Author Topic: Rejuvenating batteries  (Read 7262 times)

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Online Gyro

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Re: Rejuvenating batteries
« Reply #25 on: January 07, 2018, 10:38:59 am »
I suspect that these Rejuvenators have some level of success in flooded wet cells (car batteries), where the Lead Sulphate can be dislodged from the plates and can float away.

In a gell cell, everything is tightly sandwiched with minimal electrolyte, so there is nowhere for the Sulphate to go. There is no way to chemically break it down either in a sealed cell.
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Offline msknight

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Re: Rejuvenating batteries
« Reply #26 on: January 08, 2018, 06:54:17 am »
OK - so I now turn my attention to 3.7v LiPoly batteries.

If I can get one to fit in the case, I'm presumably going to need a small circuit to knock it down to 2v and also allow charging when in the walkman.

Where do I start with this please?
 

Offline msknight

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Re: Rejuvenating batteries
« Reply #27 on: January 08, 2018, 07:01:56 am »
Ok - I'm going to run with Armadillo's suggestion of these - https://hobbyking.com/en_us/turnigy-nano-tech-200mah-1s-35-70c-lipoly-battery-5pcs.html?___store=en_us

I'm presuming that there is some circuitry within the cap, which I should be able to remove to gain the 2mm I need to make this fit. Whether that is a charging circuit, who knows. I'll find out when they get here.

At 50.8mm long, that leaves me only 7mm to somehow drop this to 2v and make up for whatever isn't in the cap.

So... no pressure then.
 

Offline james_s

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Re: Rejuvenating batteries
« Reply #28 on: January 08, 2018, 07:19:26 am »
I've never had any luck at all rejuvenating any kind of gelled lead acid battery, especially something that old.

Be careful with high current LiPos like the ones pictured for RC aircraft, they can deliver very high currents, lack any kind of internal protection and have been known to catch fire if abused. I would suggest looking at small prismatic lithium ion cells like the kind used in cell phones and music players, ideally something with internal protection circuits.
 

Offline msknight

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Re: Rejuvenating batteries
« Reply #29 on: January 08, 2018, 07:31:55 am »
Good points. Any suggestions on where I start looking/who I should be talking with please?
 

Offline Armadillo

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Re: Rejuvenating batteries
« Reply #30 on: January 08, 2018, 07:32:10 am »
OK - so I now turn my attention to 3.7v LiPoly batteries.

If I can get one to fit in the case, I'm presumably going to need a small circuit to knock it down to 2v and also allow charging when in the walkman.

Where do I start with this please?

Why do you need to knock it down to 2V? I don't think the motor will even turn at 2V. Yesteryear semiconductor don't operate at 2V.
You can temporary wire a 2V into the circuit board to see if it will operate.
As someone has said, 3 batteries are connected together in series to form at least 6V to operate this player.
As for the lipo, 2 in series will form over 7V, so may be a diode IN4001 in series will drop the volt to 6V region but I am sure it will work fine for your player.
So you should check and confirm the voltage the player is designed to operate, definitely not 2V.

Edit: If you ever dismantle any of those GPS/Car camera etc.. you will find these bare unprotected small capacity lipo in it. Because the VA is low, you don't exactly need to be overly concerned or worried about it.
« Last Edit: January 08, 2018, 07:38:25 am by Armadillo »
 

Offline tautech

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Re: Rejuvenating batteries
« Reply #31 on: January 08, 2018, 07:54:45 am »
OK - so I now turn my attention to 3.7v LiPoly batteries.

If I can get one to fit in the case, I'm presumably going to need a small circuit to knock it down to 2v and also allow charging when in the walkman.

Where do I start with this please?
Based on what you said here:
Actually, it only needs one. I got extras from ebay because I knew the chances were  low of finding one that worked, but there was at least a chance.
And what we'd expect in the circuit design....there's likely a boost converter to bump a single cell 2V supply to 6V, but this need be checked, So we need some good pics of where the 2V supplies the PCB inside the Walkman and the general area. Some clues will be the voltage rating of the electrolytic caps that must have some voltage headroom over the main PCB voltage. There even may be some test points and makings on the PCB indicating voltages present.
In all likelihood the boost converter can handle a higher supply than 2V but to be sure some of the experienced guys and gals need a peep at the guts please.
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Offline msknight

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Re: Rejuvenating batteries
« Reply #32 on: January 08, 2018, 08:25:36 am »
I had the unit apart two days ago and took some pictures. I might be able to get them from another post, for you.

Most of the caps are 100uf 2v and 220uf 2v, with some 220uf 4v and two 470uf 6.something near the power in.

I'll hunt the pictures down.
 

