PS2 Battery

The simple way is look for the charging jack, if it's round it's the 5V board and uses the 9V battery, if it's rectangular with two pins, it's the 3V board and uses the 3V battery pack.

If you're at all handy with a soldering iron, you can make the supercap battery replacements for you 3V boards quite easily.

I just cut off the old battery pigtail and solder it to a 5V supercap, job done.

Don't understand why you were advised against the use of a BCR on the 5vPs2 locos.  Other threads on this topic suggested otherwise.

I have 10 MTH engines with this electronics package, most of which had little-to-no run time for several years.  Following the advice of a local MTH-trained tech, I recently completed replacement of the batt with the BCR...SUCCESSFULLY.    Per common counsel on start-up of these systems, initial voltage was slowly ramped up to no more than 10v for a couple minutes, during which idle sounds all responeded.  Then all 10 locomotives were put in motion, forward and backward, and performed 100% to expectations.

FWIW, I have 11 locomotives with a PS1 system, also.  All now with BCRs.  All performing properly.

Returning to the 5vPS2 locomotives...  I fully understand that the nature of the boards in that system is that there's always a chance some of them will yet fail...even with the BCR.  It's NOT a panacea.  However, for the role that a dead or undercharged battery can play in some of the failure modes, the BCR...when properly installed, and properly brought to full charge on start-up...can often prolong the otherwise operational life. 

I have not switched...yet?...engines with the 3vPS2 system to that different BCR.  There seems to be consensus that there are far fewer electronic risks in that generation for which a BCR would provide as effective insurance.

This prior thread might be helpful to you.   It was for me! 

KD

KD

So what i was told by a MTH authorized repair center was that the MTH engines with the 3 volt battery should be ok, but the MTH engines with the 5 volt  board which take the 9 volt battery, some engines have issues using the BCR he said because when you start appling power to the track the BCR draws a tremendious amount of power through the board and burns up the circuit board. Have you ever heard of this to be true ?

Regards

Prentice

That quite frankly is a load of crap IMO. The BCR for 5 v ps2 has been around a long time and used in engines for a long time, if that was true it would have come out a long time ago and the company out of business. The BCR is basically a capacitor, and it takes like a minute to charge up on track voltage. I have never opened one up, but I doubt very strongly it could draw enough current to burn the circuit board, it would have to be a pretty huge capacitor to draw that kind of current. If a BCR for some reason shorted it could draw serious current, but as long as they have a fast acting breaker that wouldn't do it either.

The current at its peak is right when the power is turned onto the track, the capacitor network charges until it hit 9v, and as it charges the current draw drops until it hits zero.  If there is any kind of significant resistance in the circuit (which there needs to be I believe to allow charging to occur) , then the current draw wouldn't not fry a board. If a capacitor shorts, then it would just be the case of having a quick blow breaker.

@bigkid posted:

That quite frankly is a load of crap IMO. The BCR for 5 v ps2 has been around a long time and used in engines for a long time, if that was true it would have come out a long time ago and the company out of business. The BCR is basically a capacitor, and it takes like a minute to charge up on track voltage. I have never opened one up, but I doubt very strongly it could draw enough current to burn the circuit board, it would have to be a pretty huge capacitor to draw that kind of current. If a BCR for some reason shorted it could draw serious current, but as long as they have a fast acting breaker that wouldn't do it either.

The current at its peak is right when the power is turned onto the track, the capacitor network charges until it hit 9v, and as it charges the current draw drops until it hits zero.  If there is any kind of significant resistance in the circuit (which there needs to be I believe to allow charging to occur) , then the current draw wouldn't not fry a board. If a capacitor shorts, then it would just be the case of having a quick blow breaker.

I'm assuming you don't actually know what a supercap looks like in circuit.  In point of fact, if you connect one that is totally discharged to a bench DC power supply, you'll see that at the initial charging, it draws many amps at first!  Truthfully, the supercap basically looks like a short circuit when you first start up.

@gunrunnerjohn posted:

I'm assuming you don't actually know what a supercap looks like in circuit.  In point of fact, if you connect one that is totally discharged to a bench DC power supply, you'll see that at the initial charging, it draws many amps at first!  Truthfully, the supercap basically looks like a short circuit when you first start up.

I realize it can draw a lot initially, I just doubt that it would be enough to burn out the boards. For one thing the current draw drops off pretty quickly if I remember my basic circuit behavior, so the initial surge isn't going to last long.  I know the reputation on 5v PS 2 boards, but I also don't think the BCR or any super cap charging will fry the board. I think that far more likely transient voltage spikes or shorts would cause it without a quick blow breaker.

I'd be more concerned about the surge of charging current would cook a component in the charging circuit.  Since we have no repair information on the boards, and a lot of the components are out of reach, that's can be a board killer.

Here's a graph that hits home for me, this is the situation in my YLB - RailSounds Battery Replacement when it is first powered up.  I have a 1.5F supercap to charge to 5V, and I have a linear regulator to supply the DC.  I have a 10 ohm series resistor to limit the maximum current to 1/2A maximum.  The full time constant is 15 seconds, but after ten seconds, the cap has over 95% of the charge.  I point this out because I had to add the 10 ohm resistor during development when I found that the initial current without the 10 ohm current limiting resistor confused the regulator and it took a very long time to charge.   A dead short, even for a brief period of time, can blow diodes by exceeding their maximum short term current limitations, been there, done that.