7.2 Volt Battery Discharger

[Papajo]

Hi, I'm looking for a simple circuit for a battery discharger for 7.2 volt RC Cars ni-cads packs. It should also include an led indicator for the 5 volt cutoff if possible. Thanks in advance, Papajo

 

[stevez]

My son used to use a number of 12 v automotive bulbs in parallel as a load. It would seem that a zener diode or comparator could be used along with a relay or transistor, to turn disconnect the load at the right point. If the 5 volts isn't that critical you might experiment with some relays to see if you can find one that drops out at the right level.

 

[chemelec]

Not sure why a cutoff of 5 Volts? It sounds like you have 6 cell and Typical cutoff is recommended at 1.1 volts per cell with a .1 Capacity discharge.

On my site is a Battery recycler, Discharge and auto Recharge. Its Not yet complete in my testing, but for the most part I believe the schematic is correct.

**broken link removed**

You might take a look and get an idea.

Take care........Gary

 

[escin]

u may try this battery equaliser.

PART LIST:
6 1N5404 3A Rectifier Diode
6 R47 5W resistor .47 Ohm Resistor
1 Tray Casing

Circuit Description
What happens is a resistor and diode have been placed across each cell. The cell will discharge until about 0.6v at which point the diode will stop the discharge process. This method nullfiies the problem of cell reversal associated with discharging the entire pack at once (cells in series).

The pack may take a few hours to discharge depending on how close it was to being flat in the first place.

If you wish to increase the discharge current, this is possible by using smaller resistors and a higher amp diode or simply more diodes.

 

[escin]

diagram

 

[escin]

add an led to battery equaliser.

PART LIST:

Resistors: (All 1/4 watt)
6 x 1 kohm
2 x 390 ohm
2 x 270 ohm
2 x 220 ohm

Transistors:
3 x BC548 (NPN)
3 x BC558 (PNP)

LED's:
6 x 5mm round or square LED's