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Discussion Starter #1
so couple of weeks ago i had a flat 12v battery

today drove about 10 miles to the retail park to do some shopping, no issues

come out of the supermarket with a trolley full of shopping including a lot of cold stuff

get to car, nothing :(

uh oh

mirrors didn't fold out, boot didn't unlock, tried button on side door, nothing, tried button on keyfob, nothing :(

my mind though oh no battery died, but i have just driven here from home

tried to pry off cover from lock and couldn't :(

wandered round the car a few times while wife getting impatient due to the shopping in the trolley

rang son in law to bring a set of jump leads and provide a donor car for power, would be over in 30 minutes :(

wandered round car again and mirrors folded out?, but nothing else, button on door or keyfob nothing ?

DING!!! lightbulb moment, battery in keyfob? right outside Halfrauds get new battery as still on original after nearly 4 years of ownership

go in figured out how to get keyfob apart (easy, take out mechanical key, pull the two halves apart lif out the inards and find a CR2032 battery slipped in a holder,

bought new battery (£3.99) fitted walked out and before i got near to the car the mirrors folded out , button on door worked and car started easily :)

wife happy again (as they say happy wife happy life)

then think back the last few days, warning signs were there

boot needed several pushes of the release before it opened
door needed a couple of pushes to open

flat battery the other week wasn't the keyfob as i held the fob against the start button and nothing
car happy again
 

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Discussion Starter #3
Is there a way to monitor or tell about the fob battery power?
not that i am aware of

once the car is about 3 years old if you notice you need to push the door button a couple of times or the boot / trunk release then change the battery from my observations, as you have at most 2-3 weeks before it dies
 

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If you are like me, one set gets used far more than the other. For the sake of £4 get a new battery at 3 years and if that fussed there a few things that take a CR2032, which hopefully are not as critical if you want to drag the last bit of life out of it.
 

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Unlike older key fobs that had a battery that was only used when opening the door, the Ioniq fobs battery is "on call" all the time and thus runs down faster. I did not change the battery in my 2006 MB for ten years! And that is not to often because it is parked in the garage most of the time with the doors unlocked.
 
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Not sure, but I think the fob is in a low current transponder mode. It is the car that is actively transmitting.
 

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Not sure, but I think the fob is in a low current transponder mode. It is the car that is actively transmitting.
That may be, but it does not explain why installing a new battery solved his problems! Even a low power transponder needs power.
 

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Just saying that the fob battery does not have unusual drain and 3-4 years is the expected lifespan. Yes, older cars the battery life is longer. Had last car for 20 years and never replaced the fob battery. There does seem to be some communication going on if fob is close to car - which has been thought to be the cause of some flat 12 volt batteries. So proximity to car may affect the fob battery life too. However, a transponder doesn't have to require any power use. You can have a transponder chip with no battery at all that will work in many cars.
 
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