Sizing battery to operate DC motor
Sizing battery to operate DC motor
(OP)
We have a 12v, 1HP, permanent magnet DC motor (that is all the data we have) that will be used as a winch. Assuming we cannot operate on AC power due to alternating current.
We have a 40AH 12v battery. Assuming 1HP = 1kVA, then current = 1000VA/12V = 83 amps.
So with a 40AH battery, i can run the motor for:
40AH/83amps = .48 hours or 28.9 minutes at full load - is that correct?
Thanks.
b
We have a 40AH 12v battery. Assuming 1HP = 1kVA, then current = 1000VA/12V = 83 amps.
So with a 40AH battery, i can run the motor for:
40AH/83amps = .48 hours or 28.9 minutes at full load - is that correct?
Thanks.
b





RE: Sizing battery to operate DC motor
If the winch is not fully loaded the current will be less.
AH are tested/specified at a specified discharge rate. At high discharge rates the specified AH tend to be less than stated.
How about a transformer/rectifier combination?
Bill
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"Why not the best?"
Jimmy Carter
RE: Sizing battery to operate DC motor
RE: Sizing battery to operate DC motor
F Y I
Did a Google search on 1-HP 12vdc Perm. Mag. motors.
Three different ones; Dayton, Hallmark Industries, and Leeson Electric .... all are spec'd at 80 amperes.
Calculates to 214 watts of losses or just under 29% losses ... Oofta!
So, your approximation of 1-HP = 1-kVA .... is close .... but perhaps a tad high.
Don't forget to factor in Thermal Protection for motor.
Historically, I think that DC Winch Motors have been Series type.
RE: Sizing battery to operate DC motor
If Li-Ion battery, then, yes, ah is ah is ah and you can do the math and say 2x ah rating will result in 30 minutes use.
If some form of lead acid battery then NO: higher than about 1/10 C rating will result in FASTER discharge than C rating. Google 20 hour rate. see examples like:
http://gbindustrialbattery.com/Battery_Options/AH_...
http://www.acterra.org/ev/files/batteries_1.html
I don't recall the guy who named this unlinearity, but it exists: if you pull significantly more current than the ah rating then the life goes down significantly for lead acid designs.
RE: Sizing battery to operate DC motor
RE: Sizing battery to operate DC motor