Power inverter for boat lift |
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jameski
Senior Member Joined: May-18-2004 Location: United States Status: Offline Points: 368 |
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Posted: June-25-2008 at 2:41pm |
I'm installing a hydrohoist floating boat lift on my dock. My dock is a long way from the house (and electricity). I'm curious, has anyone ever tried using a large (1500w) power inverter in the boat to inflate the lift?
My lift blower motor uses 1250w of power for about 3 or 4 minutes. I would only use it after I've had the boat out for a while skiing, so my battery should have a good charge on it. ...thoughts? |
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79nautique
Grand Poobah Joined: January-27-2004 Location: United States Status: Offline Points: 7872 |
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usually there is a battery and solar panel to run them that you can buy. I know that my old neighbor had a small truck box that he strored a battery, the switch/control for the hoist and a solar panel to keep it charged for his hoist, granted it wasn't a hydohoist.
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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James, It's the surge watts when the motor starts that you really need to be concerned about. Depending on the motor type (inductive or brushed), a motor can draw 2 or 3 times the current starting over running current. Check out the rating of the inverter (there should be a surge rating) as well as giving the lift manufacturer a call to see if they can give you a idea of starting current.
Edit: Chris's comment is valid but he is reffering to a 12 volt drive/motor. That is a option to look into when you call the lift people as well. |
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GottaSki
Grand Poobah Joined: April-21-2005 Location: NE CT Status: Offline Points: 3357 |
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Inflate? huh..
A smaller compressor could draw less for a longer duration, and store air in a separate tank for the next use (inflate) . the 'work' may not have to be done only during the lift. Or just run a compressed air line down from the house and use a purge tank under the dock for the main lift for high volume and a fast lift.. The tank can take its sweet time refilling so you don't need bigger than 3/8 line. |
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"There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing."
River Rat to Mole |
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behindpropeller
Platinum Member Joined: July-31-2006 Status: Offline Points: 1810 |
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It might be easier to just call harbor freight and get a bunch of air hose and run it down to your lift and put the pump at the house. Not sure how much volume you need to move but I would much rather deal with air running down the dock than AC.
Tim |
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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James, What is the distance you would need to run power or air?
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boat dr
Grand Poobah Joined: June-27-2004 Location: United States Status: Offline Points: 4245 |
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James your correct about the battery being "HOT" after a day on the lake,BUT....
Inverters are very "Power Hungry" and will render a hot battery less than desirable for that cold start the next day. I think you are opening up a "can of worms" with that line of thinking. Tim's idea of a compressor supplied by house current and a hose to the lift unit would be by far the best bang for your buck. Sometimes the easy way is not the most practicle............Boat dr |
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behindpropeller
Platinum Member Joined: July-31-2006 Status: Offline Points: 1810 |
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jameski
Senior Member Joined: May-18-2004 Location: United States Status: Offline Points: 368 |
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I think it's about 600' to the house, wooded, rocky, and a fairly steep grade ...Corps of Engineers property.
Trenching a line over that long distance was what I really wanted to avoid. I started out thinking about solar. ...a panel, a battery, and an inverter. I found a 1500w inverter for $150, a solar panel for $110, and I already have a deep cycle battery I'm not using. ...Then I started thinking about using the boat battery. Hydrohoist recommends a 1500w "generator". The inverter I found is rated 1500w continuous, 2400w surge. |
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behindpropeller
Platinum Member Joined: July-31-2006 Status: Offline Points: 1810 |
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79nautique
Grand Poobah Joined: January-27-2004 Location: United States Status: Offline Points: 7872 |
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do they sell a DC version instead of an AC to run the pump?
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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James, Does Hydro Hoist have a 12 volt option? The Doc is correct that a inveter is a very inefficient device and consumes lots of power itself converting the 12 DC to 120 AC. It is lost as waste heat and the reason they have cooling fins on them.
600' is a long ways for electric at 120 volt. The voltage drop would kill the motor and may not even start!! If you did have to run electric, is the pump/blower dual voltage? With 240 volt the voltage drop would be 1/2 the 120. The 600' for air is a issue as well! Without PSI and CFM requirements, I can't give you exact figures but the pressure drop would be rather large. You'd end up running a 1" hose down there!!! A accumulation/surge tank would be a must!! |
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NEDLUTZ
Groupie Joined: November-26-2007 Location: Seekonk Ma. Status: Offline Points: 69 |
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Hi guys check out this lift. It may work better for what he is looking for. http://www.airdock.com/index.html
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jameski
Senior Member Joined: May-18-2004 Location: United States Status: Offline Points: 368 |
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Thanks for all of the ideas in such a short time. This forum is GREAT!
