Questions for the hybrid battery expert
A big part of the "magic" that makes hybrid vehicles work involves high-voltage battery technology. So, it's natural that many of the questions Toyota and its dealers receive are about hybrid batteries. Hybrid Synergy View put questions about batteries to Gary E. Smith, national service technology manager at Toyota Motor Sales, U.S.A., Inc.
Q: What do hybrid batteries look like, and how do they work?

Gary Smith: Toyota's high-voltage hybrid batteries are collections of prismatic modules in strong protective cases bolted under or behind the rear seats. In a current-generation Prius, the battery case contains 168 1.2V batteries in groups or modules of six that are slightly different in shape but not much larger than the batteries in an 18-volt cordless electric drill. The entire pack, which includes some relays, solenoids and the metal case, measures about 14 by 36 inches, and is eight inches high. You might picture a suitcase weighing 110 pounds. Because the storage space is different in a Highlander hybrid, its batteries are in three smaller cases. So, picture three attaché cases with a total weight about the same as the case in the Prius.

These nickel-metal hydride batteries are charged by an internal combustion engine (ICE) driven generator and/or by regenerative braking that captures power from deceleration and braking.

Q: Do they ever run out of power?

GS: No. A computer makes sure the batteries never discharge completely. They never fill completely, either.

Q: Are they charged at the factory?

GS: Yes, they need to have enough of a charge to start the engine the first time. After that, the batteries are charged by the vehicle's systems. Every Toyota hybrid also has a battery similar to the one in a conventionally powered car, but it's used only for 12-volt accessories and to power the vehicle's computers.

Q: Do the high-voltage batteries ever need to be checked or serviced by the owner or by a dealer?

GS: No, there is no scheduled maintenance for the batteries.

Q: How long do the high-voltage batteries last?

GS: We designed them to last for the life of the vehicle. We're aware of owners who have racked up a quarter-million miles without replacing the batteries.

Q: What would it cost to replace a complete battery pack?

GS: Less than $3000, plus labor.

Q: How long is the warranty?

GS: The high-voltage batteries are warranted for eight years or 100,000 miles, and under California regulations the battery warranty extends to 10 years or 150,000 miles.

Q: How about the battery in a hybrid Toyota Certified Used Vehicle? Does the certification extend the warranty?

GS: No, the warranty remains at 100,000 or 150,000 miles from first use.

Q: Does Toyota offer any kind of extended warranty that covers hybrid batteries?

GS: No.

Q: How long will a Prius or Highlander keep moving on battery power if it's out of gas?

GS: Only for a short distance -- a mile or so. The battery isn't designed for primary traction power, other than driving in reverse; it's there to capture energy that would be lost in deceleration or braking, and to optimize the power of the gasoline engine, all of which extends the vehicle's fuel mileage and limits emissions.

Q: Is there any danger of electrical shocks?

GS: The battery packs are enclosed securely in metal cases, and their bright orange cables are well insulated, shielded and isolated. The on-board computers perform hundreds of checks prior to high voltage being released outside of the battery case. These checks are repeated several times each second to assure total system integrity. If an anomaly is detected, high voltage is switched off and contained inside the metal battery case. In the event of a collision, the rapid-deceleration monitors or an airbag deployment will cut off the high voltage. This protects occupants and rescue workers from electrical shock.

We continue to work closely with emergency services experts from a variety of communities, and because there are so many system safeguards, we have yet to learn of or imagine a scenario in which a first responder would be endangered by a Toyota hybrid power system.

Q: Is there any risk of electrical shock in heavy rain, or when driving in a flooded street?

GS: No.

Q: Is there any danger from electromagnetic interference or injury resulting from EMI?

GS: No. Toyota hybrids are certified to be at or below World Health Organization standards for non-ionizing radiation, either inside the vehicles or near them.

Q: Are hybrid batteries recyclable?

GS: Absolutely. In fact, Toyota pays a bounty to dealers who recover them from damaged vehicles. Additionally, our engineers are studying the possibility of remanufacturing these batteries.

Q: Is this the kind of battery that would be used if a plug-in hybrid system is developed?

GS: A system like that might use nickel-metal hydride or lithium ion batteries. Plug-in systems need significantly more capacity than currently exists in the batteries in our hybrids. Toyota is exploring the possibilities for plug-in hybrids, but has made no determination about them.

Q: What about the third-party suppliers who are converting Prius and some other hybrids to plug-in use?

GS: Toyota's current hybrids are not designed for larger traction batteries, and the company discourages these modifications, which void the vehicle's warranty. The conversions that I'm aware of are very costly, add significant weight to the vehicle, and have not gone through the rigors of full engineering evaluation such as brake balance, crash testing and durability.