Click for Mag Bay Click for Westport Click for Ocean Alexander Click for Northern Lights Click for Cross

Inverter vs Genset

Discussion in 'Technical Discussion' started by 3 ROYS, May 6, 2020.

You need to be registered and signed in to view this content.
  1. bayoubud

    bayoubud Senior Member

    Joined:
    Feb 19, 2017
    Messages:
    934
    Location:
    Florida
    I've never been able to justify a large inverter system on a boat, the cost of maintaining a large bank of batteries, chargers , and inverter vs running a generator don't make sense. Fix the main gen and look into installing a smaller night gen when your inverter system needs new batteries or major repairs.
  2. DOCKMASTER

    DOCKMASTER Senior Member

    Joined:
    Feb 26, 2012
    Messages:
    619
    Location:
    Ketchikan, Alaska
    I agree with bayoubud. I've considered an inverter numerous times. But with the electrical load requirements I just can't get enough run time from the batteries. Originally, my boat came with just a 20kw gen. It has has been modified to add a much smaller 9kw in addition to the 20kw. The 9kw runs 90+ % of the time considering I don't need A/C and heat is now from a diesel boiler vs. reverse cycle on the a/c chiller units. Even without A/C, the galley refrigeration, cockpit freezer, ice machines, etc. just draw too much load. The only way I would be able to use an inverter would be when the mains are running to keep batteries fed. That seems contrary to the point of an inverter.

    Also need to consider that battery life will be greatly diminished with increased depth of discharge. Every time you draw a battery down a certain % and charge back up you have put the battery through a "cycle". Most batteries have a cycle time rating based on a very low % of discharge (yes, even deep cycle). So if you are going to consistantly draw a battery bank down by more than 20% (some even 10%), you will likely be very disappointed in the life span of your batteries.
  3. Pascal

    Pascal Senior Member

    Joined:
    Feb 29, 2008
    Messages:
    5,872
    Location:
    Miami, FL
    While as mentioned an inverter isn’t replacement for a genset, as mentioned, It all depends on how you use the boat.

    i installed a 3KW inverter and 8 golf cart batteries on my 53 about a year after buying it in 2003. Cost was about $3000. First year I put about 1200 hours on the genny... second year 300... 900 hours difference at close to a 1 GPH... paid off in 15 months...

    It also depends on the boat. My 53 Hatteras has excellent ventilation with side doors and side windows so Air con in the the salon is rarely needed when anchored out. That wouldn’t work on a modern boat with no ventilation.
  4. chesapeake46

    chesapeake46 Senior Member

    Joined:
    Jul 26, 2009
    Messages:
    1,520
    Location:
    Chesapeake Bay, Delaware Bay & S.Jersey
    That was PacBlue but I'll take credit ........
  5. DOCKMASTER

    DOCKMASTER Senior Member

    Joined:
    Feb 26, 2012
    Messages:
    619
    Location:
    Ketchikan, Alaska
    All good info. My point was in response to OP who said he was looking at an inverter in lieu of replacing his gen. So the question was about having an inverter without a generator. I believe this would be a mistake IMHO.
  6. bayoubud

    bayoubud Senior Member

    Joined:
    Feb 19, 2017
    Messages:
    934
    Location:
    Florida
    OP needs to fix the Gen with same setup as Pascal's, both have same size Hatteras. Your right Inverter only power source would not work well for size of boat and equipment.
  7. Oscarvan

    Oscarvan Senior Member

    Joined:
    Nov 10, 2015
    Messages:
    883
    Location:
    Chesapeake Bay
    There are actually all electric high end RV's being designed as we speak. (Not by hobbyists, by the big guys). And you charge it with a modern alternator while driving. Technology there too is developing. CAN bus controlled high output alternators (even at idle) without the cooling issues... etc. etc. You can stuff a LOT of LiFe under the kitchen floor of a Hatt galley. And they weigh a lot less than lead acid/AGM etc....

    It's coming. That said, it's VERY expensive to do it right. The genny is, still, the most cost effective solution.

