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Old 06-22-2017, 02:59 AM   #17
pcarlson79
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Join Date: Jun 2017
Location: Canberra
Posts: 1
5 yr Member
Default INSTANT power cut

Quote:
Originally Posted by Pob1970 View Post
my Ninebot Elite died on me yesterday with no warning and still 3 bars on battery and I had only went 50 yards when it cut out ended up in A&E with a broken arm and badly bashed face!
Hi,

I just bought a Ninebot Elite second hand and my battery went flat after just 8km with 4 bars remaining but it vibrated and shook with Error 37 so I walked it home. Plugged it in to charge for 10 seconds then it was all good again.

I took it to the carpark to test with 4 bars and then with ZERO warning I lost ALL power and fell backwards and opened up my elbow.

Now, being an electrical engineer I decided to NOT charge the battery and open it up. The Ninebot Elite does have 2 battery packs. Each battery is 15s2p with their own BMS onboard. I found that the BMS had tripped on both battery packs which left the system with 0v to try and balance me.

After a few weeks of trial and error, I tracked down the problem to 6 bad cells on BOTH packs. I replaced all the cells and am now getting a much better 17km range and I can safely get down to 2 bars where it limits your speed to 7km/h and then nothing.

So moral of the story is that it IS INDEED possible for the system to cut ALL power with no vibrating, stick shake or beeps, just BOOM no power. Honestly, after looking at the poor LG battery cells they use in the 450Wh packs and the poor SAMSUNG cells in the 670Wh packs, what a terrible decision. Each time they have gone for the cheap low AMP cells, where for an extra $0.30 per cell ($18) they could have put REALLY good LG or SAMSUNG cells like the Samsung 30Q.

But anyway, the fact they have separate BMS inside the battery box that can be triggered without being controlled by the motherboard is a bad design. I would much rather the battery get hurt by dropping under 3v than my elbow or worse. Rather than limiting current, they use a really cheap MOSFET cut design. Looking at the BMS it's no different to a cheap $15 BMS from ebay
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