It's not "startup" that's the issue. Assume that both batteries are sufficient to start and balance (4 bars or so). Now, get on and glide.

With the Ninebot, apparently each battery can independently shut off, without informing the "motherboard" that there's a problem - which should cause a warning and controlled shutdown. - just simply quit supplying power and let the "motherboard" notice that. Now, the other battery has a sudden increased load, and immediately shuts off power. No power, therefore no warning.

My dealer confirmed that the new models are not redundant - one of the reasons they're so much cheaper than the originals.

Hope you heal up quickly and find the cause for the shutdown.

I say "startup" because the motherboard had already thrown an error code and vibrated to tell the owner something was wrong. Owner charged it for 10 seconds and tried to use it again. Mother should have refused to start up with the battery in the same condition (+10 seconds).

How do you know what "condition" the battery was indicating at that time?

I think you are assuming that the batteries were indicating "off". (by not supplying voltage).

I am assuming that, having been briefly charged, and not under any load, the battery BMSs had reset and were supplying voltage. Indicating OK.

pcarlson79 said "Plugged it in to charge for 10 seconds then it was all good again."

Footnote:

A fuse inside the battery wouldn't be really good, either.

Now that mathiegi and terryp have confirmed the newer Chinese models are non-redundant design, I would never consider riding one. I wonder how long Ninebot will keep the redundancy of the i2 / x2 design in production....

If you say so.

Great question....Will they keep it and call them a Cadillac? or

Will they drop it to make it cheaper to sell?

To me it sounds like a bad business model in the court of law when someone gets a bad TBI off one, and they prove it was designed to be less safe to save money?

If a fuse inside the battery blows, how would you recharge the battery?

True.

You would have to send it back to a service center for repair. The cost and down time is still cheaper than another hoverboard fire, this time due to a shorted wire instead of overcharging.

Alternatively the BMS in the battery case would have overload protection or a user reset-able circuit breaker. I wonder what the UL rules are for power circuits. Suck up the shorted wire heat until the owner safely gets off, or shut down immediately to avoid a fire?