I need to run some big 12V motors that usually run off of a car battery, but I'm doing it inside and thus don't want to run a car. Ideally there is some kind of bigass 120VAC or 240VAC to 12VDC transformer that I can use.
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May 20, 2009 3:46 p.m. DILYSI Dave UltimaDork
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May 20, 2009 3:53 p.m. John Brown MegaDork
I guess telling you to hook them up to a battery charger would be useless right?
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May 20, 2009 4:05 p.m. DILYSI Dave UltimaDork
John Brown wrote:
I guess telling you to hook them up to a battery charger would be useless right?
The battery chargers I'm familiar with deliver ~10 amps.
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May 20, 2009 4:07 p.m. Jensenman MegaDork
500 amps for 2 12VDC motors???? Dave, what the hell are you doing? I'll be watching for a mushroom cloud to my west.
Before doing all that, have you looked into an equivalent power AC motor, like maybe for an air compressor?
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May 20, 2009 4:12 p.m. Dr. Hess PowerDork
Yeah, you're talking like 8 HP of 12v motors. That's a lot. Not that you couldn't do it with transformers, but it would take some big honkin' ones. Cost would be through the roof. You would be better off with some batteries in the house and a big battery charger to recharge when your load is down. If you need 8HP in the house all the time, you don't need 12v. I'd like to see what 8HP of 12v motors looks like. I think you need a 220V motor instead. It would be cheaper than buying the cables for what you're talking about.
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May 20, 2009 4:16 p.m. ronbros New Reader
well if you use a transformer AC in AC out, and DC motors wont like that. to make it straight DC you would also need a BIG-BIG recterfier, and heat comes into play. cooling fans ETC.
500 amps!!! big cables too.
Ron
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May 20, 2009 4:20 p.m. DILYSI Dave UltimaDork
No mushroom clouds. Just powering some winch motors. The motor chart says that at full load it's pulling 425 Amps. 500 just gives me some headroom.
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May 20, 2009 4:20 p.m. Nashco SuperDork
Depending on your duty cycle, it sure seems like honkin' lead acid batteries are still the way to go. This is like one of those incomplete math questions on tests...need more info!
Bryce
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May 20, 2009 4:24 p.m. DILYSI Dave UltimaDork
Dr. Hess wrote:
Yeah, you're talking like 8 HP of 12v motors. That's a lot. Not that you couldn't do it with transformers, but it would take some big honkin' ones. Cost would be through the roof. You would be better off with some batteries in the house and a big battery charger to recharge when your load is down. If you need 8HP in the house all the time, you don't need 12v. I'd like to see what 8HP of 12v motors looks like. I think you need a 220V motor instead. It would be cheaper than buying the cables for what you're talking about.
Motor is rated for 6.6HP, so yeah - we're on the same page.
It isn't a constant load, but I don't want to be waiting for battery chargers either.
Maybe a 6HP 120VAC motor spinning an alternator, which charges a battery, which runs my 12VDC motor?
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May 20, 2009 4:28 p.m. Jay Dork
We have some batteries at work that are rated for 400A instantaneous load. "Huge & expensive" is the best two-word description I can give.
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May 20, 2009 4:37 p.m. Jensenman MegaDork
You could do it with the 120VAC motor>alternator>battery>load motor setup. You'd want a big deep cycle marine battery, though. For that matter, if it's an occasional load (once a day or so) you could do it with a battery charger>deep cycle marine battery>load motor. You'd need proper charger controls to keep from boiling the battery, but that wouldn't be real hard to do.
You could even run it directly off of an alternator. But it would have to be a horkin' big alternator. 500 amps DC is a BUNCH. I did a quick Google, a 350 amp GM alternator is like $769.00. 2 250's would be about the same.
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May 20, 2009 5:21 p.m. Shaun New Reader
one of these?
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May 20, 2009 5:55 p.m. JeremyB New Reader
You might be able to use a TIG welder in DC mode, but I'm not sure if it can get to 12 volts.
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May 20, 2009 6:01 p.m. ignorant PowerDork
DILYSI Dave wrote:
No mushroom clouds. Just powering some winch motors. The motor chart says that at full load it's pulling 425 Amps. 500 just gives me some headroom.
