battery charger

[mehdi]

Hi
do you have any schematic for 9v NI-MH batteries charger?

with many thanks
mehdi

[DOOLEY]

ref battery charger

did post ,have removed due to mistake on schematic,will correct , soon ,sorry.

[DOOLEY]

ref nimh chager

try this schematic ive adapted from a 3 stage charger i did a while ago.

supply needs to be : fully charged voltage + min 2v pref 3v above for drop over lm317 + diode drop so min 12.5v to 13.5v

the 7805 is an actualy lm317 set up for constant current , i didnt have model for this on circuit maker , r1 is set for cappacity of battery divided by 10 , (0.1 / c)

relay for you will be 6v with r4 to suit , this lets the 2n7000 "kill" the relay when charge voltage is reached.

s1 is pressed to start charge.

d2 is green led to indicate charged
d4 is red led to indicate charging

vr1 output to opamp - is set to fully charged voltage , 1.4v /cell =9.8v
easy to set when flat battery connected after start is pressed.

"treat" nimh's nicely , charge at capacity divided by 10 , besides being nice to battery , at this rate cell voltage increace is nearly constant , making voltage monitering / cut off possible , without the use of complex delta charger or a dedicated chip.

when charged only thing still connected is opamp + , so very low current discharge after charging has finished .

erm , poss forgoten to say something,,,,,,,

diagram bit scrappy , sorry.

[mehdi]

Hi dooley
very thanks for schematic.
regards