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Steve P

Current requirements.

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I am building a G scale outdoor railway using an MTH  One Gauge Big Boy.

Does anyone know the stall current and/or "max effort", "average", etc currents for this engine?

I need the info for planning the battery setup.

Any insight as to maximum grade I can use when installing track would also be helpful...



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max grade is tuff to answer I would think? It always depends on what you're trying to pull up the hill. I have under 2% and I add helpers to excessively long trains (50 cars+). I would pull dramatically less as the grade worsens. I don't work any single engine harder than it should.

The metal gears in the MTH engines hold up better than anything else I've run. The traction tires maybe the weak link. When they're still good rubber, they'll be fine. The triplex has a whole extra set of drivers in the tender like it's own helper attached. I re-inforced the rear end for heavy trains. My new MTH Big Boy has not peen pushed hard yet.

 One of the techs here can probably answer your decoder specs better than I can. You are driving 2 motors remember and the smoke when used. I figure around 2 amps for the engine and another amp for the smoke is average. The stall could push 5??? I've never stalled one.

I would size the batteries and decoder for that and would recommend leaving the smoke off. See what others think.

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So something like this:


should give me 4-5 hours of runtime?


Sounds like grade is going to be an issue.  I have 55' of rise in 1000',

which if I understand the math, is 5.5% grade.

I've read several articles that state 3% grade is ok (but not specific to the BigBoy).

I can keep it down to 3% with several switch backs (and a lot more track!) if

I plan ahead.


I would like to pull 30-40 cars. Maybe a pusher is in my future...


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If that's right, 5.5% is huge! You'd be limited to pulling maybe ten cars. I would consider changing that. Maybe have the lower end up on table height? Can you change the grade? Switchbacks were used in the old days and for the same reasons, I would not use them today if possible.

 Some G scale cars are heavy, some don't roll all that well. If you like big trains, you have to work on several things. Keep the grades easy, make rolling stock roll well, etc.

 As far as for the battery, I don't use them. So I have no experience at all. I do know that motors run much better in command mode. They draw less current. So you don't see the big amp draws as when there's no decoder driving the motors. I have to believe that would help even with battery use?

 My old USA trains engine drew over 5 amps under load. When I switched it to command, the amps went way down to like 2.

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Its almost a straight shot up the "canyon" from my patio to the picnic area at the top

of the property. This is my "ideal" path.  It goes thru the orchard, along a scenic hillside,

beside the pond, thru a large aspen meadow, then finally to the picnic area.

Going the entire path is more important than the number of cars I pull (but the Big Boy

screams "I should be pulling a LOT of cars").

There is a hillside half way that I could do 2-3 switchbacks, adding 100' or more each pass.


The patio is the proper area for the main terminal, and the picnic area the

proper area for the terminus.  I'm adding a raspberry pi3 to the control boxcar,

hopefully allowing the ability to stream live video back to the main terminal (patio).


The setup will be strictly command mode, using fixed input 1 for the battery feed,

and fixed output 1 directly to the Big Boy.

I will be sticking to MTH cars for the most part, to keep scale uniform.  The one boxcar I have for the

TIU/WIU build seems fairly light, with nice metal wheels.  I also am considering the necessity

of going with ball-bearing wheels to handle more cars.


The numbers are preliminary, using a handheld GPS device.

A friend is coming over in a few weeks and we will do a proper survey with a transit.

I understand the ambition of my plans, and fully expect it to take 4-5 years (or more) to complete.



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It's good using the MTH cars as they roll well and are light. Some others stuff in 1/29, need modifying.

I would still recommend the track being elevated at the bottom if possible and some type of "Horseshoe curve" or Tehachapi Loop to get down lower to the final grade. I believe most here with experience would recommend staying well under 3% to avoid headaches. I tried it and ran into all sorts of issues like couplers failing, trains breaking apart, and even string lining. Don't even think of backing or pushing the train upwards!

 Smooth trackwork and slight even grades make life better. If you can't do it, then you can't. Just do what you can to help yourself to smoother running.

I have to think that even the battery life will be much shorter. To bad they don't self recharge going back downhill!


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My roaster is a mix of MTH and Marklin 1:32. After upgrading the MTH PS2 engines to PS 3 I can now use DCC for all my engines. Last summer I measured the power consumption using the Marklin CS1 and CS2 controllers. They have the option of showing Amp, Volt etc.


MTH 70-3009-1 Big Boy with PS 3.0

Placed om the track: 0.3 A

+ Sound and light on: 0.6 A

+ Smoke: 1.2 A

+ Speedstep 30 of 126 with 15 cars + caboose with lights: 2.5 A, 18.3 V (level ground).


I can't switch the MTH PS3 to DCS so I can't verify my impression that the MTH decoders are more power efficient in DCS mode than in DCC.


