Charging Battery bank via built in Charger inverter using Generator

jbdparkjbdpark Posts: 15Registered Users ✭✭
Does any one has experience charging a battery bank through Inverter/Charger using a generator.
I have a 12 volt, 1200Ah battery bank (12 *100Ah)  AGM  batteries. I will like to use a  7000kw
B&S gas generator to charge those batteries, using the 150A charger built in
my 12V Freedom SW3000 Inverter/Charger. Is that possible, what hurdles should I be aware of?
Any advise or comments will be appreciated. Thank you

Comments

  • 706jim706jim Posts: 214Solar Expert ✭✭✭
    edited August 2 #2
    I have an old Trace that I use for charging with a small generator. It works fine although I am unable to reach its full amperage due to the size of my generator. You will find that this is an expensive way to charge batteries if you try to get them to float. In your case, you are getting in theory 1.7Kw from the inverter but are doing this from an engine rated at approximately 10Kw. So running close to a gallon of fuel per hour you can see where I'm coming from.
    Island cottage solar system with 1400 watts of panels, Trace DR1524 MSW inverter, Trace C40 PWM controller 8 Trojan L16's. My 25th year.
  • EstragonEstragon Posts: 2,838Registered Users ✭✭✭✭✭
    edited August 2 #3
    150a is some pretty big current. Like @706jim said, a 7kw generator won't break a sweat running that, but you'll want some big wire (thumb size) between the inverter/charger and battery to handle, and proper DC fuse/breaker. Small wire + no fuse = the wire IS the fuse. :wink:
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • mcgivormcgivor Posts: 2,201Solar Expert ✭✭✭✭✭
    jbdpark said:
    Does any one has experience charging a battery bank through Inverter/Charger using a generator.
    I have a 12 volt, 1200Ah battery bank (12 *100Ah)  AGM  batteries. I will like to use a  7000kw
    B&S gas generator to charge those batteries, using the 150A charger built in
    my 12V Freedom SW3000 Inverter/Charger. Is that possible, what hurdles should I be aware of?
    Any advise or comments will be appreciated. Thank you
    Personally I would be thinking of ballance during charging/dischargeing with that amount of parrallel batteries, how are they wired? Recommendations are generally 3 maximum parrallel battery strings, but 12, that's extreme.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 

  • BB.BB. Posts: 27,882Super Moderators, Administrators admin
    Here is the background on wiring a number of parallel batteries together:

    http://www.smartgauge.co.uk/batt_con.html

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Marc KurthMarc Kurth Posts: 446Solar Expert ✭✭✭✭
    jbdpark said:
    Does any one has experience charging a battery bank through Inverter/Charger using a generator.
    I have a 12 volt, 1200Ah battery bank (12 *100Ah)  AGM  batteries. I will like to use a  7000kw
    B&S gas generator to charge those batteries, using the 150A charger built in
    my 12V Freedom SW3000 Inverter/Charger. Is that possible, what hurdles should I be aware of?
    Any advise or comments will be appreciated. Thank you

    Yes, I do see this approach with large motor coaches with 100a to 150a inverter/chargers. Many of today's high end coaches run six to eight 12v batteries at 260 ah each, and custom "entertainer" rigs can run as many as (16) 12v batteries x 260 ah each. Yes, that's close to 50 kwh total, but that is split between two inverter/charger/battery bank sets.

    Generally, the larger systems are set up as 24v to get the current down to a manageable level. So, that's four to six parallel strings, occasionally more.

    Lifespan is generally 6-8 years for this application, unless the bus "lives" in the Southwest deserts - then 5 years, which happens to be the warranty period. Typical wiring is a pair of 4/0 for each leg of the main leads to and from the inverter/charger..

    The trick to making several parallel batteries (or strings of batteries) live a longer life, is to have LOTS of time in float. This is one of the reasons that many batteries in parallel should be avoided in off grid PV systems.  

    Marc
    I always have more questions than answers. That's the nature of life.
  • mike95490mike95490 Posts: 7,901Solar Expert ✭✭✭✭
    jbdpark said:
    Does any one has experience charging a battery bank through Inverter/Charger using a generator.
    I have a 12 volt, 1200Ah battery bank (12 *100Ah)  AGM  batteries. I will like to use a  7000kw
    B&S gas generator to charge those batteries, using the 150A charger built in
    my 12V Freedom SW3000 Inverter/Charger. Is that possible, what hurdles should I be aware of?
    Any advise or comments will be appreciated. Thank you
    I do it all the time in winter, just for long enough to get the batteries through Bulk and start Absorb. 
    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 ,

