How do I size motor and/or battery capacity?

[Lil'John]

The title is the generic. My interest is a drivetrain for an empty Honda Civic that would be grocery getter and lake runner.

First part of the question is how do I select a 'good' motor size? Missing engine is 60hp/76ft-lbs is ~227lbs while car weighs ~1500lbs

Related question #1: does an electric motor have a bigger drain based upon 'heavy throttle' use similar to a V8? Ex: I can get pretty good mileage out of a V8 if I'm not heavy into the gas.

Related question #2: is what do motors typically weigh?

Second part is how do I calculate needed battery capacity? I know that voltage/wattage of motor are key as is actual battery capacity. But is it as simple as a motor run time at mph gives total mileage? Or is there a 'loss fudge factor' out there? I'm space constrained but not range constrained... as long as I can get ~40 miles, I'm good (round trip to town for groceries or going to lake)

 

[PAE]

Do you know and understand power law ?

 

[Treefrog]

Motor size depends on your goal. How much power are you after? There is 60 hp options up to a few hundred. More powerful is not necessarily heavier, to a certain point. Currently availble high quality motors are in excess of 3.5 hp/lb. Cheaper ones that are more conventional for swapping stuff like old hondas are more like .5 hp/lb.

For battery, check some telsa forums for what the are getting for whr/mile. I think it is 200-350 whr/mile. Build in some room to spare for battery degradation and stuff like winter driving. I would guess 20 - 30 kwhr would be enough.

 

[Lil'John]

Do you know and understand power law ?

I haven't had any college EE classes in 25+ years(upper div) so I'm a bit rusty on all the equations related to electrical.

Motor size depends on your goal. How much power are you after? There is 60 hp options up to a few hundred. More powerful is not necessarily heavier, to a certain point. Currently availble high quality motors are in excess of 3.5 hp/lb. Cheaper ones that are more conventional for swapping stuff like old hondas are more like .5 hp/lb.

I don't have any hp numbers I'd be after. I'm used to 190hp in stock 4wd S10 or Tacoma or ~350hp in lifted FJ55(s10 blazer size) with 35" tires. I don't have a good metric for 1500lbs of car and needed power.

My travel path is Georgetown, Calif to Stumpy Meadows along Wentworth Springs... I mention road/location because more than a few know the area. It is a windy mountain road with elevation change from ~2500 to 4000 feet. Usual speeds are in the 45mph to 50mph... or a 'hair' more if I am feeling froggy My power goal would be having the ability to maintain speed... nothing pisses me off more than not maintaining speed in hills

For battery, check some telsa forums for what the are getting for whr/mile. I think it is 200-350 whr/mile. Build in some room to spare for battery degradation and stuff like winter driving. I would guess 20 - 30 kwhr would be enough.

I would be doing zero winter driving... probably shut down November to April due to snow.

How much of an impact does weight have on charge life? *edit*charge life... f'n autocorrect

I've got a 10 gallon gas tank location that could be replaced along with whatever room is left in the engine bay.

 

[PAE]

Its been 40+ years for me so I'm even rustier than you.

 

[Treefrog]

I haven't had any college EE classes in 25+ years(upper div) so I'm a bit rusty on all the equations related to electrical.


I don't have any hp numbers I'd be after. I'm used to 190hp in stock 4wd S10 or Tacoma or ~350hp in lifted FJ55(s10 blazer size) with 35" tires. I don't have a good metric for 1500lbs of car and needed power.

My travel path is Georgetown, Calif to Stumpy Meadows along Wentworth Springs... I mention road/location because more than a few know the area. It is a windy mountain road with elevation change from ~2500 to 4000 feet. Usual speeds are in the 45mph to 50mph... or a 'hair' more if I am feeling froggy My power goal would be having the ability to maintain speed... nothing pisses me off more than not maintaining speed in hills


I would be doing zero winter driving... probably shut down November to April due to snow.

How much of an impact does weight have on charge lift?

I've got a 10 gallon gas tank location that could be replaced along with whatever room is left in the engine bay.

It has been a while since I checked, but past 100ish hp, you are forced into more expensive, higher voltage motors and controllers. The fab work also goes up since there aren't off the shelf options for bolting it to a transmission. I would think 100 hp might be enough.

Elevation change hurts batteries a lot.

Charge lift? Weight has the same affect as with a gas car, heavier consumes more.

That's not a ton of room, but it might be enough.

 

[J1000]

If I were going to convert a Honda, really any Honda, I'd use everything from a Nissan LEAF. Early LEAFs had small batteries, new LEAFs have big batteries.

A friend of mine converted an old CRX and gets almost 200 miles of range, keep in mind the LEAF he pulled everything from had about 150 miles range. You basically transplant all the parts into a smaller and lighter vehicle. Win win. Oh yeah and it will haul ass.

Look up Resolve-EV controller if you are interested and buy a wrecked LEAF and boom you have everything you need.