Making a battery backup

I am wondering about making a battery backup for some small switchers where
if track power is interrupted the train will still run. I am using Digitrax
DCC and in some locos sound. I have a tiny 12 volt battery that is used for
a garage door opener and think I can fit it and some tiny switching circuit
to detect when the track power interrupted. Similar concept to the computer
battery back-up's only to fit in HO trains.
Reply to
Frank A. Rosenbaum
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"Frank A. Rosenbaum" skriver:
How will you get the train to continue at the same speed ?
Find a capacitor and mount it across the DC on the decoder, but remember that the decoder will reset, if it does not get a DCCcommand within a certain timeperiod.
Reply to
Klaus D. Mikkelsen
Good evening Frank;
In truth, a UPS is intended for a single role: emergency power to give people time to either escape, alert authorities, or do a clean shutdown. By this, I presume that you wish to park your locomotives or return the train to a specified start point.
My suggestion would be to take two UPS of the same rating and wire them in series for the locomotive voltage (24V) for the locomotive. You would also need lighting (12V) so you can see what you're doing using single taps from each UPC.
Cheers, John
Reply to
John Fraser
No that is not my intent. I want to be able to power a decoder and motor over switches and other 'dead' spots. But I want it to switch over automatically from track to battery and back.
Reply to
Frank A. Rosenbaum
"Frank A. Rosenbaum" skriver:
But how do you wat to secure that the decoder gets the DCC commands it needs to keep running ?
Reply to
Klaus D. Mikkelsen
Frank, Stan Ames discussed this subject to some extent in '94.
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Things haven't changed much since then except some decoder manufacturers have pads you can solder a "keep alive" capacitor across - probably driven as much by the desire to keep the sound alive as to keep the engine going.
You might be able to use a rechargeable battery too. I have a very small ni cd battery I'm using to keep lights from flickering in a doodlebug.
Reply to
Frank, You can get a cheep power inverter to run off a 12 volt battery and prob. run the digitrax and (depending on the batt size) your whole layout for days. Last year I had a 24 hour blackout in my house. While I was at work my wife had a small TV, cable box and lamp running for about 24 hours off a car batt.. When the power came on I just charged the batt. up. Summer is blackout season so this year my layout gets one.
Mike Rapp
Frank A. Rosenbaum wrote:
Reply to
And he'd be better off to get a deep-discharge marine battery if he's planning to run it way down - car batteries don't respond well to that.
Reply to
Steve Caple
Why reinvent the "wheel"?
Someone else in the thread has mentioend Stan Ames (and Lenz by default). Lens has a series of decoders with UPS already built-in into the design.
Check out the "Gold Series" with "USP Technology" at
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Like others have mentioned, just adding a battery is not going to work. If a decoder loses the DCC signal, it will not continue at the last speed. It'll probably start slowing down or at least it will reset and then if analog mode is enabled it will then start running in analog mode at the speed determined by the battery voltage. This will not all be seamless.
Also different decoders handle this type of scenario differently. Some might be faster in resetting than others.
The Lenz Gold Series with USP take care of all of the above.
Reply to
Peter W.
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Yes I do have a good deal of experience with backup power since about 1993.
Indeed my wife has a close relationship with Lenz. I prefer to work with multiple manufacturers (including Lenz) so for the most part tend to like products from many manufacturers.
Let me provide some background on backup power.
In 1993 I tried using a large power battery connected to the track inputs of a decoder. A digital circuit breaker was used so that when DCC was present the circuit breaker cut out the battery and when not present the battery powered the decoder. In theory it was great. In practice it did not work very well in extended use. For one thing if there was a short, the DCC power shut down and the battery continued to power all the locomotives on the layout in an uncontrollable (yet constant) speed.
Next we tried large caps (eight 4400 uF per locomotive) Some help but lots of disadvantages. Most of my locomotives have a single 4400 cap but this is more for sound then for motor control.
I am now converting to the Lenz design using 12 AAA batteries per locomotive. (12 is for voltage related to the charging scheme and is not needed for power). I plan on trying 12 button batteries as this should work as well. Lenz is developing a capacitor based system but to date for Large Scale the battery approach works better.
What is unique on the lenz design is the way they pick up the DCC signal. Past approaches all used analog conversion as the mechanism but the problem is that you do not get the DCC information. On dirty track the packet loss can be extreem so back up capacitors sound better then they work in practice.
Most decoders use a sampling or edge detection on reading the DCC bits. The Lenz approach uses a capacitance pickup technique so the change in polarity of the DCC signal causes a measurable change in the track to wheel capacitance which is used to pick up the signal. (note the metal track and metal wheel with dirt (an insulator) is by definition a capacitor).
In practice this works extremely well. The decoder always gets the signal and the backup power recharges when on clean track and discharges on dirty track. It takes about 30 seconds or so before a discharged battery pack has sufficient power to be effective. A side advantage is that I have removed the large capacitors as the sound units are also powered from the decoder which has backup power. This also makes programming much easier.
I am considering converting my entire roster to this new technology.
Stan Ames
Reply to
Stan Ames

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