power inverter in van dc to ac power

mcessna
mcessna Registered Users Posts: 1 ✭
in Caravan, Recreational Vehicle, and Marine Power Systems #1
I'm trying to run a air compressor in my van 240 volts with 17.5 amp is there a power inverter I can run with 1 12v battery and van running with alternator charging it.
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  • Marc Kurth
    Marc Kurth Solar Expert Posts: 1,165 ✭✭✭✭
    edited June 2017 #2
    In short: No, not in a practical sense.

    In very round numbers:
    240v x 17.5 amps = 4,200 running watts.
    4,200 watts/11.5v = 360 amps at the battery

    As if that isn't bad enough, the inrush amps will be the killer with an air compressor motor - even unloaded.

    Can it be done? Sure, I have put together several 12v systems that big for specialized industrial applications. But not with anywhere near what you are envisioning. BIG costs involved in special inverters, custom alternators and batteries to do this.





    I always have more questions than answers. That's the nature of life.
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    edited June 2017 #3
    That's a tall order, around 350amps @12V with massive inrush, electricity it is not the best idea, not saying it is impossible, just impractical. A better solution would be to take power from the engine mechanically, such as a compressor head driven by the crankshaft, with an AC clutch to control the demand, I've actually seen AC compressors used for this purpose, but from the sound of it you need a larger compressor. There are also gas powered compressors, as another option.see link below 
    https://www.grainger.com/product/SPEEDAIRE-30-gal-43-1-2-x-40-x-18-1-4NB85?s_pp=false&picUrl=//static.grainger.com/rp/s/is/image/Grainger/4NB85_AS01?$smthumb$
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #4
    The short answer is yes, but it will be a big inverter.

    17.5a at 240v is a fair bit of current, but you have to start the compressor motor and overcome backpressure to get it going. That will take multiples of the 17a to do. There are ways to reduce the starting current, like unloading the compressor before starting, but that can be a PITA.

    To start it reliably without modifications, my guess is you'll want ~7000 watt inverter with about double that in surge capability. At 12v, that's a lot of current, so you would want heavy cables and a good sized battery designed to deliver a lot of current quickly (eg 4d AGM).

    As far as charging it with the van alternator, that would depend on how long you run the compressor, the battery capacity, the output of the alternator, and how long you're willing to run the van. The alternator is unlikely to be able to output enough to run the compressor continuously. You would likely need to stop the compressor periodically to recharge the battery.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • Lumisol
    Lumisol Registered Users Posts: 374 ✭✭✭
    edited June 2017 #5
    It can be done but at a fairly high cost.
    Look at 12 volt 5000 Watt inverters on Amazon for a start.
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  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,101 ✭✭✭✭✭
    edited June 2017 #6
    5000 watt 12 volt inverters are just plain dangerous. At their rated power output that would be over 400 amps draw on the batteries, double that at full surge rating!!! To be able to handle that kind of load your inverter would need either a large number of paralleled  batteries (bad) or some hefty 2 volt cells. The former is probably more common. The latter is likely, rare, as anybody purchasing large 2 volt cells is probably seasoned enough to know not to even consider using such a high powered 12 volt inverter and is running at 24 or 48 volts. If there is a UL listed inverter of this size I've never seen one. 

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

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  • dennis461
    dennis461 Registered Users Posts: 109 ✭✭✭
    #7
    There are some pretty good DC powered air compressors available nowadays.  How much air do you need , CFM and PSI?  Are you running air tools?.  I have a fairly large gas engine driven air compressor,   you could mount a small gas engine driven compressor on a tow hitch.

    Solar is probably not the right solution, but please post how much air you need and we can help.
    Do you already have the air compressor specification?
    Camden County, NJ, USA
    19 SW285 panels
    SE5000 inverter
    grid tied
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  • Marc Kurth
    Marc Kurth Solar Expert Posts: 1,165 ✭✭✭✭
    edited June 2017 #8
    littleharbor2 said:
    5000 watt 12 volt inverters are just plain dangerous. At their rated power output that would be over 400 amps draw on the batteries, double that at full surge rating!!! To be able to handle that kind of load your inverter would need either a large number of paralleled  batteries (bad) or some hefty 2 volt cells. The former is probably more common. The latter is likely, rare, as anybody purchasing large 2 volt cells is probably seasoned enough to know not to even consider using such a high powered 12 volt inverter and is running at 24 or 48 volts. If there is a UL listed inverter of this size I've never seen one. 
    Totally agree! My rule of thumb is go to 24v above 2500 watts, unless you have darned good reasons not to.

