Inverters

Discussion in 'Electrical Systems' started by Jmarkley, Sep 13, 2004.

  1. Jmarkley
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    Jmarkley New Member

    Can an inverter system be a viable alternative to a generator? I would like to install one that would start and run the heat pump (A/C and heat) in my 29 Sea Ray. I have room in my engine bay four four or five batteries. Thx for everyone's input.
     
  2. Dutch Peter
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    Dutch Peter Senior Member

    Yet an other for the electricity forum!

    You can use this system ofcourse, but I think the battery capacity is to low even with 5 to have the AC running for a long time. But I don't know the math, that is why I trying to start a electricity forum!
     
  3. cgorton
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    cgorton Junior Member

    Here are some numbers:

    the smallest self-contained Marine Air unit (http://www.oceanoptions.com/mas_vectorcompact.htm) is a 5kbtu/h size. It's full-load amp draw in cool mode is 5.2 at 115VAC.
    If you invert DC power to AC to cover that, it's 115/12*5.2*1.1=55A at 12VDC. (The 1.1 is a rough power loss factor for inverting). So, you have to pull 55 amps from the batteries. If you had (4) 200 amp-hour batteries and discharged to a 50% status (recommended), that gives you 400 amp-hours to use, not including any other appliances. 400/55=7.3 hours. But, battery ratings are not generally for such a high draw, so I don't think you'd get 7.3 hours. Then again, the unit won't be under full-load the entire time unless it's really hot or the cabin is open.
    The thing is, (4) batteries of that size weigh around 640 pounds! And you have to re-charge them.
    The above explanation is why it's generally not done. I'd like to hear other's experience, though.
     
  4. Jmarkley
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    Jmarkley New Member

    Cgorton,
    You're saying that the batteries weigh 160 lbs each. Are you sure about that? Are you talking about regular marine batteries? As far as recharging goes, wouldn't the batteries be recharging anytime the engine was running and anytime shore power was connected?
     
  5. yipster
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    yipster designer

    200 amp gel baterry's may not weigh in at the quoted total 80 kilograms, but they are quit heavy i tell you. was thinking of making banks from multiple 100 or 120 watt. ofcourse you can use shorepower or have the engines run but cgorton is rite; its not done that way.
    i have a 1000 watt 4 stroke gas generator that takes care of some other 220v appliances but i never understood where the lost watts went using say 150. saw some new real chiep 100 bucks 2 stroke 200 watt generators that seemed to make sense to me, weight less too :D
     
  6. cgorton
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    cgorton Junior Member

    http://www.lifelinebatteries.com/marine.asp

    These were the batteries I was spec'ing- they are indeed 162 pounds each. These are 8D (big) batteries. If you're talking about smaller ones (group 24, 31, 34) they're lighter and have considerably less capacity.
    Yes, your engine or shore power can recharge them, but you were asking about replacing the genset with batteries. If you're plugged into shore power, you don't need the inverter! And if the engine is running, you don't need big battery banks. The genset is really for when you're on the hook with no shorepower and no engine running. With enough capacity, yes you could run the A/C for a few hours, but the batteries will weigh more than the genset. (A 3.8kW Westerbeke diesel weighs about 200 lbs.)
    Running serious AC loads from DC batteries is something I would only advise if you really can't stand the hum of a genset. Otherwise, it's costly, heavy, and space consuming.

    :)
     
  7. Dutch Peter
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    Dutch Peter Senior Member

  8. DGreenwood
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    DGreenwood Senior Member

    Two points...OK maybe three. Yiptser has noticed those myterious losses in real world use that the initial calculations don't account for. In reality a 5K BTU AC unit will not cool many cubic feet if you live in a place where it is really needed. If you are talking about a power boat a large alternator will put out enough to run that 5K BTU under way. But if you stop and run off the batteries you will have the devil to pay when it comes time to recharge them. Even with AGMs (which have a very high acceptance rate) it will take a long time for an alternator or even a small generator running through a battery charger to put that juice back into those four 8Ds
     
  9. firestorm
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    firestorm Junior Member

    my 2 cents worth more or less I am a master certified RV tech so I know a little about deep cycle batteries and inverters. My first thought is real bad idea for so many reasons I can't decide where to start. first thought 8D batteries wrong choice would do better with 6 volt golf cart batteries because the seem to hold up better under the constant load and u save a litle on weight not much but a little. Second thought is have you ever seen the voltage and wave form from a inverter it is very ugly on most of the ones I know of even the best out there are not that pretty to look at on a scope. Many of them allow voltage peaks in the 170 vac + range and use rms power figures to show the 120vac value. What this means to your A/C unit is a non stop stream of sloppy voltage very hard on start and run capitors and not that smooth on the motor for that matter. As to actual run time off the batteries I do not have the numbers for the unit you are using but I know what a Sharp R-1850A microwave draws it is nearly 135 amps from the battery which means if you cook your thanksgiving turkey off the batteries you eat in the dark. I have seen hand held hair dryers draw 100 amps thru a inverter. It takes more time and energy to put it back then it is worth now if I were on a desert Island with a good solar panel it would be nice to have. The last issue I will mention is the explosive gasses from the constant charging and discharging of a huge battery bank. In closing I think if you factor in all the aspects including what performance your boat would lose dragging all that battery weight I would opt for a small genset.
     
