2004 R53, 173k miles, orig starter, alt less than 1k miles;
no start, just a loud clicking, about every 2 seconds, not fast clicking
12.3 v at the bat
1" of water sitting in the battery compartment in the boot (thanks hurricane Florence!)
It's started normal everyday until this morning. Rain started 5 days ago, stopped 1.5 days ago
Cleared out water, disconnected neg bat, reconnected, no change
I can look for/clear codes after work today
possible BST (battery safety terminal) problem?

 

It sounds like there is something keeping the starter from turning. It may have failed, which is not too common, but at those miles may just be starter failure.
There is a drain under the battery, that gets clogged with dirt. It has a rubber goodie that gets clogged and stops draining pretty easily.

 

Thanks Wayne, I'll try jump starting it later. Someone suggested the battery may be dead after sitting in water for an extended period

 

the large and small fuses in the battery box may have blown, if the battery box filled with water.

 

A healthy battery should be pulling 12.6v. Not a ton of difference but could easily be the reason it's not starting. You might want to try a battery recharge, or jump starting the MINI, before you spend $$$.

 

I found a couple threads that indicate the cars ECM shuts down and the starter when there's inadequate voltage. I also read that with a manual transmission, I should be able to hear a relay when I depress the clutch with the key at RUN..

 

12 volts would be enough to start it. When it is running and the voltage drops below 14.0 volts, the ECM would throw codes, it should not shut down. It wants 14.2 to 14.5 volts while running, with optimal 14.2 volts. (it will throw a code)
If yours has an automatic transmission. The neutral safety switch may have failed, so if it does not turn over in park, try neutral. (it should start in either)(can be an adjustment issue)
If it is manual, the safety start switch is on the clutch pedal and it can go bad, or unplugged and it will not start until this is fixed.

 

I found a couple threads that indicate the cars ECM shuts down and the starter when there's inadequate voltage. I also read that with a manual transmission, I should be able to hear a relay when I depress the clutch with the key at RUN..

 

Water around the battery did not rise to the level of the BST...are fuses in there serviceable?

 

with a good battery, and new alternator, my voltage levels frequently get below 13.5 (with accessories on)....it's never thrown a code related to that
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in this case, my battery was dead...it jumped with no problem, and started after charging the battery.
because my battery sat in water for an extended period, it discharged.....just like when a battery sits on concrete for an extended time.