RadCity4 - Battery died - replaced under warranty

[Caxton Drift]

My wife and I have identical RadCity4s.
Hers was the first to fail. The battery just died while she was riding. Dead as a dodo! Stranded by the road-side. No power. No battery-level indicator. Both 5A and 40A fuses checked out OK. But the battery showed no signs of life. Bike worked OK with another battery.

My bike also failed a couple of months later. Same story. Completely dead battery. Stranded by the road-side.

Both bike-strandings occurred in the same place, at the bottom of a short hill, just 2km from home.

Rad replaced both batteries under warranty.
When I took the second battery in to the Vancouver (Canada) store, the tech-person wasn?t surprised and explained that the RadCity4 batteries have a known problem: if the battery is fully-charged, and the rider then goes downhill using the brakes, the power-regeneration feature fries the battery!
It seems that the internal battery-controller allows the battery to overcharge, and the battery is then dead.
And no fuses are blown, just a deceased battery!

This would seem like an easy fix for Rad?s battery-designer.
But there?s no evidence that Rad are doing anything about this design fault.

Moral of the story: If you live in a hilly-area (that?s why we bought eBikes), don?t start the day with a fully-charged battery or you may fry the battery when next going downhill.

[JedidiahStolzfus]

Well, the cells of the battery are probably still good.  Chances are the BMS died.  I'd bet the damage to the board is going to be obvious too.  Some mosfets on there probably let the magic smoke out.

[DickB]

Do you still have the bad batteries?

[Caxton Drift]

Do you still have the bad batteries?

No, it was a straight exchange at the Rad service-centre in Vancouver.
I hadn't touched the seals on the batteries, so that they would still be honoured under warranty.

What is interesting, though, is that the model numbers of the replacement batteries were slightly different from the originals:
- dead batteries:  S1304
- replacement batteries: S1304Y
I wonder what that extra Y signifies?