Home |
Search |
Today's Posts |
|
#1
posted to rec.boats.electronics
|
|||
|
|||
motor w/alternator vs. generator with charger vs.?
"Shaun Van Poecke" wrote in
: Taking a different approach then, If you were looking for usable amps for immediate consumption, say, to run a big electric motor, or many big electric motors ..... do you think youd get more bang for your buck with a big generator, or with a big stationary motor hooked up to a bunch of alternators? If you're looking for electric motive power, 12 volts isn't going to do it. For instance, the hybrid electric cars are over 400 VDC to keep the conductor size something reasonable. They have small cells and lots of them to get that voltage. Trolling motors use either 24 or 48 volts for the same reason. Low voltage systems are awfully inefficient. That's why we went from the stupid 6V cars to 12V. They screwed up. They should have gone to above 30 volts while they had the chance, but I'm sure there some profit motive why they didn't. Copper wasn't priced like Platinum at that time, like it is, now. Big diesel engines use 32VDC, which came from the steam locomotives on the trains. They've been 32VDC since the headlights were converted from gas to electric. On the boat.....if you want to run big electric motors, you need a AC power plant of sufficient size to start them. None of the DC systems have much available power and the power to weight ratio is terrible. You just get lots more electrical power from a genset, instantaneous, no hours of charging batteries, turn it on and it works power. Of course, under sail, there's a social problem. Sailors dream back to the 1800's. They're playing buccaneer and want nothing to do with engines, but want modern electronics and the conveniences electric power provides, like refridgeration, lighting, cooking, etc. Playing buccaneer is only for sailing. They don't eat gruel cooked over a woodstove, a more correct effect. The social problem occurs when someone cranks a genset to provide the needed power. It, of course, makes a noise and ruins the fantasy. They'll be called "stinkpotter" by other wannabee buccaneers back at the dock. So, they buy big batteries to power it, solar cells, windchargers and play greenie...while sitting in the dark, all hot because the batteries will only power a little fan, not airconditioning, which the genset can provide. Speaking of air conditioning, dear to our hearts here in the South, "marine" AC manufacturers take advantage of the buccaneers by making units to hide in the cabin, taking up all kinds of valuable storage space boats don't have to spare. They have to duct the cool air away from the unit, taking up more storage space. A guy at the marina I was talking to had a catamaran sailboat. He was trying to figure out where it was going to be installed on his cat. He made the mistake of asking me. It was August, very hot, and I suggested instead of wasting all that space and putting the HOT AC unit INSIDE the air conditioned space making all that noise, that he just take off a hatch on one of the pontoon cabins and install a Coleman RV unit, say 18,000 Btu...heat pump...with soft start kit so it could be run from a much smaller genset like RVs use. At first he recoiled, buccaneer style, that I dare suggest such a thing. "Look on the commercial boats and you'll see lots of them.", I retorted. All the tugs around here and dredge boats use RV rooftop AC units...no strainers and seawater pumps to clog and clean...no seawater rotting out water-cooled condensers...no heat INSIDE the cabin as the RV AC fans and compressors are OUTSIDE the spaces we're trying to cool. I shrugged and walked off. I walked the dock and saw him a couple weeks later. He wanted to show me what he'd done...that wasn't gonna make him any points with the other buccaneers on the dock, for sure. He'd installed it...(c; "We turned the thermostat up too high the first day and like to froze to death.", he said. RV units are much more efficient as they don't spend half their Btu cooling themselves...hee hee. Nothing beats a genset for generating power in a boat. It's noisy, but they've quieted them down a lot with quiet cabinets around them. Exhaust must always be downwind and in such a way it doesn't come swirling up the back over the stern....like your outboard or propulsion diesel does. If it's a gas engine, it's also dangerous to sleep running as there is always Carbon Monoxide fumes to kill you. These must also be considered. The finest, quiet genset I ever owned is: http://www.hayesequipment.com/eu3000is.htm I have one mounted on the back door of my service truck stepvan that powers my whole shop, with two 8000 BTU wall AC units, all summer. This genset, and the other little suitcase gensets Honda makes (EU1000i and EU2000I) operate completely different from the normal gensets. There is no 50/60 Hz monster core alternator! The alternator in it resembles the PM rotor flywheel around the stator coils on an outboard gas motor. There's just more coils and more magnets. It's part of the engine. This is actually a high frequency alternator, around 1000 Hz at low speed, more as speed changes. Yes, speed changes with load! We don't care about frequency. It's output is 3-phase, providing much smoother power, same as the multiphase alternator on your engine. The 400VAC, high frequency output from this little 6.5hp gas engine, turning only 1200 RPM until you get to around 1900 watts of load when the computer speeds it up for more power, is rectified into high voltage DC. This HVDC is fed to a 3KW modified sine inverter, which turns the HVDC from the engine into 50 or 60 Hz, 120 or 240 VAC, depending on what country it's sold to. Turning two 8000 Btu Korean regular window ACs, it runs about 8.5 hours on 3.5 gallons of gas in the metal tank on top of it. The cabinet is so quiet around this slow-turning engine, people constantly ask me to look at it because they have a noisy 3600 RPM beast emergency genny at home. Only thing wrong for your application is there's no way to mount it in a boat! It's air cooled and the air cooling cools the big muffler, mixing the exhaust with the hot air pouring out of it so you can't isolate the exhaust for overboard discharging. SOMEONE needs to dump the WW2 technology fast turning noisy engine directly coupled to the massive low freq alternator with only marginal regulation and build THIS genset in a BOAT cabinet/exhaust/cooling. If you're ever near a Honda Power dealer...ask him to start one for you. For your boat? Here's my answer: http://www.nextgenerationpower.com/ The Kubota diesel it runs on will run 20,000 hours before overhaul if you stop it and change the oil every 100 hours. Two of them have run faultlessly, here, on small trawlers. Don't forget to clean the seawater strainers and once a year the water pump and drive belt would be a good idea. The diesel runs a constant speed, but it's SLOW because they use the belt drive to raise the speed to 1800 RPM, or for Oz 1500 RPM (50Hz). Turns slow, lasts longer...that's easy...(c; It needs an exhaust hose, diesel fuel line and a seawater source to suck its cooling water from. It's exhaust is water cooled and is the outlet for the cooling water. 3.5KW is 30" by 18" by 16" and 160 pounds in the quiet cabinet. That's pretty small. It runs on a trickle of diesel fuel really cheaply. -- http://www.epic.org/privacy/rfid/verichip.html http://en.wikipedia.org/wiki/VeriChip http://www.verichipcorp.com/ Tracked like a dog, every license/product/tax. Revelation 13:16 And he causeth all, both small and great, rich and poor, free and bond, to receive a mark in their right hand, or in their foreheads: 17 and that no man might buy or sell, save he that had the mark, or the name of the beast, or the number of his name... |
Reply |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Vector Battery Charger | General | |||
Vector Battery Charger | General | |||
Bought cool new digital charger....$89? WalMart?!! | Electronics | |||
Bought cool new digital charger....$89? WalMart?!! | General | |||
Bought cool new digital charger....$89? WalMart?!! | Cruising |