An Aussie poster to one of the Yahoo groups reports that his traction battery died, on a '98 Japanese model he apparently "imported". All he said was that it wouldn't accept a charge any more. I don't know if the Japanese edition (the REAL "Gen 1") had a smaller battery than our Gen 1 ('01-'03), though we all know the Gen 2 battery is stronger than our Gen 1.
Gotta give us more than that!! Mileage, a link to the original post, something! Obviously this is the very earliest technology, even before 1G USA Prius. I consider it good news in that if this is the first, or one of the first true battery deaths it took 7-8 years with lower quality batteries with less advanced maintainence cycles before the first one died.
The first generation Prius battery-pack (1998-2000) was the "D" cell type, not all that much from what Honda & Ford currently use. The second generation (2001-2003) was a rather profound improvement. It's when the switch to prismatic modules happened. That allowed for much better heat management, despite the increased power. The third generation (2004 and beyond) increased the power even more.
The NHW-10 Prius is for Japanese market only. The warranty is only valid in Japan and it should be inspected by Toyota authorized engineer annually. Ken@Japan