Undercoating

Drive it a little first and decide for yourself. (For me it's not needed.) Otherwise you may go to the trouble, and risk plugging up the various weep and drain holes, for no sonic benefit.

From what I've been reading, the Prius has a full underpan to protect the high voltage system, which runs from the high voltage battery to the engine compartment. That underpan may quiet things down enough that you won't need to spray tar under the car. Also, with the underpan, it may be impossible to get the tar where you want it.

My Prius isn't here yet, and I've not seen the demonstrator on a lift, so I can't say anything about the physical extent of the underpan.

Paul

P.S. (And off topic) Has anyone gotten a look at how the high voltage battery cable is insulated? If and when that insulation fails, that battery could certainly deliver lethal energy to anyone unfortunate to grab hold of it. It could also start one heck of a fire very quickly.

Crash any vehicle hard enough and it might explode. The 12V car batteries store enough power to burn the insulation from a shorted, unprotected wire. I once reached under the dash of a car and shorted it's 12V battery to ground through my watch band. Burned a link out of the band. I still have the scar from that stupid move.

What you say about the danger of 12 volt batteries is certainly true, as any technician who has gotten a metal object accross a hefty 5 volt power supply can attest. A gentleman who came to work on a new computer installation for us in 1978 had gotten his wedding ring accross a 5 volt 200 amp power supply at another customer site. Luckily, he had been in a position to trip the power switch off with his foot. He had a very nice burn on his ring finger. After that, he always removed all of his rings and watch before opening the cabinet door.

However, while a 12 volt car battery at, perhaps 200 amps will deliver quite a charge, the battery in the Prius will deliver over 200 volts at over 200 amps. This is more equivalent to removing the cover from the circuit breaker box in your basement and grabbing hold of the main lines coming in from the power pole, with the exception that it is DC instead of AC.

Hopefully, the hot lead from the battery has more than a car lifetime's worth of insulation or it is required to be replaced at specified intervals. I've also been hoping that everyone who buys a Prius is smart enough not to pry into the high voltage battery compartment, trying to recharge the battery with a handy JC Whitney 12v battery charger. The results there could only be described as electrifying.

Paul

I no longer wear my wedding ring (with the concurrence of my wife) because of a series of accidents that started with getting it between a wrench and the hot terminal of the battery and ended with it lacerating my finger all the way around both edges of the ring.

But I don't think you have anything to fear from the Prius HV wiring. IIRC, they are coaxial arrangements with ground on the "shield" but none of the HV system grounded.

When I was 14 I got across a 300 volt DC power supply with excellent contact at the palm of each hand (helping a friend work on a console tube-type radio). It was a memorable experience, but I lived to tell the story. I even survived a momentary contact from the fingertips on one hand to the fingertips on the other with an 800 volt transmitter power supply. It just hurt and burned pits in my fingertips. Still, keep the fingers away. The electrical gods hate to be toyed with.

Mike

The DC high voltage is fused right at the battery, so any shorts would disconnect it immediately. In less than a second. The voltage is only DC, so even if you did manage to get into that part of the car without blowing the fuse and touched the ground an hot at the same time, you'd simply get a shock that would cause you to recoil. No heart stopping trauma, no fatal injuries, just a burn mark on one hand.

Daniel

Good warning. The real fact is, the Prius has 278 volts available, with a

150 Amp fuse guarding the system. If you figure they put in 15-20 amps overhead, that's approx 130 amps. That's approx 37,000 watts, or a coversion to about 55 HP.

There are VERY specific procedures to dealing with these cars. You cannot stress enough, DON'T MESS WITH IT! Especially the Orange wire. Trying to disconnectr the High Voltage supply that will cause an arc, ruining the car and possibly killing the person doing the 'work'.

The tech at the dealership I work with dresses up like he's going to work on the Power Transmission lines. Always the gloves, 3 pairs of 'em, and sometimes a heavy rubber apron.

And if you need to charge the 12V ICE battery, you're OK. DO NOT try to charge anyhthing else in the car. There is a special charger used to charge the rechargables and needs to be connected properly.

In fact, the HV system is isolated from ground, so a shock will occur only when there is a short and you contact the other side of the battery at the same time.

Mike

This is a good thing. It reduces the chance of getting a nasty schok. It also prevents a simple fault from applying the 500 volt battery accross the

12 volt battery. That much energy into the 12 volt would probably boil off the 12 volt battery in no time. (In addition to destroying the 12 volt electrical system components.)