Large Scale Central

USA Trains Engines, Batteries, Amps, and Barrel Connectors

Modeling Motive Power
#1

I have equipped my SD70’s and GP-38’s with Airwire drop in boards and batteries. The drop in boards have inconvenient charging jacks and on/off switch so I am going to add my own charging jack and switch between the battery and the Airwire board. I was pointed to the wiring diagram as shown in this doc this https://www.rcs-rc.com/store/PDF/Accessories/U-BIK-3.pdf as method to set it up. In the setup, the charging jack can be used to supply external power via an external battery. When a battery is plugged in, the internal battery is ignored.

I have lithium-ion batteries installed that provide a sustained amperage of up to 6 amps with peaks reaching 12. See this as an example. http://rldhobbies.com/hje-4s2p.aspx I would think then the charging jack should at least support 6 amps. My search online though has shown it difficult to find a barrel connector that supports 6 amps of current. I have found plenty of 5 amp connectors such as https://www.digikey.com/product-detail/en/cui-inc/PJ-064A/CP-064A-ND/2627221. There are a few supporting 6 or more but they don’t have 3 contacts. I realize that if the engine doesn’t need/draw more then 5 amps, then this isn’t a problem, however I have no idea how many amps either of those engines draws.

Does anyone know what sort of amperage these engines draw? Would it be safe to jut use a 5 amp connector? Am I miss-understanding how this would work?

#2

Well, how often will you draw a continuous 5 amps? You have done measurements on current draw, so you know.

Personally, I would never use that type of connector for anything other than charging, where you won’t maintain high current for long.

I’d use the molex style, that you already find on battery packs, designed for supplying power, not just charging.

The standard molex 0.093 pin is rated for 17 amps.

http://www.molex.com/molex/products/family?key=standard_093&channel=products&chanName=family&pageTitle=Introduction

Greg

#3

I never really took measurements for current draw. I have measured the battery voltage when not under load and tested engine performance. I do not know how much current they draw. I would assume the most current drawn is when the smoke generator is on and the engine is pulling a heavy load up a hill.

I was toying with the idea of that wiring setup, as I know people who have used it with success but I am still inclined to go with the simpler setup that is shown on the second page. The simpler setup doesn’t allow for an external battery to be supplied. It has been rare for me to need to supply external power to the engines. In the few cases where the engine ran out of juice, I just switched to another engine.

Going with one of those other connectors seems problematic. The general process with the document I shared, is that the barrel jack is setup to face out the back of the engine. If the battery car that is trailing behind becomes uncoupled, the plug pulls out and no damage is done. The barrel connector jack also provides the ability to change behaviors when something is plugged in, vs not without requiring a separate switch.

#4

I see what you mean. That jack is not rated very high, and it has an internal switch. If it was me, I would use a more robust connector and my own DPDT switch, also rated 10 amps.

If you don’t use it a lot, try it, all it can do is burn up ha ha! (won’t really catch fire, just mess up the switch contacts or overheat and melt part of the housing)

Greg

#5

Why do you find the Airwire switches and charging jack inconvenient? This seems like an awful lot of fuss to go through, just because you don’t like plugging in from the bottom.

Yeah, I’m grumpy, this morning. Snowing, again. Still, the question is valid, at least to me.

#6

My engine is stored in my train shed on tracks. To turn it on and off an engine, I have to reach down between the engine and the cars/engines on adjacent track, then reach under to flip the switch. On a GP-38 there is plenty of room under there but on the SD70 your hand hits the truck and its cumbersome.

To charge the engine I have to remove the engine from the track, and flip it over. While this is ok some times, I’d prefer to not have to flip it over. Further, the motor wires/trucks on the SD70 also get in the way of the charging jack.

I plan to put the charging jack and the switch on the side of the fuel tank. The switches are black and so is the charging jack I picked out so they will both be minimally visible but super easy to access. I am also adding a small LED volt meter with a switch to turn it on and off. I toyed with the idea of putting a charging jack on the nose, and to support external batteries, but getting a charging jack that supports the amperage that the battery can potentially provide is difficult. I also don’t really want to cut holes in the nose of the engine so I will probably sick with my plan of putting everything on the side of the fuel tank. I am also moving the battery to the fuel tank for easy future replacement. I am not ever planning on putting sound in my engines.

#7

too bad the USAT don’t have lift off covers on top like the Aristos do…

Greg

#8

Looking at the SD70, it does have screws at the top of the hull by the smoke unit. I suppose one could remove them and find a way to keep it attached in place and be a lift off.

#9

The GP9 has the lift-off dynamics. I’ve thought about putting a second jack up there. Not that that helps Nicolas at all.