R/C Tech Forums - View Single Post - How to make a deep discharge/ equalizing trey
Old 05-25-2004, 07:47 PM
  #9  
tel
Tech Adept
iTrader: (9)
 
Join Date: Feb 2004
Location: Chandler,AZ
Posts: 233
Trader Rating: 9 (100%+)
Default

The printed circuit board looks like a DIY kit from Fry's or other good electronics store (read that as NOT Radioshack). The PCB is overkill for this setup.

The LED and small resistor are connected in series across 2 cells. LED's usually turn on at 1.5-1.6V so a single battery won't light it up. The small resistors look like 10ohm 1/4w since they are just there for show. The LED's and small resistor won't drain the batteries much as it is only pulling about 20mA. This is just there to tell when 2 of the cells it connected to reach the LED cutoff of 1.5-1.6 volts.

Pitcrew was right about the zener diode in reverse has a .6V cutoff but the big resistor only a 1ohm at either 1/2W or 1W power rating. The most current you can pull with a 1.2V cell connected to the zener diode and resistor is 0.6A. The zener diode need only be a 1/2W or 1W to be safe as the power flowing through it at 0.6A at 0.6V is 0.36W.

This design will equalize your cells to ~.6V but it will take a long time as it draws less than 1/2A. Dump your pack to 5.4V total before hooking it up to tray like this.

However, as will all semiconductors the zener diode has a very small leakage current. If you stored your batteries connected to this tray the cells would eventually go 0.0V but we're talking days or weeks to do that.

I'll draw the some schematics in a bit and post them.

For those EE nuts who forgot everything from school like me, here is an online resistor color decoder.

http://ac3l.com/resistor.htm
tel is offline