ThunderSky Batteries

Hi Folks! I have been working on a few electric scooters for a local bike shop that are having a few issues.

There is a large variation in the range between brand new identical scooters. Also there have been cell failures.

The scooters use 20 X 40AHr ThunderSky cells, there is no BMS which doesn’t help! The cells are arranged in batteries of 4 cells.

I have measured the DC resistance of about 60 cells and found the lowest are about 3 milliohms with the highest at 13 milliohms.

I fitted one of the scooters with an ammeter (0-100A) which showed peak current of 75A which equates to 4kW, the motor rating, and between 30 and 40A while cruising at 45mph which seems in order.

It looks to me like the internal resistance of the cells is a real problem, these are supposed to be brand new!

Does anyone have any experience of these cells?

Thanks in advance, Martin

Hello, I had the same experience ! finely I build a BMS . The charge is not good without ! IF Not some cells will be out of order… If you want I can show you the wiring…

For interest - there is a lot of information on ThunderSky Cells at EVTV Motor Verks | Electric Car Conversion Videos in video form - long format video - patience is required - but there is a lot of informaiton in the blog and video library there. Not likely you could make it - but we will be having a HiPower Cell Dealer exhibiting at EV Fest 2012 Electric Vehicle Show here in Toronto, Ontario, Canada on Sept. 9th - see the exhibitor list at and you can contact them if you like.