Hybrids are hot. As the price of gasoline goes up, so does the demand for new vehicles that can squeeze more miles per gallon from every drop of gasoline. Hybrids do that by combining the best of both worlds: electric power for low-speed, stop-and-go driving, and gasoline power for highway cruising and long-range driving.

Current models include the Toyota Prius, plus hybrid versions of the Toyota Highlander and Camry, Lexus RX 400H and GS 450H, Honda Insight, Civic and Accord, and Nissan Altima. Other new import hybrid models that are coming soon include a hybrid version of the Honda Fit, Kia Rio and a yet-to-be named Hyundai model in 2009. The European automakers have lagged behind their Asian counterparts in hybrid development, but Volkswagen says it will offer a hybrid Jetta in 2009.

Volvo is developing a diesel-hybrid version of its C30 compact model, and BMW will reportedly have a hybrid version of its 7-Series soon. Hybrid fever among the domestic automakers is also gathering momentum, with hybrid versions of the Ford Escape, Mercury Mariner, Saturn Aura and Saturn Vue Green Line, and soon-to-come full-size hybrid SUVs from GMC and Chevrolet. Chrysler is also working with BMW on a common hybrid drivetrain that will be used in a number of future models.

Though the number of hybrid vehicles currently on the road is still quite small, some industry analysts predict that within five years 20 to 25% of all new car and light truck sales will have hybrid powertrains. So the sooner you get up to speed on this new technology, the better able you will be to service today’s, and tomorrow’s, hybrids.

SAFETY FIRST
The one feature that distinguishes all hybrid vehicles from their conventional counterparts is a high-voltage battery, which is usually mounted in the rear of the vehicle. The voltage output of a hybrid battery depends on the vehicle: Honda Insight, 144 volts; first-generation Toyota Prius, 276 volts; second-generation Prius (2004 and later), 201 volts; and more than 300 volts on some of the domestic hybrids!

This kind of voltage can be deadly and must be treated with respect. If you think a shock from a spark plug wire is bad, a shock from one of these batteries can literally kill you in a split-second!

The hybrid batteries that are used in current generation vehicles are nickel metal hydride (NiMH) and consist of many individual cells wired together in a series. To protect the vehicle’s occupants and service technicians from the high-voltage hazard, the hybrid power circuit is heavily insulated and is usually color-coded orange. So if you see a heavy orange cable snaking under a vehicle or in the engine compartment, it’s carrying the hybrid’s high-voltage current. The circuit may or may not be hot even when the engine is off, so treat all orange cabling with caution.

Hybrids still have an ordinary 12-volt battery for powering the ignition system, fuel pump, lights and other electrical accessories on the vehicle. No special precautions or service procedures are required for the conventional part of the electrical system. But before you work on any high-voltage electrical components or hybrid drivetrain components, the high-voltage hybrid battery must be disconnected so it can’t zap you.

The disconnect procedures vary somewhat depending on the vehicle, and may involve flipping a switch on the battery pack or disconnecting a cable or fuse. Always refer to the vehicle manufacturers’ recommended disconnect procedure, and wear protective rubber gloves that are rated to withstand up to 1,000 volts for added protection. Also, wait 10 minutes or longer after disconnecting the battery to start working on the vehicle. High-voltage capacitors in the hybrid controls store power and take a few minutes to discharge.

On the first-generation Prius, the hybrid battery is disconnected by opening the trunk, removing the liner from the left front corner, and pulling straight back on a small orange handle to remove the plug. The plug should be removed from the car until it’s time to reconnect the battery.

On a 2004 and later Prius, Toyota says to first disconnect the negative cable on the conventional 12-volt battery (which is also located in the trunk). Remove the trunk floor panel and cover, disconnect the 12-volt battery, then locate the service plug on the left side and pull the handle down and out to remove the plug (wear insulated gloves when doing this!). If you have to remove or replace the fuse, it’s located right under the service plug and is held in place by two bolts. Again, wear insulated gloves. When the service plug is replaced, make sure the handle is returned to the upright position to lock the plug in place, otherwise a loose plug may set battery codes.

On a Honda Civic hybrid, the battery is disconnected by removing the rear seat back cushion, removing two screws from a small cover with the word “UP” on the cover, then flipping the power switch off.

Actually, hybrid vehicles are not as dangerous to work on as they might seem at first. If the key is off and the key is out of the vehicle, the hybrid system is powered down. The battery can’t shock you unless you go poking around the high-voltage battery connections with bare hands or uninsulated tools. Even so, there are some hidden dangers with these vehicles.

If you pull a Toyota Prius into your shop and forget to push the “Power” button to turn off the car or remove the key, the hybrid powertrain will still be hot even though the engine may not be running. At stop, the vehicle reverts to an electric-only mode of operation, shuts off the gasoline engine and makes no noise. Meanwhile, the engine control module continues to monitor the voltage of the hybrid battery, and may automatically restart the engine if the hybrid battery voltage is low and the engine needs to run to recharge it. That could mean a nasty surprise for you if you happen to be working under the hood, changing the oil or doing anything else that puts you in close proximity to belts, pulleys or high-voltage components.

Most hybrids have some kind of “Ready” indicator light on the dash to let the driver know when the hybrid system is on. So always make sure the Ready light is out, the ignition is off and the key is out of the vehicle before you start any service or repair work. Removing the key from the vehicle is especially important if the vehicle has a keyless entry system and recognizes the key fob anytime it’s in close proximity to the car. Keep the keyless fob at least 20 feet away to prevent any accidental starts.

