Author Topic: Smart Pie External Rear Hub - This & That (Battery & Speed)  (Read 40 times)

Offline Ron Burgundy

  • Confirmed
  • Junior Member
  • **
  • Posts: 34
Smart Pie External Rear Hub - This & That (Battery & Speed)
« on: August 01, 2020, 06:11:47 PM »
Now that I have been using my 36V Smart Pie I have the NEED 4 more SPEED. I am fairly certain that I was sold a throttle & controller MX25 V2.0 that is capable of 48v. My top speed on level ground with 700c rear wheel (260lb rider) is about 28kph/17mph (no pedalling). I am fairly happy with that but would love to pump it up a bit and wondered if anyone could estimate how much faster it would be with a 48 V battery?

I was also wondering if it is worth trying to upgrade my GM Hailong 36V 13.6AH battery to 48v myself or drop it at a battery store to do it instead of purchasing a new one from GM Canada?

Offline Bikemad

  • Global Moderator
  • Professor
  • PhD. Magic
  • ******
  • Posts: 4,936
Re: Smart Pie External Rear Hub - This & That (Battery & Speed)
« Reply #1 on: August 01, 2020, 09:23:43 PM »
Hi Ron,

If you currently achieve 28km/h (17mph) with a 36V battery the most you could expect to achieve would be 37km/h (23mph), but in reality this speed will probably be a bit lower due to the additional wind resistance encountered at the higher speed.

Converting your battery from 36V to 48V is definitely not a straightforward job, as your pack's existing 10 groups of 4 cells (10S4P) would need to be reconfigured into 13 groups of 3 cells (13S3P) and you would also need a suitable 13S BMS.
The cells should ideally be spot welded together as soldering them could cause permanent damage to the cells due to the amount of heat that is likely to be absorbed by the cells during the soldering operation.

The 42V maximum charging voltage of your existing 36V charger would be too low for the reconfigured battery, as a 13S pack would require a charger with a 54.6V maximum charging voltage.

Please note that the battery capacity would also be reduced from 13.6Ah to 10.2Ah resulting a noticeable reduction in your available range.

Your existing 36V throttle would still work fine as a throttle control with a 48V battery, but the LED battery gauge would be severely overvolted and would continually indicate 100% remaining battery capacity (all three LEDs would remain lit until the battery voltage was so low that it would eventually cut out completely), and the throttle unit would also get very warm during use.
Check out this post for further information.


Offline Ron Burgundy

  • Confirmed
  • Junior Member
  • **
  • Posts: 34
Re: Smart Pie 36V External Rear Hub - This & That (Battery & Speed)
« Reply #2 on: Yesterday at 03:10:32 PM »
Well that was very informative, thank you. I think I will stay put and be happy, I can easily pedal assist up to 37km/h.