Battery Eliminators

 A typical booklet from 1933 provides an illustration of the point radio had reached only ten years from the commencement of national broadcasting. Battery powered sets were rapidly being superseded by mains powered sets.



Click the front page to read the catalogue, including the enclosed letter to the customer (note its about 7 MBytes)


If you'd like to buy one or two items you could try filling in the form and posting it?


 Here's another booklet produced by Cossor produced about the same time.. no battery eliminators included, but you can see the type of batteries used and their prices. Click on it and see the whole booklet.


 I also found an advert for Telsen battery eliminators in which one of their selling points is "an artistically finished metal case" because they wanted to make clear the top item would be suitably covered up perhaps?

This was included in the magazine "The Telsen Radiomag" Vol 1 Number 6 which is very coy about the date of publication. I did notice though that Daventry is noted as being on 1500 meters and, as this only started in 1934, the magazine must date from no earlier than this... not much later however as Telsen went bust by 1935 and, after being purchased from the Receiver, made domestic electrical appliances.

You can read Issue 1 of their Radiomag here...

I wonder why the company folded? Maybe there's a clue in their magazine as Issue 1 seems to have one advert and Issue 6 no adverts. That is for anything not made by Telsen. If you look at other magaziunes of the period you'll see they were financed through advertising. It seems Telsen was basically charging radio enthusists for their parts catalogue.



 The Ekco company were leaders in the manufacture of mains eliminators and battery chargers for radio sets

(click the valve to read more)


 Here's an early advertisement from 1928 which covers a total of 16 models. Their new factory at Leigh on Sea had just been opened and the company was just starting out on in real manufacturing. Note the crafty way of increasing published prices by excluding the valves essential for operation of their equipments and Mr Marconi's tax. I'm not sure this practice would be tolerated nowadays. Here's my £3:7:6d can I have an M2 please. Not unless you shell out another 25 bob mate. That's £4:12:6d. Forget about 20% VAT, that's a whopping 37% extra... and don't forget that Marconi pinched 18.5%.. almost like paying modern-day VAT to Marconi, just because he had the foresight to buy radio patents.

I'm now wodering anbout the ad... As the magazine from which this advert was taken was aimed at retailers, presumably the prices are fixed selling prices and don't include wholesalers discount, retailers profit and purchase tax?

Why did Ekco and others use the tactic of adding valves as extras? Why not just offer their products fully assembled ready for use at higher list prices? It was all a subterfuge. You bought your battery eliminator from Ekco then popped round to your local wireless shop who had a range of foreign valves under the counter. Here you are sir a nice rectifier valve for your M2.. that'll be two and sixpence..


 Click on the front page below to see the whole booklet. This was my grandad's and you'll see some notes he made in 1932 including one about the years guarantee for his battery eliminator running out in December 1933. He was born in June1885 so would have been 47 when he made the notes, including the wiring to the mains adaptor. Ring mains were unheard of and skirting board sockets rare. Mostly things were plugged into a light socket. Sometimes three or four sockets dangled under the light bulb...

You'll see, if keen-eyed, the mains adaptor on the 1928 M.2,A.C. above looks different to that below. It was probably turned from wood whilst the newer one is in bakelite.

Bakelite is another story. Such was the pressure from wireless manufacturers on the government Ekco were forced to open a bakelite manufacturing plant to circumvent duties imposed on their importation of bakelite radio cabinets from the continent. I wonder if they made their own bakelite mains adaptors in their factory? Who knows??

 The following models are from their later range, introduced about 1930 See some earlier models


The Ekco AC12

Model AC12 with its case removed

Stamped on the chassis is the Serial No 247149


Ready for refurbishment is this Ekco Model AC12. Ekco made battery eliminators from 1925 and the booklet (left) dates from August 1931. In it are described seven models for AC mains and one model for DC mains. Written inside the back cover in my granfather's handwriting is the note that the guarantee expires in December 1933. He must have purchased his model in time for Christmas 1932. Other similar models were the AC18 and the AC25.


 Specifications for two typical standard AC models available in 1931 are given below:-


120 volts up to 12mA or 9mA if the 80 volt 2mA or the SG 60-80 volt 1.5mA tappings are in use.


