What if someone is planning on powering their entire house from a solar array and batteries when the house is finished?
If someone is planning on acquiring those things ANYWAY, why not mount your solar panels on a ground mount and take advantage of your house's future power supply during construction as well?
https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj5xF1nztDr9oFjC9w43GwWjF7BuUqILLYh_q6MNGDFm8HeIe3FpWngehTvrc90dW9TYrw__ViLsEVSH93if6uRKdYkLjXYL549-IpTgBAdlUB9-hBMHtNB6ViwzoPsIYqFf-sGK_DbG7vI/s1600/DougPVMts01.JPG
The same argument can apply to wind, or any other power source.
If you are going to acquire it anyway to power your home, whatever it is, it makes sense to go ahead and get it early and use it to power tools and machinery during the construction of the home. That is just working smarter.
Spaceman wrote:
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.
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