    Large motor homes have inverter systems to run multiple rooftop A/C units on battery power. You will rarely see anything above 3000 watts on 12v, they jump to multiple 2500/2800 watt inverters.

    There are good reason that Magnum and Xantrex max out at around 3,000 watts at 12v. For the RARE and specialized instances that 12v must be used, some models of good inverters can be paralleled.

    I do some industrial mobile applications for the oil/gas and other industries that do need heavy power from 12v. Their trucks are rigged with twin 250a alternators with forced outside air induction and 400-600 ah battery banks, fed with a bundle of 4/0. They choose to stay with 12v because of other heavy consumption 12v equipment, quite aside from the inverters.

    People tend to forget that inverters are constant wattage devices, so as the battery voltage drops, the current draw climbs. A pair of 3000 watt inverters in parallel under full load will draw: 6000 watts/10.5v 570 amps before low voltage cutout takes place. The cabling, fuses and connectors become behemoth and expensive in this specialized arena.

    Batteries are actually the easiest part because of the AGM's that we use in these applications. A 400 ah battery bank will maintain more than 11.3v with a 400 amp load, all the way down to 75% DOD. In general, the alternators are doing the work so the batteries tend to float between 20% and 30% DOD which is above 12.0v under heavy load.

    Marc

    I always have more questions than answers. That's the nature of life.
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  • Lumisol
    Lumisol Registered Users Posts: 374 ✭✭✭
    #9
    He wants to use the battery in the van, not add a new bank though.
    A DC powered compressor, or a smaller AC one is a start to get where you want to be.
    Maybe a belt driven compressor you can mount in the engine compartment and use the engine to turn is an option?
    http://www.fourwheeler.com/how-to/engine/1404-engine-driven-compressor-belt-blower/
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  • Marc Kurth
    Marc Kurth Solar Expert Posts: 1,165 ✭✭✭✭
    #10
    @Lumisol: Yes, I realize what he wanted to do and I said that it would not work. See the first post under his, above.

    He didn't ask about a smaller AC or DC compressor or belt driven compressor either. Even with a 5000 watt inverter it will not come close to working. Without knowing what his consumption rate or pressure requirements are, alternative suggestions could be great, or they could be not so great. But brainstorming to get more ideas can be valuable indeed!

    Did you notice that the compressor you linked to, needs to be greased every 5 hours of operation?

    Marc


    I always have more questions than answers. That's the nature of life.
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  • mvas
    mvas Registered Users Posts: 395 ✭✭✭
    edited June 2017 #11
    You really need something like this ...
    A 7000 Watt Honda EU7000iS generator - already has a 240V AC outlet.
    7000 Watts (surge) / 240 Volts = 29 Amps (surge)
    Or maybe even more surge watts?
    You can figure that out yourself, by using a peak amp meter

    Or what if you stepped up to a 48 Volt inverter = 4 x 12 Volt Batteries
    $1,200 Aims 14,000 Watts (surge) / 240 V = 58 Amps (surge) for 7 seconds 
    https://www.amazon.com/Power-PWRIG700024048-7000W-Industrial-Inverter/dp/B008HSAZC0
    300 amps (surge) / 90 amps (running)

    or a 12 V DC Air Compressor
    https://www.aircompressorsdirect.com/Puma-PD1006-Air-Compressor/p13972.html?gclid=CNvYnOLDr9QCFceKswodHWcE6A
    https://www.zoro.com/oasis-air-compressor-continuous-duty-12vdc-xd4000-12/i/G9989025/?gclid=CKXVzYjHr9QCFV5MDQod4H0F0Q

    mcessna said:
    I'm trying to run a air compressor in my van 240 volts with 17.5 amp is there a power inverter I can run with 1 12v battery and van running with alternator charging it.
    With the van running at idle?
    NO!

    Do you have a 3 HP Air Compressor ?
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  • Lumisol
    Lumisol Registered Users Posts: 374 ✭✭✭
    #12
    Marc Kurth said:
    @Lumisol: Yes, I realize what he wanted to do and I said that it would not work. See the first post under his, above.

    He didn't ask about a smaller AC or DC compressor or belt driven compressor either. Even with a 5000 watt inverter it will not come close to working. Without knowing what his consumption rate or pressure requirements are, alternative suggestions could be great, or they could be not so great. But brainstorming to get more ideas can be valuable indeed!

    Did you notice that the compressor you linked to, needs to be greased every 5 hours of operation?

