Three problems related to battery dead have been reported for the 2018 Honda Odyssey. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2018 Honda Odyssey based on all problems reported for the 2018 Odyssey.
In the middle of the night my car alarm went off for no reason and I was unable to turn it off because the car was stuck in a loop of powering on and off. An error message on the dash suggested a failure of engine auto idle. I pushed the engine auto idle override button and managed to turn car off. Next morning I jump started it and was able to drive it for a few errands. The following day the alarm went off again. This time pushing the engine auto idle override did nothing. I was able to stop the alarm, but could not break the loop of the car powering on and off. I had to let the battery die. I tried jumping it again but it now won't power on long enough to try to start. Honda told me I was on my own to get it towed in. Tow truck came but there is a serious defect in the transmission � there is no way to manually shift this vehicle into neutral. You must be able to power the car on and use the transmission push buttons to shift to neutral. Honda is refusing to provide assistance getting the car in to be looked at. I'm lucky this power on/off loop didn't happen while driving, but a piece of trash van sitting in my driveway unable to be moved does me no good either.
The issues started while still under warranty. It started with the entertainment system crackling and cutting out. Then the car would not start or would rough start and I was told the battery has a bad cell (now 1200 miles out of warranty) and needs to be replaced. While driving the right sliding door notification light came on and the door no longer opens. I just received a notice that there is a recall for the back up camera. This is the 3rd recall having to do with the electrical system. I believe the electrical system issues are what damaged the battery and that Honda should pay to replace the battery and fix the door issue. Because it is about 1500 miles out of warranty, Honda will not cover the repairs. I am getting an independent mechanic to weigh in. I just saw there was a recall in may 2019 for loose battery connectors. I never received this recall and am trying to determine if my VIN was excluded, and if so, why. Honda clearly does not stand by its product.
Car was powered off on level ground, no lights, radio, nothing was turned on in car. No sensors displayed in dashboard, no sounds from car. Hatch was left opened for 2 days for an event. When event over, car would not turn on. Took to dealership who said car battery died. They said it was probably bad battery since nothing was on battery should not drain. I suspect it's a fuse issue with the hatch door draining the battery not a bad battery.