Can I save an old NiMh battery?

[Chippychap]

Hi Guys,
I have a portable DVD player with a NiMh rechargeable battery.
It has not been used for about four or five years.
Presumeably the battery has discharged and been therefore left uncharged for a long time.
suffice it to say that now it will not charge.
There is a coloured LED on the battery to show if it is charging or not.
Starts off red when charger plugged-in and then goes green.
Not sure if green means charging or charged.
The red light is now on for longer when on charge.
In my leccy illiterate mind it means that something is changing/happening inside.
Do I continue messing or is it brown bread?
Any suggestions please?

 

[tpetar]

Green led on/off depends from design of battery charger. In many chargers green led turn on when charging process is over. To check your battery capacity you can do few cycles of it, I mean complete charge and discharge few times.

This NiMh wide consumer batteries have life of 3-4 years used or not used or 1000-1500 cycles. If they working then good.

NiMH and Nicad batteries, start to lose power when stored for only a few days at room temperature. But they will retain a 90% charge for several months if you keep them in the freezer after they are fully charged. If you do decide to store your charged NiMH cells in the freezer or refrigerator, make sure you keep them in tightly sealed bags so they stay dry. And you should also let them return to room temperature before using them. If batteries dont show some life, then you can try to start some chemical process, try to freeze them several times.

 

[Chippychap]

I'm on it.
Both repeated charging and then I'll try the freezing
Thank you.

Ken

 

[tpetar]

Also when one of the characteristics of Ni-MH batteries is that the battery temperature tends to rise during charging. To prevent a reduction in battery service life due to high temperatures, it is necessary to cool the battery during charging.

 

[Chippychap]

Only problem I have with that is that the battery is encased in a plastic moulding which clips into the DVD player so i am unable to feel the temperature of the battery.
The moulding itself is cold to the touch so I will stick with the charge and then put it onto the player.
Then we go to the freezer method which methinks should have gone first.
Hey ho.
Thank you.

---------- Post added at 15:44 ---------- Previous post was at 15:43 ----------

Only problem I have with that is that the battery is encased in a plastic moulding which clips into the DVD player so i am unable to feel the temperature of the battery.
The moulding itself is cold to the touch so I will stick with the charge and then put it onto the player.
Then we go to the freezer method which methinks should have gone first.
Hey ho.
Thank you.

 

[tpetar]

Its good to have such device, maybe you can built this:

Rechargeable Battery Capacity Tester
https://www.instructables.com/id/Rechargeable-Battery-Capacity-Tester/

 

[BradtheRad]

Try running it for a few charge/discharge cycles. It may behave normally once the battery chemistry has been exercised, so to speak.

I was going to suggest a procedure known as 'zapping'. Running a brief pulse of high current through the battery, to remove conductive whiskers that can grow over time between the electrodes. However the zapping method can be dangerous (especially with Li cells), and it does not always restore performance. Furthermore the NIMH type has a different construction from nicads which are better suited to the method.

A website with lots of tips about rechargeable batteries:

https://www.ka7oei.com/nicds.html

 

[Chippychap]

The battery is in the freezer as I write this.
After repeated charging efforts I am now getting a flickering on the screen and the red LED is staying on longer so will continue with both methods.
I'm not really into building stuff, am more a plug-it-in-bloke.
Thank you both.