    Marc


    Yes, and that was an example, not the ONLY compressor of its kind in the world. :)
    I am not sure that maintaining a compressor is a bad thing though. It's like maintaining a car itself. You need to grease your zerks every time you change your oil too. Grease is cheap compared to compressors and front end components. I know mechanics that lube the zerks on their own cars every week.
    You make it sound like you shouldn't nave anything that needs maintenance. Most compressors need oil too.

    It was a suggestion and one more option that might not have occurred to the OP.

    It's better to speak to the topic than to the replies to it though. But since you trolled me I figured I should reply.
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  • cow_rancher
    cow_rancher Solar Expert Posts: 117 ✭✭✭✭
    #13
    Marc Kurth said:
    Did you notice that the compressor you linked to, needs to be greased every 5 hours of operation?
    You did notice that the compressor that was linked to has an electric clutch so it only operates then you need it, filling up tires, air shocks, or that cool air-pneumatic jack that harbor freight sells.  So it's 5 hours of uses, which could be a normal oil change length of time.

    Rancher
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  • Marc Kurth
    Marc Kurth Solar Expert Posts: 1,165 ✭✭✭✭
    #14
    cow_rancher said:
    Marc Kurth said:
    Did you notice that the compressor you linked to, needs to be greased every 5 hours of operation?
    You did notice that the compressor that was linked to has an electric clutch so it only operates then you need it, filling up tires, air shocks, or that cool air-pneumatic jack that harbor freight sells.  So it's 5 hours of uses, which could be a normal oil change length of time.

    Rancher

    Nope, I did not see that the 5 hours only applied to run time on the compressor.

    Marc
    I always have more questions than answers. That's the nature of life.
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  • Lumisol
    Lumisol Registered Users Posts: 374 ✭✭✭
    edited June 2017 #15
    Why would it be necessary to grease a machine that didn't run? The grease is to allow movement without metal to metal contact causing excessive wear. No movement means no need for grease.
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  • Marc Kurth
    Marc Kurth Solar Expert Posts: 1,165 ✭✭✭✭
    #16
    Some of us take this place seriously.
    I always have more questions than answers. That's the nature of life.
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  • Lumisol
    Lumisol Registered Users Posts: 374 ✭✭✭
    #17
    My comment was not only serious, but factual.
    Thanks.
    I hope the OP finds a solution that works for him and offering new ideas will be a greater help than bickering.
    Good luck finding a way to do what you need to do with the air on the van.
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  • Lumisol
    Lumisol Registered Users Posts: 374 ✭✭✭
    #18
    I find it odd that some people disagree that the purpose of grease is to minimize metal to metal contact between moving parts.
    https://www.etrailer.com/faq-grease.aspx
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  • Marc Kurth
    Marc Kurth Solar Expert Posts: 1,165 ✭✭✭✭
    #19
    Lumisol said:
    I find it odd that some people disagree that the purpose of grease is to minimize metal to metal contact between moving parts.
    https://www.etrailer.com/faq-grease.aspx
    I find a lot of things to be quite odd. Help me to understand your point in posting that here.
    I always have more questions than answers. That's the nature of life.
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #20
    Grease comes in many flavors, I use copper ($) and silver ($$$$) loaded grease to enhance electrical conductivity in high amp connections.   But not sure why we are suddenly talking grease,
    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 ||
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  • Lumisol
    Lumisol Registered Users Posts: 374 ✭✭✭
    #21
    I don't know either. Mark was the one to mention that a compressor needs grease and made it sound like a bad thing.
    ??
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  • Marc Kurth
    Marc Kurth Solar Expert Posts: 1,165 ✭✭✭✭
    #22
    I mistakenly assumed that the compressor/idler bearing assembly needed interval greasing. Rancher pointed out my error and I immediately agreed that I was wrong.

    Go back and reread this thread and see if you can identify the real problem.
    I always have more questions than answers. That's the nature of life.
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  • Lumisol
    Lumisol Registered Users Posts: 374 ✭✭✭
    #23
    You assumed a machine that wasn't running needed to be re-greased. But that's all been cleared up, let's move on now, shall we?
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  • cow_rancher
    cow_rancher Solar Expert Posts: 117 ✭✭✭✭
    #24
    Lumisol said:
    You assumed a machine that wasn't running needed to be re-greased. But that's all been cleared up, let's move on now, shall we?
    No what he really assumed was that the compressor was running all the time, which was a valid assumption until you read the set up of how it was being used.
    Let's see how many posts we can drag this dead cat thru.

