2 questions about the Prius

<div class='quotetop'>QUOTE(YodaddyAlex @ Dec 20 2006, 12:27 PM) [snapback]364609[/snapback]</div>

Clarification: the slot does NOT recharge the battery in the fob. Inserting the fob into the slot is only a fallback procedure if the battery inside the fob dies. Otherwise, inserting the fob into the slot is harmless but pointless.

 

<div class='quotetop'>QUOTE(YodaddyAlex @ Dec 20 2006, 09:27 AM) [snapback]364609[/snapback]</div>

Just be sure to take the key with you when you leave! If you keep the key in the car, not only will you not be able to lock the car but after a few days you may find a dead battery, since the car keeps scanning the key fob.

I don't think I've ever taken the key fob out of my pocket when driving.

 

<div class='quotetop'>QUOTE(YodaddyAlex @ Dec 20 2006, 11:27 AM) [snapback]364609[/snapback]</div>

Whats wrong with me? I have 17,000 miles on mine and have no clue as to what this is in reference to?

 

Since this is the technical discussion forum, I'll share some technical questions raised by this discussion.

I understand that most RFID (radio frequency ID) tags have no battery. I'm confident that the buttons on a key fob won't work if it's battery is dead, but can anyone confirm whether or not it will work as a smart key without a good battery. Do the key fobs that don't support the smart key system (SKS) have any electrodes or metal terminals that can make contact with the car when you place the key in the slot in the dashboard? Since the key fobs with SKS have no metal contact points to contact the inside of the dashboard slot, how does placing the SKS key fob in the slot help the car read the key, or does it?

<div class='quotetop'>QUOTE(grasshopper @ Dec 20 2006, 02:28 PM) [snapback]364728[/snapback]</div>

The message referred to is from the navigation system, which you and I don't have.

 

<div class='quotetop'>QUOTE(theorist @ Dec 20 2006, 05:50 PM) [snapback]364826[/snapback]</div>

Oh! Thank you.

 

<div class='quotetop'>QUOTE(theorist @ Dec 20 2006, 04:50 PM) [snapback]364826[/snapback]</div>

While I don't know for certain the engineering design in use, I can add to the technical discussion in regards to RFID.

Ideally RFID is without battery, being powered by the radio signal itself. Realisticly however this isn't always true because the range would be near useless. To that end, some RFIDs have batteries. My best guess is that the range of the Prius key fob is enhanced by using the battery in the fob, but that the car's sensors are in the key fob slot itself so that even if the battery is totally dead the range between the slot and the key fob is so short that it can still register while battery-less (and thus without amplification) if it's inserted into the slot.

 

There are different types of RFID systems. The active type uses a battery as power source. The passive type does not. Power is draw from the RF signal itself. The near field (inductive) type also does not use battery (I assume that's what you are referring to, Silver Phoenix), but needs to be at very close range. The higher frequency (UHF) passive type can be used at longer range, have seen specs up to 20 ft range.

Anybody know what type of RFID is used on the Prius?

 

I read somewhere that the fob is NOT charged or powered by the car, as is true with BMW's and others. So it'll work for longer periods if not inserted in the slot, but won't recharge if the battery is dead. Does that help at all?

 

I put the remote fob in the slot at the car wash, so the attendant doesn't have to look for it. I've only valet parked it once, and it's good for that too. Otherwise, its in my pocket or briefcase.

 

Since my 2004 Prius, the only times I have inserted the fob in its slot is when I am having the Prius serviced at my Dealer or Independent Shop. Haven't had any service needs yet on my 2007 TE Prius.

It is an "URBAN LEGEND" that placing the fob in its slot recharges the fob battery. The fob battery is a 2032 button battery easily available at drug and grovery stores. Instructions are provicded in your Owner's Manual for replacing the fob battery.

 

When the fob is in the slot, it uses the same short range passive RFID that immobilizers in other cars use, where there is a chip in the key. Only difference is our 'key' is a rectangular box.
This kind of RFID powers the coded chip by a pulse from the reader, which provides the chip with enough energy to send a response.

For SKS and remote lock, a more powerful radio signal is needed, and that requires the use of a battery. The SKS actually borrows from the remote lock function except instead of you pressing the buttons on the fob, oscillators in the car 'press' the buttons for you.