Tie in Generator to DC Load

Hey all,

In the midst of installing a small off-grid PV system into a family cabin, primarily to add in lighting. Cabin has been in the family for 40+ years and to date, we've always used lanterns and propane lighting. When the place was built, we had it wired for AC and when we need to use a vacuum or lighting, we can fire up an older Honda 1400W generator.

The generator can supply either 110VAC to power appliances or 12VDC (at roughly 7-8 Amps) to charge batteries.

System consists of:
3 x 125W 7.1A panels
1 x Morningstar 45A Charge Controller
1 x GoPower 2000W inverter
2 x Trojan T105 6V 225Ah batteries (may increase this to 4)

Cabin is primarily used Spring and Summer and we should get more than enough sunlight to provide for our needs.

Question to the forum: In the event that we need additional charging capacity, it seems to me that a simple way to tie in the generator is to connect the DC side of the generator to the charge controller. I'd likely tie it in via a Combiner switch so that I can combine the solar and generator DC loads or isolate either load if I wish. Can combining the DC loads damage the system in any way? Is what I've proposed an acceptable practice or not?

Comments

  • mike95490mike95490 Solar Expert Posts: 9,097 ✭✭✭✭✭
    Re: Tie in Generator to DC Load

    I would get a regular 120V smart automotive charger. Research the PF (power factor) on the unit before you buy, because lower than .8 will mean you have to oversize the genset. Size the amps output, to something the genset can provide
    ie 12V @ 30 A = 400W, 12V @ 50A = 600W
    inputs will be about 110% of the output (losses in the charger)

    If you can do a bulk charge from genset for half hour in the morning, that will help a lot, and let the solar top off the batteries the rest of the day.
    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 ,

  • BB.BB. Super Moderators, Administrators Posts: 31,171 admin
    Re: Tie in Generator to DC Load

    I agree with Mike,

    Get a 10-20 amp 12 VDC battery charger (it can either be a simple battery charger, or you can get a dedicated deep cycle charger--but since you have solar power, the deep cycle stuff may not be too important).

    If your generator is ~900 watts max of rated power, you can probably power the typical 20 amp 12 volt battery charger. If you have a 1,600 watt geneset, you can probably run a typical 40 amp charger without problems.

    The 8 amp output from the genset is usually not much more than an emergency, unregulated 12 volt charger. For Honda eu1000i/eu2000i gensets, you have to have eco throttle turned off (run at high speed), and some manuals say you cannot have a 120 VAC load at the same time.

    If you want to see the details of picking the "optimum" AC battery charger for a Honda eu2000i--take a look at this thread--This was not a simple project:

    Question about battery charger selection with EU2000

    Also, the Honda eu1000i and eu2000i are very quiet and quite full efficient with smaller loads... You might want to look at one of these if your current genset is getting old and/or too noisy.

    The thread is an interesting read if you are technically inclined... But perhaps not a good for somebody who is not.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • TenMileTenMile Solar Expert Posts: 62 ✭✭
    Re: Tie in Generator to DC Load

    Thanks guys,

    I'm not sure what model the Honda generator is -- will take a look the next time I am up there -- needless to say -- it's old -- probably 15+ years. No eco-throttle and no quiet modes. The only time it's generally run is when we need to vacuum so the noise from it is negated anyhow.

    So either way, if I use the 8 Amp charger built into the generator, or if I pick up a 20 Amp charger -- my question was still around the best way to tie into the DC load. Should I tie the load from the Generator/Charger and Panels into a DC Combiner switch and then feed the Charge Controller?
  • BB.BB. Super Moderators, Administrators Posts: 31,171 admin
    Re: Tie in Generator to DC Load

    You should connect all chargers directly to the the battery bank / common bus point.

    Each battery charger needs to see the full and correct battery voltage and will charge the batteries as it sees best (and the battery charger with the highest voltage will be the last one charging).

    There is no issue (in general) with paralleling battery chargers...

    For some AC battery chargers, they actually may place a load on the battery bank when AC power is off (i.e., generator stopped). So, you may want to check that and/or disconnect the AC charger when not needed.

    Each positive cable that leaves the battery bank should have its own fuse/breaker to protect your connected wiring.

    Storage Batteries can output 100's to 1,000's of amps into a dead short, and you should have a fuse or breaker panel to protect all of your loads and charging sources (fire safety).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarusicarus Solar Expert Posts: 5,400 ✭✭✭✭
    Re: Tie in Generator to DC Load

    Come to the 21st Century regarding charges and gennies for small applications. I would suggest a Honda EU 1000 (Or one of the many clones,,I just saw a clone for under $200!) Couple that to a Xantrex TC 20, or an Iota 15 or 30 amp charger and you will have a very simple, slick system that make almost no noise, and burns very little fuel.

