Mongoose ledge 2.1 conversion

[lxgoldsmith]

Hi. This will be my first ebike conversion. I know the bike is a bit heavy, but it's what I have available right now.

It will be used for college transportation. I want to use lithium ion 18650 batteries with a pcb.

I'll be replacing the wheels and making a custom battery cage for the inside of the triangle.

What kind of overall cost will it come to?

 

[lxgoldsmith]

So I ended up doing all the research myself. I'll be doing a 48v(13s) 1000w 12ah+(I hope more) build. I'll be using an imax b6 to test the cells and charge in groups. For now, I'll buy the batteries and the imax b6 and a spare multimeter in case mine is no longer usable after 4-5 years. 32 laptop batteries should yield at least a 50% success rate, probably around 60-75. If that doesn't work, I'll have lost 50 for the cells and will add it to the total cost of the bike.

 

[lxgoldsmith]

Forgot to mention I'll be getting the cells from used/dead laptop batteries

 

[lxgoldsmith]

So If I'm not talking to a wall, could a controller upgrade increase the top speed at 48 volts by increasing the amperage?

 

[Voltron]

Yes

 

[wesnewell]

So If I'm not talking to a wall, could a controller upgrade increase the top speed at 48 volts by increasing the amperage?

Increasing the amperage and not the voltage will give you better acceleration and very little speed increase , except under heavy load situations, where the max speed will be more. BTW, you don't have to get a new controller to just up the amperage.. You can just up the amperage on the one you have. The problem you will have is most laptop cells have really low discharge C rates. This will limit the amount of amperage you can get from them before killing them. But if you're looking for more speed, build a 14 or 15s pack. But I hope you realize that a 12ah pack made from .5C cells is only rated for a 6A discharge. 12A for 1C cells, etc.

 

[lxgoldsmith]

On my first build, I'm alright with sticking to 28mph top speed on a 48v 1000w motor.

1000w/48v = 21A; 21A/12AH = 1.74C discharge rate. Seems a bit high for laptop cells (should try to draw at 1c), so I'll add more cells in parallel if I need to.

I got the cells for $36. here's the listing - http://www.ebay.com/itm/310926493363

http://www.instructables.com/id/How-to-make-an-E-bike-battery-using-dead-laptop-/


A reference site - http://www.fasttech.com/forums/vapers/t/1076878/ripping-apart-old-laptop-batteries-for-18650/1

Here, they pretty much cover that often, someone can get a 75% good cell turnout from "dead" batteries. "Good" means 75% capacity or higher. anything below that is no good b/c of internal resistance. If this holds true, then I'll end up with ~144 good cells. 13 cells to get 48.1 volts, 143/13 = 11 cells in parallel. 53wh/11.1v/2p = 2.4ah/cell new, *.75 = 1.8ah used. 1.8ah*11p = 19.7ah, which gets closer to 1c. To cover the difference in possibly a lower turnout, I'll be asking around for any unused/dead batteries.

 

[lxgoldsmith]

Will I have to match different capacity, similar resistance cells in parallel to avoid putting them in series?

 

[lxgoldsmith]

Should I mount front or rear?

 

[DrkAngel]

Will I have to match different capacity, similar resistance cells in parallel to avoid putting them in series?

See - Homemade Battery Packs
Various testing methods, including bulk testing.
Use the Index, or read the whole thread.