120 volts up to 18mA or 150 volts up to 13mA or 14mA and 9mA respectively if the other HT voltages are used

Adjustable 50 to 90 volts up to 3mA

Lower voltages obtained with base connector screw in position "L", when 100 volts at up to 14mA to 120 volts at 10mA depending on drain from other outputs.

There were a number of AC mains models which included battery chargers, two of which are described below..


As the AC12 but includes an accumulator trickle charging output

As you can see in the picture above, the design of the AC units is pretty basic, using a double wound mains transformer, an iron cored HT choke, a capacitor block and some resistors. Rectification was carried out by a small, finned, full wave metal rectifier. Voltage outputs were dependent on the amount of current being drawn. This is due to the relatively high resistance of the rectifier and the use of resistors to provide the lower voltage tappings.




The Ekco K25

click picture to see large images

This model is larger and heavier than the others depicted in the catalogue shown above and carries the label "Combined Unit" as like the K12 includes an accumulator charging facility or filament supply as well as an HT supply.

Underneath are tappings for 200-225v and 225-250v mains at 40-100 cycles and also a setting for 2, 4 or 6-volts. this would allow the unit to feed either an accumulator or a set of indirectly heated valves. If directly heated, battery type, valves were to be fed directly the level of hum from the crudely rectified low voltage would be overpowering but this rough low voltage DC supply would be perfectly good for mains type valves, with their isolated heaters.

On the high tension front, numerous voltages are provided for screen grid valves and several tappings for different HT levels.

This example has had some modificatiuons made. You can see a stud diode, a variable resistor and lots of capacitors which look like they're from the 1960s.

The red/black mains lead dates from the same era.

Serial number 103885



The Ekco DC15/25

click picture to see large images

As DC mains were quite common before WWII, Ekco included a DC model in their range. Because of the vagaries of current and voltage (as explained in Ohms law) there's a tapping under the unit for running at either 15 or 25mA (The designation for milliamps loosely inscribed as "MA")

Tappings for screen grid and HT are provided, as the with the AC units, by sockets and a jumper on the centre panel.

This example has been refurbished by its last owner and finished in a matt black paint. Originally it would have had a shiny bronzed finish.

Serial number 215432


 Also manufactured by Ekco was the TC1 accumulator trickle charger for 2, 4 and 6 volts


Click picture to see more

This is an accumulator charger, dating from around 1929 or maybe a little earlier and is the precursor of the later TC1

This early model is in the same range of products as the boxier looking models shown here



Exide High Tension and Low Tension Charger, Type AC64 S/No 1280

Click picture to see more

This old unit probably dates to the early 30's and could charge an accumulator and also supply HT for a battery operated radio.It used a metal rectifier for HT rectification.



Safety-wise the newer units complied loosely with new IEE regulations in force in 1931. These called for a number of recommendations, for which the units only comply if the user follows the instructions in the booklet.

Earthing the case is done via a wire to a terminal provided on the underneath of the chassis. Most people would use two-wire mains cable, often connected to a light socket via an adaptor. An external earth wire would have to be carried from the receiver to a suitable earth connection.

There is no fuse included in the unit although the regulations called for two fuses, one in each side of the feed to the unit. Ekco got round this by advising the user that such fuses were to be found at their mains distribution board and if this wasn't the case then they were advised to fit a couple of 3-amp types.

Headphones and loudspeakers used on the radio being powered by a mains eliminator had to be connected through a double-wound transformer and customers were advised to procure one from their radio dealer. No doubt many users were surprised by tingling sensations as they adjusted their headphones.

I would imagine that in many cases none of the above recommendations would be followed. Nowadays the manufacturer has to ensure that his equipment is foolproof, leaving no latitude for the end user to ignore safety.

An interesting quote from a 1938 publication by Westinghouse..

"It is essential to use a mains transformer in all cases where a rectifier is used in the voltage doubler circuit, in order to ensure that the receiver circuit is isolated from the supply mains. If a transformer in not used, there is a possibility of the "live" side of the supply becoming earthed through the receiver earth, with consequent damage to the receiver and rectifier".

No mention of electrocution if the receiver is not actually earthed.


see more old battery chargers