Elektor Team
About the article

Fast Charger for NiMH Batteries

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.

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Component list


R1 = 0.22Ω 5W

R2 = 68kΩ

R3 = 22kΩ

R4 = 1kΩ

R5 = 4kΩ7



C1 = 220pF

C2 = 100nF

C3,C4,C6,C7 = 10mF 63V radial

C5 = 1μF 25V radial



L1 = 220mH suppressor choke



D1 = LED

D2,D3 = PBYR745

T1 = BF245B or -C

T2,T3 = BC547B

T4 = BC557B

T5 = IRF9520




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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