I have a keyless car, and the battery keeps dying. Idk why my vehicle cannot start up after 4 days of not starting it, and it was not the first time in these three months, (probably because of working from home now. )
Sometimes, I can still use keyless to open the door, but the engine won’t start up. Sometimes, I have to take out the key to open my door because the battery completely died.
The auto store and dealership cannot find the problem because the battery basically is good. I’m just wondering has anyone ever had a similar issue before? The diagnosis will charge a lot, and they do not ensure that they can find the problem.
Often times it will be the very thing that is supposed to maintain the battery that kills it. Your alternator can be the source of this problem… You can do a little test on a cold engine…charge the battery and let it sit… feel your alternator to see if it is warm to the touch on an otherwise cold engine.
The battery itself needs to be healthy as well. Sometimes tests dont always catch the type of batt failure present.
A digital volt meter will help you immensely here… You can measure amp draw and or voltage…whilst unhooking the hot wire to the alternator to see what you get. Shouldn’t be too difficult to suss out.
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Well worth it if you cannot do the work yourself.
If this car has non-factory radio, amps, subs, alarm, or remote starter assume one of these has partially failed and is draining your battery. Pull the fuse, or disconnect each of them and see if the problem goes away. If it doesn’t… pay the money for diagnostics.
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Thank you for your help. They also tested the alternator, and it’s good tho.
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I dont buy that… Keep in mind…it can have the proper output yet still be a drain on the system. The only way to verify this is hands on testing with a volt meter and removing the hot lead from the alternator…otherwise it can test just fine.
Of course the drain can be something else… I’m just directing you to the most common culprit.
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Em mmmm, but they wont ensure they will find the problem after tests…
I can assure you the problem won’t be solved if neither you nor a shop even looks for it. I can also assure you that if you just guess at the offending part you will spend more than the diagnosis costs and still not have it fixed.
Do you keep your fob close enough to the car that they can communicate? That will keep the system awake and drain your battery.
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What is the vehicle’s model-year?
When was the battery replaced? How long ago?
What’s the difference between “the battery basically is good” and the battery is good?
CSA
thx first.
and yes:)， its close enough like before.
Thank you first,
and is 2015 sentra; The battery replaced at the end of 2018.
The auto store and dealership told me the battery tests good. By the way, the dealership gave me a number about my battery 300+/500+.
How close? The range of the door handle antennas are only 3 feet.
A vehicle that is not driven on a regular bases should have the battery recharged once a month. If your battery is at a low state of charge when you park the car it may not start 4 days later.
The reason the shops are telling you that they may not find a problem is because in most cases there is none. The battery is discharged over a period of 3 to 4 months until the engine will no longer start. Driving for 15 minutes twice a month will not maintain the charge of the battery. This would be like recharging your cell phone battery for 15 minutes every two weeks, it will be dead in short order.
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Thank you for the specif reply. 
Before COVID 19, I drove my car to school almost five days a week, so my car never had this issue.
However, I work from home now, and I drive my car for 20-30 minutes twice or once a week. My car hasn’t started up three times during these months, and I only can use a jumper to fix it.
I think it’s close enough because I have already sat in the car. When I can’t start up my car, the door can open via keyless sometimes, and the screen is light up, only the engine can’t start.
20 to 30 minutes twice a week should be sufficient. A failing battery can test good with modern test equipment yet go dead in a few days. How old is the battery? you may choose to replace it.
Where did you get your battery and what did it cost? The reason I ask is that if the numbers the dealer gave you are cold cranking amps/cranking amps then that battery is undersized for your car. The least powerful battery that Autozone sells for your car is 500 cold cranking amps and the highest is 650.
It shouldn’t be much an issue for a good shop to find this kind of a problem. A good tech knows exactly how to pin down these kind of problems. It should take a good tech less than an hour to find the trouble. Normal current draw should be less than 50 milliamps when things are in the sleep mode. You should be able to leave the car sit for at least a couple of weeks without having to start the engine if things are working like they should be.
Yep… what @Cougar said…