@itwire For your car you should just get a power inverter (~$20) and connect it to your car battery... leave the car running and charge the Onewheel as many times as you want.

@SkyPilot @wr420 yup, pin 2 & 3 are both "+", per the instruction page (though that tidbit is easy to miss):
http://onewheel.wiki/Charging_on-the-go
and I tested both + pins with a voltmeter to make sure they both had good connections.
Thanks for brainstorming. Let me know if you can think of any other potential issues.

@JacoNZ Thanks. Yeah, I think so too, though I'm still confused about why the 12V battery can't output 3.5A, but I will try a higher voltage battery and see what happens.

So, I built one of these, thanks to this thread (thanks @cr4p ) and this great instruction guide: http://onewheel.wiki/Charging_on-the-go

I've attached a few pictures below.
I've tried two methods:

1. 12v/10Ah (120Wh) LifePo4 battery + 300Watt power inverter + Onewheel supercharger
   Total Weight (including Onewheel charger): 5lbs, 8oz
   Results: Charge Onewheel 65% in 30min

2. 12v/10Ah (120Wh) LifePo4 battery + 58v up-converter
   Total Weight (no Onewheel charger needed): 3lbs, 15oz
   Results: Charge Onewheel 72% in 90min

Needless to say, I'm disappointed with my results using setup #2 (basically the setup described in this thread) both in terms of the minimal charge improvement over the 120v inverter method but also/mostly in terms of the 90min charge time.

The thing I don't understand (which is probably why the charge time was so long) is that I programmed the up-converter to deliver 58v and 3.5a but it only actually was delivering at 1.1a. Did I do something wrong? Do I need a different kind of battery? Any suggestions would be appreciated.

Method 1:

Method 2:

Charging display during 90min/72% charge session, showing only 1.1a draw:

I just received my OneWheel+ (yay!) and my screw-on pump no longer screws on enough to engage the valve-stem. This used to work, and the pump screws on to other, similar, valve stems (e.g. bicycle, motorcycle).

Has anyone else experienced this problem?

I use this pump for my tire:
https://smile.amazon.com/Progressive-Suspension-GP3-30-0-30-Gauge/dp/B000GZPGCQ/ref=cm_cr_arp_d_product_top?ie=UTF8

@jc
https://smile.amazon.com/Progressive-Suspension-GP3-30-0-30-Gauge/dp/B000GZPGCQ/ref=cm_cr_arp_d_product_top?ie=UTF8

@MichaelW I have that same gauge and love it

I just received my OneWheel+ (yay!) and my screw-on pump no longer screws on enough to engage the valve-stem. This used to work, and the pump screws on to other, similar, valve stems (e.g. bicycle, motorcycle).

Has anyone else experienced this problem?

I use this pump for my tire:
https://smile.amazon.com/Progressive-Suspension-GP3-30-0-30-Gauge/dp/B000GZPGCQ/ref=cm_cr_arp_d_product_top?ie=UTF8

@s2kboy Yes, plus, I got the email at 1pm, FedEx showed info a few hours later, that it was coming today! (one day delivery). Shipping from San Jose, CA to Lake Tahoe... SICK!

Just got my shipping notification for my board! #7312