I know what exists, I'm trying to do this without spending a ton of money, it's just a research project.Gents, I was just trying to illuminate what to expect in terms of pertinent battery technology.
Lionel has been pretty steady with 19 VAC as the absolute max for their stuff. You're right, there is a rectifier that comes first, at least for LionChief stuff. However, I don't want to get reckless, as you say, I'd be the one replacing the parts. I did measure and found out that I can "just" cram two of the 9.6V packs in the tender if I move the charging jack, that would give me 19-20 volts DC, I could live with that. In order to get the pack to sit flat and allow two to fit, I had to attack the shell and lose the ridges half way back inside the shell. I don't know if they're there for the casting process, or what, but they're not there now! Since I already have the second battery, this is a very low cost option, no additional expenditure.John, you know that the 18 VAC peaks at ~25.5 V. And I presume all the newer electronics rectify the track AC and provide DC voltages for the various functions (though maybe just a relay for smoke, etc.). In any event, I would think 22-23 V DC would be within limits. Then again, they're not my expensive loco.'s
If it ever comes in handy ... There's a simple alternative to charging one pack at a time. Bring out both packs + & - to a 4 pin connector - isolated from each other Then the matching charging harness can charge both packs in parallel. After charging install a connector (plug) with a jumper to put the packs in series to run the loco.
I just tested the outputs of an old printer "brick" against a LED PS that looks similar to your charging PS: less than 4 ohms between the minus DC outputs. I got too many things going on today to contemplate the significance of that in your dual charging scenarioMike they couldn't be sold anywhere in the country if either leg was connected directly to the 120V outlet. Given that fact, they can't help but be isolated. I'll be a bit surprised if you can turn up one that actually connects one of the outputs to the incoming AC! Remember, I'm talking about two wall warts, not a dual output charger.