if you have the car manual it should also show which way it goes into the fob. I do have spares but quicker for you to go to halfords or even Tescos may sell them
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Baz, I do have two sets of keys.
I removed the battery holder out of the key but l havenât taken the battery out of its holder.
best to change both then one at a time. if one is flat the other will be on the way out as well. I did mine the other day as they are about 5 years old and the originals
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Roj, When you speak of the âpolarityâ. I take it you mean that the battery is placed in the right way up?
Or, are you referring to something else regarding the battery?
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yes, normally there is only one way they will fit into the holder properly
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Thatâs OK then, you have a reference to the polarity with the way the battery goes in. The YouTube link below is just how easy it was on my VW Golf, probably the same on other makes and models too:
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Yes, Or when you take it out just mark the top of the old battery with a marker pen so least u know which side of the battery is up.
The one I did was on a old Nissan and the battery could be installed either way .Mistake I made I just swapped it out without checking the polarity,screwed it all back together and it didânt work.So I had it open it up again and turn the battery over.
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Learning the hard way is something you never forget though, thatâs what Iâve always found.
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I keep spare batteries in a partitioned box, and usually have the CR types, as well as those for remotes and smoke alarms, etc., so the 9v, and the AA/AAA.
I have several alarms here now, to include gas detectors, so need to ensure I always have spare 9v in.
However I had to buy higher priced AA this week for my garden cam, but Tesco were dealing deals.
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I found l had a spare CR 2025.
As l was removing the battery to replace it, l found there were two batteries in the key fob.
I am going into town soon, so l will get some more. I suppose, Duracell are the best brand to get⊠arenât they?
Or should, l go to Halfords to buy them?
Would you believe it? One key fob wouldnât work this morning as I was going out, came back for the spare. This afternoon prised the fob apart to check battery typeâŠand I havenât got one! Argh. 
. For some reason I have several 2016, but not the 2025. Just have to hope the other one doesnât go in the meantime, then I will need to use the key.
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I donât get in any hurry to replace them. After all how hard is it to hit the lock all button when you get out. As far as getting into the car, car fobs are relatively new, back in caveman days we simply used the key. Apparently there was too much work involved in that soâŠBTW I donât need my car to drive itself, or park itself when I am unable to do this myself itâs time to give up driving.
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I agree, Danny.
I have my key fob, plus an ordinary manual spare key without batteries.
Even if the battery in the fob did go again, I can still use it manually and turn the key in the lock like we used to.
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As a non driver/non car owner, I am a bit confused about this battery for the keys, and onboard computers? I know technology has improved, but not sure how it applies to cars. I havenât been in a car for 3 years, and that was a taxi, soâŠI know this sounds silly, but are cars like computers now?
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I wouldnât touch duracell with a barge pole @Artangel
The button cells might be okay, but all the other Duracell batteries leak and damage your terminalsâŠ
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The definitely are like that PixieKnuckles, laptops on wheels!
Very confusing when, like me not having driven anything but the âold-fashionedâ no technology cars before I bought a new one. A degree course was almost required just to find out what everything did and seven yearsâ later there are still the odd options I havenât yet explored!
Thank goodness for YouTube!
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OhâŠokâŠso is there such a thing as a regular car then? One that you just put the key in and the engine turns on?
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No, not new ones like that as far as I know. I do have one like that though, I bought it new 37 years ago. The most âmodernâ accessories it has are electric windows, a radio / cassette player and a heater. The benefits of it though are that I donât need a degree in computers to service and repair it when needed!
A âmaybe one day classicâ is how I describe it!
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Some Timpsons and local motorist supply shops can do it.
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Well, l traipsed the town looking for the cheapest Duracell batteries. The CR 2025 in most places were ÂŁ8.40 for 4! I could have got Kodak ones in Poundland for a quid.
Convincing myself that the key fob was very important, l decided l should get Duracell and found a Duracell two pack in Boots for ÂŁ4.30.
At home, l took the fob apart, removed the old batteries and fitted the new ones. I went out to my car, click⊠nothing happened! There wasnât even the red light flashing on the fob.
I took the key fob apart to check, l hadnât fitted them incorrectly. They seemed ok but l took them out and refitted them. Went outside again, click, nothing!
I felt so despondent and decided it was the key, or the batteries that were faulty.
I refitted, the old batteries, went out to the car, clicked and they worked!
Thinking, they might not be reliable, l took them out and refitted the Duracell batteries. Clicked and the red light flashed. Tried them on the car and âŠYipppee⊠they worked.
What l think the problem was⊠the batteries did seem slightly loose in situ and l think it was to do with the metal contacts not securing them enough.
Anyway, thatâs the end of my saga and l thank you all for taking the time and trouble to advise me.
If l could have given you all three hearts⊠l wouldâve done!
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