I'm guessing thats rotor stall or the inrush current at full load. I'll put money on it that is a much less continuous load.
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May 20, 2009 6:30 p.m. Kendall_Jones New Reader
DC power supply. Batteries are nice, but the voltage drops over time, recharging is a pain (test once, wait overnight).
You can probably rent one from test equity or some other tech rental place.
Kendall
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May 20, 2009 7:14 p.m. stuart in mn Dork
Remember that welders have a duty cycle, usually something like 20%, so they can't be run continuously. I worked on a project some years ago (a plasma arc torch) that had a low voltage DC power supply put out around 500 amps continuous, but that power supply was about the size and shape of a Scion XB. I'm trying to figure out what kind of motor you would have that requires 500 amps but is designed to run off a car battery.
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May 20, 2009 7:16 p.m. Paul_VR6 Reader
6.6hp = 4.9kw 4.9kw/12v = 408a
That doesn't take into account the losses in the motor to make the 6.6hp.. 500A is definitely in the ballpark.
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May 20, 2009 7:21 p.m. Shaun New Reader
what is the duty cycle? What am I missing? why wouldn't a 800 CCA marine starting battery for $100 bucks not take care of it. 135 minutes at 35 amps... that is allot of twist, surely the detainees would talk before the winch needed more than that.
93270 24M-XHD 800 CCA 135 minutes at 35 amps 11" x 6.88" x 9.5" M Each 7 Days $96.38
I have 2 650CCA versions of these cranking over my 3/4 ton chevy 350 small block van and it will go around the block on them. I suppose the starter would melt, but Marine staring batteries are not wimpy.
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May 20, 2009 8:50 p.m. blizazer New Reader
So I take it that 120v/240vac motors are out of the question?
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May 20, 2009 8:53 p.m. blizazer New Reader
Otherwise I'd recommend one of these guys.
AV’s MT-30 is ideal for testing smaller applications, such as fuel cell stacks, battery modules, partial modules and smaller components. This system provides an economical solution to many of our customer’s development needs, and only uses a small footprint of laboratory space. The MT-30 offers power up to 30kW, with a voltage range of 5 to 120VDC and a current range of ±500ADC.
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May 20, 2009 9:56 p.m. erohslc New Reader
Yeah, you're talking 6KW (12V x 500A), roughly a 50A draw @ 120V, 25A @ 240V. Not huge power, but substantial. A transformer big enough to deliver that kind of power is not cheap new, but you may be surprised at what can be found surplus. (Hello, Skycraft?) Try to find one from a trashed MIG welder, or maybe even a pair of smaller transformers that could be connected in a parallel configuration. Next problem is turning the AC into DC. The rectifier diodes for that kind of current are not uncommon, but tend to be umm... large. Does it have to be smooth DC. Gotta find some mondo filter capacitors.
Good news is that popularity of DIY EV has made many more components available.
Please post pix of your solution!
Thanks,
Carter Shore
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May 20, 2009 10:35 p.m. Shaun New Reader
So when you use one of these (linked below), which makes 4.6 H.P. and draws 507 amps at its highest rated load, do you need to tow some sort of mini powerplant behind you, or do you simply get a dual battery set-up?
The OP says it runs on car batteries, and it's a winch. why not a couple batteries and some cable? You guys are confusing me with all this rocket science stuff. What am I missing?
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May 21, 2009 4:27 a.m. petegossett Dork
How long does it need to run continuously for? My old battery charger has a 300amp crank mode. A couple of those in parallel would work in short bursts.
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May 21, 2009 6:15 a.m. 44Dwarf Reader
Check your ARC welder most seem to be 18-24volt when on DC but i've seen guys charge batterys with them. I would not with out checking but seen it more then once...
44
PS: you might want to put a battery in line with the welder to knock down any AC ripple that makes it throught the bridge rectifer
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May 21, 2009 6:31 a.m. MrJoshua SuperDork
I have tested my optima yellowtop 34/78 and it maintained 10.2 volts for 30 seconds of 500a discharge pretty easily. You are probably running waaaay less amps on average. What is your duty cycle? Is the winch setup being used for long periods of time? A couple of cheapo 20a Chinese battery chargers and 2 batteries and you could run a heck of duty cycle.
