charging a BCR via an external charger.

What criteria are you using to determine that the BCR isn't charging while in the engine?

Personally, I'd remove the shell, power up the track (leave loco shut down) and with a voltmeter check to see if there's voltage at the BCR terminals.  If none, I'd check the voltage, with BCR disconnected, at the leads from the board. Voltage on the charging circuit with BCR disconnected would tend to indicate an internal short in the BCR.  If voltage, I'd let it sit a minute, then disconnect the BCR and see if it was holding power---voltage should stay quite constant.

I had a supercap (similar to a BCR) that wasn't working, and found a connection had come loose.

PS-2 charging circuit doesn't necessarily work that way.  Reading an unloaded voltage at the battery terminal, is like testing a battery without a load.

voltage may be present, but as soon as a load is placed on the terminals, it may go away or short the power supply board.

Just move the BCR to another engine and see if it works.  If so, the power supply board charging circuit is defective.  This is repairable for a PS-2 3V board.  G

I agree, GGG, but 0 voltage with BCR disconnected would indicate a failure of the charging circuiy.  If a BCR or supercap were internally shorted, could that not damage the charging circuit if left connected for awhile?

I'd be inclined to check for a BCR short by connecting it to a pair of alkaline batteries and check voltage and current, rather than risk another charging circuit.

If there is 0 volts at the battery terminal unloaded, the board would not start up.  If you had a shorted BCR that board would short out and not function or start up, or shutdown if started up.

So technically your recommendations are not correct.  To test for a shorted capacitor, put a meter on it.  Shorts tend to be easy to find.  Open or non function cap is harder to test.  G

Open or non function cap is harder to test

 I apply power to the capacitor from a pair of alkalines for a few seconds, and then see if the capacitor will hold voltage for awhile, or run a grain of wheat bulb for awhile.

If none, I'd check the voltage, with BCR disconnected, at the leads from the board. Voltage on the charging circuit with BCR disconnected would tend to indicate an internal short in the BCR

You are saying that is not correct?

 Given the reliability of capacitors and the charging circuits, I'd say the most likely culprit is a loose plug or a wire that has come loose where is is fastened to a plug.

Yes, Not correct.  There are 3 parts.  The boost circuit, the charge circuit and the cut off circuit.

Just because of voltage present unloaded doesn't mean voltage will exist under load.  So with nothing plugged in the presence of voltage still does not mean it will charge.

Actually, the most likely issue is a failed charge circuit.  I fix a lot of them.  G

Where did I ever state that the presence of voltage on the charging circuit means the charging circuit is good?

I stated "Voltage on the charging circuit with BCR disconnected would tend to indicate an internal short in the BCR."  I then went on to say check the BCR for a short and its ability to hold a charge.  "Tend" is a key word you may have overlooked. 

I also stated, "0 voltage with BCR disconnected would indicate a failure of the charging circuit." I stand on the correctness of that statement.

I also stand on the statement that step one is to check the wires and connectors, before sending the board out for repairs.

RJR, You are hard headed.  Your first 2 statements are wrong.

I have fixed hundreds of these boards.  What else do you want me to say?

You said Voltage on the charging circuit (what ever that is) I assume you mean 2 pin battery terminal with BCR disconnected would tend to mean a BCR short.

WHY?  You didn't state it was good, but you implied it was, because you state it means the BCR is shorted.

Go search on some of my other post where I explain how the power supply works.

The charging circuit is separate from the voltage present at the battery terminal.  You need to observe the voltage on the terminal dynamically while under load of a battery or BCR to understand what is going on. 5V unloaded means nothing in troubleshooting.

0 Volts at the terminal means no voltage present, but does not mean charging circuit is failed.  Though nothing will charge if 0V present.  But if zero voltage present, the PS-2 board will be dead and never start up.  So why would anyone assume it must be a bad BCR if a board won't start up.

If 5V is present that does not confirm that the charge circuit will or will not work.

So nothing you stated helps isolate whether the BCR is bad or the Charge circuit is bad  if a PS-2 board starts up, but won't play shutdown sounds.

There are failures when even a good fully charged battery won't play shutdown sounds, and it has nothing to do with the charging circuit.  It could be the cut of circuit.  So it is very possible the BCR is charging  fine, but when power is turned off the cut of circuit prevents the BCR from powering the board.   G

"Hard-headed."  Moi?