MORE ABOUT THE BATTERY
Most hybrids are designed to isolate the high-voltage battery if the vehicle is involved in an accident that’s serious enough to deploy the air bags. If you’re working on a collision-damaged vehicle with blown airbags, you might assume there is no danger. There probably isn’t, but the battery itself will still be hot and should always be treated with caution. That means no direct contact with terminals or cables without wearing heavily insulated gloves.

The high-voltage battery and wiring circuits on hybrids are separate from the other electrical circuits in the vehicle, and don’t use the body or chassis as a ground. The Prius also has a ground fault sensor that will disconnect the hybrid battery and turn on a warning light (an exclamation mark inside a triangle) if it detects any high-voltage leakage to the body. A DTC P3009 fault code would indicate such a problem on the Prius.

On the Prius, the battery has its own separate electronic control unit (ECU) that monitors battery voltage and temperature. The ECU is buried under the floor behind the back seat on the left side. Getting to it requires removing the seat, trim panels and a floor cover.

BATTERY LIFE
How long will hybrid batteries last? A long time, according to the vehicle manufacturers who make them. The design life is up to 12 years or 150,000 miles, and Toyota says that it has yet to replace a Prius battery pack under warranty. Good thing, because the pack costs nearly $2,500 and is available only from Toyota.

Hybrid batteries generate a lot of heat and require extra cooling. Most hybrids have some type of special venting for the battery pack, which may even include a separate cabin air filter. On the Prius, there is a cooling fan for the battery inside the right rear trim panel, and two battery temperature sensors in the hybrid battery compartment.

In theory, a hybrid battery should never run down. The control module should run the engine to maintain battery charge any time the battery drops below a certain voltage. But if a vehicle is not driven very often or has a problem that drains the battery or prevents the engine from running to recharge the battery, the hybrid battery could go dead. If this happens, a special jump-start procedure or charging procedure may be required to get the vehicle moving.

On a Prius, there is a special jumper connection under the power distribution center cover in the engine compartment. A 12-volt battery charger can be used to boost the regular 12-volt battery enough to start the engine (Toyota recommends using its special 12-volt charger instead of a conventional 12-volt battery charger). Once the engine is running, it should be left running for at least 30 minutes to recharge the hybrid battery. Note: Do not attempt to recharge the high-voltage hybrid battery directly, as doing so may damage the battery, the charger or you!

A DTC P3000 or P3056 on a Prius means the hybrid battery is reading low or no voltage. Toyota technical service bulletin EG023-04 covers a procedure for diagnosing and repairing the vehicle when these codes are caused by a problem with the B11 wiring connector in the back of the car.

CONVENTIONAL SERVICE
Though hybrids include some exotic engine control technology and a high-voltage battery and electric drive, they still have conventional gasoline engines that require scheduled maintenance and may need various repairs. The same thing applies to the cooling system, brakes, steering, suspension and exhaust system. The parts in these systems will wear out over time, just the same as the parts in a conventional vehicle, so don’t overlook these other service and repair opportunities on hybrids just because the powertrain seems a bit unfamiliar or unique.

The front brakes on most hybrids typically last much longer than those on other vehicles thanks to regenerative braking. When the vehicle is braking, the drivetrain takes advantage of the vehicle’s momentum to drive the generator and put power back into the battery. This replenishes the battery charge without having to run the engine. Consequently, the brakes do not have to work as hard and may last up to twice the mileage of a conventional car. Even so, the brakes will eventually wear out and have to be replaced. Same for the rotors, the calipers and the rear brakes.

Oil changes may not be needed as often with a hybrid because the engine runs less during low-speed, stop-and-go driving. But the oil still needs to be changed (refer to the vehicle manufacturers’ oil change interval recommendations).

The cooling systems on some hybrids have some extra parts, such as an auxiliary pump to keep coolant circulating to the heater. The power inverter under the hood may also have its own coolant supply and a 12-volt pump to circulate coolant. Otherwise, service and operation of the engine cooling system is the same as any other vehicle.

The air conditioning systems on hybrids may also be different. Honda and Toyota both use an electric-driven compressor for cooling when the engine is not running. The Prius is all-electric, while the Honda hybrid models’ systems are both belt-driven and electric (for cooling when the engine is off). A special non-conductive refrigerant oil is required in these vehicles. Also, the 12-volt battery and hybrid battery should be disconnected before replacing one of these compressors.

The transmissions on hybrids tend to be rather exotic, with the Prius using a planetary system with two electric motors. The Altima has a continuously variable transmission. Next month, we’ll look at some common problems with hybrids and the diagnostic procedures that may be required to fix them, so stay tuned…

Honda Promises Hydrogen Sedan in 2008 Honda says it will sell a unique mass-market hybrid in the U.S. within two years, and it will be priced less than the $25,000 Civic hybrid. The new hybrid would complement, not replace, the Civic hybrid. The Civic hybrid has lagged behind the sales of Toyota’s Prius hybrid partly because it doesn’t look different than the gasoline-powered Civic. Honda also announced it will put a sleek hydrogen fuel-cell sedan (FCX) into limited production next year. Honda expects the sedan will get the gasoline equivalent of 68 mpg in the federal city-highway combined driving cycle. Because fuel-cell cars are much more efficient, the cost per mile is much less than vehicles using gasoline. Honda claims that the fuel-cell cars will have a top speed of 100 mph. Honda did not say how many 2008 FCXs it will offer. Just two current-generation FCXs are being used by individuals, who lease them for $500 a month. Fuel-cell vehicles are electric-powered. The electricity is generated by a fuel-cell stack in the car. The stack mixes hydrogen and oxygen in a process that produces electricity and emits water. Nearly all hydrogen is made from natural gas, abundant in North America.