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Old 02-11-2009, 03:31 PM   #1 (permalink)
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Just received lots of free Li-ion batteries- Thinking electric car?

Hello everyone!

I have been fortunate enough to come across a bunch of used/ partially defective lithium ion batteries that a company was having to pay to recycle. Basically there are enough good cells (18650 size: about 1.5cm diameter, 6.5cm long) to make a big battery pack. like 3- 55 gallon drums of batteries (approx 30% are fine I think)

First things first:
I am an engineering student (mechanical) and I am basically at zero income with school costs. I can probably put $1000 to the entire EV project- I might get some help with that though and get up to $2K- but money is super tight!

So here are my questions:
1. how the heck do I charge the batteries in a large scale EV application? Li-on batteries from what I have read are very dangerous if charged improperly. <and have rigid discharge limits too> I have basically no specs on the batteries I have...

2. I have read up on the cheap EV conversions (like forkenswift), that is what I am looking at doing. I really need help on motors and control hardware.

---2a. forklift motors- I can't seem to find any around Wichita KS- where do you get one?

---2b. I really would like to get up- to 55mph top speed with the ev... I would probably only be doing around 40 in town driving, but I want the acceleration up to 40mph to be good.

3. The controller- I read something about Paul & Sabrina's cheap 144v motor controller-- is this close to a reality? This is my area of lack of knowledge- I do not know what it takes with motor size and voltages to get a car up that fast.

4. The donor car- I have no idea yet. maybe a metro? where do you get those? It has to be really cheap...

The first task I have before I do anything else is to make sure I can make battery packs that are useful and chargeable. I have a donated 36V golf cart with dead batteries that I figured I would use for my initial project. does anyone know about li-on batteries and using them in a big home made pack???

Thanks everyone for the help!


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Old 02-11-2009, 05:06 PM   #2 (permalink)
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Wow, hey Joey,

Looks like you have quite an opportunity there.

I was about to say that you have the cart before the horse, as you (possibly) have some very nice batteries there, yet no money, motor, charger, or car!

Since you have the golf-cart, make that thing work! Learn all you can about motors, controllers, etc. Go to the library and read all you can and check out the EVAlbum. There is some good general information in there.

Otherwise, since you haven't done a conversion before, you might want to start with a bicycle or motorcycle. A golf-cart is a good little EV, but it's not fun to put in that much work and then not be able to legally drive on the road!

Another possibility is that you could sell or trade the batteries to somebody else who already has a conversion and would want different batteries for it. Try getting a hold of a local EV group, through the EAA for example. You might be surprised.

Also, check out the sticky in the Fossil-Fuel-Free Forum here, it has some information to get you started.

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Old 02-11-2009, 08:05 PM   #3 (permalink)
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Wow - jealous! Maybe.

It's going to be a real challenge sorting out all those cells.

Before doing anything else, you're going to have to get the specs on them, and design/build some kind of test rig to sort the good from the bad.

Since it sounds like they're going to be of varying quality, you're also going to need a good battery management system (BMS) to prevent over-discharging.

I have an idea that I may be able to get my hands on an ongoing supply (trickle) of lithium batts - power tool size packs. I know someone who runs a tool/appliance repair/warranty depot for a major tool/appliance manufacturer. I have to remember to ask him about it this spring when I get back to Ontario.

Mind me asking what this company does that it's chucking out piles of batts?
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Old 02-11-2009, 11:52 PM   #4 (permalink)
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Less than $1000? I'd play with the Golf Cart for awhile-if Batteries are all it needs then you might have enough money for BMS and a good charger.

Later you might want to gut the Golf Cart, replace or modify the Controller (Golf Carts have built-in Speed Limiters I hear) and you could create a really nice Motorcycle. Anything larger would cost more money-bigger Motor, higher-Voltage Controller, donor vehicle...
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Old 02-12-2009, 04:10 PM   #5 (permalink)
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WoW that is amazing, I wish I could find a load like that!

Really, if you find your not up to using the batteries or finish your project and don't use them be sure to pass them around, there are a lot of EV'rs who would like to play

I would say follow the KISS principle and the KICS principle (keep it cheap)

Whatever you have access to including that little golfcart would work as parts and the motor in the golf cart would definately be big enough to drive a motorcycle or trailbike, maybe not super fast but keep the weight down and it would work as in town transport and if it is a larger golfcart motor AKA 5hp or larger you can probably modify it to get up to 55mph on a light vehicle like a motorcycle or even a small aerodynamic car (like my subaru 360), occasionally junkyards have vehicles that are OK but have a blown motor most are getting quite expensive even though the price of metals has dropped.

Go to diyelectriccar.com and bring the model of motor in your golfcart you might be surprized, both of my ev's use golfcart/forklift motors and one does hit 55mph at 72v, though it is a 10hp which are not as common. You may need to tune your motor a bit differently, advance/replace brushes, to get it up to speed but don't underestimate as long as the vehicle is light it should be enough assuming it isn't a little 2hp plug .

As for donor vehicles generally look around classifieds for motorcycles and cars that do not run or place an ad on craigslist (stating what you are attempting), if your area is large enough you might get lucky and find something suitable.

The best EV is the one that is the most reliable, that you don't invest money into but you do invest time and ingeniuty into.

Good Luck
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Old 12-04-2009, 01:10 AM   #6 (permalink)
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Li-ion is very tempramental. First you have to get the specs. Not all Li-ion cells are the same. Max charge voltage can range from 3.6V to 4.2V. Be very careful with those cells. You will have to get a BMS that can monitor each string of parrallel cells individually. If you over charge a string ( too high voltage) it will heat up and may cause a fire that is very difficult to put out. Also monitor the tempertaure of the pack. If it goes above 50C cut the power.
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Old 12-04-2009, 11:13 AM   #7 (permalink)
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Congratulations on the battery find!

Here are a few basic thoughts on EV performance to keep in mind as you gather parts for your EV build:

1. Acceleration = Amps. The higher amperage a controller and motor, etc. can handle, the quicker the vehicle will accelerate. A 500 amp controller will accelerate faster than a 300 amp controller.

Series motors use fewer amps as they accelerate. As an example, my motor uses about 400 amps (controller limit) for the first couple of seconds during acceleration, but tapers off to about 130 amps at top speed.

2. Speed = Voltage. In general, series DC motors (kind most commonly used in EV conversions) will spin faster with higher voltages. Your golf cart might go 20 MPH at 36 volts, and perhaps 25 at 48 volts.

One parameter of series motors is their RPM/Volt number. Some series motors will turn faster at a given voltage (high speed motors) while others will turn slower (high torque motors).

3. Range = Battery Volume. More/larger batteries (more total amp/hours) = more range, regardless of chemistry. If your golf cart had three motorcycle batteries (36 volts) it would probably work, but only for a short distance. With three 12v car starting batteries, it might go a few miles. With three 8D truck batteries, it might go ten miles. (of course, true deep-cycle golf cart batteries are normally used for max range and battery life).

Biggest problem here is that more batteries = more weight, which takes away from acceleration and speed, and in some cases the number of passengers you can carry in a vehicle... Lithium batteries certainly address these issues.

Here is a link to what your lithium batteries could look like...

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Old 12-04-2009, 12:01 PM   #8 (permalink)
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It's Whoa, & I doubt he's ever seen the show.

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