Kato SD40-2 - Deadrail Install with Railpro

[KPack]

I found the information I needed on this thread: http://rpug.pdc.ca/index.php/topic,235.0.html  Thanks Terry!

I purchased some 3.7V 700mah batteries from a hobby vendor online (banggood I think), that came in a 5-pack with charger for something aroud $20.  I then bought a few Pololu voltage converter boards from Litchfield Station, and some 2-pin plugs from Evan Designs (modeltrainsoftware.com). 

The hardest part of doing on this was figuring out where to fit the battery.  I used a Kato SD40-2 and the only place a battery like this would fit was in the fuel tank.  That meant milling off most of the metal from that area, which was a huge pain in the rear.  My friend was kind enough to do it on his mill for me. 

Once the milling was complete, I set the battery inside the fuel tank, routed wires through the frame and past the motor, then soldered it to one end of a 2-pin plug.  The other part of the 2-pin plug was soldered to the voltage converter board.  Then the power wires for the LM-2S were soldered to the converter board.  And that was it, really.  It wasn't much more complicated than that.

Here is an overview of the installation.  The Pololu converter is mounted to the styrene board right in front of the LM-2S module. 


Another view showing the wires coming up by the side of the motor


The battery inside the fuel tank


Look at how much room is above that speaker!  I love how Kato's motor is so low.


Here is a quick video showing how the battery works:

-Kevin

[William Brillinger]

Nice work Kevin!

[Alan]

Very cool. You really must report back on battery life after you have a bunch of hours of operation on the battery. The model plane guys seem to center around 100-200 charges for their batteries although they tax them heavier. Several battery testing web sites seem to agree on 500-1000 recharges max. Very curious to see how it plays out on model trains.

BTW Pololu makes all kinds of neat stuff for robotics. Their 2571 step-up regulator would allow you to get the normal RP 14.8V if you wish. It is slightly larger but should fit most places.

If you are thrifty like me, and can find the mounting space then check this out: http://www.ebay.com/itm/2pcs-MT3608-Step-Up-Power-Apply-Booster-Module-DC-DC-2V-24V-2A-NEW/171907688472?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D2%26asc%3D41451%26meid%3Dcfce865084c74c2f8361c6af72b22476%26pid%3D100005%26rk%3D5%26rkt%3D6%26mehot%3Dpp%26sd%3D191871557118

[nodcc4me]

Nicely done Kevin. Hard to believe you could fit all that hardware inside a diesel. 
Being somewhat electronically challenged, I'm not sure how you are able to run it with sound on only 3.7v?

[KPack]

Thanks guys.  Alan, the battery will eventually have to be replaced, and with Kato's fuel tank being mostly open, that will not be much of an issue.  I will end up cutting out some of the plastic in the center of the tank, and slide the battery out.  A replacement will go in and I will either tape/glue it to the frame, or add some styrene to the tank to hold the battery in.  I do need to look into Pololu more and see what other products they have that we can use.  I was really impressed with the size of the their board....it takes up almost no space at all.

Al - I have a ton of space in this locomotive.  Partly because Kato mounts their motor so low, and partly because the only things I'm adding into the shell are the very small Pololu board and the small 2-pin plug.  I purposefully mounted the battery in the fuel tank because I wanted to keep the interior of the shell clean.  The other thing I did (you can see it in the 1st picture if you look carefully) is I mounted a small strip of brass on the stryene board to use as the "common" for all the lights.  All the lights have their positive wire soldered to that board....it really helped to keep things clean and tidy.  And I always like to tuck as many wires as I can between the motor and the module so they aren't hanging all over the place like a rat's nest.

-Kevin

[Alan]

Being somewhat electronically challenged, I'm not sure how you are able to run it with sound on only 3.7v?

Kevin is using Pololu voltage converter boards from Litchfield Station. They convert the battery voltage from 3.7V up to 12V.

DC voltage up converters work very similar to the ignition system of old cars. In a car, points close allowing low voltage to charge the ignition coil. When the points open the coil discharges at a higher voltage. DC up converters function the same except at a much higher open/close frequency than car points and a much lower coil discharge voltage than an ignition coil. The coil discharge, instead of being sent to a spark plug, is temporarily stored in a capacitor. A regulator then drains the capacitor at 12V output. Before the capacitor runs out of juice the points have closed/opened again repeating the cycle.

EDIT Made an illustration showing the components:



Does that help?

We have to respect the laws of physics. Energy cannot be created, merely transferred. The wattage (power) needed to move the loco and play sound is the same on Kevin's system as it would be on powered rails. W=V*A. The DC up converter board is delivering the same wattage as the rails would be but it is doing so with 3.7V. Therefore, the amperage must be higher to make the equation balance. That is why I am so interested to see how Kevin's loco fares after the battery gets some life on it. New batteries always work good. Aged batteries, not so much.

[KPack]

That is why I am so interested to see how Kevin's loco fares after the battery gets some life on it. New batteries always work good. Aged batteries, not so much.

This will be interesting to find out. I don't run a ton unless I'm at someone's place on their layout.  So I may not have much to report for a while.  Worst case scenario is that the battery ends up going belly up much sooner than I anticipated.  But if that happens, I just swap the battery for another one.  These things only cost a few bucks a piece....maybe $5-6.  Plus batteries will likely improve over time, allowing smaller packages with higher storage capacity (at least I hope).

