Right way to charge NiMH and NiCd batteries

Thread Starter

uraniumhexoflorite

Joined Oct 23, 2016
216
Wherever I go on the internet, I see different methods for charging NiMH and NiCd batteries. These range from NDV charging to just putting a battery in parallel with a power supply and putting a diode in series with the battery to prevent current from going backwards. I have seen NDV all over the internet. I saw the simpler charging setup in a old craftsman electric screwdriver that I opened up earlier this year. There are other methods that I have heard of too such as putting the battery in parallel with a power supply and limiting the current with a resistor. Which of these will charge a NiMH battery without destroying it. I am looking to make a simple USB powered AA charger and I would prefer to use the simplest charger that won't damage batteries even if it's slow.
 

Audioguru

Joined Dec 20, 2007
11,249
AA Ni-Cad battery cells are toxic and are obsolete. Battery manufacturers and www.batteryuniversity.com say that Ni-MH cells should be charged with a Ni-MH battery charger IC that is smart enough to detect a full charge then turn off. Only a very small trickle charge current is allowed. Most modern Ni-MH battery cells copy the Eneloop that holds a charge for 1 year then a trickle charge is not needed.
 

Audioguru

Joined Dec 20, 2007
11,249
The Amazon charger switches to a trickle charge because its circuit is so old that it does not know that modern Ni-MH cells do not need and do not want a trickle charge.
Buy a newer one.
 

Audioguru

Joined Dec 20, 2007
11,249
The cheap Amazon charger shuts off when the Lithium battery is about 90% fully charged and is still charging with 100mA, but you might not notice the 10% loss of charge. The charging for a Ni-MH battery "might" be OK "if" the delta V detection is correct.
Chinese? Cheeep? No-name-brand? From "the electronic expert company" called Amazon who knows nothing about electronics?? Beware.
 
Can I hop on board here with a little question? I've got a set of NiMH batts (AA) that are nearly ten years old by now. What kind of reduction would I see in terms of how long it can hold a full charge when not in use?
 

Thread Starter

uraniumhexoflorite

Joined Oct 23, 2016
216
I think it would depend on how you stored them, how much you used them, and how you charged them, but I'm no expert so I would wait for someone more experienced with NiMH batteries to respond.
 

Audioguru

Joined Dec 20, 2007
11,249
The length of time for an NI-MH cell to hold a charge depends on when it was made and which company made it by copying the Sanyo Eneloop which was invented in 2005. Energizer began selling Ni-MH batteries "that hold a charge for one year" in about 2010 or 2012. I don't remember when Duracell did. Your cells are too old.
Here are some clips from three Energizer Ni-MH cells application manuals:
 

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The batts I've got are Powerbase. Back five years ago they were used all the time for Nintendo Wii remotes and for LEGO motors. These days they lose their full charge within a week, so when it's time for video games were always dismayed that they aren't ready to go when I take them out from the drawer.

I guess the question I really meant to ask is if these AAs are worth keeping around any more.
 
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