Talk me through an EV! I'm tempted to build, but no real knowledge!

[mora]

70 miles at 50 mph is no big deal. Get a big motor (11") and have external cooling so it will stay within temperature limits. More mass absorbs more heat. Use as high voltage as you can. Your contoller selection will likely limit voltage. If I'd go DC motor route I'd get something from Soliton series and use 250-300V pack. Those controller can limit motor voltage. You can use thinner cables as pack currents should stay low. Or then you could get suitable AC setup with controller from HPEVS for example. Voltage will be limited to 144V or something like that but then you can use batteries with bigger Ah rating. This will solve regen braking issue at the same time (can't do it using DC easily).

Oh, cost. Assuming your vehicle consumes 0.3kWh per mile (300Wh / mile) as mentioned before. 70 miles * 0.3 kWh/mile = 21 kWh. CALB batteries (LFP chemistry) cost about 440$ / kWh, so your pack alone will cost 9240$. You don't want to run the pack empty every time you run the car so let's leave some margin. 80 pieces of 100Ah cells make a good pack (25.6kWh). Price bumped to ~11k$. This pack will allow you to do ~70 miles in one go and still have 20% left. Your cells should last well over 100 000 miles this way. Even double that is within reality, though no-one using these cells hasn't driven that much yet. No real life evidence on that yet. But looking good so far.

This is not to shoot your idea down. Just to give some thoughts about it. Sometimes driving and owning an EV is not about money saving or being green. Heheh.

I've driven my EV for about 3 years. I calculated it takes less than 25 000 miles for me to "break even". About three years of driving. Almost there, heheh. Battery cost vs. gasoline cost I mean. But here gas goes for over 8$ per gallon.

[Ryland]

I agree with going with as high of voltage as you can, at some point speed controllers start costing more for higher voltage, but 144 to 300v is becoming more and more common, but up to 144v can be bought or made cheaper.

It's important to remember when building your car that you want it to last 100,000 miles, that is, if it's worth building for a 65 mile per day range.

Even if you have a 65 mile range, it's worth asking your work place about being allowed to plug in, if you can offer to take the least appealing parking space, 40 seconds of extra walking per day is good for you and it could save you a ton of money or at the very least give you a full charge on your way home.

[320touring]

Originally Posted by Daox

This is basically what you want:
http://ecomodder.com/forum/showthrea...nge-22955.html
He still spent $11k on batteries.

EEEk!
That’s a lot of pennies!

Originally Posted by mora

70 miles at 50 mph is no big deal. Get a big motor (11") and have external cooling so it will stay within temperature limits. More mass absorbs more heat. Use as high voltage as you can. Your contoller selection will likely limit voltage. If I'd go DC motor route I'd get something from Soliton series and use 250-300V pack. Those controller can limit motor voltage. You can use thinner cables as pack currents should stay low. Or then you could get suitable AC setup with controller from HPEVS for example. Voltage will be limited to 144V or something like that but then you can use batteries with bigger Ah rating. This will solve regen braking issue at the same time (can't do it using DC easily).
Oh, cost. Assuming your vehicle consumes 0.3kWh per mile (300Wh / mile) as mentioned before. 70 miles * 0.3 kWh/mile = 21 kWh. CALB batteries (LFP chemistry) cost about 440$ / kWh, so your pack alone will cost 9240$. You don't want to run the pack empty every time you run the car so let's leave some margin. 80 pieces of 100Ah cells make a good pack (25.6kWh). Price bumped to ~11k$. This pack will allow you to do ~70 miles in one go and still have 20% left. Your cells should last well over 100 000 miles this way. Even double that is within reality, though no-one using these cells hasn't driven that much yet. No real life evidence on that yet. But looking good so far.
This is not to shoot your idea down. Just to give some thoughts about it. Sometimes driving and owning an EV is not about money saving or being green. Heheh.
I've driven my EV for about 3 years. I calculated it takes less than 25 000 miles for me to "break even". About three years of driving. Almost there, heheh. Battery cost vs. gasoline cost I mean. But here gas goes for over 8$ per gallon.

These figures seem to suggest that there may be an argument for a diesel car in the interim, until battery tech and cost becomes better

Originally Posted by Ryland

I agree with going with as high of voltage as you can, at some point speed controllers start costing more for higher voltage, but 144 to 300v is becoming more and more common, but up to 144v can be bought or made cheaper.
It's important to remember when building your car that you want it to last 100,000 miles, that is, if it's worth building for a 65 mile per day range.
Even if you have a 65 mile range, it's worth asking your work place about being allowed to plug in, if you can offer to take the least appealing parking space, 40 seconds of extra walking per day is good for you and it could save you a ton of money or at the very least give you a full charge on your way home.

I hear you re work charging- means I could build for a 40 mile range instead

[puddleglum]

Originally Posted by 320touring

I currently have a 64 mile commute each day- taking upto 1.5hrs each way,

Electric Motor

What size do I need? 70 mile range at 50+mph

I understand that its amps drawn that's the key to matching output/heat/range?

Batteries

What type?

How many Volts?

How to connect and balance?

I'm a fellow noob, but I've been researching lots. If your one way commute is 32 mi. and it takes 1.5 hours you must have a lot of stop and go or traffic jams to contend with as well, do you? are you planning on converting one of your existing cars? You didn't tell us what your budget was.
If your budget can take it, I think you should go AC. You get the regen you want and less maintenance. Price for a HPEV AC50 is not that much more than a new DC setup and I don't think you would want to go the cheap forklift motor route with as much driving as you plan on doing. A forklift motor may be fine, I plan on using one eventually, but they will be a little less efficient and maybe a little less reliable long term. Plan to go Lithium for sure, it will be cheaper in the long run. The gray CALB cells are getting good reviews and have a higher discharge rate. Don't know who has them in the U.K. If you are using large cells for range, though, it may not matter as much and you may be able to get away with cheaper ones. This might be a source. Sinopoly Cells $1.10/AH - All Sizes, Worldwide Delivery - DIY Electric Car Forums
There seems to be a lot of debate on balancing cells so you will have to make your decision on top or bottom balancing and if you want a BMS or not. Personally, the bottom balance camp seems to make a lot of sense to me and saves the expense of a BMS system.