Remote keyless entry and the cost of batteries

[artificialist]

My car takes a CR2016, and I only need to replace them every 2 years. I don't remember what I paid, I just go to CVS and get a duracell or energizer, most of which come from Japan. I have had a few from Indonesia, I don't know the difference.

Sometimes I think that with CR 2016, CR 2032, and similar batteries are made by some other company, and energizer or duracell is written on them.

 

[y_p_w]

Originally Posted By: artificialist
My car takes a CR2016, and I only need to replace them every 2 years. I don't remember what I paid, I just go to CVS and get a duracell or energizer, most of which come from Japan. I have had a few from Indonesia, I don't know the difference.

Sometimes I think that with CR 2016, CR 2032, and similar batteries are made by some other company, and energizer or duracell is written on them.

I was at a store with an extensive selection of lithium button cells. They had Rayovac, Duracell, and Energizer. The Energizer coin cells are now labeled as made in China. I think for the last few years they were probably sourced from Sony from their Indonesia factory, until this recent switch.

Last time I remember looking at the price of a lithium battery at CVS, it was something like $5 or a two-pack for $7.

 

[Vikas]

why every two years? they should usually last over years easy; in the 15 yr ownership of three different remotes, I had to change the battery only once so far in each remote

 

[Trav]

Originally Posted By: y_p_w


Why use these? I know it's 12V, but I've gotten pretty good life out of 1 or 2 lithium button cell remotes. Frankly - this Civic remote has lousy range. The (Alpine) remote from my 2004 WRX uses a single CR2032 and I've been able to see it work from 500 feet away in a parking lot when I was in a high-rise building. The Civic is lucky if I can get it to work 25 feet away with nothing in between.


Some remotes are range neutered to prevent code grabbers intercepting the transmitter code.
With a 500 ft range if any such criminals was actively scanning he would have yours quickly.

http://dev.emcelettronica.com/hacking-car-security-system-and-remote-keyless-entry-rke

 

[y_p_w]

Originally Posted By: Trav
Originally Posted By: y_p_w


Why use these? I know it's 12V, but I've gotten pretty good life out of 1 or 2 lithium button cell remotes. Frankly - this Civic remote has lousy range. The (Alpine) remote from my 2004 WRX uses a single CR2032 and I've been able to see it work from 500 feet away in a parking lot when I was in a high-rise building. The Civic is lucky if I can get it to work 25 feet away with nothing in between.


Some remotes are range neutered to prevent code grabbers intercepting the transmitter code.
With a 500 ft range if any such criminals was actively scanning he would have yours quickly.

http://dev.emcelettronica.com/hacking-car-security-system-and-remote-keyless-entry-rke

Likely a rolling code these days.

 

[rjundi]

Amazon is dicey as some of those cheap batteries are dated. Many I think folks import them from abroad and sell thru Amazon. You can tell in packaging. Hopefully a brand abroad means the same thing here.

 

[y_p_w]

Originally Posted By: rjundi
Amazon is dicey as some of those cheap batteries are dated. Many I think folks import them from abroad and sell thru Amazon. You can tell in packaging. Hopefully a brand abroad means the same thing here.

The Amazon seller I use is MYBATTERYSUPPLIER. Every battery I've ever got from them is from the same packaging for US sales. They're not individual blister packs though. They're more the five to a pack tear cards like you'd find at watch repair places. The Maxell tear cards say Maxell of America.

I've gotten about the same price at a reputable jewelry/watch repair supply wholesaler. The place I'm thinking of is Otto Frei in Oakland, CA. It was frankly ridiculous how cheap they sell batteries. At Target it might be $3 for a single watch battery. There it's $3 for 10 from the most reputable brand on the market. They have Maxell lithium batteries. These are common in some watches - especially digital ones or Casios that advertise a10-year battery life. It was maybe $1 for a single, but discounted if I would get a tear card of at least 5.

