I need help building a Lithium battery for my E-Bike

kingcodez

Newly Enlightened
Joined
Dec 6, 2009
Messages
1
Sorry if this isn't the correct forum, I didn't exactly know where to post this.

I think it may be called an E-Scooter, I call it an electric bike, but it dosen't have pedals.

Anyways, this is the info I know about the bike:
It uses 4 12v car batteries I think, Each batt must be 2.5v.
The batteries are 3" deep, maby 7" wide, and 5" tall roughly. it would take three of these to equal the size of my Toyota Corolla's battery in America.

The Motor, right now, is 800w, needs 48v of power.

The battery controller is set to only handle 48v.

What I want to do, is either double, or extend my battery life 1.5x it's current life. My bike can go 40km/h, for 20KM, or 20km/h for 30-40km depending on speed and occupants.

My goals are to get the bike to go probably 50KM/H or at least have it get better acceleration. Goal distance is double of what it is now, so 40Km @ max speed.

I have no clue how to do this, the guy here in Beijing said it will cost me 1,000 USD, and he will get me a battery, but the cells are semi/half 'used' from the US. He says he uses A123 cells.

I know enough about batteries from airsoft, I know all about LiFePO4, and building batterys but only up until 11.8v. I kind of know a little about Parallel and serial wiring, I simply need to know a price.

I plan to throw in a 1500w 60v motor, but most likely a bigger one. If it is super detrimental to speed.longevity, then I will stay @ 48v.

What really sucks now, Is that on a fresh charge, my volt meter on the bike says the battery is @ 56v, once I drive it up the ramp out of the garage, 10 meters, it's down to 54. lower and lower it goes, until the cutoff point at 43v where I have to walk it, or sit and wait a few mins for 'the cells to equalize' or something. Then I have a short burst of power until I do it again.

I'm sick of lugging my four big batteries up and down 4 flights of stairs every day. Their too damn heavy, and my girlfriend can't carry them either, so I have to go out and do that whenever she uses the bike for the day.

I go back and fourth to school maby 3 times a day, plus other short trips, but the constant starting and stopping kills the battery so much. And when I ride with my and my girlfriend on the bike it dies even more.

How many cells do I need, and where in the US can I buy them?
Can I buy from a good dealer in China/asia? I'm not sure if it's cool if I stash 300 batteries in my suitcase and fly to china.

Here are some pics of the bike if you are interested:
Picture 1
Picture 2

Also another quick question, I bought an alarm for the bike, but it sounds like a bird chirping, and it's not loud at all, it's really embarrassing lol. Can I: Wire a car horn, or something not bird like, to the alarm box (which has the shake sensor inside), to the bike, and also wire the headlights, and taillights, to a 'blinker box' and set it on a 1 min or so timer?

I'm really paranoid about it getting stolen, I park it in a garage, but I've had one stolen from right outside my apartment before. I have a good lock, it has a little nub that slots right into my front disc brake. I dunno if it can be picked, but if I had the right tools, and time, I might be able to pry it off, but I know it'd probably damage the front disc (bend it) and mess the brakes up badly.
 
King,

What you need is at least a 48V/16Ah LiFePO4 battery pack with battery management system and a decent charger. Since this forum generally does not deal with batteries as applied to electric motors, it would be best to hit the right forum.

http://endless-sphere.com/forums/

The endless-sphere forum deals with batteries, battery pack building, electric motor drives, electric controllers, hub motors, RC motors, multi-motors, electric motorcycles to electric cars.

Since you are in China, you should be able to pick up the new 16Ah cells from a company called Headway. These Lithium Iron Phosphate cells can discharge from 80 to 160 amps so no worries about the batteries getting hit too hard. Each cell weighs 500 grams so a "48V" battery pack uses 16 cells for a 8KG weight. Throw in another KG for the battery management system board and packaging and you're still under 10 kilos.

Good luck and welcome to CPF
 
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