I'm chasing a random dead battery in our 2020 Odyssey. Other than googling, I haven't done anything to the vehicle except put a voltmeter in the accessory jack to watch the voltage as we drive (outside temps have been single digits for a long time).
In an old vehicle, I would expect to see around 14.2V when first started then dropping slowly to around 13.8V when the battery is charged.
Ours will be 14.2V for a while, but soon after when cruising or accelerating, it drops to show battery voltage around 12.4V. When idle, coasting or decelerating, it will climb back to 14.2V. Sometimes it will sit at 14.2V for an hour drive.

Does the ECM control the alternator output?

Thanks
Dave

 

Normal, my Pilot and Ridgeline have the same charging pattern.

Are you still running on the factory battery? The OEM battery usually only lasts 3 years. If so, I would replace the battery.

 

Good to know. The battery is mostly covered by the intake cowl, I'll have to pull it apart to see if there's a date code on the battery.
Any idea how to tell if it's the OEM Honda battery?

 

Even though I'm the second owner of my 2017 Pilot, there's no record of the battery being changed. Here's a pic of the battery label of what I think is the original factory battery. I did not have to remove the cowl to take the pic.

 

a bit late but Honda uses a Dual Mode Charging System in the newer cars.

https://opensiuc.lib.siu.edu/cgi/vie...text=auto_pres