Rejuvenating batteries

[SMdude]

This is the internals of the battery case. It is covered by a metal surround which fits tightly. The internal is 58mm x 14mm x 6mm.

I'm not going to get the pcm in there with the battery. If I can get the plastic header off the lipo, I think it will just fit, with 7mm of room at the top for the diodes.

LOL OK, from the original pics I thought these packs were much larger than that!
I must say, it is really impressive that such a small battery was able to do anything.
What was the runtime like with the original batteries?(back in its day)

Ok, so unless you intend to replace current sense resistors on the tp5100, just forget about it. I thought we could fit at least 1 or 2A lipo in the battery space, but it is much smaller.

For simplicity sake, are you sure you really don't want to fit the voltage reducing diodes within the walkman? Then you can charge from the original contacts and keep the battery looking original..

[Armadillo]

Just buy this TP4056 at $0.99cents

https://www.ebay.com/itm/2Pcs-1A-5V-TP4056-Lithium-Battery-Charging-Module-USB-Board-Electronic-Component/302255054546?hash=item465fce1ed2:g:mksAAOSw32lYy3vU

Change the Current Programming Resistor as shown according to the schematic and table attached and you are all set.

[msknight]

I can't remember how long it ran back in the day. I used to run the thing most of the night when I was out walking.

I've already bought some of these - https://www.ebay.co.uk/itm/3-7V-500-mAh-Li-polymer-Rechargeable-Battery-501646-for-Recording-Reading-pen/262500045648

And these to charge with - https://www.ebay.co.uk/itm/2pcs-5V-Mini-USB-1A-TP4056-Lithium-Battery-Charging-Board-Linear-Charger-Module/152070669880

I've reached the end of my disposable income for this month... actually slightly overstretched myself.

Talked with a friend last night, and I'm starting to understand the current voltage charging thing. .... I think.

I believe that the current goes in at a constant level, and the voltage sharply rises to its normal voltage. At the end of charging, the voltage shoots up and the resistive properties of the battery change, so that the current takes a nose dive.

[SMdude]

Yeah, that is about right for the charging, it will start in a constant current mode(max charging current) then when the voltage reaches its maximum(4.2v for 1s, 8.4v for 2s), the voltage then remains constant, until the current is about 1/10th of the max current. Then the cell is deemed charged. 1s= 1 cell, 2s= is 2 cells in series.
You will also notice that some  battery packs will be labled 2p2s. That translates to 2 cells in parallel and 2 series(8.4v), just so you know
In terms of .5c 1c 2c, what that means(c) is the capacity of the battery or cell, eg 450ma.
So a battery that is 450ma capacity, if its max charge rate is 1c, then the max current during charge should be not more than 450ma. If it were 2c, it would be 900ma.
Normally for safety sake and battery longevity, I try to limit the charge to .5c or even less. It is just nicer.
You can charge a lipo at less than its rated charge current, just not really safe to charge at higher current.

[msknight]

The long story short is that when I was young, early twenties, I had one of these machines. I was facing a very large decision in my life, one which would ultimately rip me from my family (took years to heal some of the wounds and still healing) .... and this unit kept me company on some very late night walks around Sheffield.

Anyway... I was burgled. The sod took all my hifi equipment. I managed to get most of it back through some quick thinking (covered in fingerprint dust) but the Aiwa was fenced before the police caught up to him. He denied taking it. Got 100 hours community service and the landlady kicked me out, "for fear of reprisals."

You know how you get those ghosts in your life that are with you for years and you just have to lay them to rest? Well, this is one of those things for me. A 25 year-ish ghost that I'm hoping to put to bed.

So... I've been trying to find one of these for some time. They are quite rare and people tend to keep hold of them once they've got them. However, everything needs recapping and I'm practising on a HS P505 walkman. Have currently decapped it, isolated a microswitch fault, cleaned off the worst of the capacitor leakage and am about to do a 1 part distilled water to 3 part bicarb paste, to neutralise whatever is left. Then another bath and long dry, before installing the new caps, and run it up on the bench.

If I can get the P505 working fine, and my soldering technique sorted (I'm currently practising on SMD training kits) then I'll start work on the 303 units. I'm also expecting microswitch failures, and am wondering how I'm going to get parts.

All the caps are here, and I do have an Aiwa 2V PSU, but no battery compartment. I'm sort-of in talks with someone who has one, and a silver PX303... but that's going slowly at the moment.

Someone has gifted me two on the proviso that if I get them both working, I send one back to him... and it looks like it might be an IC failure, from what little I've seen so far. That's one reason why I can't put the diodes inside the unit.

So... power is a thing.

I have also got some of these coming - https://www.ebay.co.uk/itm/AMS1117-1-2-5V-DC-Step-Down-Voltage-Regulator-Adapter-Convertor-Supply-Module-B2/322980775873 - in the hope that it will run on 1.8v, and if it does then I can rig an external battery that will run off a USB battery. I'd have to make a custom case, though. Not sure how I'd handle that yet. Basically, I've got a lot of bench testing to do... which will be done through the month, as it will take many weeks for all this to come from China.

I did receive news yesterday that someone has made PB-3 cells with a LiPo inside, but given what's been said in this thread, I'd rather be in control of my own build, rather than someone elses.

[SMdude]

Geez, that was a bit rough to get kicked out for being burgled..
What is the actual output of the 2v ac adaptor when it is hooked up in circuit with the walkman on? Might be able to run from 2.5v, perhaps with better audio performance(just spectulating).
Just bear in mind that you will have to cut power from the regulator board when you are not using it as it will drain the battery quite fast.

Good luck getting these going! I hope it all goes well 
With a little bit of patience and lots of thinking, anything is possible, just 1 step at a time.

[msknight]

Yes... she just served notice and I had to find somewhere else to live... sharpish. That's how things go, I guess.

I can't currently hook up the 2v supply to the 303 without the battery unit. Plus, both PX303's are dead. Suspected IC, but I've got to get the P505 off the bench before I can take a good look. However, although I can hook it up to the 505 ... that one is currently in pieces awaiting a wash and recap :-) ... when I find out, I'll let you know. But it will be a few days.

[msknight]

Actually... a jack socket, a few wires and a soldering iron....