Greetings,
Just sharing the battery upgrade pics from my mom's 2013 Touring to a Group 35 battery from Costco.
The factory battery was replaced at 3 month and the replacement lasted till now (May 2019), so about 5 years. Last week car had a no start condition with "check brake system" message.
I reused the bottom tray, but cut the side plastic off and put a piece of plywood at the bottom, then fabbed a new hold down. I had to bend the hold down ears and the ECU mount slightly. Also remounted the wire clip that attaches to the hold down rod closer to the front of the car to relieve wire strain and protect the wires from rubbing on my metal hold down.
It's a tight fit, but nothing rubs, there are a few millimetres of clearance even in the tightest areas.
My only recommendation for someone doing this would be to find a battery that has flat tank covers on top. The costco one has protruding covers and the negative terminal rests on top. This doesn't cause any issues, but I'd prefer it were flat.
To make it looks more factory, I was thinking of trying a hold down from an Odyssey or other vehicle that comes with a larger battery.
Original 51R:
Costco Group 35: