You should probably get another battery.

BTW, I am using a new battery. I just got a bit further with my tests. If I go to the BIOS setup chipset section, and set both onboard serial/com ports to disabled, then the "ESCD error" is displayed on POST. If I set both serial/com ports back to their default Enabled values, the "ESCD error" disappears. Strange. 😖

DOS stuff shouldn't bother about ESCD.

http://en.wikipedia.org/wiki/ESCD

It makes your PC boot minimally faster.

Hmm, my PVI-486SP3 used to do something similar once, but I can't remember exactly what caused it.
Try clearing the CMOS memory (without flashing the whole BIOS) using the UniFlash utility. Also, what BIOS version do you have?

Solved; see here ->

Before I solved this problem, I tried running Uniflash (Version 1.4). Its main option screen says -

(FFFF,FFFF) Flash ROM Chip: Unknown
Organisation: N/A (Is write protect disabled?)
etc...

I then used Uniflash's "clear CMOS" routine, and rebooted. The BIOS POST screen did not display the "Error -- can't write ESCD" message. Actually, I expected that. I then went in to the BIOS setup area. I made one change: set serial/com port 1 to disabled. (Reboot.) The BIOS POST screen then displayed the "Error -- can't write ESCD" message. Strange. The BIOS is Award 4.50PG.

here -> I looked at my other rev 1.22 board, and saw that its "BIOS jumpers" setting is set to the "12V" setting, and not the "EPROM" setting which this 'faulty' board is set to. I then changed the BIOS jumpers over to "12V" setting. This worked! This has got rid of the BIOS POST "ESCD error". Also, Uniflash reports the BIOS as -

SST 29EE010/5V

I notice that it displays "5V", and not 12V. Perhaps I should change the mobo's "BIOS jumpers" setting to 5V?

Might be worth trying. Worst case is it won't have enough power to remember and/or write settings, versus getting overpowered and blowing out a chip.