 

[Mr_Incredible]

I buy small batteries where ever I am when I remember that I need to get them, or, where ever that special little bugger can be found in the area.

 

[y_p_w]

Originally Posted By: NateDN10
I recently paid $5 for a CR1620 replacement battery for our Mazda. Ridiculous.

I borrowed my folks' Nissan and I figured I'd replace the battery in my dad's key w/ remote since my parents never get around to this sort of thing as preventative maintenance. They never even replaced the windshield wipers on this thing after 6 years at which point they rotted away.

Popped it open and looks like it's still functioning on the original Panasonic CR1620 battery. Date code was 75, which I believe means it was made in May 2007. I just happened to have a Sony CR1620 (Made in Japan) where the package says use by 2016. It was originally bought for a Casio watch that I don't particularly use any more (and frankly can't find). When I removed it from the blister pack, the date code was 6Y, which means Dec 2006. I figure it hasn't been used so should be better than the current one.

Popped it in and nothing. I can't find my multimeter to measure voltage, but I'm guessing it didn't live up to the "Use By" date. I just put the old battery back in after wiping it off and I'll have to look for a new battery. I'm kind of skeptical of a 10-year shelf life, especially when the manufacturer can't control storage conditions.

 

[Apollo14]

Keyless entry fobs are always on, so last approx 2 years although sometimes much longer.

 

[Vikas]

Originally Posted By: Apollo14
Keyless entry fobs are always on, so last approx 2 years although sometimes much longer.
Really? I thought they used RFID detector inside the car.

If the keyless entry fob is always on, there is no way it will last for 2 years! It will be dead in days if not in weeks.

 

[Apollo14]

Originally Posted By: Vikas
Originally Posted By: Apollo14
Keyless entry fobs are always on, so last approx 2 years although sometimes much longer.
Really? I thought they used RFID detector inside the car.

If the keyless entry fob is always on, there is no way it will last for 2 years! It will be dead in days if not in weeks.


I guess I should have used the term "Smart Key" as I was talking about those fobs where proximity is enough to recognize it for opening and starting the car.

Google "Smart Key Battery Life" and you'll see lots of results talking about 1-2 year life.

From: http://en.wikipedia.org/wiki/Smart_key

Quote:
The key is identified via one of several antennas in the car's bodywork and a radio pulse generator in the key housing

Backup in case of low battery

If the battery in the Smart key becomes depleted, it is necessary for there to be a backup method of opening and starting the vehicle. Opening is achieved by an emergency (fully mechanical) key blade usually hidden in the Smart key. On some cars starting is achieved by a transponder inside the Smart key that does not need batteries to work. The user either has to put the key in a slot or hold it near a special area on the cockpit, where there is another LF antenna (transponder coil) hidden behind to compensate for a weakened fob battery.

 

[y_p_w]

Originally Posted By: Vikas
Originally Posted By: Apollo14
Keyless entry fobs are always on, so last approx 2 years although sometimes much longer.
Really? I thought they used RFID detector inside the car.

If the keyless entry fob is always on, there is no way it will last for 2 years! It will be dead in days if not in weeks.

I think the reference is to the kind with a remote built-in, such as for a Nissan. My dad's key looks like this one:

The key itself is solid metal with no apparently place for an RFID tag. It can be easily pulled out of the remote portion by removing a screw and just yanking it out. Now I suppose there could be some sort of RFID placed in the remote portion. Could even be on the main board.

I don't know for sure if there's any separate RFID like with a Honda key. I suppose I could find out by having it duplicated to an ordinary metal key. I have rented cars that used similar keys with a "switchblade" button release.

I wouldn't imagine that it's always on. I've work in the electronics industry including on battery powered devices. There are certain standby modes that barely use any power, but I don't know why that would be necessarily with a keyless remote entry system. I would think it would only have to power up when a button is pressed. Of course the receiver in the car would need to be on.

