Using a multimeter and reading voltage isn't enough. You Have to put a load on it to tell if it's dead.
Reading the 20hr rate isn't useful either as most use either the 8hr / 10hr / or 20hr rate.the datasheet's power or current graph is the way to go if you want to be technical.
Any of these batteries will work. If you just want a battery backup, just buy any of them but don't mix. In the end, you're supposed to change them every 2-3 years but I suspect that you don't as that's what the majority does.
Reading the 20hr rate isn't useful either as most use either the 8hr / 10hr / or 20hr rate.the datasheet's power or current graph is the way to go if you want to be technical.
Any of these batteries will work. If you just want a battery backup, just buy any of them but don't mix. In the end, you're supposed to change them every 2-3 years but I suspect that you don't as that's what the majority does.