The way I have raised my layout might give you some ideas. See my-elevated-semi-permanent-technical-layout

Upwards 2.6 % and down 3.3 %.


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Just to clarify my previous statement, the motors run with lower current draw under the control of a decoder (cooler and smoother!). I did not compare all brands myself. I did measure the USA Trains SD40-2 under conventional vs. using the NCE decoder I had. I also looked at it now using the MTH PS2 decoder that's currently in it. Both use about the same current draw.

 So my finding agrees with Blid's.

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Thanx for the hard numbers, confirms my earlier impressions. I could go to a 22000mA battery but at added weight, think I'll stick with the 16000.

The "Horseshoe curve" or Tehachapi Loop mentioned earlier looks interesting.  I found a wiki on the concept of "track transition curve".

Does anyone out there go to the trouble of banking curves, or calculation of a transition?


I hope to have the TIU board mounted by end of the day and operational again.  I'll post pictures in a few days.


Thanx to everyone for the ideas.


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Got the TIU and WIU installed into a boxcar, pics attached.

The power wires currently are routed out thru the back boxcar door.

Its wired to my HO Big Boy track and running!

I have a 5-30v to 5v USB dongle on the way, will wire that into the boxcar to run the WIU

from the main battery.


So, the questions of the day are:


What gauge wire should I use from the battery to the control car (ie TIU)

and the control boxcar to the engine?

I'm thinking fine stranded (for flexibility) speaker wire in 16 gauge...

but perhaps thats way too big considering the run is only about 2', would 18/20 gauge be better?


What connectors should I use between cars?

I plan to keep them minimal in number, each one is a failure point.

Probably fixed wire out of battery car terminated with plug than goes

into socket on rear of control boxcar.

Fixed wire from engine, running under/thru tender, terminated with plug

that goes into socket on front of  control boxcar.




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Just some ideas. I never ran battery.

Wire is sized by the length and the current. Being so short, the length isn't much concern. So size it for the current, and then some extra cap. 18 would be fine for a single engine. 16 Maybe 2?

As for the connectors, I would suggest that on the output sides, if the connector came unplugged the ends shouldn't short. So at the engine/tender for example, use some type of female. Maybe better, to add some type of fuse?

There's so many connector types to choose from that could handle that current.

To bad they don't make super mini ones like these

Image result for neutrik connectors

Neutrik speaker connectors.

Maybe use the same type on the Aristo engines?


they are a little large. they only have 22 ga wire attached.

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It's been quite a while since I visited...  I have been detailing my progress on the Dead Rails/Free Rails site as my efforts are primarily on the deadrail aspect of the hobby.

For those interested I have 3 threads going there:

My control car/battery car design/build project:


My track design/build project:


A home brew signals, switch control, RFID project:


As winter around here shuts down outside play, current activity is on design of G-scale signal lights with 3-watt LEDs, switch control with RC servos,

and RFID identification of rolling stock.  I went with the 3-watt LEDs (those suckers are BRIGHT) as I can clearly see them from several hundred

feet, important with the size of my setup.  Everything is based around arduino clones for computer control. As with my engines, I am using WiFi

for the data link.  I hope to make them LCC compatible in the long run.







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About grades: Advice from an old boy in the hobby- Back in my HO days I had an around the room oval with a branch going down under from one side in double track to an underground fiddle yard (Do not copy this, it's a bad solution! As John Armstrong said) and came out the other end as a single track branch. For space reasons the grades were pretty stiff and as I prefer this I had most of my engines without traction tires. At that time there was very little steam era French freight cars on the market, so I used a lot of Zamak cast freight cars, very heavy!  Well it soon became apparent that anything above 2% grade was hopeless and that it was a good idea to keep the gradient under 1.8 %. Now this I learned from experience. That is also what I used much later on my gauge one garden pike for the branch leading to the indoor terminal and which crosses under the main oval. This has turned out quite good operating wise over time. More recently I learned from reading PRR history that  PRR master engeneer Thomson who engeneered the horse shoe curve solution for the Pennsy, that he kept to that limit on the westbound grade (the eastbound which was expected to haul much more traffic was kept to 1%).


I also model in HOe with a Saxon narrow gauge theme in the winter when its too cold and wet for outdoor operation, Now the Saxon system often used 3% on branches leading into the hills. I did likewise and thank god those consists are limited to 10 or 11 cars and those saxon 2-10-2 tanks are quite good beasties because otherwise not much could operate on those kinds of gradients. As I had known Edaville very well as a kid, I bought a Car Works SR&RL N° 23 prairie (the biggest it had almost) it couldn't handle a car and a brass caboose on that grade! It was quickly sold. So my advice is stay away from anything over that 1,8% and keep those curves as wide as you can, curves really take up as much tractive effort as grades. I am moving south to hopefully enjoy my garden railroad more months per year and to be able to use bigger curves then 10' radius I use today.

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