Adding additional solar to system

Northern_BCNorthern_BC Registered Users Posts: 28 ✭✭

Hello.

I currently have 3kw solar and am about to hook up another 3kw. Each 3kw of solar will come into a conext mppt 150 charge controller. Is there any concerns that I could overcharge my batteries? I have a 1520 A/h battery bank. 6kw is not overly big, so I don't think there is, but want to make sure my batteries are safe. I think the charge controller has the ability to limit what it outputs to charge, so must be some scenario people do this. Please let me know if you need any settings or specifications to help answer this.

Thank you.

XW6048 inverter, EnerSys 1520 Ah battery bank, 1500 watt tracker & 4500 watt stationary solar, 10kw Baldor NG generator

Comments

  • new2PVnew2PV Solar Expert Posts: 305 ✭✭
    edited November 2016 #2
    What kind of battery are you using?  wet flooded? forklift battery?  You can limit the charge controller via combox or on the controller direct. The controllers communicate on the xanbus network, as a primary and secondary controller. Need more infor on your battery. As an example a 500 AH forklift flooded battery should be charged at min 40 amps and max 85 amps.
    XW6848 inverter with 2 X mppt 60 150 CC , with Canadian solar 260Watt panels 2 x 3.5 kw array
  • PhotowhitPhotowhit Solar Expert Posts: 4,996 ✭✭✭✭
    Northern_BC said:
    I have a 1520 A/h battery bank. 6kw is not overly big,
    So are we to assume this is a 48 volt battery bank? Amps is a measure of current.

    If it's 48 volt, I suspect you are fine, I have a 4kw array feeding a @650 Ah 24 volt battery bank, It's doubtful I ever accede 15% of capacity charging.

    Most flooded lead acid battery banks want 10-13% of capacity charging current. If you have a 48 volt 1520 Ah battery bank you would like to have roughly 13% of 1520 or (1520x .15=) 197 amps feeding it. a 6000 watt array should provide about (6000/48=) 125 amps and it will normally only produce 70-75% of that or 94 amps.  So a larger array would be suggested.

    If it's a 24 volt battery bank at 1520 amps then 6000 watts would be reasonable size array.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
  • westbranchwestbranch Solar Expert Posts: 5,142 ✭✭✭✭
    I just looked at the Enersys site and they list no less than 15 different families of batteries, and a few I checked were AGM batteries.  Please tell us the make and model of batteries you are using.
    Also where are you sited ?  If you are in  northern BC there are cold, clear weather issues to take into account...!! especially the string voltage.
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • Northern_BCNorthern_BC Registered Users Posts: 28 ✭✭
    It is a 48volt system. 32 x 12volt 190 Ah batteries. I am located near Fort St John. It is cloudy today but the sun peaked out and the charge controller is telling me an output of: 1663W, 52V, 32Amps. Sun just coming out it is on a bulk charge from 3kw of solar.  I am waiting for the breakers to arrive to hook up the other 3kw.
    .
    XW6048 inverter, EnerSys 1520 Ah battery bank, 1500 watt tracker & 4500 watt stationary solar, 10kw Baldor NG generator
  • Northern_BCNorthern_BC Registered Users Posts: 28 ✭✭
    The batteries are the Enersys SBS 190F. They are an agm battery.
    XW6048 inverter, EnerSys 1520 Ah battery bank, 1500 watt tracker & 4500 watt stationary solar, 10kw Baldor NG generator
  • PhotowhitPhotowhit Solar Expert Posts: 4,996 ✭✭✭✭
    If you have any problem it's having too small an array, even at 6000 watts.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
  • Northern_BCNorthern_BC Registered Users Posts: 28 ✭✭
    I thought that could be the case, having too small an array. In the summer I get onto a float charge by mid-morning.  But the winter is drastically less solar. I do have my generator set for the 24 trigger @ the float voltage, so if I don't get enough sun it comes on each day for a few hours on consecutive cloudy days.  Hopefully that will keep the batteries happy. 
    XW6048 inverter, EnerSys 1520 Ah battery bank, 1500 watt tracker & 4500 watt stationary solar, 10kw Baldor NG generator
  • softdownsoftdown Solar Expert Posts: 2,397 ✭✭✭✭
    Recommended rate of charge is usually 5% to 13%. Forklift batteries are built to handle more aggressive rates of charge. Your battery bank is pretty gigantic, at least compared to what I am accustomed to.
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
  • new2PVnew2PV Solar Expert Posts: 305 ✭✭
    Question, not to take away from the point of this thread, but do you think its wise to have 8 strings of batteries working all together?>
    XW6848 inverter with 2 X mppt 60 150 CC , with Canadian solar 260Watt panels 2 x 3.5 kw array
  • mike95490mike95490 Solar Expert Posts: 8,373 ✭✭✭✭✭
    edited November 2016 #11
    new2PV said:
    Question, not to take away from the point of this thread, but do you think its wise to have 8 strings of batteries working all together?>
    Good to have more eyes looking at stuff, I didn't pick that up

    Never parallel AGM's - their internal resistance is so low, it's hard to tune the cables for identical current sharing. You might be able to deal with 1 pair, diagonal wires perfectly matched.

