Specs first, then you can read the story if you're more interested :

• Purchase price : $700
• Power : ~ 5 kW
• Controller : 60v, 80A
  • In practice, you can give it up to 68v and it's happy. It's designed to take the charge/discharge curve of a Lead-Acid pack.
• Brushless hub motor
• Original battery pack 60v ; 40 Ah Lead Acid battery pack - 3 yo and a lot of abuse :
  • 8 months, no maintenance charge storage
  • When driving it you could feel that the battery pack was in the end of its life. Huge voltage sag and low current delivery after the first bursts.

So I could feel that it was a good machine, it just needed some attention for it's battery pack. As usual with batteries, once they're damaged or old, there's little to do about it but getting a new pack. Perfect case for our project.

Description for humans is - the batteries would actually last long, but any high current demand would make them kneel (voltage would drop from 62 to under 44). I could drive it for about 5 miles but whenever I'd try to climb a gentle hill, it wouldn't respond well to throttle.

At night, lights would turn off when accelerating.

One factor to motivate people out of Lead Acid for EVs is : look up Peukert's law for capacity reduction over high discharge rates. And that's what we do with EVs - average power is pretty ok, but "acceleration punches" are pretty demanding to the batteries. Lead Acid really doesn't like it.

I know, decent LiPo packs are not cheap. Which is why it's great to go small. I can do my commute with 1 kWh and that costed me only $200 on a deal for Drone MultiStar LiPos. If I were to replace the original 40 Ah 60v lead acid pack I'd pay more than that.