Sounds great.So is that not the stock battery that comes with our XP’s? Larger capacity battery sounds like a great option.
Several others have reported being happy with the Ortlieb E-Mate pannier. It is specifically designed to carry a spare battery.
Personally I had a pair of Ortleib Back Roller panniers that I was very happy with so I just kept using them on the new ebike. To carry a spare battery (that I borrow from my wife's ebike) I line the pannier with closed cell foam and velcro extra foam to the battery and slide it into place. It's been working very well.
I just got my spare battery from AliExpress today, 48v 14ah battery. Here are pictures I have with my Ibera Panniers. I used the Styrofoam that came in the packaging for the battery and cardboard whiskey bottle dividers to hold the battery securely in the pannier. These panniers are water resistant I believe and it comes with water/weather proof covers which I put on in the last two pictures. If anyone is looking for a way to carry their spare battery here is a good option. These panniers also have a lever to take on and off the rear rack a lot easier. Next thing to do is test out the spare battery range. I am going on a 30 mile bike ride within this week if weather permits that has a lot of very steep hills. I will keep everyone posted on how this 48 v 14ah battery did.
Can you link to the battery you purchased? I am seeing some on there, they are pricey at $300 + $30 s/h...