    So to the OP, unless you're in it for the science and have an "open checkbook policy"...... just get a nice fresh genny.
  8. Capt J

    Capt J Senior Member

    Joined:
    Jul 11, 2005
    Messages:
    13,400
    Location:
    Fort Lauderdale
    ACTUALLY, the 53' Hatteras was designed to be run with the generator on always. The air horns are powered by a 120 volt air compressor in the engine room and the electronics battery is also the generator battery bank......so either the generator alternator OR it's battery charger charge it. Can't charge it with the engines because it's a 12 volt bank.
  9. bayoubud

    bayoubud Senior Member

    Joined:
    Feb 19, 2017
    Messages:
    934
    Location:
    Florida
    Sea Lion post #23 is interesting. Intergel Solutions, a generator system that mounts to the engine and can charge at idle. The video showed charging lithium ion batteries which are great but very expensive, 8D's cost about 2k to 3k depending on amperage. Did not see a cost for the system but said it will also charge AGM's.
  10. Oscarvan

    Oscarvan Senior Member

    Joined:
    Nov 10, 2015
    Messages:
    883
    Location:
    Chesapeake Bay
    Yes it works. Yes it's expensive to install. And I don't like their presentation in that it is trying (too) hard to sugarcoat the fact that main engine fuel consumption WILL go up. Every horsepower has a price. The laws of physics apply.....

  11. bayoubud

    bayoubud Senior Member

    Joined:
    Feb 19, 2017
    Messages:
    934
    Location:
    Florida
    These type gens would eliminate most of the maintenance required by conventional gens. Just think, no thru-hull, raw water strainer, impeller, HE, zincs, oil change! Sounds good to me! I doubt the fuel cost on the main engine would be any more than a regular gen. BUT, CaptJ says it will not work for the 53 Hat, would require electrical mods.
  12. DOCKMASTER

    DOCKMASTER Senior Member

    Joined:
    Feb 26, 2012
    Messages:
    619
    Location:
    Ketchikan, Alaska

    I think it is very plausible. However, if you are sitting at anchor for an extended period or even a dock or slip without shore power, do you really want to have to run a main engine to charge batteries once they get depleted? And how long and how often would you have to run that main to get batteries charged back up? Better yet, do you want somebody next to you running their m/e at idle for hours because they have no gen?
  13. SeaLion

    SeaLion Senior Member

    Joined:
    Nov 11, 2013
    Messages:
    181
    Location:
    Ft. Lauderdale
    Plus AC and A/C underway at all times. And on the hook for a while with a big enough bank. Lithium batteries are getting better and cheaper and can be more deeply discharged and more quickly recharged for more cycles than FLA/AGM etc. Maybe cheaper than FLA/AGM in the mid-long run by now, but I haven't analyzed it that deeply, and the analysis is VERY application specific. It's safe to say that the best battery setup is as easy to agree on as the best anchor.
  14. bayoubud

    bayoubud Senior Member

    Joined:
    Feb 19, 2017
    Messages:
    934
    Location:
    Florida
    Agree, idle hrs. not good on hi-performance marine engines. Might work on small mains.

    As Sea Lion just posted, very application specific. Probably worked well on that Catamaran in the video. Most likely small mains. System as designed probably works best for moderate loads. Still a good concept, on the right boat would be a good system.
  15. rtrafford

    rtrafford Senior Member

    Joined:
    Jul 13, 2019
    Messages:
    843
    Location:
    Vero Beach
    Lithium batteries burn white hot.....just adding that piece to the discussion...
  16. SeaLion

    SeaLion Senior Member

    Joined:
    Nov 11, 2013
    Messages:
    181
    Location:
    Ft. Lauderdale
    True. All the Li family require a BMS and smart charging to monitor for overheating, etc.
  17. v10builder1

    v10builder1 Senior Member

    Joined:
    Sep 22, 2012
    Messages:
    31
    Location:
    Centreville/Kent Narrows, MD
    I reviewed the Integrel site and watched the video - I offer these comments. The Integrel system includes additional and updated components that represent performance improvements, but the idea is the same as the system I have on my trawler - I could say, in jest, that they adapted my idea.

    FYI, I have a 340 Ah 48 VDC battery bank and a 3kW inverter/charger, no generator (yet). I have identified 2 vendors who can provide a 48 VDC engine driven alternator/regulator/charge controller, but I have not yet moved on that.

