fine under minimal loads. If and when you start to heavily discharge your batteries more than 2kw AC in my case it is entirely normal to see voltage drop as a result.
    Essentially you've removed all surface charge and if your batteries are at all weak, they will be sluggish to respond to the heavy call for amps. Not enough reaction surface, partial sulfation, as is the case with my used bank.
  • topper
    topper Solar Expert Posts: 113 ✭✭
    Re: 2nd Battery Bank for XW???

    Wish SG would chime in on this one.
    Now don't quote me on this but I'm thinking the inverter's charge voltages have to be lower than the MPPT's. or the MPPT's charge voltages have to be set higher than the inverter's charging voltages. Other wise would the MPPT's just drop into float rather than raising the voltage to grid support level.
    I am not totally sure where each should be set. But I hope to see answers so I don't have to ask the same questions next year.
    Best of luck to you.