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bwilson4web · 03-09-2009, 06:18 PM

Hi,

The squaring of the voltage comes from a combination of Ohms law and the definition of power:

I = amps
V = volts
R = resistance

I = V / R (Ohms law)
P = V * I (Power)

If you only have volts and resistance, combine the Ohms law with power:

P = V * ( V / R)
= (V * V) / R

What this means is for the same resistance, the power increases as the square of the voltage. So if the resistance stays the same, doubling the voltage results in four times the power. Cutting the voltage in half gives only 25% of the original power.

Now there is another approach that solves your voltage problem quite nicely, a step up/down transformer. I see any number of 1kw to 1.5kw 110/220 step up / step down transformers on Ebay in the $40-70 range. This would be an 'off the shelf' solution.

Bob Wilson

03-09-2009, 06:18 PM	#9 (permalink)
bwilson4web Engineering first Join Date: Mar 2009 Location: Huntsville, AL Posts: 843 17 i3-REx - '14 BMW i3-REx Last 3: 45.67 mpg (US) Blue Bob's - '19 Tesla Std Rng Plus Thanks: 94 Thanked 248 Times in 157 Posts	Hi, The squaring of the voltage comes from a combination of Ohms law and the definition of power: I = amps V = volts R = resistance I = V / R (Ohms law) P = V * I (Power) If you only have volts and resistance, combine the Ohms law with power: P = V * ( V / R) = (V * V) / R What this means is for the same resistance, the power increases as the square of the voltage. So if the resistance stays the same, doubling the voltage results in four times the power. Cutting the voltage in half gives only 25% of the original power. Now there is another approach that solves your voltage problem quite nicely, a step up/down transformer. I see any number of 1kw to 1.5kw 110/220 step up / step down transformers on Ebay in the $40-70 range. This would be an 'off the shelf' solution. Bob Wilson __________________ 2019 Tesla Model 3 Std. Range Plus - 215 mi EV 2017 BMW i3-REx - 106 mi EV, 88 mi mid-grade Retired engineer, Huntsville, AL Last edited by bwilson4web; 03-09-2009 at 08:41 PM..