New batteries for ps audio power pack 1500 mark ii

I have three ps audio powerpack mark II. After a move, I’ll be putting them back in use. Each uses two hr1236w lead acid batteries. 12V 36W/cell.

Replace using same or any suggestion to upgrade? Units have low level buzz in use. I’ve suffered through this because I’ve always lived in areas with frequent power problems. These fire up before the lights even flicker. I use them to offer enough time to turn computer and other components off or to pass through on and off cycles till power stabilizes.

I have followed discussion of using battery backup ahead of power plants. Could not find info on this topic.

Thanks in advance

You can use larger capacity SLA batteries if you wish. Just feed the PowerPackMk2 battery terminals out the hole cut in the back panel for this purpose and connect them to your battery of choice.

I used these: