Maker Pro
Maker Pro

NiCd Battery Charger Schematic

Chip

Nov 28, 2012
10
Joined
Nov 28, 2012
Messages
10
I need a schematic for a 2N3055 variable current power supply using a full wave rectifier and a 24V (filament transformer from Radio Shack), the cuircut lets the voltage float and regulates the current. A pot is used to vary the current output. I use an ammeter to set the current. Current runs about 200 milliampers to maybe 1.5 Amps. I use it to charge NiCd batteries. It also has a LED in the circuit and a diode. I intend to substitue and TIP3055 vice the 2N3055. I have seen tons of schematics using voltage regulators to control the battery charging rate. I am not so sure about using that as it allows unregulated full current to flow until battery voltage is obtained. The current regulating circuit is better as I charge at lower rates for longer times. And since the voltage floats, I can charge up to ten or more cells at one time.

I have lost the original schematic and have had a problem. I suspect the 2N3055 has been blown.

Advise please.
 

Chip

Nov 28, 2012
10
Joined
Nov 28, 2012
Messages
10
A NiCad battery changer is more complicated than that. You will destroy the batteries if you just leave it on with no capability to detect that the charge is finished. Go here for lot's of info:

http://batteryuniversity.com/learn/article/charging_nickel_based_batteries

Bob

Bob, no intention to continously charge the battery, but trickle charges are a lot better than fast chargers. Charging 10 - 14 hours at the C-1 rate (10% of the rated capacity in milliampere hours of the battery) is the ideal rate. All R/C wall wart chargers do just that. They are cheap and work but with many different capacities ehich means many different current rates and wall warts are limited to 4.8 V and 9.6 V batteries. I used typically 5 cell receiver batteries (6 V). Thus the wall wart does not work for me with its fixed low voltage output. I have 6 V batteries rated from 600 milliampere hours to 2500 milliampere hours. It would take a wall wart even if I could get more than 6 V out of it, a couple days to charge the battery to its full capacity. That is why I am looking for an adjustable current charger.
 

Chip

Nov 28, 2012
10
Joined
Nov 28, 2012
Messages
10
Actually, Bob. I have used my home built charger for several years quite successfully. Unfortunately, I believe I suffered a power peak and blew out the transistor or diode rectifier in the circuit. Regardless, the old charger no longer works. Other than going piece by piece through it, I was looking for something a little more modern. But all the circuits seem to be voltage based, which is okay, except they either charge at very high rates or similar conditions. I rather charge at low rates and prolong the life of the battery. It is my peculiarity.

I grew up in the vacuum tube days and have very limited transitor experience. I realize there are many chips out there that make life easier. In fact, I worked for TI for several years in the defense business as a system safety engineer. I am retired now and fly RC for fun. And use home brew circuits to charge batteries.

Not particularly interested in charging LI-po and the like as I do not fly electri powered airplanes. But I do fly airplanes that require receiver batteries to run the receiver as well as the servos. And both my transmitter and receivers have rechargeable batteries. I rather use NiCd batteries in the airplanes as they can deliver very high current demands for short periods of time. NiMh do not do that well. And the NiCd has a graceful discharge characteristic while NiMh have a definite knee in their discharge curve and have cost me one airplane already.

So I charge batteries from one cell to as many as 8 cells.

Chip
 
Top