TEG

So when I recently bought a Highlander Hybrid, I found out that the battery warranty is longer in California than elsewhere.

I have also seen mention of typical 10 year warranty on batteries in BEVs sold in California.

Wondering if this was just the manufacturers being "nice", I did a little search, and it appears that the CARB requires a 10 year warranty if the manufacturer wants to get the ZEV credits. (The ZEV credits could apparently be sold to other manufacturers that need them to avoid polution fines).

This link to a CARB document says:
""Warranty of Partial Zero-Emission Vehicles (PZEVs)
Vehicles for which the manufacturer has requested certification to the requirements in 13 CCR 1962(c)
(i.e., vehicles for which PZEV credit allowances are requested) shall have defects and performance warranty coverage for 15 years
(10 years for batteries for traction of hybrid electric PZEVs) or 150,000 miles, whichever occurs first.""

This document says:
""In 2003, the Air Resources Board (ARB or Board) amended several portions of the California ZEV regulation. One of these modifications was to simplify the assignment of credits to ZEVs. Section 1962(d)(5)(A), “ZEV Tiers for Credit Calculations,” identifies the criteria for a 2003 and subsequent model-year ZEV to qualify for the “Type III ZEV” tier:
• Urban Dynamometer Driving Schedule (UDDS) ZEV Range: >= 100 miles
• Fast Refueling Capability: “Must be capable of replacing 95 percent maximum rated energy capacity in <= 10 minutes”
...Type II and Type III is crucial to manufacturers who wish to take advantage of the additional incentives ARB is providing for Type III ZEVs in model years 2003 through 2012.
Type III ZEVs serve as the key to many vehicle manufacturer’s expected plans to pursue the ZEV Regulation Section 1962 (b)(2)(B) Alternative Requirement for Large Volume Manufacturers.
...Additionally, in the case of Type III Battery Electric Vehicles (BEV), ARB would not expect a manufacturer to restrict warranty coverage for customers that fast charge using manufacturer approved equipment. ""

(note the regulations seems mostly geared towards fuel cell refueling, but there is some acknowledgment that BEVs can meet the requirements as well)