  • jonrjonr Posts: 1,073Solar Expert ✭✭✭✭
    Note that the Smartguage site is completely wrong about "perfect balancing" - you will get much closer to that using an ammeter and wiring that may be quite different than what they show.    It also glosses over self balancing (a huge effect ignored in their calculations) and uses link resistance that is about 30x what 4/0 cable has (let alone bus bars).    That being said, method #3 makes individual fusing an option.
  • bigblueshoebigblueshoe Posts: 4Registered Users
    I have this same question, i want to use my backup generator (10,000 watt)
    To charge my lipo bank (16x1000ah) in the winter..is this really capable?
  • mcgivormcgivor Posts: 2,201Solar Expert ✭✭✭✭✭
    I have this same question, i want to use my backup generator (10,000 watt)
    To charge my lipo bank (16x1000ah) in the winter..is this really capable?
    The SW 4048 can be programmed in the same manner as the controller or you could  copy the settings via Xanbus  
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 

  • BB.BB. Posts: 27,882Super Moderators, Administrators admin
    Do you really have a 16 series cells x 1,000 AH LiPo battery bank? That is not small...
    oper
    The short answer is that LiPo (as far as I know, which is not that much) does not need a minimum charging current for proper operations (flooded cell lead acid need 5% to 10% minimum of their rated 20 hour capacity, and some AGM seem to require 20% rate of charge).
    ou
    So, you are really back to what is it you want... For example, say you want to charge your 60% discharged bank (20% to 80% state of charge range) in 6 hours (basically running your genset flat out for 6 hours, no other loads). That would require a 10% rate of charge (10% to 20% rate of charge is pretty common for genset charged systems). The math for to size the genset may look something like this (note: Lots of derating/fudge factors--But close enough for our discussion here):
    • 80% derating for genset... Most residential gensets should be operated at a recommended maximum of 80% of their output for long life/avoiding overheating. Charging batteries is actually quite hard on a genset (and wiring/breakers/etc.). The battery charger will draw rated current/power for much of the charging time (many hours). When most NEC rated wiring is really only good for ~80% of its rated (breaker/wire ratings) current (i.e., 15 amp breaker * 0.80 derating = 12 amps continuous current rating).
    • 80% derating for charger... This is a bit more Fudge Factor. Some charge controllers should have their wiring/input circuits designed for /0.67 (67%) derating because of relatively poor efficiency and poor power factor (non-linear current draw). Other chargers and inverter-chargers may be much more efficient and could use a 1/0.90 (90%) derating pretty nicely. Depends on your hardware.
    • Note that the details here also include power factor... Watts is the true power going into the battery bank from the genset. VA (Volts*Amps) is another rating method which accounts for "poor power factor"--Basically a electric load that does not "efficiently" use the sine wave current--And draws more current than would be indicated by "power" (Watts) alone. Most residential gensets/AC inverters/etc. are rated for a maximum Watts... And VA rating is typically the same (2,000 Watts max = 2,000 VA max). Commercial units may be rated at 0.8 PF (2,000 Watts * 1/0.80 PF = 2,500 VA).
    The basic math may look like this:
    • 1,000 AH * 3.7 volts per cell nominal charging * 16 cells in series * 1/0.80 genset derating * 1/0.80 charger losses/PF issues * 0.10 rate of charge = 9,250 Watt (really VA) rated genset
    The current available to charge your battery bank at 3.7 volts per cell from your system would be:
    • 10,000 Watts * 0.80 genset derating * 0.80 charger derating * 1/(3.7 volts per cell * 16 series cells) = ~108 Amp from charger @ ~59.2 VDC charging
    Obviously, you need a charger capable for outputting ~108 amps, and no other loads on your genset (recommended).

    However, many higher end chargers and inverter-chargers can be programmed for maximum charging current--So you could back down on charging current to allow other loads on your genset.

    And there are highly interactive inverter-chargers... Basically you connect the genset to the generator AC input of the inverter, and connect your load panel/breaker box (and your AC loads) to the inverter-charger AC output.

    Program the inverter-charger for maximum generator output current (10,000 Watts / 240 VAC = 42 Amps maximum). And the inverter-charger will vary charging current to the battery bank based on your loads (5,000 Watt AC load, only 5,000 Watts available for DC charging). Note that some inverter-chargers will automatically derate the 42 amps * 0.80 = ~34 Amps...

    This is a complex setup and you need to study all of your major components and your energy needs to make sure that everything plugs and plays correctly. The above is a very quick and dirty back of the envelope set of calculations and assumptions.

    Do detailed paper designs first before you start purchasing any hardware. Otherwise, you may be disappointed in your system's performance.

    Bigblueshoe, if you wish to discuss your needs in detail--I ask that you create a new thread about your needs and hardware/setup... This will keep the Q&A focused on your needs.

    Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490mike95490 Posts: 7,901Solar Expert ✭✭✭✭
    I have this same question, i want to use my backup generator (10,000 watt)
    To charge my lipo bank (16x1000ah) in the winter..is this really capable?
    Just reminding that below frost temperatures, Li batteries should not be charged.  If they are in a heated compartment you are ok.
    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 ,

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