So how much power do you use?
 

Wondering how many volts and amps (watts) an ev uses while cruising the highway at different speeds. Maybe hint as to the weight of the project

Also, how long do golf cart batteries last compared to rv deep cycle batteries? Cycles of half discharge and recharge

Got a land rover discovery I love to drive but nets only 10.5 mpg. Just a thought. I can get deep cycle rv batteries at $30 a piece and electric motors at discount. 3 years ago I was offered 20 batteries for free but had no place to pu them

430 watt hours per mile at 50mph (80kph).
Aaron's 1995 Land Rover Discovery

At faster speed I would guess you might use 500 to 600 watt hours per mile.

Deep cycle RV batteries are not traction batteries, they are not designed for high discharge rates that it takes to drive a vehicle down the road and the people I've seen who use RV deep cycle batteries tend to have them last 3 years or so before their capacity has degraded to half of what they were new, golf cart batteries should be 5 years or more if you don't over discharge them or leave them sit discharged for days at a time.

I don't get watts per mile that's why I asked for volts and amp reading

watts is volts times amps. in theory, you can take 48 volts at 50 amps and get 2400 watts, or you can take 96 volts at 25 amps and get 2400 watts, and go the exact same speed and acceleration.
Further, if you spend enough time pricing batteries, you find it all about works out to about the same cost and has the same distance and capacity.

alright, still not quite what I'm asking for. if i were to look at an instantaneous reading, volts and amps, what sort of readings would a vehicle get. If I have 12 12v batteries, 144V available, not all will be across the motor, voltage and current would be limited by the controller.

I'm still trying to wrap my head around this watt/mile. 600W a mile for 60 miles (1hr@60mph) would that be 36000 watts? it cannot be 1000A at 36V, or 360A at 100v.

aaaahhhhh sorry bout that.

somewhere on this site is the horsepower calculator. It is a pretty good one. You plug in car size, weight, speed,etc, and it tells you how much horsepower it takes to cruise at steady speed.

From there, a horsepower is about 750 watts, and a watt is a volt times an amp.

So, lets say it takes 10 horsepower to cruise at 75 mpg. that would be 7500 watts.

If you are using a 100 volt system, that means 75 amps. If you are using a 48 volt system, that means 150 amps.

That is exactly what it would be and because 1000 amps is a whole pile of amps to be pulling and it would make even a cable the size of your thumb warm after a few minutes, and it would tend to burn out the smaller wires going to the carbon brushes in a motor after a few minutes you tend to go with higher voltage to reduce the amps while keeping the wattage the same.

You are right Wh/mile sounds confusing if you don't practice thinking about it.
That is the way of figuring the fuel economy of an EV.

In the above link for the Land Rover the owner claims 430Wh/mile at 50 MPH.

How did he get that figure?

430(W) X 50(MPH) = 21500 W (or 21.5 KW).

The Land Rover's nominal voltage in the link says 240 Volts.

So 21500(W) / 240(V)= 89.5 Amps!

Therefore it looks like the vehicle is pulling an average of about 90 Amps at 240Volts at 50MPH.

So let's reverse this to see how he got the figure! (rounding numbers).

At 50MPH his Ammeter shows 89.5A and his Volt meter at 240V = 21480 W!

If he held this speed for an HOUR then he used 21480 W/h of energy and covered a distance of 50 miles!
Now divide the number with 50 to see the Wh/miles figure: 21480/50=429.6Wh/mile! (close enough).

There is a thread on real world volts and amps figures at various speeds and cars ( EVs) here:
Highway cruising amps? - DIY Electric Car Forums

Barna

Now I got it, thanks!

Not to confuse you more but a lot of people measure their watt hours per mile at the outlet, just like you figure out your gas mileage at the pump, they put a watt hour meter on the outlet they are charging from and see how much it takes to fill their batteries then they look at how many miles they covered.
There is also a brand of meter called the E-meter that some people use because it can log how many amp hours you have used out of your battery pack and tell you how full it is, but I think that meter also converts it's readings in to watt hours as well, so you can figure out your watt hours per mile at the end of a trip even before charging, I like to factor in the energy that is wasted in the battery charger too so my watt hours per mile (about 300 WH per mile) is higher then if I were to log the energy that I was pulling out of the battery pack, I do it that way because I have a meter that gives me a state of charge in percentage, so I just do my best to make sure to recharge before I get to 50% full.

Just to add another perspective, the units of watt*hr/mi are newtons, which is force. You are measuring how much force is acting against the car at a given speed. Higher speed means more force pushing against the car.

(watt) * hr / (mi) =
(newton*meter/sec) * 3600sec / (1609.344meter) =

2.237 newton

------------------------------------------------------------------------
One newton is 0.225 pounds of force, so a 400watt*hr/mi car would need a guy pushing it with
2.2237*0.225*400 = 200 pounds

of force to keep it moving at the rate it's going.

