Question
I have a small manual bandsaw mill that I would eventually like to convert to electric to reduce noise and exhaust. I researched using a 10 HP single phase motor (to replace my 16 HP Briggs), but determined that my service was not adequate (would introduce flicker in my neighbor's circuits).
Has anyone used a DC motor and a bank of deep cycle batteries with a heavy duty charger to run a mill?
Since I only saw 500 BF per day in my one man, manual operation, I would think a 5-10 HP DC motor with a bank of batteries would give me the power I need to make the big cuts and the time between cuts would allow the batteries to be recharged. Any sources of used DC motors in that horsepower range?
Forum Responses
(Sawing and Drying Forum)
From contributor C:
The best way to avoid the neighbors getting that flicker is to use a phase converter and run a 3 phase motor. A 3 phase motor will have a better efficiency rating, and have a smoother torque curve. Another advantage of 3 phase is that the motors are a lot smaller and lighter.
The other is to purchase a VFD, which is a power supply that creates the three phase from a single phase input. Probably a good choice for motors 5hp or smaller, after which the supply cost will go up. There are always a lot of these used around. A buddy has a Delta VFD-B 10 hp that can run a 5 hp 3 phase motor with only a single phase input.
Most of the static phase converters are not true phase converters, only a low amp phase shifter, hence the disclaimer on the product that the motor will only develop 2/3 of rated power. Variable frequency drives will offer less brownout than some of the other options only because you can set them up for slow starts, which will only reduce the starting power requirements.
A DC motor will work fine with a battery bank, but is going to be expensive to set up, maintain and control. So that you are aware, DC is physically more dangerous than AC because electric shock causes muscle contraction. With the cycling of AC there is a moment where voltage will be 0 when you might get yourself disconnected from the equipment, but you don’t get that with DC. And don’t forget that because electrons have to move in and out of the wire linearly (in one end, out the other), with DC larger wire gauge and heavier contacts are needed. The above warnings are based on the same working voltage.
Getting back to the motor, 7.5 HP is more than enough. That is equal to a 15 HP gas engine. I have a Cooks’ mill; the blade is 1-1/4”x 168” and runs on 19” all metal wheels. I have 500 hours on it and 1000 hours on my 28 HP gas powered portable mill. The all electric mill runs a little slower, but not much.
Point of information: 7.5 HP motor should draw close to 40 amps at full load. 10 HP should draw 50+ amps at full load. I have found 10 HP motors that draw 40 amps. It is not 10 HP, it is 7.5 HP. Just remember - more amps, more work! If your equipment does not draw these figures, your motor has not been accurately advertised. I get pissed when an equipment dealer tells me that a 1 HP motor draws 9 amps. Wrong! A 1 HP motor draws 13-15 amps. Sorry for going off. This really gets me going. When looking for motors, look at the amp draw at full load. On the tag or stated it will be (FLA) Full Load Amps.
