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.
"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
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.
Frank, Stan Ames discussed this subject to some extent in '94.
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.
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
Frank A. Rosenbaum wrote:
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
Check out the "Gold Series" with "USP Technology" at
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
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.
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
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
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.