Speedway 5 cutting out under acceleration

cespiner

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Joined
Nov 24, 2019
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Hi all, wondering if someone with a bit of battery/BMS knowledge can help me.

I have a Minimotors Speedway 5 scooter, 60V 24Ah battery, about 1000kms on it, owned it about a year and a half. Live in a hot dry country (UAE). It's a beast, if anyone's ridden one, huge acceleration and top speed of nearly 70km/h, range depends on use but around 30-50km 'real word' riding.

Anyway recently it's started cutting out under even mild load. The first time it happened at 38% battery charge, and I assumed the BMS had kicked in because of a low-voltage sag. Charged it up and all was well for a month or two. Then it did it again, this time at 53% charge. Same deal, mild acceleration, just cut dead. No power, nothing. Had to wait an hour or so and it turned on again.

Third time it did it was this week - at 78% charged. I was watching the display screen at the time, and the voltage under acceleration dropped by just 2 volts (from around 52 to 50, nowhere near the 44V cutout I think the scooter has built in to the BMS). As it cut, the display flashed, and the volts fell to 2V, bounced to 20V, and then the display cut out.

I've asked around the Minimotors community and most peeps say that it doesn't sound like a controller issue - usually in these dual motor scooters controller issues manifest themselves with motors refusing to turn over, or only one working. This is sudden loss of all power to the scooter, which resets itself after about an hour (or, if I plug it in and charge it).

So I'm thinking it's likely the battery, either some bad cells or, possibly the BMS itself malfunctioning? The battery still charges to 100 per cent (around 57V showing at full charge) and the range (when the scooter doesn't cut out) hasn't seemed to have diminished over the past 18 months. Acceleration is as powerful as ever.

Could it be just one or two cells in the pack have gone bad, and they are tripping the BMS under load? Batteries for these things are darned expensive, so I'm loathe to just fork out for a new one on the hope that this is the problem. But then again I don't want an explosion or a fire if I'm continuing to use a battery that is having issues.

Any help very much appreciated.
 
cespiner said:
Third time it did it was this week - at 78% charged. I was watching the display screen at the time, and the voltage under acceleration dropped by just 2 volts (from around 52 to 50, nowhere near the 44V cutout I think the scooter has built in to the BMS). As it cut, the display flashed, and the volts fell to 2V, bounced to 20V, and then the display cut out.

With this description it is most likely a bms low volt error on some cell. Could be confirmed if there are the same type of cutouts but increasingly more at lower voltage. If it happens randomly then i’d bet on a wiring issue somewhere.
 
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