Review: Massoth 8151601 eMOTION Powercap micro

Review published: 9 July 2015
Latest update: 10 July 2015

A power buffer (also called ‘Goldcap’, ‘powercap’) is used to compensate short-term track power interruptions for G scale locomotives. When track power is interrupted (e.g. dirty track, insulated track section, switch frogs), the power buffer provides power to the motor so the locomotive keeps running and also the locomotive functions (lights, sound) keep working. Once track power is ‘back’, the power buffer recharges itself. The buffering time depends on the connected load, driving speed and the current charge level.

Massoth offers two Powercaps: the ‘micro’ (#8151601) and ‘maxi’ (#8151701). Massoth designed the ‘micro’ for small locomotives with 1 motor, as these locomotives typically don’t offer much space. The ‘maxi’ is larger, and is aimed at bigger locomotives.

For this test, I will install the ‘Powercap micro’ in the small V 20 diesel engine from PIKO (read my review of the V 20 here: Review: PIKO G 37550 V 20).

Product Information:

Manufacturer: Massoth
Article Number: 8151601
Product Description: eMOTION Powercap micro
MSRP (2015): € 49,95

Massoth 8151601 eMOTION Powercap micro

Technical Specifications (copied from Massoth manual):

  • Operating voltage: 6…24 V DC
  • Maximum charging current: 500 mA (at 22 V track voltage)
  • Self consumption: ~ 10 mA
  • Maximum output voltage: 18 V (at full charge)
  • Maximum output current: 1 A
  • Buffering time: up to 30 seconds
  • Charging time: ca. 45 Seconds (at total discharge, 22 V)

Power Buffer Install:

Included in the package is the powercap itself, a manual (German / English), and a switch.

Massoth 8151601 eMOTION Powercap micro Review

The powercap consists of three segments. The first one contains the charging circuitry, the second and third contain three big capacitors each (they store the energy).

Massoth 8151601 eMOTION Powercap micro Review

First of all, find a good place inside the locomotive to install the powercap.

In the case of the V 20, it has plenty of space inside the cab, and there’s also a ‘hole’ in the chassis which offers some extra space. Before I mount the three segments properly, I will connect the wires to make sure it’s working.

Massoth 8151601 eMOTION Powercap micro Review

The powercap comes with a black/red/white cable. The wiring depends on which decoder you have, there are three ways to connect the powercap:

  • Massoth decoder with ‘Buffer Control’ (BC) terminal – Some Massoth decoders offer a ‘BC’ terminal, which automatically deactivates the Powercap during programming procedures. No additional programming is needed.
  • Massoth decoder without BC terminal  – Older Massoth decoders may not offer a BC terminal, but they can still offer the automatic buffer control on a function connection (A4 or A5 depending on the decoder type, check the decoder manual). Some additional programming is needed.
  • Other decoders – Decoders without buffer control can still be equipped with the powercap using the enclosed switch. In this case, it is required to switch off the powercap during programming procedures.

Check the manual of your decoder and also the Powercap manual to decide which approach you need to take. The installation and configuration steps below may be different for your particular use case!

In my case, I have a PIKO decoder installed. Since the PIKO decoder is produced in cooperation with Massoth, luckily my decoder features buffer control on function connection A5, so I won’t need the switch.

The black wire connects to the minus (-) terminal of the left side of the decoder:

Massoth 8151601 eMOTION Powercap micro Review

The red wire connects to the positive (+) terminal on the right side of the decoder. The white wire connects to the A5 terminal.

Massoth 8151601 eMOTION Powercap micro Review

Once the three cables are connected, some programming is needed. According to the manual of my PIKO decoder, I needed to set CV 118 to value 31 to activate the buffer control function. In addition, I needed to disable analogue operation with CV 29 (bit 2).

With the programming done, I did a quick test to see if the buffer was working. It did, so now I can give the powercap segments a permanent place inside the cab.

I mounted all three segments with double-sided sticky tape, so they don’t move around inside the cab. A pretty neat install, if I say so myself 🙂 .

Massoth 8151601 eMOTION Powercap micro Review


The video below shows the locomotive keeps running for some time after the track power is disconnected. The sounds cuts out first, and a bit later the loco comes to a complete stop.

Of course, this video shows an extreme case of power loss. In typical outdoor railway conditions, track power losses usually are much shorter which makes it almost unnoticeable when the power buffer is kicking in.

The lights stay on the longest, the front lights kept working for another four and a half minutes and I’m not even sure if the power buffer was fully charged at that point.


Having contact problems with some locomotives on your layout? A power buffer can definitely help you out. The Massoth powercap does exactly what it says on the tin. It can be installed on any DCC decoder, however connecting them to a Massoth decoder is the easiest as in that case you don’t need the switch. The included manual is very good, and answers all your possible questions. Highly recommended.



All modifications at your own risk.
Found a mistake? Please let me know.