Might they fit??
Or gram/penny saving strategy?
My button press fob for the nc2 lasts a noticeably shorter time than any other I’ve ever had…
It’s not many months before I am holding the fob near the drivers window and pressing a few times to get it to work…
I don’t think its different to that for my 2008 NC1, push button open/lock and key ignition. Judging by Az purchase date history my NC’s CR1620 fob batteries seem to last two-three years.
However with the 2016 Mazda3 (push buttons to open/lock it but proximity ignition button enable like ND1), CR2032s in both run down in 18 months regardless, even though the spare lives inside an ancient Old Holborn tobacco tin rescued from work. I guess a CR2025 will need to be changed about the same time as an annual service - another mega-profit revenue stream like the screen wash!
I’ve had the car 18 months and I’ve changed the fob battery twice.
It now needs changing again 
That would suggest 6 months until it gets so frustrating to use, you have to change.
I’d say it only lasts 3 months until you need to press more than once etc.
Sounds like fake batteries.
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Could well be.
I’ll see if I can get some Duracell or similar 
I thought my Mk3 was “eating” batteries… turns out that the contacts withing the fob needed “persuading” up a little… result… it works!@ 
Might yours have the same issues? Oddly… my other car… a Mazda 3… with very similar fob fees not suffer the same affliction 
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I have had other cars with keyless entry and none of them get through batteries like the MX5. Both keys are the same.
I have a 2017 RF, I had my first battery replaced on the second year service FOC at the dealer, the second time the key fob battery needed replacing after another 18 mths which was between services, the dealer charged me £3.00, my RF is now nearly 4 years old in Sept and covered only 9000 miles, on the subject of key fob batteries my other car is a Hyundai Santa-Fe and his in its 4th year and covered nearly 30,000 miles and is still on the original key fob battery
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Got an Energiser battery from Halfords.
Very expensive at 4 quid for one but I no longer have to hold the fob to the window to get it to work.