Just a few observations. Wet cell batteries aren't the best for standby service. AGM or gel are better suited plus can be kept indoors without worries of outgas or corrosion.
Fully charged batteries don't need much in the way of "current" all the time. You float them at a specific voltage based on the make and model of the battery, and ambient temperature. Generally the maintenance current for a hundred Ah setup will be well under an amp.
With proper care you can use a shack power supply as a float charger. But if power is lost, the battery becomes discharged and power restored, the battery charge current can tax a station supply beyond it's rating. Not always, depending, but it's something to check before you leave it go unattended.
12V equipment often poops out well above the lower limit of a lead battery discharge point, leaving battery capacity unusable. My solution is to use a sine wave computer UPS. Everything runs on 120V AC in the event of an outage as though nothing happened, and the UPS manages the battery charging. I got my UPS's for free, IT folks get nervous about equipment not under warranty or service plan in the server room. Been running the shack off UPS's for over a quarter century at this point, it checks all the boxes for me.
If all you're looking for is "standby" power vs always hot, leaving the battery offline on a maintainer and connecting it to the station equipment when needed (switch or plug) would be a simpler solution.
Mark K5LXP
Albuquerque, NM