Dear me,

I really don't seem to be making myself clear tonight.

Yes, I anticipate losing about one third the power capacity, per the owner's manual.

What I am really interested in is how to interpret the gauge. In other words, what does it mean when it starts to bottom out under load? What do I have left?

I suppose that I could drive around the block until it got to absolute zero, but that is somewhat hard on the battery. SLA does not like going to zero.