Battery Capacity tester using an ATMega168

When you’re one of the guys who use AAs and AAAs like crazy, you might have figured out that getting rechargeable is an easy way to get away from a big pile of disposables batteries – and when you finally got a charger and a bunch of rechargeable you would then face the dilemma of knowing which of them has the proper charge and whose juiced out! Most battery testers measure voltage – no no no..we need a much smarter tester – one that can measure capacity and predict performance in terms of mAh – neat huh? This particular battery tester has an LCD where it displays both graphics and pictures – its brain is the ATMEGA168 microcontroller that controls the battery testing process [the discharging] and supplies signals to the display LCD. This tester discharges the battery while simultaneously monitoring the voltage of the battery. These changes in voltage are kept until a certain low threshold – from which one could calculate both capacity and supply time. One more thing this tester can identify NiCd and NiMh by checking… Continue reading

Handy battery analyzer

Market is flooded with batteries. It is hart to select and trust the ratings. If you want to be sure your project will run predictably from selected power source it is best to measure characteristics by yourself. Elm-chan has built a battery discharge analyzer some time ago that proved itself. It is based on Atmega48 microcontroller which reads data parameters while it’s being discharged. Battery analyzer supports three load modes that imitate different applications: constant current (imitates linear regulator), constant power (imitates switch mode power circuit) and constant resistance (imitates lamp, heater). Circuit logs data via RS232 interface that can be recorded to file for graphing and analyze. Analyzer additionally can measure internal series resistance of battery (ESR). Continue reading

DIY battery capacity tester

When you buy a new battery there is always a doubt if rated capacity is correct. Especially you can’t trust highly rated batteries that usually come from China. The only way to find out is to measure battery capacity by yourself and use a thick marker to write real value. So this project is pretty simple it uses a Teensy USB development board based on AVR USB chip. So data can be easily sent to PC via USB connection. There can be several ways of measuring battery capacity but this one uses pretty simple solution – it discharges battery with constant current. Circuit is built of LM317T adjustable voltage regulator. It is set to 2.5V which is lower that battery and stays like this during all discharge. Then output is loaded with 10 Ohm 10W resistor that draws constant 250mA of current. This way microcontroller simply reads voltage drop on battery during time and calculates battery capacity. There is also LCD screen attached where current status is displayed like current on load, voltage across battery, time and calculated capacity. So… Continue reading