Duncan, tell me where I can buy those infinitely stiff (in Voltage) lithium batteries you used in your formula!

Let's do a few examples. Let's assume these efficiencies: 98% controller, 85% motor, and 85% tranny/diff/bearing losses.

Typical floody conversion: 0.010 Ohm resistance per battery, 500 Amps, 12 twelve V batteries for 144V nominal.

Voltage sag for each battery: 12V - 500A * 0.010 Ohm = 7 Volts

Lossless power: 500A * 144V = 72 kW = 96 hp

Power with sag and losses: 0.98 * 0.85 * 0.85 * 500 A * 7 V * 12 batteries = 30 kW = 40 hp

Formula "Max battery Amps * Pack Voltage / 2 / 1000" = 40 hp

Wow, exactly right!

Same thing for 1000 A controller and 12 Optima batteries with 0.003 Ohms of internal resistance each:

Power with sag and losses: 76 kw = 102 hp

Formula "Max battery Amps * Pack Voltage / 2 / 1000" = 72 hp

Underestimates by 25%

Some thing for 2000 A controller and 12 Optima batteries with 0.003 Ohms of internal resistance each:

Power with sag and losses: 102 kw = 136 hp

Formula "Max battery Amps * Pack Voltage / 2 / 1000" = 144 hp

Overestimates by 6%

600 A controller and 144V of 200 Ahr LiFe batteries (0.003 Ohm internal resistance each for 44 batteries)

Power with sag and losses: 28 kW = 37 hp

Formula "Max battery Amps * Pack Voltage / 2 / 1000" = 43 hp

Overestimates by 16%

336V of A123 batteries, 170 A each battery so 12 in parallel, 100 in series:

Power with sag and losses: 230 kW = 308 hp

Formula "Max battery Amps * Pack Voltage / 2 / 1000" = 336 hp

Overestimates by 8%

Rich persons setup: 2000 A, 336 V of A123 batteries (0.010 Ohm internals resistance each, 24 parallel and 100 in series). 0.010 Ohm / 30 = 0.42 milliOhms per 24 in parallel. That's 70 A per A123 battery.

Power with sag and losses: 349 kw = 466 hp

Formula "Max battery Amps * Pack Voltage / 2 / 1000" = 336 hp

Underestimates hp by 39%

This pack would cost about $40,000 USD

So not perfect, but pretty good for something you can do in your head.

Agreed that electric hp are "stronger" than ICE hp for day-to-day driving, as electrics typically have a fatter torque curve.

Hi JRP3

The idea was to compare IC engine horsepower with electric, a 100Hp engine has 100 Hp at ~ 5000rpm and 50 hp at 2000 rpm

*Max battery Amps * Pack Voltage x 1.33 x*** 2** / 1000 ~= equivalent IC engine horsepower

In driving a 50Hp electric motor will "feel like" a 100 Hp IC engine,

bit like a diesel, if you rev the nuts off a petrol (gas) vehicle it is faster - if you drive normally the diesel feels quicker

It was also an over the top responce to DavidDymaxion

*500 A * 144 V / 2 / 1000 ~= 36 hp -- old VW bug speeds*

Hi JRP3

The idea was to compare IC engine horsepower with electric, a 100Hp engine has 100 Hp at ~ 5000rpm and 50 hp at 2000 rpm

*Max battery Amps * Pack Voltage x 1.33 x*** 2** / 1000 ~= equivalent IC engine horsepower

In driving a 50Hp electric motor will "feel like" a 100 Hp IC engine,

bit like a diesel, if you rev the nuts off a petrol (gas) vehicle it is faster - if you drive normally the diesel feels quicker

It was also an over the top responce to DavidDymaxion

*500 A * 144 V / 2 / 1000 ~= 36 hp -- old VW bug speeds*