Modifying an iZip Street Enlightened

[CBR1100XX]

I picked up this bike for 500 dollars 3 years back and the battery is starting to really go now (it was made ~2007 so the batteries are getting up there in age). My first thought was just to buy new cells and try to rebuild the battery pack since they want an arm and a leg for a replacement and they're likely most of a decade old as well. But I'm wondering since there are so many e-bike conversions out there is it possible to modify this one to improve its performance? And how complicated of a process would it be?

Here's the info I could find about it online:

MOTOR 180W Exclusive Alloy Shell DC Brushless Geared Hub Motor
BATTERY NiMH EV Rated Batteries Down Tube Concealed, 24V / 9AH Pack, (20) 1.2V Rechargeable Cells
CHARGE SYSTEM UL Listed NiMH Currie High Power Smart Charger with LED status display
CONTROLLER Exclusive Currie Electro Drive 24 Volt fully potted with Power Gauge function

http://www.electric-scooters-galore.com/streetenlight.html

 

[gogo]

What aspect of the performance do you want to improve?

 

[docnjoj]

First read everything DrkAngel has written on E and I-zips. He has done a ton of stuff to make them better.
otherDoc

 

[wesnewell]

read this first.
http://endless-sphere.com/forums/viewtopic.php?f=3&t=66302