    Based on the research I did, the Integrel claim of 9 kW from their engine driven unit is optimistic. Both my vendors say they can provide a 100 A maximum 48 VDC alternator on a conventional high output alternator frame - a separate drive belt would be required, and the pulley would be sized to operate the alternator at about 2500 - 3000 RPM when my Cummins 6BT -5.9 is at 1950 RPM cruise. This would be 4.8 kW, a conservative match for the 3kW inverter/charger, and I will have ac underway, and the 48 VDC bank will be topped off when I'm finished with the engine - I don't plan to run the engine when not underway, and won't have ac off of shore power. The load on my 210 HP engine would be about 6.5 HP (4800 watts divided by 746 watts/HP = 6.43 HP. Integrel's 9 kW alternator (don't care what they call it) would be 12 HP. I don't doubt they can provide a 9kW alternator, but I need to be enlightened about how a 30-40 HP sailboat auxiliary diesel can output 12 HP just idling along. Their advertising is true though - you can do without the generator, you just have to accept a bit of sacrifice of comfort.

    As we have discussed earlier, the 48 VDC lithium technology battery bank shown in the video is latest technology, and, IMHO, the correct choice for their system. The many advantages of a 48 VDC bus, in addition to the 12 VDC system retained, is a topic for another thread. I don't know about 48 VDC appliances, but these folks are not US based.... Also, it would take a big 48 VDC bank to provide much ac overnight .... But you can't please everybody.

    Dream system ( or nightmare based on your view). Separate 12 VDC or 24 VDC system for navigation electronics, running lights, engine power and starting, bilge pumps, etc. Inverter based 230/115 VAC system. Primary and secondary high quality inverter/chargers, switch selected, correctly sized for worst case loads. 48 VDC input, 230/115 VAC output. 48 VDC lithium technology battery bank, sized per your wallet, charged from 2 sources. Source 1 = shore power via inverter/chargers. Source 2 = Onboard new diesel generator (this is technically an alternator) - product of established marine rated equipment manufacturer. 48 VDC output, sized for worst case loads. Although not typically marinized, these units are often used for backup power for long line telephony equipment stations, and marine rated units will be available soon if not already.

    In my opinion, this configuration would be very robust, and expensive, but practical up to about 12kW. Because of the control capabilities built in to the modern inverter/chargers, there would not be a need for much by way of interfacing components - only primary/secondary inverter switching. Larger boats, larger systems, multiple generators, another discussion.

    Briefly, the advantages: Clean power, at proper/consistent voltage, for all onboard equipment, no sags or switching of power under normal circumstances - the inverter (virtually no moving parts) operates 100% of the time, even shore power quality issues are eliminated. Generator (alternator) run time is minimized to reduce maintenance and fuel cost. Automatic operation. 12/24 VDC batteries charge whenever there is a need, without engine run. No need to over-size the generator to provide for starting motors.

    Thanks. I especially appreciate those posters who have provided their descriptions of inverter issues.

    Joe
  18. bayoubud

    bayoubud Senior Member

    Joined:
    Feb 19, 2017
    Messages:
    934
    Location:
    Florida
    Yep, did not consider that. Still a good system with AGM's on the right boat.
  19. 3 ROYS

    3 ROYS New Member

    Joined:
    Jan 25, 2020
    Messages:
    3
    Location:
    California
    I very much appreciate the robust and detailed discussion of my original question; lots of experience & knowledge here.

    I am going to continue to evaluate my expected ‘off shore power’ requirements, which drives everything else. Regarding that, I think that the need for AC in SF Bay has been overestimated. Not that it’s never used but, I’ve lived here 15 yrs over the past 30 yrs, and never had a house with it or really needed it more than a couple days a year here and there. Of course, there are other big loads: range/oven and hot water heater; the first of which I can work around, with the second one being a bit more problematic, but perhaps manageable.

    I will say that one big take away for me so far is the ongoing cost of batteries. I’d not realized how often they’d have to be replaced. That one factor seems like almost a deal killer for the inverter option versus a genset when I’m comparing them in the 12kw+ range.

    I have plenty of time to do more research as I learn this new boat. So, I’ll keep studying, talking to those with more experience, and visiting here. Thx again for all your feedback.
  20. Capt J

    Capt J Senior Member

    Joined:
    Jul 11, 2005
    Messages:
    13,400
    Location:
    Fort Lauderdale
    What is so wrong with running a generator? They burn next to nothing in fuel and they do the job.