Offline msknight

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Re: Rejuvenating batteries
« Reply #33 on: January 08, 2018, 08:28:25 am »
Here you go.  The cutaway in the board is where the gumstick battery sits. There is a separate input at the top right.... that is where the external battery pack comes in.

The external battery pack contains two AAA batteries, and also is pass-thru for the external Aiwa transformer, which is 2V at 350mA.

And yes, the board is a bit of a mess. I've got replacement caps on order.

« Last Edit: January 08, 2018, 08:30:12 am by msknight »
 

Offline tautech

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Re: Rejuvenating batteries
« Reply #34 on: January 08, 2018, 08:45:30 am »
No sign of a boost converter.  :-//

Do you remember if there was componentry on the other side of the PCB ?
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Offline msknight

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Re: Rejuvenating batteries
« Reply #35 on: January 08, 2018, 09:09:35 am »
Nothing. Only traces.
 

Offline SMdude

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Re: Rejuvenating batteries
« Reply #36 on: January 08, 2018, 09:23:02 am »
What an obscure bit of gear!
Given that the supply voltage from the AC adaptor is 2v and looking at the caps, I think it is very likely this is a special 2v system! How bazzar!

If going with li-po, or li-ion, make sure you use a pcm(protection circuit module) between the batteries and power supply, so the batteries get disconnected before they are totally drained.
https://www.ebay.com.au/itm/1S-2-5A-3-7V-Lithium-Batterry-Protection-Board-Polymer-BMS-PCM-PCB-Li-ion-Module/252826406992?epid=700767788&hash=item3adda0d050:g:6GoAAOSwsW9Y02HF.

For the charger, use a tp5100 board (ebay) they run from 12v, just don't reverse it!

Now, to step down the voltage, probably the best way to do it is to just use some general purpose 2 or 3A diodes in series. Start with 4 or 5 in series and reduce them back until you have just over 2v with the fully charged lipo(4.2v approx). It will need to be connected up to the load to test the voltage, if there is no load you will still read 4.2~v after the series diodes.

Going the route of diodes is good in that you don't need to worry about turning off a power supply that lives between your battery and walkman.

 

Offline tautech

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Re: Rejuvenating batteries
« Reply #37 on: January 08, 2018, 09:41:15 am »
For a electronics novice SMdude's solution will be the simplest, just silicon diodes in series each of which offers 0.6-0.7V forward voltage drop. All you need is a voltmeter to confirm how many you need while the battery is under load. They can be added to the negative or positive rail wherever you can shoehorn them into the circuit and case.
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Offline msknight

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Re: Rejuvenating batteries
« Reply #38 on: January 08, 2018, 10:11:39 am »
Yes, it is obsolete :-) - It is a tape deck - the Aiwa HS PX-303 - http://walkman-archive.com/gadgets/walkman_aiwa_04_px303_eng_v3.htm

The story behind this is long... nearly 30 years long :-)

My target is still the LiPo as mentioned a few posts earlier. It stands the best chance of fitting. The question is... I want to put this back in the gumstick and seal it back up... so how would I charge it once I have the diodes fitted? Or would I have to connect the charger between the diodes and the battery?
 

Offline msknight

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Re: Rejuvenating batteries
« Reply #39 on: January 08, 2018, 10:17:39 am »
The TP5100 I'm finding are listed at 4.2V to 8.4V - and these LiPo's will be 3.7 - https://www.ebay.co.uk/itm/TP5100-2Cells-Single-Lithium-Lion-Battery-Charger-Module-18650-4-2V-8-4V-BS2/322917861077 - Can I realistically still use these?
 

Offline tautech

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Re: Rejuvenating batteries
« Reply #40 on: January 08, 2018, 10:22:08 am »
My target is still the LiPo as mentioned a few posts earlier. It stands the best chance of fitting. The question is... I want to put this back in the gumstick and seal it back up... so how would I charge it once I have the diodes fitted?
Fit the diodes into the Walkman case (Cut a PCB trace if necessary)and the LiPo into the gumstick.
Arrange a charging system that charges the LiPo in the gumstick maybe with small "charging only" jack point and include the 1S 2.5A 3.7V Lithium Batterry Protection Board on the outlet pins to the Walkman.
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Offline msknight

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Re: Rejuvenating batteries
« Reply #41 on: January 08, 2018, 10:32:41 am »
The walkman charges through the extended battery adapter.  That adaptor has circuitry in it to drop the two AAA cells to 2V as well.

I think I'll be safer to work on charging the battery outside the walkman. I'll have to build a charger that matches the pins. So... in this case... do I still need to attach the charger behind the diodes, or can I still connect it at the front, assuming the case is sealed? - I'd rather not attach the diodes inside the unit if possible.  There may be the ability to fit a socket to the front, or rear, of the case itself. I'll have to look at that option first.

But if it doesn't matter that the diodes are in there, it will enable me to use the external points.
 

