Fast NiCad Charger

A 7.2V 1C NiCad/NiMh battery charger.

Current Satus:   Complete/
Date:                August 2003
License:            Creative Commons Attribution 3.0 Unported License/
 

Creative Commons License
This work is licensed under a Creative Commons Attribution 3.0 Unported License.
Design summary

This design uses the Maxim, MAX 713 NiCad/NiMh battery charger IC to control the fast charge time and provide cell voltage monitoring.

Update May 2nd 2011
Added pictures of my prototype design and the PCB layout.
Note: the MAX712/713 device from Maxim semiconductor is now listed as Not Recommended for New Designs (NRND) meaning that the device will be phased out soon.

It charges a battery to approximately 80% charge in 22 or 33 minutes at a current of 2.4 Amps. Once the fast charging has ended, it trickle charges the battery. Power is from a 13.6V, 3 Amp, switchmode power supply. There is also provision to use power from a 12V accessory (cigarette lighter) socket. As there are no transformers inside the case it is lightweight.


Note:  You will require a power supply of greater than 13V to operate this circuit. Failure to do so will cuase the fast charge termination to operate incorrectly. I used a car accessory adaptor from Halfords, it provides 13.6V @ 5 Amps, more than enough for this circuit.
The design is based upon the example circuit from the MAX 713 datasheet. Due to the high current, there is a large heatsink on the power transistor, T1 and I also added a small CPU cooler to cool everything down. The cooling fan runs from the 12V supply to the PCB.

It was used as my travel charger for my 'Fun' R/C cars as it is lightweight and works great with the 2000-3000mA NiCAD and NiMH cells I use

Partlist

Part

Value

Device

Package

Description

C1

10nF

C-EU050-030X075

C050-030X075

CAPACITOR, European symbol

C2

10nF

C-EU050-030X075

C050-030X075

CAPACITOR, European symbol

C3

10uF

CPOL-EUE5-6

E5-6

POLARIZED CAPACITOR, European symbol

C4

10uF

CPOL-EUE5-6

E5-6

POLARIZED CAPACITOR, European symbol

D1

1N4004

1N4004

DO41-10

DIODE

H1

MOUNT-HOLE3.2

MOUNT-HOLE3.2

3,2

MOUNTING HOLE with drill center marker

H2

MOUNT-HOLE3.2

MOUNT-HOLE3.2

3,2

MOUNTING HOLE with drill center marker

H3

MOUNT-HOLE3.2

MOUNT-HOLE3.2

3,2

MOUNTING HOLE with drill center marker

IC1

MAX713CPE

MAX713CPE

DIL16

NiCd/NiMH Battery Fast-Charge Controller

KK1

SK104

SK104

SK104

HEATSINK manufacturer Fischer/distributor Buerklin

R1

1K

R-EU_0207/7

0207/7

RESISTOR, European symbol

R2

150R

R-EU_0207/7

0207/7

RESISTOR, European symbol

R3

68K

R-EU_0207/7

0207/7

RESISTOR, European symbol

R4

22K

R-EU_0207/2V

0207/2V

RESISTOR, European symbol

R5

0.1R (5W)

RKH206-8

KH206-8

Power Resistor

R6

150R

R-EU_0207/7

0207/7

RESISTOR, European symbol

R8

1K

R-EU_0207/7

0207/7

RESISTOR, European symbol

Q1

TIP33

TIP33

TO220V

TIP33 vertical mount NPN transistor

LED1

LED5MM

LED5MM

LED

LED2

LED5MM

LED5MM

LED

X1

W237-02P

W237-132

WAGO SREW CLAMP

X2

W237-02P

W237-132

WAGO SREW CLAMP

X3

W237-02P

W237-132

WAGO SREW CLAMP

Schematic

Click me for the full schematic

PCB and schematic in Eagle CAD format

NICAD.Zip 94 Kb

Prototype unit pictures

The ventilated PSU case is available from Maplin, part number YU32K.

Fast_charger_1

Next inside the case showing the wiring and the placement of the cooling fan.

Fast_Charger_2

Finally, detail of the power and LED connections

Fast_Charger_4

 

Updated 23 August 2017