I already have a 3500w generator. That is what I have been using so far. It works fine, but it's loud and a hassle to roll down to the dock and back. I guess if I had one of those little tiny Hondas like behindpropeller recommended, i could keep it at the dock. ...but they are REALLY expensive. Pete, we're not talking about any kind of high pressure, just LOTS of volume. The lift consists of two fiberglass pontoons with a large hole in the bottom of each, and an air inlet/outlet hose on top of each. A "compressor" would work I guess, but I think we're looking for something more like a "blower". The one that came with the lift (which I bought used) is comparable to a shop-vac motor (maybe identical). I think I'll check with "airdock.com" to see if I can buy the 12v blower from them. |
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jameski
Senior Member Joined: May-18-2004 Location: United States Status: Offline Points: 368 |
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update:
I checked with Hydrohoist. They do not offer any DC blowers, but he said that Grainger has a 24v blower that should work. I checked with Airdock. They could sell me a 12v blower for $110, but he said it would not have enough pressure/flow to lift my type of lift. He recommended an inverter, but he said I might need 2 batteries to power it. |
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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The 2000 watt generator will not handle the inrush (surge) of the blower. I can tell from the 1250W figure that it is a 1/2HP. You are absolutely correct that you have a blower and not a compressor as such but it is really volume that requires HP. The pressure needed is to displace the water depth from the top of the water level to the bottom of the pontoon. Probably only 12" of H2O. (pressure below about about 5 PSI is measured in a water column - a manometer) What else does this blower say on its name plate that came with the lift? |
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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James, Just some more basic additional thoughts!
Your 1250 Watt 120 Volt blower is 10 amps. To do the same job, a 12 Volt blower will draw 100 amps. That's #2 size battery cable. Now if you use a inverter to run the existing and the efficiency is 80% (typical), the 12 Volt load will be 120 amps. That's a lot!! You would be hauling batteries back to the house to charge on a regular basis (depending on how many times you raise and lower the boat) or need well over $600.00 for decent wattage photoelectric panels and then hope for sunny days and not use the lift very much. I tried to explain this to some ski club members after I built their water sprinkling system for the jump - they thought you could just go and get one of those cheap photo panels you plug into the cigarette lighter!! Both a 12 volt blower and a inverter would be like starting (cranking) a small 4 cylinder engine for the 3 or 4 minutes! Just reconsider running power from the house. If you do, let me figure out some wire sizing to reduce the voltage drop and do look at the blower if it is dual voltage and can be run on 240. I hope you got a deal on this lift! It certainly sounds like a PITA if your aways from power! |
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Munday
Gold Member Joined: August-17-2004 Location: United States Status: Offline Points: 538 |
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We fought this battle for a couple of years before running power to the dock.We used a 3500w gas generator and it was noisey.After reading thru this thread i wonder if a gas leaf blower might work?I'm sure it would be faster than than the stock blower fan.Just a thought but I'm sure you will end up running the electric just a matter of time.
Munday |
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If the only tool you have is a hammer,everything starts to look like a nail.
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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Munday, Not a bad idea on the leaf blower! Sure would be easier than hauling a gen set down there! The only problem is will the blower have the balls to do it? I doubt you would be able to find the pressure rating so, James if you want to experiment, here's what I would do. With the blower running, take the nozzle and stick it in the water seeing how deep you can go before you see a noticable decrease in air flow. This will give you the rough idea of the blowers pressure capacity to overcome the static head of the water. The leaf blower needs to go as deep as the bottom of the pontoons are when they are fully submerged.
James, how is the air to the pontoons valved off when they are full? A manual valve? |
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GottaSki
Grand Poobah Joined: April-21-2005 Location: NE CT Status: Offline Points: 3357 |
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kewl,I have a stihl BR600 and it will throw 3/4" rocks... at idle...
rated 1200cfm but like pbrain sez static pressure is important I suspect you have a new solution |
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"There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing."
River Rat to Mole |
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Hollywood
Moderator Group Joined: February-04-2004 Location: Twin Lakes, WI Status: Offline Points: 13513 |
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79nautique
Grand Poobah Joined: January-27-2004 Location: United States Status: Offline Points: 7872 |
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run the cable out to the dock install a light and an extra outlet while your at, it will make your life much easier in the long run.
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bkhallpass
Grand Poobah Joined: March-29-2005 Location: United States Status: Offline Points: 4723 |
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I don't know about all the electrical calculations, but the blower that comes in a hydrohoist is not much more than a commercial vacuum motor. It takes less than 5 psi to lift the boat. Larger lifts just add more and/or larger pontoons.
Pete, I don't agree that the blower needs to go to the bottom of the pontoons. On most of these floating lifts, a single hose comes out of the blower. It then goes to a y, and a hose is mounted to each pontoon, mounted toward the top edge at the front of the lift. Mine is a 1" hose. You turn on the blower with a flip swithch at the console, and then open a valve so air can flow through the hoses. When the lift is up, you turn of the valve, and turn off the motor. The whole in the bottom of each pontoon is six inches round and allows the water to push out, or flow in. |
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Livin' the Dream
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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Brian, let me try to explain in simple terms about head pressure of water. If the bottom of the pontoon is 12" under water, then you need 12" of air pressure to just start to push the water out the hole. It doesn't matter how big that hole is in the pontoon. As a reference, 12" of water column is .434 PSI. You need to displace the weight of the water down to the bottom of that pontoon. Water weighs 62 lbs. per cu. ft. or .0358lbs per cu. in. x 12" gives you the .430 PSI. Yes a vacuum cleaner type blower will do it. Have you ever looked at some of the commercial vac head ratings? Some will lift a 70" column of water! That also means it will push a column of air down into water 70" |
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bkhallpass
Grand Poobah Joined: March-29-2005 Location: United States Status: Offline Points: 4723 |
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OK, I understand the analysis now. BKH
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