538hp at 100% efficiency* (nothing is - so this is conservative) is 401,348 watts. That is a tremendous amount of power. Half of that (using one motor) is still ludicrous. That is equivalent to over 800 amperes of 480v. three phase power, more than many factories or shopping malls use! Certainly that is instantaneous power that is only sustained for a few seconds with a dragster vs a mixer that would use less force for a longer time.
IMNSHO you would need a huge battery bank with an equivalent huge charging system. If you are off grid then you will either need large wind generator(s) or lots of solar panels, both with associated large battery banks and chargers, controllers, etc. None of that is cheap, small, portable, convenient, or intrinsically safe.
For example, say instead of 538 hp, you decided to go with 60 hp, or 44,760 watts. Forklift motors come in various voltages, let's choose one with a 96v motor. To get that 60hp you'll need 466 amps at 96vdc. That is a bank of eight 12v. batteries in series to get 96v, and you'll need either very large batteries or lots of them in parallel to get that kind of amperage.
More than one of us on the list have established that 1hp is marginal for a drum mixer, 5hp is more like it. Extrapolating from there you should be able to run a 200 gallon mixer from 20hp, so divide the above amperages by three. "Only" 155amps at 96 volts or 310amps at 48 volts. Not momentary like a starter motor or a dragster, but continuous for several minutes. I often ran my no-tow mixer for 20 minutes before I was happy with the mix. Towing at 5mph for a couple of miles is about equal in time to that. Since it is a relatively long time, you would need to size your cables large enough to handle that amperage without melting. For that 310 amperes at 48 volts you'll need 250Kcmil copper cables. Your battery bank would also have to be large enough to supply that for twenty minutes at a time several times during a day, and/or recharged continuously from a suitable source.
I agree that a high torque motor like a series wound forklift motor would make a good papercrete mixer. I think by the time you add in the battery banks and chargers and controllers you are going to have a large investment and a heavy trailer to drag around. I would use a generator to charge since solar/wind is expensive for this type of application. 10,000 watts of panels at today's prices would be around $5,000. It would take a large generator to recharge in a reasonable amount of time.
To me, your fork lift motor mixer would be more suitable for an industrial situation like that papercrete block factory outside of Silver City. There is a lot to be said for the tow mixer that will go anywhere you can drive and nothing else is needed except the vehicle/draft animal that got you there. Or a few really good friends that don't mind being harnessed to a mixer.
*In reality you cannot get a horsepower from 746 watts, it takes much more. Electric motors are not very efficient.
JayH wrote:
It looks like we are going to disagree. That doesn't mean I do not respect and appreciate your experience. Obviously you have a system you are happy with and works well for you. That's great. I find nothing wrong with that. The "best" system is the system each individual thinks is best for themselves. You may find it amusing, but many of the reasons you cite in support of a tow mixer are the same reaons I suggest using something else. You talk about how much power it takes to pull a mixer, but the examples you cited perfectly illustrate how low end torque, not power, is so critical to the operation of a mixer. Internal Combustion engines are notorious for being very weak and inefficent at supplying power at low rpms and high torque. This also happens to be where a Series Wound DC Electric motor shines. These motors can supply enormous torque. For those unfamiliar with what torque is, it's how hard of a push something can offer in a turning motion. This is exactly why the biggest modern freight train locomotives are diesel electric. The diesel engine is used at higher rpm all the time where it is most efficient to generate electricity to power the high torque electric motors that actually power the train wheels. At zero RPM, internal combustion engines supply zero torque. At zero RPM, a Series Wound DC Electric Forklift motor can supply. John Wayland used two of this class of electric motors I suggest. He uses them to power his electric drag racer. He consistently beats the best internal combustion engine cars at the drag strip. He gets 538 Electric Horses, and a WHOPPING 1250 ft/lbs of torque... AT ZERO RPM. Dude can go from zero to 60 in 1.7 seconds! He doesn't even use a transmission. He directly couples the electric motors to the drive shaft of his car. Here comes the hilarious part. It's an old Datsun economy car. He can blow the doors of most macho muscle cars that come to the drag strip on a trailer, and John's ugly Datsun is still street legal and can drive to the race and back home in his race car. No street legal gas car has a chance to compete against John Wayland's hole shot. http://www.youtube.com/watch?v=fNT-dnrzqKk http://www.youtube.com/watch?v=RESC54vHr40 A measly mixer doesn't need that kind of power or torque. That would be insane. John uses two motors. I suggest using one would still be overkill. John advances the timing on his twin motors and over volts them beyond their specs. I suggest staying within the design specs of the motor and going with 36 to 48 volts, just like a typical electric fork lift. There will still be plenty of torque and power to mix papercrete with room to spare. If your Polaris ATV were converted to electric drive, it could easily tow your mixer at low speeds as long as it had good tire to ground traction. That would be the big problem with using an Electric ATV. Traction. These motors are not for wimps.
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