240V and 90A is 21450 Watts. at 746W per hp it's taking 28.8 hp to push that car along. how can 28.8 hp equal 200 pounds of force required to push it along? something not right

is there a page for how much hp is required to push a car along at highway speeds? would like to see some figures

Voltage*current is Power. Watts is power, and HP is power. It's not force.

BUT!

If you divide power by speed you get watt*hr/mi (which is FORCE). So, if you know the speed you are which you are traveling, you can find the watt*hr/mi...

In the example you gave:

240v*90amp = 21450 watt of POWER. That is the same as 28.8 horsepower of POWER.

Let's say you were measuring that 240 volts and 90 amps at 50 miles per hour.

That would be 240*90/50 watt*hr/mi = 429 watt*hr/mi.

Let's say you measured 240v and 90 amps at 100 miles per hour.

That would be 240*90/100 watt*hr/mi = 214.15 watt*hr/mi.

Let's say you have a big fat slug of a car. 240v and 90 amps at only 10 miles per hour.

That would be 240*90/10 watt*hr/mi = 2160 watt*hr/mi.

Ecomodders would come from all around and hunt you down and kill you! hahaha

my car is a big fat turd. 10.5 mpg. if calculated to power it would be lots. there is no way it is only 30 hp to push it to 50mph

slightly off topic, how come a 2.25L turbo diesel gets 30mpg, a 4.0Lv8 gets 15mpg and an electric motor needs 30hp to do the same work?

ROFL!!!!

Hey! we could convert mpg to watt*hr/mi I bet! gallons per miles is amount of energy per mile which is watt*hr/mi!

And what would that big number be?

Let's do some figgerin'!

130,000,000 Joules of energy in a gallon of gas.

Let's assume that the engine is 15% efficient?

So, 0.15*130,000,000 Joules to go 10.5 miles.

19,500,000 joules to go 10.5 miles.

There are 3600 joules in a watt*hr, so...

(19,500,000 joules) * (watt*hr)/(3600 joules) / (10.5 miles) =

515.9 watt*hr per mile!

The real world value would be a bit worse, because volts and amps first have to go through a controller and a motor. So I bet it's more like 650 watt*hr/mi.

Holly crap it's close. What about diesel?

Diesel is 155,000,000 joules per gallon instead... If you get 10.5 mpg still, then the watt*hr/mi is even worse! 155/133 * 650

Hello bandit86,
To answer your second question, if you mean a list of actual cars, I dunno. But if you look at the top of this page, see Garage & Tools? Click Tools and then click "Aerodynamic & rolling resistance, power & fuel consumption calculator" you get here.
And you can see the HP for any car if you can think of the weight and wind drag and stuff like that.
Now about your first comment. the power required is the force times the speed. So 200 lbs X 60 mph. Of course we don't think of power in terms of lb mi/hr, we like ft lb/ sec. And 550 ft lb/sec is one hp. So 200 X 60 = 12000
now divide by 3600 seconds in an hour = 3.3 multiply that by feet in a mile 5280 X 3.3 = 17600 ft lb/sec. Divide by 550 and get 32 hp. So 200 lb of force at 60 mph is 32 hp.
There is a little less than 50 hp-hr available in a gallon of gas. Engine efficiency at cruise might be between 10% and 20% say 15% So you'd get about 7.5 hp-hr per gallon. Using 30 hp for an hour takes 4 gallons, and you went 60 miles, so 15 mpg. And that's just cruising. If you need to get to that speed from a stop, and then throw away your momentum braking again, well 10 mpg is reasonable for a big heavy old brick.

-mort

Hi bandit86,
If you mean replacing a gasoline engine with a diesel, what should you expect fuel consumption wise? Diesel has about 10% more energy per gallon than gasoline. But the diesel cycle is way more efficient at cruise conditions. Maybe better than 30% efficiency at the 30 hp or so needed. So about 50 hp-hr per gallon at 30% efficiency is 15 hp-hr available. So to get 30 hp you need 2 gallons per hour, and at 60mph that's 30 mpg. Now this assumes that the diesel engine is plenty big enough to produce cruise power at high efficiency, and yet not so heavy that more force is needed to push the truck.

-mort

I meant the diesel version, 1/3 smaller. It turbocharged gets an easy 30 mpg

I don't understand your question.
The diesel version gets 30mpg because just like mort said, diesel fuel has more energy in it per gallon and diesel engines are more efficient so they pull more of that energy out of the fuel, wasting less of it, because a diesel engine is always running wide open throttle and only limiting the fuel, then a throttled turbo (dump gate) can help boost power output when needed without hurting fuel mileage, allowing a smaller, more efficient, lighter weight engine to be used.