I discovered this while working on modifying my original fob to fit the one discovered by KC... https://www.jaguarforums.com/forum/x...t-fobs-209575/ ...I wanted to keep my Jag fob and was going to post the procedure until this....

The old fob has (2) CR2016 batteries we all have been using per factory specs, because that's what was available back then. Well, as I was working on the mod I got to looking at the battery thicknesses and found the one that came with the new fob (CR2032) to be of the same thickness as both the 2016's stacked and in diameter. So I said, what the heck, lets try it...I go out to the car and wha-la it works! As a matter of fact, it works way better than the (2) 2016's which were fairly new (about 3 months). When I say it works better, it works every prompt. I do not know if the stacked 2016's may not be putting out as much as the single 2032, but I was quite amazed at the response. Plus the fact that these run about the same cost each, you'll save a couple bucks.

So this didn't end there, I went and got my other old fob which literally responded sparsely even after (2) new 2016's. I put a 2032 in that and it worked every time. I have to say, I do not know what the future results may hold on this (longevity mainly), but if you were having intermittent to very nill responses (like most all of us), this may be a cure?

The experiment wasn't done, I decided to check the range...and again, if yours is like mine, you had to be within 15ft to make it work as you frantically prompted it 5-10 times. The process, two activation's of locking and unlocking with single prompting...so I went to the middle of my driveway, roughly 20 ft...worked ...end of my driveway, ...about 30ft... worked ....to the middle of my street... about 40 ft...worked ...to my neighbors driveway ...about 60 ft ...worked ...to the middle of my neighbors driveway ...about 80 ft...worked. I finally found the end there, though it did lock at about 85ft with 2 prompts, it didn't unlock until I got back to the 80ft mark.

I hope this may be a fix for what we have thought our fob's to be bad (still need to clean the contacts though), when they may simply have been under-powered? In any case, its a cheap thing to do to check your fob.

 

My main issue with the stock FOB was my cat only showed up with one and the best deal I could find was $85 for a used one on ebay. Knowing the original (with 2 fresh batteries) was still less than enthusiastically unlocking the car I followed the King's lead and picked up the two-fer deal on the "cheap" replacement FOB's I won't toss the original but maybe thanks to your research I'll have a third means of opening the car remotely. Jag's aren't the only cars ripe for improvement here as my 2001 beemer keys (with almost unreplaceable batteries, WTF?!) are starting to show their age again. Fortunately for that car I cut the alarm off at the b*lls when I was replacing the rear shocks so all it can do is flash its lights if I use the key the old fashioned way...and guess the wrong way to turn it to gain access to my own car. The jag still has all her stock vocal chords so twisting the key is a 50-50 proposition that I'll have to race to jam the key in the ignition before waking the neighbors!

 

Very interesting the fob works well with one 2032 because two stacked 2016-s are 6 volt and one 2032 is 3 volt. However, for some devices, the amps (milliamps actually) provided by the battery are more important than the volts and, since 2032 can supply more and more stable milliamps to the fob than the 2016, this may be the reason why the fob works better. I think I heard, some time ago, that someone had done the same thing (on another car's fob) with great results.

 

So I went to my inde' to discuss this with him and he comes right out with "...that's what we do whenever we change them..." surprised, I come back with "...well, why didn't you tell me this before.." and of course he being the smartass Irishman he is, he snickers back "...you didn't ask." ...and grins. I felt like I was in a slapstick routine...lol.

 

Okay, so about three weeks ago I cleaned my fob per instructions In another thread and replaced batteries, it worked much better. Then I read this at lunch and just for kicks stopped by Walmart and picked up at two pack of Energizer 2032 for less than five bucks and holy smoke !! You were right, this thing works great now, and I mean really really great. Its like I now have some kind of high performance hot rod racing fob in my pocket and I keep trying it over and over again, through glass, bushes, from far away, you name it. I'm having a blast with this thing and cannot thank you enough, best five bucks spent in a long time :-)

 

 

Here some specs of the two batteries for comparison....
As you can see, this wholly backs what MS is stating in post #3 regarding the MA (milliamp) output. Even as a pair, the 2016's cannot generate what the 2032 does.

 

A pair of 2016-s, since they are stacked (connected in series) will still have the capacity of just 75 mAh (it does not double) but at 6 volt. The 2032 has capacity of 210 mAh (at 3 volt) meaning that it will last almost three times longer than two 2016-s. Also, as the fob is basically a radio wave transmitter, it requires quite a bit of mA to generate a strong radio pulse when operated. The higher capacity 2032 provides the required mA with little voltage drop whereas the two 2016-s (even though they are at 6 vollt) will, due to rather low capacity, have a large voltage drop when loaded by the fob operation and this can mess-up its transmitting frequency

 

Range isn’t important to me, but first time function is. I love watching people with modern cars unlock them from far away only to find the car has locked itself again by the time they reach the door!

 

That is not what I was saying in regards to doubling, though I should have been more specific instead of general because I understood where you were going in #3. The voltage is not doubled, but the amps are increased, not necessarily doubled either. But the 2032 as a single unit puts out more amps because all the power is from one point than the two 2016's in series because of the transfer of power of one battery to another with lower amps, you gain in amperage, but also lose its full effect so it does not double. The 2016's will also lose power quicker because they are a lower amp and trying to provide more amps than they were designed for. So in aspect the 2032 should last longer since its a single source for the amps and is providing power for what it was designed for.

 

When two 2016 3V batteries are stacked, the total voltage will be doubled = 6V; their ability, as a stacked pair, to provide amps (mA) will not be increased at all but will be equal to what one battery can provide (75 mAh). However, if you connect two 2016 3V batteries in parallel (plus to plus and minus to minus) the total voltage will still be 3V but their ability to provide amps (mA or mAh) will double (150 mAh). Still, as you said, it is obviously better to have one fat battery of 3V as it has 210 mAh and it also eliminates losses that two stacked batteries have in the contact between themselves.

It is a great discovery you made, I will certainly go with one 2032 when my 2 x 2016 batteries need to be replaced.

 

My buddy has a Toyota Tundra (a US model only) that does that. I laughed at him when he first got it, from my perspective I don't understand the timer relock...a prox unlock and lock yes (which is going in my Vette), but not a timed unit.

 

Correct, I was thinking paralleled, not series.

 

Did this update yesterday. Works like a charm. Thanks very much !

 

Ok, so here it is 5 months later and I thought it about right to check the longevity aspect (as I questioned this in the OP). I skipped the incremental test and simply did a 20ft (7m) and 60ft (20m) one, doing the same procedure in the 1st test. Both worked first try, so up to this point, longevity is good. If I remember, in about another 6-7 months, I'll update again. I (as other members may) would like to know your results also.
I do want to point out I am testing going away from the rear of the car, since its forward in my garage.

 

Ok, so here it is almost a year later....I went out and initiated the test again, ..same conditions. I did it from roughly 15 and 25 ft and it worked fine. I did this with the fob in hand, lower chest height, pointing at the rear of the car.

I can add that trying to use the fob in your pocket at a longer distance and angle, it tends to only be 50/50. Plus, my driveway drops down about 24 inches to road surface, so level ground will bare better results. But when your within 15 ft, it is damn near 100%. Remember, these are steel body cars and when the fob line of sight isn't receivable via signal blockage by the body or whatever, you will have to pull the keys out and provide that better line of sight.