Honda EU inverter - feed DC direct

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I wonder if someone has tried feeding DC directly to honda EU series of inverter generators. The EU series produces good quality pure sinewave from its inverter and wonder if it is possible to dicrect feed it from DC batteries. For a log cabin will a good match (EU inverter / batteries / solar panel) and save the money on the additional inverter plus get pure sine wave quality.

Any comment is much welcome.

Comments

  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
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    Re: Honda EU inverter - feed DC direct

    i see you made it onto the forum. hope you didn't have too much trouble.
    as to the honda, why would you want to do that? i'm really not too sure of what the input to the inverter is like in the way of voltage and frequency. is it your intent that an optional source be available rather than just the generator? if it's like some grid tie inverters with a wide range on it that could be versatile and even useful when an outage occurs to a grid tie only system, but i'm sure it will probably be high voltage input. anybody even check their honda for this? or know from other sources?
  • BB.
    BB. Super Moderators, Administrators Posts: 33,500 admin
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    Re: Honda EU inverter - feed DC direct

    Lion19,

    Glad you got on OK--Your are very welcome...

    You can download the Honda owners manual if you want--there is a wiring diagram (between major components, not internal electronics).

    It appears that they inverter uses a 3 phase variable frequency (and probably voltage) alternator (main windings) plus a ~12 VAC single phase winding for running some of the internal electronics.

    I would guess that the 3 phase winding is a higher voltage (120 VAC +???) to reduce the use of transformers/inductors in the inverter section (just a wild guess).

    Does not seem like an easy project to convert to a free-standing inverter.

    It is possible (I guess) that the unit might run on DC (high and low voltage) but given that you might have to derate the output given that you can probably only supply two DC phases, instead of the three AC phases it was designed for--plus you might have to add a large fan for air cooling (if it was designed for forced air cooling given that the engine is already there).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
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    Re: Honda EU inverter - feed DC direct

    bill,
    lion19 can correct me, but i think he/she may be thinking of their grid tie system with pvs outputting several hundred volts being fed into this inverter as a stand alone inverter running off of the grid tie pvs when there's no power on the grid. my guess on the inverter without knowing would be cheaper hi voltage mosfets so ac input would be under 85v. each phase could be rectified and filtered and sent into the input of the inverter with dc levels being higher and most likely around 120vdc or less.
    like i said this is speculative on my part and the voltages on most grid tie systems will be higher than this.
  • nigtomdaw
    nigtomdaw Solar Expert Posts: 705 ✭✭
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    Re: Honda EU inverter - feed DC direct

    Hi am I missing something here but a EU generator turns rotational energy from the ic engine in to electrical energy via a alternator, the rusulting power via some electronic wizardry comes out AC and a small amount rectified for DC. Feeding DC current from a PV array into a genny like the EU will only achieve one goal, opening of several doors and letting the smoke out.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,500 admin
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    Re: Honda EU inverter - feed DC direct

    Actually, many types of electronic power supplies basically take the AC input and rectify it to a high voltage DC intermediate stage, and then using FET switches, convert it into whatever output voltage/current desired.

    A high voltage of ~380+ VDC is not unusual at all (would voltage double a 120 VAC or not voltage double 240 VAC--that is what the switch between US and Europe would do in the old manual switched power supplies did--change the voltage doubler setting on the input).

    I looked into spec'ing a universal AC/DC power supply at one time for a voice mail system I was designing (something like 40-72 VDC, 95-264 VAC) and it was very doable. IIRC, the biggest issue is that the input stage needed to manage a 7:1 current range--made the input stage kind of expensive because of the over sized wiring/electronics required to use 40 VDC was wasted on 120/240 VAC systems.

    I know much less about inverters--so it is a guess--but it certainly seems that it could be possible. I was more wondering about the 3 phase input stage and the overall electronics designed for a 3 phase alternator input and if somebody without the the actual design information would be able to "trick" the electronics to accept DC inputs or if there were checks for engine RPM (as well as oil level monitoring, etc.). There is an exciter coil and throttle feed back control, so it is possible that the inverter may also need to manage its input and expect feedback on those functions too--and may "fault" if those don't work as expected.

    -Bill

    PS: The DC for battery charging comes from an independently wired stage of the alternator (single phase) and is simply rectified with a full wave rectifier. There is no connection (that I saw from the system schematic) between the battery output and any other inverter/engine function module. There are three AC phase coils (Y wound). Two separate DC windings (inverter and battery voltages), and an exciter coil.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • RCinFLA
    RCinFLA Solar Expert Posts: 1,484 ✭✭✭✭
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    Re: Honda EU inverter - feed DC direct

    120vac inverter-generators produce between 180 vdc and 280 vdc depending on speed and load. They are three phase alternator (like automobile alternator) with full wave rectifiers. The frequency of the alternator output is again variable depending on speed, several KHz. This (and three phase alternator) minimizes the rectified output filter cap size necessary.

