[Duncan]

Hi
You don't mention what you are converting
Anyway a small car will require about 300 watthours/mile
So 50 miles is 15,000watthours or 15W Kwhrs

Those batteries are 12v and 75amphours = 900watthours
BUT
You only get 75ah at a very low discharge rate (C20 - 3.75amps) - you are going to need more than 100 amps
At that rate you will get about 35 amphours out of that battery
- look up Peukert - (Does not apply to lithium ion)
That drops your battery to about 450watthours
BUT
If you discharge to 100% you will only get about 10 cycles
So you need to discharge to 80% max
Now we are down to 360watthours
We need 15Kwhrs
So that would be 42 of those batteries (not 12)
at 50lbs each that is 2100lbs

BUT
with an extra 2100lbs on board you will need more than 300watthours per mile!
so you have to add more batteries - which adds more weight.......

50 miles range is actually nearly impossible with lead acid batteries

Do you really need 50 miles range?

If you do then you need to go lithium
a few years ago that would mean a big bill - but you are in the USA and battery packs from crashed electric cars are now available
I paid $1800(US) for a Chevy Volt pack - 16Kwhrs
That would be just about OK for you but a Nissan Leaf pack - 24Kwhrs - would be even better

 

[dougingraham]

You don't tell us anything about your project except for 72 volt system. The big problem with Lead Acid is that of false economy. Those batteries are listed as 75 AH and they can do that if discharged over a 20 hour period. Used in an EV they would probably only be half that due to the high currents. You were thinking of paralleling them to make 150AH batteries at 72 volts. This would be closer to an actual 75 AH at EV currents and figuring capacity that way would give a battery capacity of 5.4 kwh. To get 50 miles of range your EV would need to weigh around 1000 lbs or less. The other big downside is that if you actually drive out most of your range they wear out quickly. Deep discharges kill Lead Acid batteries. You have to limit use to about half of capacity to get decent life. 3 years is decent life. If you deep discharge them regularly then you cut the life dramatically.

A reasonable suggestion is to buy a Lithium pack from a salvage Leaf or Volt. You get a lot more battery for your money.

Best wishes with your project.

 

[Ironbacon]

I'm converting a 1989 Mazda b2200. Thanks for the tips. Where is a good place to find volt batteries?

 

[Ironbacon]

Also what about Prius batteries? They don't seem that expensive or hard to find.

 

[dcb]

leaf batteries are also pretty easy to find, though volt is a little cheaper and has water cooling options.

prius (hybrid) batteries are typically a different chemistry (NIMH, not lithium) and are more challenging to charge, and are not much better than lead in terms of storage/weight.

 

[Ironbacon]

Is there a place that deals in wrecked EV's? I cant find any in my local junk yards. Or do I have to buy online? Also can volt battery packs be broken down? I see several different voltages on eBay and was wondering if I could buy any or if I have to buy 72 volt.

 

[Duncan]

Hi there is a site called Car-Part.com
Search that for your battery

The volt or leaf battery consist of a number of modules
http://www.diyelectriccar.com/forums/showthread.php/2012-chevy-volt-battery-93101.html

Now - what is this with 72v?
That is very low for a road going EV
Why do you want 72v???

 

[Ironbacon]

I was going to go 72v because I wanted to use a golf car controller and didn't want to break the bank to buy one. I am not skilled enough to build the open revolt controller.

 

[Duncan]

I was going to go 72v because I wanted to use a golf car controller and didn't want to break the bank to buy one. I am not skilled enough to build the open revolt controller.

Hell I managed to make one and my previous electronic experience was absolutely zero!

72v will get a 'Town car" - but it will probably have a top speed of about 40mph

 

[Ironbacon]

What voltage should I go for to drive at 55 or 60? Most of my commute is in horrible traffic so I would only have to go that fast I I wanted to drive it around on the weekends.

 

[piotrsko]

Back in the day....... we used lower voltages because the power SCR's and transistors only ran that high. worked ok in a bug or rabbit or other small light car but those only had so much room for monster FLA packs.

There are plenty of cheap 144 curtis controllers, used others up to 300 ish volts. Unless you have a golf cart controller already, I would do it different.

Problem is: nice for a while but the siren song of accelerations comes along and......

 

[Yabert]

I was going to go 72v because I wanted to use a golf car controller and didn't want to break the bank to buy one. I am not skilled enough to build the open revolt controller.

I understand you. Cheap and easy 72v conversion is really attractive and usable 72v conversion are possible, but probably not for a truck with low budget in mind.
http://www.diyelectriccar.com/forums/showthread.php/72v-systems-small-car-68596.html

Maybe look here for cheap controller (exchange rate is good for you): http://www.zeva.com.au/