45 volt battery pack - valve/tube portables

 

Many fine valve/ tube portables fell into disuse when supplies of batteries dried up. Typical is the 45v ht battery used in many sets. Collectors wishing to run these radios are faced with a dilemna. Should they use a mains powered battery eliminator (and so lose the "portability" which is so much of the attraction of these radios) or build an onboard substitute ht battery using modern cells? Having just acquired one such set (a pristine Sears Silvertone 1956) I faced this problem. Simply taping together five 9v PP3 batteries was ruled out - it was only a one-shot fix, expensive if repeated and it just looked so aweful! So how to generate 45 volts from maybe 6-9 volts battery input ?Through an Ebay search I tracked down a "voltage up-converter boost module". This measured just 60/30/20mm and would accept any dc input voltage from 4.5-32v with a user-adjustable output 7-60 volts. Emails to the supplier confirmed that it would do the job. They quoted that, as an example, for an output of 45v @ 200mA the unit, if powered from a 9v transistor radio battery, would consume current at 1.3 amps. This particular unit has a maximum current input limit of 4 amps so no problems (and higher current modules are also available.) And I later discovered that these small portables ht can be as little as 50mA. I plan to power the module from four 3000mAh 1.2v Ni-MH size  AA cells. I estimate from   a full charge they should provide 45v@ 50mA for over four hours. Cost - the module is on Ebay sale currently at $7-20 USD including international postage. Ebay item number 390629620299. Add to this batteries, battery holder, in-line fuse (good practice) and a small plastic box and this should all cost no more than about £12/$18 based on Ebay sellers' current prices. So with a readily availabe 1.5v D cell for the heaters my radio and many more similar can be  truly portable once more.

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Actually the HT is is 9mA to 14mA depending on model. The inverters give poor battery life and often RF noise. A problem is also on/off switching. 10mA perhaps typical on a 4 tube set.

I have built several inverters for 45, 67 and 90, (many years experience designing SMPSU) and used a reed relay & coil as LT current sense to automatically power.

But I prefer now to make battery packs as authentic as possible with out rechargable cells (they go flat quickly if not used). My aim is to recreate the orginal capacity as close as possible.

You don''t say which 45V pack you need though.

Here is one that can take 30 x AAA cells easily UK Ever Ready B104 (similar to US Eveready 482). With a bit of care and a custom holder 30 x AA cells are possible which if Alkaline is slightly more than original Layer cell capacity (over 2700mAH at 10mA). The AAA cost the same but give 1/2 capacity (1200mAH approx at 10mA for Alkaline). The PP3 are worst value and the Alkaline ones use 6 x AAAA cells approx so don't fill the case as well as the layer type (560mAH vs 450mAH approx). The 5 x  PP3 though  can be used. The B126 90V pack is small so it can only easily take 10 x PP3, but I have used 6 x stacks of CR2032 coin cells paralleled with 6 x 1N4148 diodes. These are about 10c each in bulk from Asia and last much longer than the PP3 with up to 15 years shelf life.

Have a look at the replica batteries on my collection.  I can supply the instructions and file to print. At this stage I can create a reasonable facsimile from a photo and the dimensions.

 

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Hello Michael and thanks for all of that. Inside the radio it says that is uses the Silvertone No.6485, a version of the generic US 45v "B" battery .Google took me to Eric Wrobbel's excellent battery collection, one picture showing the Silvertone 6485 is in the picture flanked by Emerson and RCA equivalent "B" types. Looks like the grand-daddy of the PP3 with the metal cased body and familiar polarised snap connectors. I suppose a replica could be made of tinplate? My thinking with the module is that it's cheap to buy and run and can initially be used outside the set for testing, even gradually winding up the ht gently at first, on old sets like this "variometer" style. It might even end up as the core of a handy variable voltage bench psu. All the fun of experimentation!

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No point in "winding up HT slowly".

I take tubes out and on current limit start at 10V on Bench PSU on HT rail and gradually go to 32V. That tells me if any Electrolytics need replaced.

I check out leakage of paper caps, especially on O/P plate, grids and screens.

Sounds like a Eveready 455 , NEDA 201, IEC 30F40 originally in card, then tinplate and now (still available!) in plastic.

The Eveready 467 (NEDA 200) is similar style, but larger and 67.5V. It's often simply labelled as a "B" battery with the 467 in very fine print. The Eveready 460 is also smaller 45V

But a quick check reveals a different shape 45 pack

Silvertone 6485 = RCA VS 086, Burgess U30  Eveready 415, NEDA 213, IEC 30F20, A415  , BLR102

 Size 92.5 mm × 16 mm × 26.2 mm

A CR2032 coin cell is 20mm  x 3.2 mm 

A stack of four fits in 16 x 26.2 easily. = 12V,

Four stacks will fit to give 48V, leave one cell out and you get 45V

15 cells is under $2.50 from Asia.

What model of radio is it?  It must have maybe 6mA to 8mA HT to use such a small pack!

Something like an Emerson 747 will use maybe 4mA to 5mA HT. So will the Silvertone 4212, I really fancy one model with 1V6 1AH4 1AJ5 1AG4 as I especially collect Battery valve (tube) sets.

 

"batterybob dot com" sells NEDA 213  415A replacements at $35!!

Eventually I will get all the batteries information I have uploaded!

Search Eveready, Varta, Pertrix, Ever Ready & Vidor makers here.

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Yes, the radio is a Silvertone 4212.. Given the minutre ht current drain,I see your point about using dry cell packs as they would last a very long time. Thanks for the info as to sources of new "B" batteries - it is pity this is not more widely known , if only to keep the poor guy who makes them in business! I'm still happy with my $7 psu, though. I'm not up to buildiing a psu myself and good variable voltage dc bench supplies are not cheap, most commonly available ones topping out at 30 volts. Once I've tested the set, I'll decide what battery choice best for me. Good to have given the topic a good airing for other members' benefit and thanks for the wealth of information you have provided, Michael.

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The current Alkaline 45V 415 / NEDA213 / BLR102 is about 110mAH, as the Buttons don't fill the package as the layer cells did perhaps 200mAH).  The CR2032 is abour 250mAH at 50uA, but may be as little as 150mAH at 5mA due to internal resistance.  Actually only 14 are needed due to lower "droop" wiith discharge. So cost is under $2 inc postage from Hong Kong in bulk. Buying 80 or 100 pack is half the price of a current Alkaline 415 / BLR102 pack. In the UK it was only used for Meters & Instruments.

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