Anyways, I still need to do some testing with this.  I haven't hooked it up to normal Railpro locos yet to see how the start voltage/MU capability is affected.  In the end, this locomotive will always be paired with another SD40-2 (ScaleTrains) that will also be battery powered, so any negative effect on the start voltage won't be an issue.  I'm building a matched pair of SD40-2's that service my area....#1778 and #1999....they have been coupled together for years now serving the Central Washington area.

-Kevin

[nodcc4me]

Kevin, I was actually referring to everything you put in there, including the module, two speakers, Pololu board, battery and plug. I think the low Kato motor does make the  difference. Good idea on the brass strip.

Alan, your very cool diagram and narrative does help explain the required voltage gain. In another thread you mentioned that you were just an amateur at this stuff. LIES! 

BTW, what program did you use to make the diagram?

[Alan]

These things only cost a few bucks a piece....maybe $5-6.

On other forums I am on record as an anti-battery guy. Not because I love track wiring but for two primary reasons, one of which you mentioned:

First, my layout is all first gen 4 axle diesels. Batteries will not fit. Shucks, even an LM won't fit in my S-2s without shedding its plastic case and milling a flywheel! Doubtful batteries will ever be so small in my lifetime as to be practical in a little loco. This restriction is unique to my situation (or others with same). I get that. Not a direct fault of battery technology.

The second and more universally important reason, "These things only cost a few bucks a piece....maybe $5-6" There it is. My Fitbit made me aware I walk far more steps in a day than I would have ever guessed. I suspect the same may be true with hours on a loco. I like to play with trains and have a fair bit of track to do so on with quite a few locos. The life expectancy of a battery worries me greatly. If I had to install a new battery in each loco every year or even every other year, the operating cost would get ridiculous especially when compared to a one-time-purchase of power supply and wire. And I would still be left with locos that have to be charged regularly. Cell phone and power tool ownership has clearly demonstrated to me batteries are great when new. Two years of use later they peter out fast.

I dwell on this subject because way back in the LK&O design days I seriously considered battery power. You have to admit, there is a strong allure to having no track wiring. I am not trying to make my equipment run on other folk's crappy track nor am I too lazy to properly clean my track. Battery power makes no sense. Am I missing something?   

[KPack]

Alan - Batteries with their size and possibly long-term failure, make them less than desirable in many cases.  I can fit them in my locos (though with some difficulty....milling that frame took forever), but mine are also MUCH larger than what you have.  With my SD40-2, I can easily pop the hatch and plug in it, but with other locos (SD70 family, any GE) I can't, so I'd have to come up with another solution if I were to use battery power....have the plug in the fuel tank, etc. 

Would I ever convert all my locomotives to full battery?  No.  At most I will do this and the other SD40-2 I mentioned earlier.  As it stands right now I don't feel that battery is practical for the long term, but I have to admit it is a blast to play around with.  The fact that the locomotive will never stall, ever, on any track, is appealing.  But I don't relish the idea that constant battery replacements may in order for the long term.

Arguably the best way forward to prevent the occasional power loss problems would be to do a keep-alive, as has been discussed in the other thread.  I don't think that layout wiring is going away anytime soon, so might as well use it and keep-alives to maintain a constant source of power to the module.  That is probably the route I will take on the remainder of my fleet.  I have several locomotives that never lose power, but many others that seem to be more prone it.  A bridge rectifier and KA would make easy work of that problem.

-Kevin

[Alan]

BTW, what program did you use to make the diagram?

Photoshop, started with the image from eBay.

A regulator then drains the capacitor at 12V output.

You may be wondering where is the regulator on the eBay cheapie board. There isn't one. That's why it is $0.58 from China. The output voltage on the eBay unit is controlled only by the switching frequency (potentiometer setting). Temperature, load, and driven circuit capacitance and inductance are just a few variables that will cause this unit's output voltage to fluctuate somewhat. But hey, what do you expect for 50 cents? 

The real-deal DC up converters (like Kevin's Pololu unit) do use regulators. And they cost a good bit more than fifty cents. The question is... is that level of precision needed for model trains? I don't know. I tend to think it isn't.

[TwinStar]

This could change everything.

http://www.dailymail.co.uk/sciencetech/article-4219518/New-battery-store-charge-TEN-years.html

[Alan]

Yes, that would be a game changer.

Relative to my earlier comment... 'Lithium ion batteries don't even survive 1000 complete charge/discharge cycles,' said Dr Michael Aziz, a professor of Materials and Energy Technologies at Harvard University."

[KPack]

Quick testing update.  MU'ing with normal track-powered Railpro units does not seem to have any negative effect.  The battery-powered locomotive pulls just as well being the leader or a follower.  Also, I haven't charged the locomotive for two weeks.  Granted I'm only running for short periods of time, but it shows me that I don't have to always have this thing on a charger.

-Kevin

[KPack]

I just read through Bruce Petrarca's column in the March 2017 issue of MRH, covering the options for going deadrail with DCC.  All I can say is "wow".  Nothing wrong with the article, and Bruce is extremely knowledgeable when it comes to DCC.  I'm just amazed at how complicated it is in order to get deadrail with DCC.  So many different components are required in order to make it work.  You'll need a transmitter to plug into the existing DCC command station, a receiver on the locomotive, the DCC decoder, a battery management board, and the battery.  That's a lot of equipment to stuff inside a HO locomotive.  Oh, and if you want to program that locomotive like you would a traditional DCC locomotive, you'll need yet another adapter that allows commands to be sent to the locomotive and for the locomotive to read back.

With the set up I did here I used a battery, the Railpro module, and very small Polulu converter board.  Done.

Give the article a read if you can.  It will make you ever more grateful for Railpro, even if you don't plan on doing deadrail.

-Kevin