[Taniwha]

The original Prius batteries can easily have individual cells replaced (mine is 20 years old, we've replaced 2 cells) - of course Toyota want to sell you an entire battery, the wrecker will sell you a whole bunch of spares

(do this with care, an entire pack is hundreds of volts)

[dzhiurgis]

Generally you can't replace cells unless you find perfect match - needs to be same resistance and capacity. Only on very large scale this is possible.

That said on most EVs blown cells are very very very rare. Mostly it's balancing lead that looses contact.

[Taniwha]

These are NiMH cells (7V) wired in series (not parallel so matching is less of an issue) - one bad cell and the series resistance of the whole string is shot

[dzhiurgis]

kia ora. interesting to know. so they are pretty small packs and their design doesn't really apply to large packs.

[timbit42]

I replaced some of the NiMH cells in my Prius traction battery by buying some Prius traction battery cells on eBay for $20 each. Still working fine after 2 1/2 years and a lot cheaper than buying a refurbished traction battery for $3,000. My Prius is 2006 so any cells from the Gen II models (2004-2009) work fine.