    Never that many in parallel, unless you have matched cables and bus bars (and individual fuses for each parallel connection)
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • new2PVnew2PV Solar Expert Posts: 305 ✭✭
    edited November 2016 #12
    I have found an interesting article on battery strings its a good read.
    XW6848 inverter with 2 X mppt 60 150 CC , with Canadian solar 260Watt panels 2 x 3.5 kw array
  • new2PVnew2PV Solar Expert Posts: 305 ✭✭
    XW6848 inverter with 2 X mppt 60 150 CC , with Canadian solar 260Watt panels 2 x 3.5 kw array
  • mike95490mike95490 Solar Expert Posts: 8,373 ✭✭✭✭✭
    That paper is for Telcom Float applications
    Technology issues:
    Most stationary battery systems spend more than 99% of their lives on float charge, so the main operational consideration is that the recommended float voltage be the same for each string.
    Off-Grid rarely spends more than 10% of it's life in float, and cyclic usage charts/voltage need to be used.   But you can do whatever you want.


    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • westbranchwestbranch Solar Expert Posts: 5,142 ✭✭✭✭
    here is a very good site for battery info...especially multiple strings...http://www.smartgauge.co.uk/batt_con.html

     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • Northern_BCNorthern_BC Registered Users Posts: 28 ✭✭
    My battery bank and racking is modeled after the outback battery's (enersys) and battery rack system. It was sized on talking to outback and the solar installer I work with. 

    Softdown: when you say recommended rate of charge is 5 to 13%; what % are you referring to?  5 to 13% of what?

    XW6048 inverter, EnerSys 1520 Ah battery bank, 1500 watt tracker & 4500 watt stationary solar, 10kw Baldor NG generator
  • softdownsoftdown Solar Expert Posts: 2,397 ✭✭✭✭
    My battery bank and racking is modeled after the outback battery's (enersys) and battery rack system. It was sized on talking to outback and the solar installer I work with. 

    Softdown: when you say recommended rate of charge is 5 to 13%; what % are you referring to?  5 to 13% of what?

    BB coughs up that magic formula a few times/week. I'm half surprised that he hasn't shown up to dazzle us with the equations. Your panels and batteries seem matched to me...if Outback approved it, I would likely feel pretty good about it.
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
  • new2PVnew2PV Solar Expert Posts: 305 ✭✭
    5-13 % of your total battery bank AH rating ex. [email protected]%=150AMPS  charge rate at 5% its 75 amps. 13 % its 195 amps.
    XW6848 inverter with 2 X mppt 60 150 CC , with Canadian solar 260Watt panels 2 x 3.5 kw array
  • BB.BB. Super Moderators, Administrators Posts: 29,509 admin
    A typical rating for storage batteries is a 20 hour discharge rate. The rate of current which will take a storage battery from 100% to 0% state of charge. I.e., a 220 AH battery at the 20 hour rate:
    • 220 AH / 20 hours = 11 amp draw
    20 hour rate is a pretty common industry standard--And you can find others (6 hour rate, 8 hour rate, 24 hour, and 100 hour among others). For us, a 20 hour rate works out pretty well... I.e., 5 hours per night, for two nights, and 50% maximum discharge => 20 hour discharge rate.

    So, 5%, 10%, and 13% rate of charge for a 220 AH battery (typical 6 volt golf cart):
    • 220 AH * 5% = 11 amp charging
    • 220 AH * 10% = 22 amp charging
    • 220 AH * 13% = 28.6 amp charging
    5% seems to be a good minimum for flooded cell lead acid batteries (remember, many of our rules of thumbs are for standard flooded cell lead acid batteries--AGM, Li Ion, etc. may be different). 5% will charge the battery bank fairly quickly and meet the "optimal" current for equalization charging. Good for weekend/sunny weather usage. Charge during the day/sunny weather, discharge at night (into your loads).

    10% is a nice value for full time off grid. You charge quicker (make hay when the sun shines) after a few days of bad weather, and some deep cycle lead acid batteries recommend 10% as a minimum rate of charge (optimum charging current for battery chemistry). Also, if you run some loads during the day (house, office, irrigation, etc.), the extra loads do not take the battery below 5% rate of charge.

    13% rate of charge is about as fast as you can force charge a lead acid battery without overheating. Also, for most folks, any more charging and the battery bank is filled by noon and just floating the rest of the day. At 13% and more rate of charge, a remote battery temperature sensor--Which lets the charge controller dial back charging voltage set point as the battery temperature rises (hot batteries need lower charging voltage).

    You can go higher charging rates (20-25% or so), but that high of current should only be when the battery bank is less than (roughly) 80% state of charge. Flooded cell batteries are very efficient and can sink high charging currents when less than fully charged. As you approach >90% state of charge, more and more of the charging energy goes into making gas and thermal energy (losses). 20% and larger charge rates are typically for AC battery chargers/gensets where you want to get the battery up >80% full and keep the genset loaded.

    It is easy to justify other numbers--But these are a "good start" for a workable/cost efficient/reliable off grid power system based on feedback from many off grid users. Once you have a basic system penciled out, you can compare its capabilities to your needs to confirm.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Northern_BCNorthern_BC Registered Users Posts: 28 ✭✭
    Thank you all for the help!
    XW6048 inverter, EnerSys 1520 Ah battery bank, 1500 watt tracker & 4500 watt stationary solar, 10kw Baldor NG generator
Sign In or Register to comment.