My daughter call me yesterday. "My battery light is on". So I say "bring it over". She can be smart most of the time and left it running. I put a meter on the battery and with it running it shows 4.65 volts. I was actually quite surprised it was still running.
So, I ask "how long has the light been on?" She says "since Monday after work".
So, basically if you have an Escort ZX2 you can expect it to run on a battery down to 4.65 volts.
That's pretty impressive. Best I ever did was about 60 miles on battery alone. The battery light never came on but the car was doing funny things and it wasn't until it finally died that I went "duh..."