ever: N3; Battery packs

I have put 60 x AA cells in the B107 "case"

The battery pack consists of two back to back battery trays:

Bottom (pictured) has 8 columns of 4 x AA cells.

Top has 7 columns of 4 x AA cells

 

The trays are uncut A4 sheets of card "concertina" folded and then strips of coffee tin slipped into the folds and bent around. The last column at one end has a wire to connector and the other end has coffee tin spring clip to the tray on the other side.

The Battery case design is modified to be a top & bottom "chocolate box" style box with inkjet paper printout stuck on card proir to cutting, folding and joining.

 

The AD14 pack has two long strips to short 8 x C cells in parallel (do not mix makes or types, don't use rechargeable).  I beleive the largest ever pack may have been 6 x F cells in parallel or 8 x D cells in parallel. Not sure which. The AD14 box is also made with lid and base like a "chocolate box".

The sockets are made out of blank PCB drilled and cut to lands with "coffee tin" sockets cut and folded, then soldered to the PCB.

 

Here is a close up of a B114 pack under construction showing the technique for the socket

 

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Don't use rechargeable cells or mix cells. Carefull with Polarity. Alkaline are best as above 50% capacity they do have limited charging so cells will level with minimum loss. Testing a pair of new D size Alkaline cells the current was under 50uA initially and quickly dropped to under 2uA.

Battery makers commonly paralleled up to 8 Zinc Carbon cells.

Don't parallel "stacks" of cells without spilter diodes though (1N4148 for 45V to 90V and 1N5819 for 7.5V to 12V packs).

 

The metal is reverse side of a coffee tin bent over a polystyrene packing piece. You can see the edge of the two pin socket soldered to it. A sheet of stiff card folded to make cell compartments. The negative contacts is a large piece of coffee tin cut into fingers to half width and rectangles cut off. A plastic backing to add strength.

One wire from connector to -ve metal strip.

With Zinc Carbon the life might be over 16,000mAH and with Alkaline over 32,000mAH. On N this is 64  or 128 hours  and on the N3 is 130 Hours or  260 Hours (possibly more). I assume with 125mA vs 250mA there is less Cell internal losses.

The single D cell in Ever Ready Personal B is about 5000mA for Zinc Carbon or about 10000 for Alkaline, thus it is 20 hours on Zinc Carbon.

The size of Battery packs gives the N3 an impressive operating life.

 

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Layout of the battery packs and also visible is the new paper insert made from scanning and cleaning the original (which is underneath!)

Sadly the case is still naked. Original style cloth in "red" matching the original red centre band is available, but not the grey with white embossed pattern on the lid and bottom part.

The Polariod Zinc Carbon cells have two plastic bungs inside to reduce the amount of active chemical. They are noticabley lighter than "full" Zinc Carbon AA cells or Alkaline. But 10 x PP3 cells would be about 350mAH for Zinc Carbon and 590mAH for quality  Alkaline. Even the Polariod AA should  be about 800mAH or more. That's about  100 hrs use (assuming HT current is 8mA or less).  Eight packets of  8 x AA Zinc Carbon is about €12 in local "bargain shop". Best local price Alkaline AA cells would be about €32 for eight packs of 8, though likely last x3 longer, so the Alkaline are better value if you use the set much. Ten PP3 work out a lot more expensive in listening time. Using Alkaline AA cells the HT life could be over 300 Hours.

 

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The N3 arrived naked (cloth stripped and lid painted black)

 

Here we have it stripped of paint, chassis and fittings:

 

Then since I can only get plain Grey  rather than original, though I can get the "proper" Red Cloth from Ratchford, I cover with Upholstery Leatherette for €4.60

 

I Used four pieces.

1. Lid
2. bottom
3. Around middle to hinges
4. Middle part between the hinges.

The join at the slot between bottom part and middle part needs "cleaned up" a bit. Even so I got a blister forcing the cloth in. It's a little thicker than the proper cloth. I found a regular table knife was best to force the edge in and then the sharp blade afterward.

It's recommended by Ratchford that the "proper" stuff is stuck with PVA. So I used that. It was a "learning" experience doing the corners properly. I may redo the lid sometime.

I think it would be about €30 to get the minimum 1m of Grey and Red to do it "properly" in two tone (though not the original style of grey). I'm glad I have "practised" with the cheap stuff and next time I can make a better job of it.

 

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