Hello everyone I have volvi v 40 2015 model . For quite some time I can see the low battery option on screen if I drive daily then no problem with battery but after 2 days of standing still when I try to drive my car battery didn't work.. I went twice to the garage to change the battery they said battery is absolutely fine I don't know what should I do with it

 

did your garage test the alternator? It sounds like you have a parasitic current draw that is slowing draining the battery. If you have a volt meter, you can test the system yourself. 1) with the engine off, start measuring volts across the battery terminals = 12.6V is typical of an 80% charged battery (consider this normal) - if you are lower than say 12.2V then your battery is 20% charged and may not start the car. 2) with the engine running (assume it starts with a jump or after using a battery charger), measure voltage at the battery again. It should be 14V - 14.5V. 3) with the engine still running, turn on various electrical "loads" - high beams, rear defroster, AC blower on high etc. Measure voltage again - it should stay above 13.5V even with all these accessories running. If you pass tests 2 and 3, your alternator is working. Last test is a bit more intrusive. with the engine off/key off etc (ie parked), disconnect the battery terminal, switch your meter to measure milliamps and insert the meter in series - ie one probe goes to the battery terminal, the other probe goes to the cable. If you see more than say 20mA give or take, its likely you have a circuit that is drawing too much voltage even with the key off. Better yet, see if Autozone will rent a "clamp meter" that doesn't require you to disconnect the cable (the meter loops around the battery cable to measure current). Given you say it takes two days to drain the battery, I wouldn't be surprised if you measure 50 or 100 mAs.

So now say you find you have a parasitic drain... Next step is to look around for obvious issues - vanity light in the glove box or trunk or behind the sun shades stuck on? You can also start popping out fuses to see if you can find the active circuit. (only do one fuse at a time and use a fuse puller tool.)