I've been having problems with my 2016 Honda CRV for the past few months where the car won't start due to low battery. The car starts when I jump it and no problems until I don't drive the cars for a few days. I thought it was the Costco battery I got and had it replaced since it was within the 2 year warranty, but the problem still persists. It isn't an issue after I jump it, I can start it fine the same day or next. If I don't drive it 2 or more days, I noticed the battery is drained. It is not an issue with the key being near the car while parked overnight since the key fob is half a block away. Most of the driving is short trips, but seems weird that this happens whenever I let the car sit for a few days. I took it to the mechanic and he suggested the alternator needs to be replaced (see pic below) but someone else there suggested that might not be the issue and it might be something else (parasitic battery draw). After some googling, I thought the problem was caused by a parasitic battery draw, so I replaced the AC Relay, but the problem still there.



Anyone have an idea what the problem is? Thanks in advance.

 

Parasitic battery drain. Short trips and dual mode charging alternator can cause this issue. Try making longer trips and running with headlights on.
Note: do not forget to turn off headlights when leaving vehicle.

 

If a fully charged battery will not hold for three days you have a parasitic drain and will need to do some fuse pulling.

 

 

If you store your car for awhile and don't start it up about once a week you can kill the battery. You need to get a float charge which will keep the battery gently topped off so that the battery doesn't get drained an lose its capacity to be charged.