Offline msknight

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Re: Rejuvenating batteries
« Reply #42 on: January 08, 2018, 10:53:31 am »
OK ... I'm speed reading all this in gaps at work, so this is how I read this so far....

  • I can use the 3.7v LiPo cell, with some 0.6-0.7v diodes on the +ve side to drop the voltage to 2v.
  • To charge, I'll need to do this externally, using a TP5100 board (even though the board is putting out 4.2v and the battery is rated at 3.7v) but I will have to do this behind the diodes, so I'll need to fit a small charging port in the gumstick.
  • Because of this, I won't need the protection circuit module, but I won't be able to charge via the walkman itself.


Some questions remain...

*) What mAh must the external transformer be to power the TP5100 (the unit appears to run from a range of voltages... and I'm wondering that if I power via 5V from USB, would that handle it?)
*) I presume from reading the rather sketchy e-bay description, that the TP5100 has protection to avoid over charging.
*) What would happen if I were to forget about the gumstick being in the unit, and hook up the external 2V supply via the battery bay?
*) I'm actually wondering how the original charged the Lead Acid, because there is no apparent circuitry inside the battery... maybe there is voltage protection already on the board?
« Last Edit: January 08, 2018, 11:00:18 am by msknight »
 

Offline soubitos

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Re: Rejuvenating batteries
« Reply #43 on: January 08, 2018, 11:06:21 am »
The lipo you will need is very small, you dont need a TP5100 rated 2A to charge a 300-350mAh pouch, you dont even need a stock TP4056 rated 1A to charge such a small battery... if you want to keep it safe your max charge current should be 0.5C max 1C .... this means 300-350mA charge current...  this is one of the reasons i made and one of the issues solved with my TP4056FLEXADV board unless you want to desolder the 1.2K stock smd resistor (can be 0805-0603 or even 0402 in some pcbs) and replace it with a 2.4K to set charge current somewhere between 0.5-1C of a said 300-350mAh lipo (250mA)
 

Offline SMdude

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Re: Rejuvenating batteries
« Reply #44 on: January 08, 2018, 11:19:16 am »
I would still use the pcm, it is very small and it saves the battery from discharging below its critical limit. Overdischarging a li-po (li-ion) kills them.
3.7v is the nominal voltage. Fully charged they are 4.2v.
I would pack the cell and diodes back into the original battery packaging if at all possible. I would even include the charger board with a 2.1mm dc socket to the outside for charging. How big is this battery?
There are many different size/shape lipo's, try and see how much room is taken up by the diodes etc, then see what battery space you have left. You can use 2 or 3 cells in parallel depending on what you can find.
And yes the charger needs to connect in directly to the battery or output of pcm if you have one.
Allow about 1A for the 12v input to the charger.
If you hook up the 2v supply with the battery in, nothing will happen to the battery.
The 2v supply is probably a bit over 2v and that is most likely how it charged the original battery. They never made nice chargers like we have today for li-po!

And you probably don't need the tp5100, I just like them as they are a very handy cheap lipo charger. To adjust the charge current you can just remove one of the 0.1r resistors, and or replace the other one to .2r and it will charge at max current of 500ma~ But something else may suite better depending on the battery capacity.
 
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Offline msknight

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Re: Rejuvenating batteries
« Reply #45 on: January 08, 2018, 12:39:24 pm »
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.

 

Offline Armadillo

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Re: Rejuvenating batteries
« Reply #46 on: January 08, 2018, 01:49:23 pm »
« Last Edit: January 08, 2018, 01:51:28 pm by Armadillo »
 
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Offline msknight

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Re: Rejuvenating batteries
« Reply #47 on: January 08, 2018, 01:59:00 pm »
Wow. Stunning :-)

I would charge this with the same TP5100, yes?
 

Offline soubitos

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Re: Rejuvenating batteries
« Reply #48 on: January 08, 2018, 02:03:06 pm »


Quote from: msknight on Today at 03:59:00 PM
Wow. Stunning :-)

I would charge this with the same TP5100, yes?

Is it me, or you simply ignore my posts?
OK, last post here... this lipo or the one i found several posts above is 380mAh.... try charging it with a TP5100 module safely and let us all know how it goes.....


 
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Offline msknight

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Re: Rejuvenating batteries
« Reply #49 on: January 08, 2018, 02:06:45 pm »
OK, last post here... this lipo or the one i found several posts above is 380mAh.... try charging it with a TP5100 module safely and let us all know how it goes.....


Apologies... I'm at work, speed reading between tasks to keep the conversation running. Otherwise, it would wait until I got home to be able to respond to people. That would slow everyone down.

The one two posts above which is 500mah.

To be honest, everything coming out here is opening my eyes. I didn't even know that half the things here existed, let alone how to start searching for them.
 


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