    I just had to run my charger today for the first time in several months since we have had several days of no sun, and lots of draw. The Eu 1000 ran 5 hours on ~ 1/2 tank, which is ~ 1.5 litres! Outside the house window I can't even hear it or know it it going.

    Tony
  • TenMileTenMile Solar Expert Posts: 62 ✭✭
    Re: Tie in Generator to DC Load

    Thanks Icarus,

    A new generator may be in the cards one day. I'd like to find this $200 Honda clone you mention as all my price searches locally for the EU1000 are >$1000. I'm located in Canada as well - on the left coast. I've just dropped some real coin on my solar system and wasn't looking to keep spending, so well I agree that our generator could be better, today it's "good enough". ;)

    PS: Thanks for the words of wisdom on fuses etc... I didn't go into the details of my system setup but it goes as follows:

    Panels --> Disconnect --> Fuse Block --> Charge Controller --> Fuse Block --> Battery --> DC Breaker --> Inverter --> AC Panel
  • icarusicarus Solar Expert Posts: 5,400 ✭✭✭✭
    Re: Tie in Generator to DC Load

    "tool town" I think that is what is called, a chain with an outlet in T-Bay. Pretty much junk stuff but a friend of my just bought one.

    T
  • BB.BB. Super Moderators, Administrators Posts: 31,171 admin
    Re: Tie in Generator to DC Load

    At least in the US, you can get a eu1000i for ~USD$750 or an eu2000i ~USD$920 delivered (California version is ~$20 more) from a couple online dealers (as of a couple weeks ago).

    Obviously, out of the US, I have no clue.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarusicarus Solar Expert Posts: 5,400 ✭✭✭✭
    Re: Tie in Generator to DC Load

    Here is the link to "tooltown" and thier Eu2000 clone.

    The 1000 is not a Eu 1000 clone, I don't know if they sell one in the store that is different.

    http://www.tooltown.ca/king-2000w-digital-generator.html
  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Tie in Generator to DC Load

    Personally, I wouldn't refer to it as a "Honda clone". The Kipor yes because they got sued by Honda for cloning...all the rest are not Honda clones, but just cheap Chinese inverter generators.

    The one you linked to looks like a YongKang Xingguang XG-SFx (made in many sizes and variations):

    http://www.ykxg.com/en/products.asp?tc3_id=191

    http://ykmqc.en.ec21.com/offer_list.jsp?gubun=S


    EDIT: To the OP - I'd forget about using the 12v from the generator at all and just buy a good charger to run off the 120v output of the genny. Forget about running the gen's 12v out into a solar charge controller - the charge controller will want a higher input voltage so it can pump up the battery to 14.4v and the 12v output on the genny almost certainly won't supply it.
  • icarusicarus Solar Expert Posts: 5,400 ✭✭✭✭
    Re: Tie in Generator to DC Load

    I used the term "clone" broadly. Personally I wouldn't buy any of them. I have a friend who had a Kypur, and was so pleased with it, until it quit in year 2, started putting out wild voltage.

    Tony
  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: Tie in Generator to DC Load

    And they burn more than 1 liter per hour, a lot more than the Hondas, especially the 1000 model @ ~ :D0.3 L / hr :D at low load!
    cheers
    Eric
     
    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
  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Tie in Generator to DC Load
    westbranch wrote: »
    And they burn more than 1 liter per hour, a lot more than the Hondas, especially the 1000 model @ ~ :D0.3 L / hr :D at low load!
    cheers
    Eric

    Well...actually, that's a myth.

    I have a Honeywell with 125cc engine, which is just an XG-SF2000 with a Honeywell sticker on it. It runs 13+ hours on a 1.5g tank with a light load (my little 10a Shumacher battery charger).

    1.5g = 5.7l / 13h = .43l/h

    Sure, that's more than the eu1000i, but the eu1000i only has a 50cc engine.


    If you just look at the published ratings, the numbers work out like this:

    Honda eu2000i - 10 hours per 1g fuel at 25% of rated load (400w).
    Honeywell HW2000 - 6 hours per 1.5g fuel at 50% of rated load (1000w).

    So...

    10h * 400w = 4000wh / 1g = 4000 watt*hours per gallon
    6h * 1000w = 6000wh / 1.5g = 4000 watt*hours per gallon


    Same difference.

    A certain sized engine will burn a certain amount of fuel at a certain RPM under a certain load - regardless of who made it. Honda doesn't have any magic formula to work around the basic physics.


    EDIT: Duh. Just now thought about why not do the math on the eu1000i while I'm at it...

