Have a failed traction (HV) battery? Assuming the failure was diagnosed correctly, below are several courses of action.
The warranty on the HV battery in the US for 1st gens (NHW11 aka 01-03 models) is 8 year/100K miles. On 2nd (NHW20 aka 04-09 models) and 3rd gens (ZVW30 aka 2010+) liftbacks, it's still 8 years/100K in most states but is 10 years/150K miles in California and other CARB states. More CARB emissions states were added over the years.
Examples of CARB emission states (this may not be a complete list) include: California, Oregon, Connecticut, Maine, Massachusetts, New Jersey, New York, Rhode Island or Vermont. Consult your warranty information booklet for correct information on applicability.
The warranties for other members of the Prius family (e.g. c, v wagon and Plug-in) may vary. For example, the Prius c appears to only have the 8 year/100K mile HV battery warranty, regardless of state.
Some of the actions/suggestions below only apply to the 1st gen Prius (NHW11), 2nd gen Prius (NHW20), 3rd gen Prius liftback (ZVW30) and Prius v wagon. The Plug-in Prius (PiP) and Prius c have totally different packs.
- Replace with a new battery - free if under warranty, expensive if not. Toyota lists some prices at http://pressroom.toyota.com/article_display.cfm?article_id=2727. If one isn't too far out of warranty, it wouldn't hurt to see if Toyota is willing to pay for part of the replacement cost. http://priuschat.com/forums/toyota-hybrids/107113-high-voltage-battery-3500-a.html#post1525770 has some useful information on labor charges and dealers possibly calling for a new battery ECU, which may be unnecessary.
- Replace with a remanufactured/rebuilt battery such as from http://www.re-involt.com/ or http://www.lusciousgarage.com/blog/comments/rebuilt_hv_battery_packs_toyota_prius_hybrid_et_al/.
- Use an indepedent garage that will either install a rebuilt battery or rebuild yours such as Mellor's in Florida.
- Replace with one from a wrecked Prius - cheaper and supposedly available for ~$500. Ones from wrecked Gen 1s (NHW11) are likely harder to find since it sold in much smaller numbers than Gen 2 (NHW20). Possible sources for HV batteries from wrecked Priuses or rebuilt ones at http://priuschat.com/forums/gen-ii-prius-care-maintenance-troubleshooting/101598-hv-ecu-vs-hybrid-battery-bad.html#post1440854, http://autobeyours.com/PriusParts.htm.
- Rebuild it yourself - Can be VERY time consuming and potentially dangerous if one isn't experienced in dealing w/high voltages, which are can be lethal. Before embarking on such a task or any of these options, these are worth reading: http://priuschat.com/forums/gen-ii-prius-technical-discussion/97806-there-guide-how-rebuild-battery-pack-how-many-cells-does-need.html, http://priuschat.com/forums/generation-1-prius-discussion/84114-prius-battery-rebuild.html and http://priuschat.com/threads/introduction-to-traction-battery-rebuilding-refurbishment.112868/. http://priuschat.com/forums/gen-ii-prius-care-maintenance-troubleshooting/104535-replaced-1-bad-cell-9-a.html#post1486339 has a cautionary tale of a poorly done repair. If you have no experience in working on/inside equipment w/live voltages of >200 volts, it's highly discouraged to go this route.
http://priuschat.com/threads/hybrid-battery-replacement-options.111494/ is an excellent post with lots of background information and various courses of action.
Problem: Traction battery failure
Symptoms: MFD traction battery or hybrid vehicle warning icon will appear. Engine will run more than normal.
Frequency: Will be a solid failure, not likely to be intermittent
Diagnostic: DTC P0A7F (which shows excessive internal battery resistance) and P0A80 (uneven battery module voltages) are likely DTC codes. P3011 through P3024 may also appear to show which battery block has failed.
Cure: Replace traction battery; consider purchase and installation of a salvage battery if cost of new battery is prohibitive
Other information/Alternate diagnosis possible: Need to ensure that the battery ECU or the inverter are not causing the problem.