Generator input to a solar charge controller?

This might be a dumb idea, but here goes:

I have a Honda EU1000i generator and will be adding a small PV system to my funky old RV. I plan on running a 65W panel through a SunSaver Duo to charge a Costco Group 27 deep cycle house battery + the start battery. Loads are minimal, and I'm not trying to fulltime.

So far, so good. Now here's the potentially dumb part: Is there any reason I can't run the Honda's unregulated 12V@8A (reportedly c. 15VDC, but I need to measure) through the SunSaver's "solar" input?

I understand that a dedicated charger would put out more current, but 8A is probably a good rate for a 85Ah battery anyway and I'd like to avoid the cost and added complexity associated with e.g. a Xantrex TC10TB.

The generator might not play nice with the panel if run in parallel, but would the charge controller care where it gets its juice?

Comments

  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Generator input to a solar charge controller?

    not so dumb of a question. you may be able to, but i suspect that the voltage may not be high enough to operate the controller and deliver the charge. try it, but at your own risk. odds are nothing bad will happen, but i have to cover my butt with a disclaimer as i even placed a unregulated battery charger up to a sunsaver and it worked. the thing is the charger failed and sent 120vac down the dc leads and blew out the controller. if you do this then put a fuse on it as you never know.
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Generator input to a solar charge controller?

    I suspect it is not the case that the cc doesn't care "where it gets it's juice", but more importantly, what does it do with that juice when the battery is full. A solar panel can be just "shut off" or 'dialed" down with the cc (depending on cc design), but a generator cannot just shut off. That is why most solar ccs won't work with wind for example. Your eu is (in this example) just like a wind generator.

    Tony
  • System2
    System2 Posts: 6,290 admin
    Re: Generator input to a solar charge controller?
    icarus wrote: »
    Your eu is (in this example) just like a wind generator.

    Interesting point. I should do some testing to see what the open circuit voltage is with various engine RPMs and AC loads. If the EU's electrical generation is done with something like an automotive alternator, then I don't think the same worries about open circuit voltage apply. Or do they? I spent many years doing high end car audio and security, but my experience with alternators was limited to go/no-go diagnosis.

    Come to think of it, I'll bet there's also a lot of ripple that could cause heartburn for the controller. Time to fire up the meter and 'scope ... or maybe I should just resign myself to getting a dedicated charger?

    Thanks for the responses! More thoughts invited.
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Generator input to a solar charge controller?

    I confess a great ignorance as to the workings of alternators, I will leave it to Bill, or Neil, or Jim to chime in as to the workings of alternators. Let the EEs speak!

    Tony
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Generator input to a solar charge controller?

    i doubt the alternator has much meaning as far as this goes as the dc output from the eu1000i is probably regulated. not a bad idea to check for the ac ripple though.
  • System2
    System2 Posts: 6,290 admin
    Re: Generator input to a solar charge controller?

    From the EU manual, p. 16: "The DC charging output is not regulated."

    I might be able to take a look at the output with an oscilloscope this evening or tomorrow and report back.

    I don't mind paying a little more for a dedicated charger, but I like the idea of doing the mostest with the leastest. 8) I'd also get full instrumentation from the Duo's meter and not have potentially odd interactions between the Duo and a charger (or do I need to concern myself about that?).

    Thanks again!
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Generator input to a solar charge controller?

    If you can monitor/estimate the charge supplied by the eu1000i--then just do a timed run (say 2-3 hours) with the generator's output connected directly to the battery (watch the battery voltage with an accurate DVM) and as long as it does not over voltage or boil the battery too much, then let it go (you can turn of the gen. when the voltage starts to rise and the battery starts bubbling--no reason to charge beyond that point while paying for gasoline unless you are equalizing)--and that would make sense if you have other AC loads that you are using at the same time...

    If, you are just running the eu1000i for the 12 volt output--then it probably is not very fuel efficient (8amps*14volts=112 watts)...

    It would be more fuel efficient if you ran the AC output at ~1/4-1/2 rated load (900 watts * 1/4=225 watts minimum) or more. If you can get a decent automotive charger with "deep cycle" setting--you probably would be fine (although--packing the extra charger is probably more of a pain than the cost of purchase).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2
    System2 Posts: 6,290 admin
    Re: Generator input to a solar charge controller?

    This is a great forum--lots of great comments!
    BB. wrote: »
    If you can monitor/estimate the charge supplied by the eu1000i--then just do a timed run (say 2-3 hours) with the generator's output connected directly to the battery (watch the battery voltage with an accurate DVM) and as long as it does not over voltage or boil the battery too much, then let it go (you can turn of the gen. when the voltage starts to rise and the battery starts bubbling--no reason to charge beyond that point while paying for gasoline unless you are equalizing)--and that would make sense if you have other AC loads that you are using at the same time...

