12v SLA Batteries?

Starter box batt has more capacity - mine use 7ah batts. One you show is about 1/3 of this. It will work, just might not last as long.

Get a float style charger if you use it as a starter box batt - you keep it hooked up to the batt and it charges it and maintains it at peak charge. Nothing like getting to where you're going to run and realize your box is not charged! Makes for a short day....