Spotlight on LU”s Battery Locomotives

Published: 10:34AM Jan 19th, 2012

London Underground relies heavily on the odd-looking, diminutive battery locos used in pairs for its enginering work.

Spotlight on LU”s Battery Locomotives

LITTLE & LARGE: LU battery locomotive No. L15 at the rear of a weedkilling train at Earls Court on May 18, 2010. A District line D-Stock train conveniently waits on the westbound main track to demonstrate for us the size difference between tube and subsurface stock. Kim Rennie

ONE of the more unusual locomotive types to be seen on the London Underground is the battery locomotive used for moving around engineers’ trains. Strictly speaking, these locomotives are not just powered by batteries because they can take power from the 630 volt DC current rails too, so they should be called ‘battery/line locomotives’ but everyone refers to them simply as battery locos. When current is available, they run off the conductor rail supply but, on work sites, when current is switched off to allow maintenance to take place, they rely on their batteries for power. The batteries provide only 320v so the traction motors work at both voltages.

They are usually left on charge in depots or sidings during the day to make sure they are ready for night work. Woe betide you if you forget to switch over to ‘charge’ when the loco is stabled.

Prewar design

Another remarkable feature of these machines is that their design goes back to 1936, when the first order for nine of the locomotives was placed with the Gloucester Railway Carriage & Wagon Co. Over the years, various additional machines were ordered right up to 1985, bringing the total built to 52. All of them were built to the same basic design, having a cab at each end with the batteries between them. The total weight was 60 tons, the whole lot squeezed into the tube tunnel loading gauge.

Usually, the locomotives had old bogies and motors removed from scrapped District, Metropolitan and Tube stock trains and the later ones had similar bogies built specially for them. The traction equipment was supplied by GEC and it was unusual for the Underground in providing series, series-parallel and parallel control of the four motors.

The oldest locos have now been withdrawn but most of those dating from the 1960s and 70s are still around. Curiously, the most recent ones, built in 1985, have all been withdrawn. They had electrical equipment supplied by Kiepe and were not compatible with the older members of the fleet. They did not prove very reliable and eventually fell into disuse.


The underground always uses two locomotives per train, one at each end. This removes the need for a single locomotive to run round the train when it needs to reverse. The idea is now common for main line engineers’ trains too. Because it’s often impossible for the driver to change ends in the tube tunnels, the train will have a driver on each loco.

Locos are provided with Buckeye and hook couplers at each end. Originally they had hinged buffers that had to be manhandled into position to allow coupling to standard main line wagons. They were later replaced by retractable buffers.

Automatic Train Operation

When the Victoria Line opened in 1968, it was designed from the start with Automatic Train Operation (ATO). In order to allow engineer’s trains to run without having to take a possession, eight new locos were fitted with ATO. Although it was allowed to fall into disuse, the ATO was reinstated on six locos in 2007 to help with the line upgrade programme and they will now be converted to the new ‘Distance to Go – Radio’ ATO system installed as part of the 2009 Tube Stock replacement project. Another block of 18 locos have both Central Line ATO and the Jubilee Line’s Thales supplied transmission based control system.


Abiding memories of them were the button-type deadman master controller handle that soon bored a hole in the palm of your hand, the cold and draughty cabs and the old style brake rigging that had cast iron brake blocks weighing 28lb (12.7kg) each.

Getting one of those up into the small gap between the 240hp electric motor and the bogie frame was not easy. On the early locos, there were only eight blocks per machine; later ones have 16 blocks.


Speaking of cab amenities, or the lack of them, one loco, No. L24, has been through a rebuilding programme at the Underground’s workshops at Acton Works. It was completed in 2010 after almost two years in work. Most of the modifications are internal and related to the installation of new, more efficient batteries that are easier to change but they also provided much needed cab improvements. The programme is being extended to the remaining 28 locos, with two of them currently in the works.

LU World by Chris Westcott & Piers Connor

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