Charging 5 NiMh cells

[audioguru]

The current equation is I= 1.25V/R. So the 12 ohms you had earlier would give a current of 104mA, if the input voltage to the LM317 is at least 10.75V.
Then the battery will charge to 7V (1.4V per cell) and will continue overcharging until it vents and releases some of its chemicals, or until it fails.

Why is everybody talking about LITHIUM??? Ni-MH is nickle-metal-hydride and it is completely different from a lithium battery.
A lithium battery makeas a nice hot fire when it is overcharged.
A Ni-MH battery just goes POP, then FIZZZZZ when it is overcharged.

 

[ericgibbs]

hi audioguru,

We have two different circuits in the posts, I'm referring to the one that has the transistor.

Its the R3 resistor in the base to ground that I suggested a 6hm: .

This circuit does have some voltage max limit at which the current is finally limited.

The other circuit as we both agree would just keep trying to charge the battery, until it fails.

Lets know what you think about circuit I have described.

I misread the Ni for Li !!!
Regards
EricG

 

[audioguru]

I found the schematic with the transistor and the 6 ohms resistor.
It will overcharge the battery because it doesn't switch to a very low trickle-charge current. It is for charging a lead-acid battery.

 

[mikesmixes]

Hi eric,

Sorry i miss read ur equation. I will use a 6ohm resistor.

The unit has a timer that turns the charger on for a few hours, so this is abit better that it doesnt charge continuously.

I will me modifiyng the circuit today and testing current draws and charging currents.

Thans.
Mike

 

[audioguru]

Don't set the timer then try charging a fully-charged battery.