I've had all sorts of remotes last a long, long time on an old battery. Often I just figure I might as well replace it so I don't have to in the future. Maybe I'm just bored. My big worry is about leakage, which supposedly can be worse the greater the discharge a battery has.

 

[Apollo14]

^ no, the reference was to "Smart Keys". Sorry for the confusion.

 

[y_p_w]

Originally Posted By: Apollo14
^ no, the reference was to "Smart Keys". Sorry for the confusion.

Oh - the kind without a mechanical key at all (except as a backup)?

I don't know if they're necessarily "always on". There are various methods of going to sleep. I remember some of the systems I worked on could conceivably operate on the same battery for years if nothing happened to wake up the system. A well designed system can go into a deep sleep mode with a rudimentary section that's powered up to detect when it should turn on.

 

[Apollo14]

What's the trigger to turn it on? What is there to wake up?

It needs to transmit continuously so that if it is near to the car, the car will unlock if a handle is operated.

The distance is very short hence it is low powered and the battery lasts a few years. Any difference in battery life is due to temperature and battery quality.

I've had these systems for a while. My spare key died around the same time as my main key. Cheap batteries died in a few months.

 

[y_p_w]

Originally Posted By: Apollo14
What's the trigger to turn it on? What is there to wake up?

It needs to transmit continuously so that if it is near to the car, the car will unlock if a handle is operated.

The distance is very short hence it is low powered and the battery lasts a few years. Any difference in battery life is due to temperature and battery quality.

I've had these systems for a while. My spare key died around the same time as my main key. Cheap batteries died in a few months.

Could be anything. If I were to create a trigger, it would be a low-level RF pattern signal and a detection unit that then powered up the rest of the unit for authentication. Among small battery-powered electronics systems, the lowest standby current consumption is considered a huge selling point. Many devices using these lithium coin cells only operate fully powered up for short bursts. Other devices like digital watches or backup clocks (on motherboards or cameras) barely use any current at all because the circuits are so minimal.

A lot of the stuff I worked on basically did nothing useful in standby other than wait for the powerup trigger, which was usually someone touching a sensor or physically pressing a button. You could put sections in a standby state where the electronic state is "frozen" by turning off the clock, but there's still "leakage current". The biggest power savings came from literally cutting off the voltage to unused "power islands" and only keeping what was absolutely necessary to wake up. The time to wake up is actually an eternity in electronic time, but to a human it could imperceptible if it's starting up a vehicle.

I had a Sharp calculator (technically a handheld computer) that used two CR2032 batteries. First time I'd every heard of these things. They weren't cheap at the time. I remember paying $3 each battery in 1987 dollars. I was lucky if I could get a few months out of the batteries if I actually used it, and by that time the LCD display was getting dimmer. On a fresh set of batteries, the display was nice and dark. I don't think it was a huge power user, but they just used those batteries so it could be really thin. I remember doing tricks with it, such as getting it to do 67 factorial. It was just a brute force calculation, but it would take several seconds, the display would lighten, and I could hear an electronic whining sound coming from the CPU.

 

[Apollo14]

OK, so it is always on!

 

[y_p_w]

Originally Posted By: Apollo14
OK, so it is always on!


Ever saw The Princess Bride?

"Mostly dead"

Certainly with some of the stuff we had, you could just let it go into standby mode and not trigger it, and it could last for years and years on the same batteries just waiting for something to happen. It could be so low current that self-discharge of the battery would be a bigger issue. If you wanted to use a device to just to play around with it, it could probably drain the batteries in a few days of that use or even a few hours if you just kept on using it without stopping. A lot of electronics are designed for occasional short pulses, like car remotes or TV remotes.

 

[Vikas]

If there is a RFID transmitter/receiver/detector inside the car which is always on, then the Smart Key does not need to be powered up.

Power density of CR2032 is just not enough to last few years if continuous load (to transmit) is put on it.

We are all speculating here; so that is my take on it.