- on Power Supplies
- Published in issue 7/2007 on page 0
Fast Charger for NiMH Batteries
At the time of writing, the latest AA NiMH (Nickel metal Hydride) batteries have a capacity of up to 2900 mAh. Using an original-type conventional battery charger (supplying 125 mA), the charging time will be extremely long.
The charger we propose here should accelerate the recharging process of NiMH batteries, which hare becoming more and more common (we must do our bit for the environment).
The design is based on the MAX712 made by Maxim.
Resistors
R1 = 0.22Ω 5W
R2 = 68kΩ
R3 = 22kΩ
R4 = 1kΩ
R5 = 4kΩ7
Capacitors
C1 = 220pF
C2 = 100nF
C3,C4,C6,C7 = 10mF 63V radial
C5 = 1μF 25V radial
Inductor
L1 = 220mH suppressor choke
Semiconductors
D1 = LED
D2,D3 = PBYR745
T1 = BF245B or -C
T2,T3 = BC547B
T4 = BC557B
T5 = IRF9520
IC1 = MAX712CPE
Miscellaneous
K1-K4 = 5-way SIL pinheader
K5 = 2-way PCB terminal block, lead pitch 5mm
K6 = DC supply jack, PCB mount
PCB no. 070213-1
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