    When you enable the 'energy saver' feature it reduces the engine speed to save gas when load is light on generator. Since the gas engine can not instantaneously increase its speed to produce more alternator output, this feature results in a dip in AC output sinewave peak when a sudden increase in load is applied. Some devices do not like this. (like refrig compressor). Maximum RPM of engine is around 3800 RPM.

    You could take the inverter and feed it from a 200 vdc battery pack. These inverters are push-pull H-bridge FET design, so like low cost inverters, do not like if you ground bond the neutral side (wider of two plug blades). The air flow intake to engine flywheel is passed over the heatsink of the inverter to provide cooling. A 3KW model's inverter probably consumes about 100 watts at no load but compared to engine loss this is insignificant to gas consumption. This consumption running from a battery stack would be a bit excessive.

    I have a Yamaha EF3000i feeding SW4048 through isolation transformer to allow for the neutral ground bond of house breaker box.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
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    Re: Honda EU inverter - feed DC direct

    i have my voltage range answered and it would seem the inverter on the hondas are possible candidates for being fed high voltage dc from some grid tie pv systems when the grid tie inverter has stopped due to anti-islanding from a power failure. this would allow the use of the pv power on that localized basis to allow that power to be utilized, but only as the sun does shine. not very convenient unless you can come up with a battery bank of the proper voltage and a suitable charger for it and many i would assume would really like to have all of this for full utilization of their system.
  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
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    Re: Honda EU inverter - feed DC direct

    ...it would seem the inverter on the hondas are possible candidates for being fed high voltage dc from some grid tie pv systems when the grid tie inverter has stopped due to anti-islanding from a power failure.
    niel,

    I'd be surprised to see this work, as grid-tie is fairly complex. In addition to passing the "passive tests" (line voltage and frquency) and the 5-minute timeout, UL 1741 requires grid-tie inverters also conduct "active" tests of their own. If the inverter doesn't "see" the correct reaction to its tests -- even when line voltage and frequency are within limits -- then it shuts down.

    Also, unlike a charge controller, a grid-tie inverter must be able to dump the full power delivered from the PV array. This is not an issue when back-feeding the grid. But, it can be a very real problem when trying to feed a "micro-grid".

    I think I got all of that right...:roll:

    HTH,
    Jim / crewzer
  • GreenerPower
    GreenerPower Solar Expert Posts: 264 ✭✭✭✭✭✭
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    Re: Honda EU inverter - feed DC direct

    There was a thread over OB forum that somebody did and confirmed the GX would connect to the EU sine output. I suspect it would connect to any "true-sine" inverter output. Jim is right, don't want to "sell" your excess power to the EU.

    If this is just for charging the battery when grid drops on a GX system, I rather use a gennie with a DC charger. If you are handy, you can build an in-expensive one with what I found here (sorry works for 240VAC in and 44-60VDC out only).

    Enjoy.
    GP
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
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    Re: Honda EU inverter - feed DC direct

    i am not debating the use of the inverter for being fed from the pvs in a grid tied system as i only speculated that lion19 may have been going that route in thinking. as to actually doing that many people have been looking for ways to utilize their high voltage pv system when the grid is down. they just sit there snidely looking at you during an outage doing nothing for you. i realize the problems in doing this and please don't anybody think i'm an idiot about it as i covered that it would have to be set as a localized operation without being connected to the grid and that isn't good with the solar intensity going up and down necessitating batteries and a charger anyway. that was a mouthful er fingerful.
  • System2
    System2 Posts: 6,290 admin
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    Re: Honda EU inverter - feed DC direct

    Thanks all for the useful information. From a technical standpoit I had always been fascinated how those little generators can produce pure sine wave. Years ago I did a very basic battery (4 golf batteries)/EU2000/coleman 400W inverter setup for a friend off-grid home. If worked fine for him for several years on weekend use (EU on day, battery on night). For budget reasons, no solar panel at that time (and gas was cheap then too), but I had always the idea of feeding the EU inverter directly to get the pure sinewave power quality. It seems that on theory it is possible, but pratically doesn't seems to be a good idea. Any way I feel very good that so many of you got interested in the topic.

    Best Regards!
    Lion19