Check fuses and relays first as jumping it should bypass the battery even if its shot and start the car or crank it over, there’s two fuse boxes one in the engine bay and one on the passenger side of the dash, if you open the door there will be a small handle to pry the plastic trim away and its behind there.
Another thing to consider is if the battery was discharged to a low amount of power usually if it drops below 10v it can damage them and they won’t hold charge very well even if you re-charge them again or try every trick in the book so get the battery tested as this may be making the problem more complicated than it is now or may well continue to do so, there’s usually a date stamped on the battery to indicate when it will most likely need a service or recharge in a sense) Normally if the battery is damaged one of the signs is slight corrosion on the terminals.
If you battery is healthy and the fuses and relays are all okay then If you want to continue to try and fix the issue yourself I would also buy a multimeter (there cheap to buy and useful for auto and home electric testing) and watch a couple of youtube videos on how to use one, some simple functions are easy to use on them. Ideally if you can get the car to start the multimeter will be more help so if you are able to get hold of a new battery or borrow one of someone that is in good working order and the same power as yours swap it over and see if it will start straight away. If the new battery will start the engine no problem I would do a couple of checks with the multimeter (watch a couple of videos for each task to make sure you select the correct dial on the tool)
Whilst the car is running check the alternator is charging the battery, if it is charging the battery it should read between 13.8-14.2v usually.
whilst the car is off check for a parasitic drain, this is when a current in the circuit which should stop when you turn the car off doesn’t and slowly drains the battery, on newer cars its a bit harder to check as parts on the car sometimes stay on for up to half an hour after you turn it off so this ones a bit trickier.
If both or one of these tests indicates an issue then you can try to pinpoint the fault from there or get an auto electrician to take a look as sometimes it can take a long time to find the issue if you haven’t done it before.
All this will depend on if the car is mechanically in good working order too as parts there could cause this issue too like the starter motor, alternator or anything faulty that would require the car to draw more power to keep the engine running.
sorry for the long answer but there can be quite a few things that will cause it and I hope some of this helps, if you don’t know much about cars and do need anymore help then just post any issues you have trying to find the problem along the way.
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