The original poster mentions he's "new to MTH locomotives" and so may not know that "BRC" is a typo
"BCR" (Battery Component Replacement) by J&W Electronics is a capacitor-based power cell that replaces the stock MTH NiCd. It requires that you leave your locomotive in neutral for about a minute at the beginning of your operating session, then the BCR retains its charge until you're done for the day.
The upshot is the capacitor doesn't develop the "memory effect" that NiCd batteries are notorious for, and therefore isn't subject to its output suddenly collapsing while the Protosounds 1 (PS1) electronics is saving its setting during its shutdown sequence.
The only downside is the user might forget the initial charge cycle and possibly letting a retrofitted unit go into shutdown before the capacitor has enough charge to "see it through".
If the locomotive is frequently used, a NiMH battery (8.4v) could stand in for the 9V cell, or if not so frequently, a new NiCd will allow you to "kick the can down the road" a few more years. Before investing any money, you can test for proper operation with a fresh 9V alkaline battery (but don't leave it in there long-term as alkaline cells don't like being recharged, which PS1 tries to do anytime its operating)
---PCJ