  10. DGreenwood
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    DGreenwood Senior Member

    Prosine, Trace, and Mastervolt are a few of the companies that sell true sign wave inverters, making waveform not an issue. It is true that square and modified wave form inverters are not kind to motors...particularly induction motors.
    With AGM batteries(Lifelines are an example of these) you get the advantages of no gasing during charging, an excellent lifespan and, most importantly, the ability to accept a very high percentage of alternator output, thereby reducing charging times considerably. None the less, firestorm is right about the idea of running a device of that amperage draw off of an inverter...you better get a genset. It can be done but the costs and comprimises are too high.
     
  11. yipster
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    yipster designer

    a given horse...

    a frend gave me a small 300/1000w invertor. plugged on the light battery its shorepower free 220 volts for some still to find small apliances and on our mastervolt amp meter we than probably monitor the battery running empty quik...

    is that invertor to be wired in on our sea ray's 220v shorepower circuit? i mean can you put the shorepower plug in the same circuit? i have to think...
     
  12. firestorm
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    firestorm Junior Member

    would need to know exact model and info on the inverter but most of the small inverters we use are wired inline with the load and the source and battery power coming in. That does not sound very simple but many of them have incoming A/C power from your shore supply outgoing A/C to your outlet or appliance and incoming 12Vdc power to run the inverter section and they use a internal transfer switch to go from inverted power to shore power. Many of the larger inverters also charge your battery when you are on shore power 300/1000 is not a very large inveter would be good for tv or stereo is 300 watt continous 1000 watt surge. We use many of these to run the TV in mid sized campers and a lot of them simply plug into the wall and have a outlet on the front or back panel and 12Vdc wiring to hook to the battery with a switch to turn on the inverter section and indicater lights. If this sounds like what you have then you should have a basic idea how it goes in most important thing to keep in mind is wire size and fuse size a 1000 watt surge would probably hit at least 125 amp draw at 12Vdc so use the proper fuse and preferably a slow blow type so as not to lose power at every surge.
    If you send me more info on the exact unit and how you want to use it I can perhaps be more specific.
    Good luck
     
  13. yipster
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    yipster designer

    "a internal transfer switch to go from inverted power to shore power" was what i wanted to hear, hope it has that. i did see some lights, plugs and switches but havent looked good and got to check. pluggin the invertor in and out the AC circuit would be the easyest (and even there i wasnt sure) but not a nice permanent solution. good advice on a slow blow heavy duty fuse, thanks for the info!
     
  14. yipster
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    yipster designer

    e-mailed the dealer and this given horse misses the "internal transfer switch to go from inverted power to shore power"
    buying new and when planning to plug it in a local AC circuit it may be worth asking for...
     

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  15. firestorm
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    firestorm Junior Member

    THis is becomming one of the most popular inverters in the RV business it hs incomming a/c power a transfer switch internally to switch output a/c from shore to inverted power and also charges your battery pack when on shore power. It has a very clean output and comes with a remote control panel that can be located most anywhere so you can mount it near your batteries and run the control into your cabin control is connected to unit with a small phone wire type cable.

    Prosine 2.0 Inverter from Xantrex


    2000 Watt Sine Wave Inverter/Charger
    The Prosine 2.0 Inverter from Xantrex provides 2000 watts of true sine wave AC power from a DC source and 100-amp multistage battery charging. The Prosine 2.0 Inverter from Xantrex is a powerful all-in-one solution to deliver up to 2000 watts of unsurpassed clean true sine wave output power and combines this with a 100 amp, multistage battery charger.

    Series stack ability allows for two units to power 240 VAC applications such as power tools, over ranges, washer/dryer combinations and air conditioners. This product is ideal for upgrading your electrical system in a boat, RV, or utility vehicle, for building a standby power system for critical equipment or incorporating an alternative energy system for a remote home. The system includes a full function LCD remote control panel and battery temperature sensor.

    Product Features
    2000-watt inverter (4500-watt surge)
    100 A power factor corrected multistage charger
    True sine wave output (crystal controlled)
    Built-in 30 A transfer switch automatically transfers between inverter power and incoming AC power
    Series stackability for 120/240 VAC (requires two units)
    Power sharing reduces charging current when AC loads are activated to prevent tripping of shorepower breaker
    Equalization mode conditions batteries for longer life
    LCD remote control panel and temperature sensor included
    Compact, lightweight, and easy to install
    Two year warranty
     
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