NiMH battery charger with capacity measurement function. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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NiMH battery charger with capacity measurement function. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Chargers, batteries, galvanic cells

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The device is designed to charge NiMH batteries and control their capacity. Switching between charge / discharge modes is carried out by the SA1 button. The operating mode is displayed using LEDs and decimal points of the first two digits of the seven-segment display.

Immediately after turning on the power, the device enters the charge mode. The indicator shows the charging time. After the programmed time has elapsed, charging stops. The lit point of the fourth category testifies to the end of the charge (and the same discharge). The charge current is defined as C / 10 where C is the battery capacity, set by the trimmer R14.

The principle of operation of the meter is based on calculating the time during which the battery voltage drops to 1,1 V. The discharge current should be equal to 450 mA, R16 is set. In order to measure the capacity, you need to insert the battery into the discharge compartment and start the process by pressing the button! The device is capable of discharging only one battery.

(click to enlarge)

Wires for connecting the battery compartment should be used as short and thick as possible.

To change the charge time, you need to fix the top two bytes in the firmware, which are marked in red. For example, you need to set the time to 12h 00m: using the Windows calculator, we translate the number 1200 into hexadecimal calculus - we got 4B0. The first byte is B0, the second 04 - we write where necessary and rejoice!

NiMH battery charger with capacity measurement function. Firmware

The third byte (08) is a proportionality factor that relates the discharge current and capacity. For example, we want to discharge the battery with a current of not 450 mA, but 200:
1 ma * h = 3600 ma * s, 3600 ma * s / 200 ma = 18 s - this means that every 18 s the counter value increases by 1. Convert 18 to hexadecimal s. and get 16. Write instead of 12, sew, we set the current to 08mA with a variable resistor, we use it !!

Indicator type - common cathode. Install the transistors on the radiator.

About batteries can be found here: powerinfo.ru/

Download firmware

Author: Ignatchik Igor, ICQ: 464548055; Publication: cxem.net

See other articles Section Chargers, batteries, galvanic cells.

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