    If, you are just running the eu1000i for the 12 volt output--then it probably is not very fuel efficient (8amps*14volts=112 watts)...

    It would be more fuel efficient if you ran the AC output at ~1/4-1/2 rated load (900 watts * 1/4=225 watts minimum) or more. If you can get a decent automotive charger with "deep cycle" setting--you probably would be fine (although--packing the extra charger is probably more of a pain than the cost of purchase).

    -Bill

    I don't want to run the generator unless the PV isn't keeping up due to weather, etc., so I'm not too worried about efficiency for occasional use. If the shortfall gets chronic, I'll add more PV.

    BUT ... I just proved that I'm NOT a genius and that the whole issue is moot anyway since I'd be without a shore power solution if I left out the charger! :blush:

    I don't like being tied to hookups, but they have their place and it seems silly to pass up "free" power if available.

    Now I think I owe the forum some information on what's coming out of the generator's 12VDC port in case someone else wants to try the same thing in the future.

    It helps to thinks things through, eh?
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Generator input to a solar charge controller?

    If you can size your shore power charger (20 amp Xantrex TC) to work with the eu1000i (or whatever charger you pick)--then you would be killing two birds with one stone (a good thing here ;) ).

    I believe Tony/Icarus uses a TC-20 with his eu1000i (the TC-40 is a bit too big?).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Generator input to a solar charge controller?

    Tc 20 is a great fit for the eu 1000, runs it a idle, burns as close to no gas as you can imagine. Won't run a tc-40 due to the power factor. (I sent my tc 40 on to eric/westbranch!)

    Tony

    Ps I believe, and I know Bill will correct me if I am wrong, but the generator's total capacity is a combination of the 12vdc as well as the 120vac, in VAs, so even if you were to run the eu 1000 at rated 120vac output, you would then have an additional 8 amps available at 12vdc.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Generator input to a solar charge controller?

    Good Question Tony,

    From when I looked at my eu2000i manual--the 12 volt battery charging winding was drawn as a separate coil/phase from the other phases used to power the inverter (there may be two other AUX windings--one to power the inverter and another to run the ignition system)... And there were no statements about running full AC load + full battery load (one way or the other)... And there appears to be no circuitry/load protection that takes the 12 vdc + 120 vac output wattage summed together into account.

    It would be pretty difficult probably to add AC loads + 12 vdc loads to max the nameplate rating--and if you do and damage the unit--send it back for warranty.

    Also, in the eu2000i manual, they state that when using the DC output, you have to have "ECO Throttle" turned off (engine runs at full speed). So--this would be a drawback as your genset will be burning quite a bit more fuel that it would otherwise when running such a light load.

    The DC output looks to be a "free-bee" and I would not plan on using it for anything more than a handy outlet in an emergency when nothing else is available.

    In the end, you have loads that add up to 900+ watts--then I would go up to the next sized unit (eu2000i)... The eu1000i is probably too small for the job (the eu2000i will still be very fuel efficient at 400-900+ watts of load--possibly even more fuel efficient than the eu1000i at similar loads).

    The above was the long way of saying I have no clue... :cool:

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2
    System2 Posts: 6,290 admin
    Re: Generator input to a solar charge controller?

    According to the selection chart at Xantrex, I should use a TC10/TB with my single 85Ah flooded battery. Even assuming a crazy load factor, my little EU1000i will loaf along at a little less than quarter power while running the charger.

    My DC loads are minimal: by my calculations, I have a fighting chance of keeping everything going with a single 65W PV panel from March through October. I'd probably have to triple the PV array to be energy positive in the winter, but I'm not trying to fulltime. Considering the economy, maybe I should think about it. ;)

    I'll add a 5000BTU A/C unit next year, and that will give the little gennie a run for its money. I see a hard start capacitor in my future. :D
  • System2
    System2 Posts: 6,290 admin
    Re: Generator input to a solar charge controller?
    BB. wrote: »
    Good Question Tony,

    [snip]

    The above was a the long way of saying I have no clue... :cool:

    -Bill

    More of a clue than yours truly. That was some interesting info on the little Hondas, thanks.
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Generator input to a solar charge controller?

    Jnoble,

    Consider a tc20 rather than a tc 10. The tc 20 will reduce it voltage and amperage as the battery come close to full, so it shouldn't over charge the smaller battery. The reason I suggest the larger charger is that systems almost always grow, and having a charger big enough to charge a bigger battery bank would be handy.

    Tony