2017 OR AC 'Humming' after AGM battery replacement

I recently decided that it was time to replace the original battery in my 2017 Tacoma OR. I've banged the truck around quite a bit on trails, and AZ heat is brutal on batteries as well.

The replacement I went with was a x2 (Northstar) 27F from batteries & bulbs. Install went ok; had to trim a lip off the stock battery tray to get the battery to fit (tip I found on here...). I'm going to get a new battery tray, but haven't decided on which one yet. There was quite a bit of crud on the negative terminal, and it looks like there has been some spilling going on from the stock battery.

Truck started without issue, and I did a few laps around the block. However, when I turned on the AC, I noticed two things. One, it seemed to have more airflow. Two - there is a 'hum' that gets louder the higher the AC fan is running.

The 'hum' has me concerned; if I crouch down by the glove compartment, it seems louder, but it's not clear if it's the blower or not. With the engine running and hood up I can't discern if the hum is from the engine compartment or not.

Prime should be delivering an AGM charger tomorrow, and I plan on topping the battery off with that and then seeing if that changes anything.

I really do not want to re-install the old battery to see if the hum goes away due to the batteries condition - any advice on debugging?

 

How about seeing if the hum goes away when you turn off the blower, if so its something with the blower, if the humming continues with the blower off then its something else.

 

As strange as it is.... the humming went away after another day or so of driving the truck with the new battery.

Also, I hooked up the AGM charger to the battery, and it only ran for ~20 mins and then it said the new battery was 100% charged.