appiah4 wrote on 2020-11-03, 17:34:

Motherboard in question is a PC Partner PM601TMS3-T898C (picture below) that works 100% perfectly as long as it is connected to […]
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Motherboard in question is a PC Partner PM601TMS3-T898C (picture below) that works 100% perfectly as long as it is connected to wall power but as soon as I remove it from the wall it loses its CMOS settings. The CMOS battery is brand new. Any ideas why it might be doing this? Any particular components on the battery circuitry I should check? As far as I can tell from the manual (http://support.pcpartner.com/support/man/via/t898xx.pdf) the CMOS Reset jumper is in correct position (not that I think it would retain settings even with wall power that way). Open to all suggestions.

Before you go any further, I suggest you test the new battery with a multimeter, if you haven't already . The battery may be new, but it may still be bad . You could also make sure that the tabs in the battery holder actually make contact with the battery and are not corroded .

EDIT: Sorry if I am stating the obvious, but I have actually had non expired retail store bought brand name batteries be bad fresh out of the box . I actually unnecessarily bought a replacement remote control going on the assumption that my new batteries must be good (they weren't).

Just one of a billion reasons to always have a multimeter on hand. But still, I was under the assumption that the battery was primarily to keep the clock and other non-essential settings saved, not absolutely everything.

Good point darry, I would also suggest to look at the traces from the battery holder.
I remember having trouble because one of the contacts got disconnected from its trace.