    From the Honda web site:

    8.3 hours per 0.6g at 25% of rated load (225w)
    8.3h * 225w = 1867.5wh / 0.6g = 3112.5 watt*hours per gallon

    Hrmm...someone double check my math please...
  • Ralph DayRalph Day Solar Expert Posts: 927 ✭✭✭✭
    Re: Tie in Generator to DC Load

    Nice little math lesson. And if you have enough Honeywell gensets around...what number are you on now?

    Ralph
  • BB.BB. Super Moderators, Administrators Posts: 31,171 admin
    Re: Tie in Generator to DC Load

    Wasn't going to say anything but the eu2000i is a 1.1 gallon tank, so 10% off of their kWH/Gallon numbers...

    Also notice that the one is quoted at 400 watts (1,600 watt rated) vs 1,000 watts (2,000 rated?)...

    kWH/Gallon goes way down as % of rated loads drop... The Honda eu (and other inverter/generators with variable running RPM based on current load) generally have better kWH/Gallon ratings then the cheap 3.5-5kW "noise makers". However, the cheap noise makers may have slightly better efficiency near 100% (less conversion losses).

    Honda made a big change in their 1/4 load ratings for their eu2000i gensets, prior to a few months/year ago, they quoted 15 hours at 1/4 load for 1.1 gallons of fuel.

    Current spec.
    is 9.6 hours per 1.1 gallons of fuel (actually also says per 1 gallon of fuel)... Several oh-oh's here...
    • Fuel efficient - up to 9.6 hrs on 1 gal of gas
    • Eco-Throttle - runs up to 9.6 hr on 1.1 gal. of fuel
    • Run Time per Tankful 4hrs. @ rated load, 9.6 hrs. @ 1/4 load
    In the end, "balance" is the key word here.

    And, if it sounds too good to be true (15 hours @ 400 watts on 1.1 gallons of fuel)--It probably is... Even if it is Honda.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarusicarus Solar Expert Posts: 5,400 ✭✭✭✭
    Re: Tie in Generator to DC Load

    As Bill says,, The right tool for the right job1

    I wouldn't run my 5 kw lister Diesel just to run my 20 amp Xantrex charger, even though the lister can deliver 5 kw more efficiently than the Honda.
  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Tie in Generator to DC Load
    Ralph Day wrote: »
    Nice little math lesson. And if you have enough Honeywell gensets around...what number are you on now?

    Ralph

    On #3 now. The first two were returned so I only have the one. This one does get 30% better run time than the first two did, but it's also a newer model. They did change their specs - the older ones claimed 5 hours @ 50% load, where the box for the newer one says 6 hours.

    It took me a while to work through the marketroid doublespeak and come up with a quick way to compare the published ratings.

    One thing that threw me off was reading in many places how the Hondas got so much better fuel economy than the Chinese inverter gens. Once I worked out the math though - I found it just wasn't true.
  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Tie in Generator to DC Load
    BB. wrote: »
    Also notice that the one is quoted at 400 watts (1,600 watt rated) vs 1,000 watts (2,000 rated?)...

    Yea, I know...

    The older Honeywells were rated 2000w continuous, 2200w surge. The newer one's specs say 2000w continuous, 2100w surge. The XG-SF2000 family usually state 2000w continuous 2200w surge but they've built so many different units under that same Model Number that it's hard to get a lock since the specs seem to be slightly different for every version.

    Still...it's good enough for government work. :D
  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Tie in Generator to DC Load
    icarus wrote: »
    As Bill says,, The right tool for the right job1

    I wouldn't run my 5 kw lister Diesel just to run my 20 amp Xantrex charger, even though the lister can deliver 5 kw more efficiently than the Honda.


    Absolutely. I bought the Honeywell for the 2000w rating because I had planned to install an a/c unit in the camper. But that was right after I got the camper. Actually using the camper, I found that a few extra fans were good enough and I didn't need the a/c after all.


    If I had it to do over, to buy a gen just for battery charging, I'd probably buy the little Champion 1080w/1200w/1500w synchronous which claims a 10 hour run time at 50% load on 1.2g fuel (80cc engine). Champion has a great rep over on the RV forums:

    http://www.amazon.com/gp/product/B0028VB6XO/ref=s9_simh_gw_p86_d0_i1?pf_rd_m=ATVPDKIKX0DER&pf_rd_s=center-4&pf_rd_r=1A7M8G0RT5R0R9E27X0A&pf_rd_t=101&pf_rd_p=470939031&pf_rd_i=507846


    BTW, if I haven't mentioned it before - Champion now has a 1600w/2000w inverter gen - and two can be synced ala Honda/Yamaha. I hear they're going for about $500 ea. at Costco:

    http://www.amazon.com/Champion-Portabler-Inverter-Generator-73531i/dp/B0041K09D8/ref=sr_1_1?s=home-garden&ie=UTF8&qid=1300904110&sr=1-1
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