Just got a quartet of 12 V 7 A·h lead batteries, prompted by a big Belkin UPS that instantly shut down during a power blink. It needs only two batteries, but the shipping was the same for two or four and I’m sure the spares will come in handy.
A stiff 2 A discharge test shows that SLA batteries really don’t like high currents, which is exactly what they must provide in a UPS:
The capacity is barely 4 A·h at 2 A, not to mention that I’m using a conservative 11.4 V cutoff.
The two batteries with the highest capacity also were the closest matches, so they’re now in the UPS.