    Rancher
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  • Lumisol
    Lumisol Registered Users Posts: 374 ✭✭✭
    #25
    Better yet, let's not.
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  • dennis461
    dennis461 Registered Users Posts: 109 ✭✭✭
    #26
    Lumisol said:
    Why would it be necessary to grease a machine that didn't run? The grease is to allow movement without metal to metal contact causing excessive wear. No movement means no need for grease.

    The design of that particular model uses grease rather than oil for lubrication.
    The design is not unique to the brand, and supposedly keeps oil out of equipment which should not have oil in them.

    and

    we scared away the OP


    Camden County, NJ, USA
    19 SW285 panels
    SE5000 inverter
    grid tied
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  • Lumisol
    Lumisol Registered Users Posts: 374 ✭✭✭
    edited June 2017 #27
    Obviously but why are you still talking about it? It was an example of one possible solution to avoid large inverters being used in the van.
    There are a lot of other ways to go and I hoped people would mention some other possibilities so the OP had more to choose from.
    Perhaps a stand alone self contained model using a small engine to drive the compressor like suggested above.
    https://www.factoryauthorizedoutlet.com/dewalt-d55153r-heavy-duty-11-max-hp-4-gallon-electric-hand-carry-compressor-reconditioned?google=1&CAWELAID=230005750000085547&CAGPSPN=pla&CAAGID=19732019651&CATCI=pla-315134618331&gclid=CjwKEAjw1PPJBRDq9dGHivbXmhcSJAATZd_BKNTdCtWHY82hyAmXF7RxFCyHFjJdiBKOsCXMAkJwBBoC2uvw_wcB

    Or

    https://mobiledistributorsupply.com/5-5hp-30g-horizontal-tank-with-honda-engine-1.html?gclid=CjwKEAjw1PPJBRDq9dGHivbXmhcSJAATZd_BM1cx_2e0AHusy3suYiSlCVcmfPYrvhiM0Y4X1Q10mRoCdGbw_wcB
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  • dennis461
    dennis461 Registered Users Posts: 109 ✭✭✭
    #28
    Lumisol said:
    Obviously but why are you still talking about it? ....
    Shall I not talk?
    Camden County, NJ, USA
    19 SW285 panels
    SE5000 inverter
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  • Lumisol
    Lumisol Registered Users Posts: 374 ✭✭✭
    #29
    About the OP, certainly. What suggestion do you have?
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  • toppinish
    toppinish Registered Users Posts: 6 ✭✭
    edited July 2017 #30
    I'd stay away from AC 240 volts unless you have an very efficient 240V inverter. I don't believe Inverting DC to AC is as energy efficient as  belt driven.

    You may want to consider a belt driven air compressor.

    How much psi and air capacity do you require? You may consider an air holding tank. Anytime when working with air either on-board air in a vehicle or for at home in a workshop an air holding tank become very useful.

    Off-roaders have converted AC compressors into air compressors.

    http://www.jeepforum.com/forum/f11/how-convert-c-compressor-air-compressor-578972/
    http://www.jeepforum.com/forum/f11/complete-c-oba-write-up-tons-pics-194132/
    http://www.fourwheeler.com/how-to/1308-compressing-air-on-board-compressor/

    For on-board air you may want too look for suggestions and solutions from the off-road and 4-wheel drive communities.

    ARB High Output OnBoard Air Compressor

    https://www.quadratec.com/products/16104_90XX_PG.htm?gclid=COnsuLrM8tQCFcVffgodTtAFKQ

    Perform a google search for "onboard air compressor"

    I think it really depends on what your going to be using compressed air for, how much psi and capacity is required.

    You can use an electric compressor, possibly with a larger holding tank. However 17.5 amps @ 240 volts requires alot of power. I don't think your compressor will have the sort of efficiency required for mobile 12 volt vehicles.

    I have a Triplite inverter design for industrial and heavy duty use, that I sometimes use in a vehicle. It produces between 2000 and 4000 watts that  works with motors, power tools, etc.  however if I were to load it down for a length of time over 4000 watts it will eventually  stop inverting DC to AC.

    Many of the newer inverters aren't really designed to be used with high load motors, even though they have a higher load rating, some have problems when connected to motors.

    There are RV's and boats that use 4000 - 5000+ watt inverters but their usually is a cost factor, probably too much to spend,  only to provide some air.
     



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  • jonr
    jonr Solar Expert Posts: 1,386 ✭✭✭✭
    #31
    The original poster may be long gone, but if the application is compatible, I'd use a very small compressor plus a pressure tank.

    I am available for custom hardware/firmware development

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