Comments on: Battery capacity tester

By: Dids

Dids — Wed, 02 Dec 2009 12:28:10 +0000

Check this out: http://spaceb.org/spaceb0rg/2009/11/24/voltage-analysis.html

Components needed:
- an Arduino
- a battery
- a computer

Real-time graphing with screenshot and recording capabilities for easy analysing of different type of batteries and battery life in general.

Tons of more projects in the works, from xbox’s to nixie tubes. :-)

By: ApprenticeWizard

ApprenticeWizard — Mon, 30 Nov 2009 21:22:51 +0000

Note that standard practice for battery manufacturers is to discharge the battery at 0.1C, then multiply that value by 10 to get the (m)Ah capacity. This is probably why you are getting results that differ from the manufacturer’s stated value.

By: therian

therian — Thu, 12 Nov 2009 22:26:46 +0000

@TNW
a lot of people read before answer. He already have all hardware needed

By: Jancans

Jancans — Thu, 12 Nov 2009 14:30:35 +0000

Therian, for one NiMH cell 2.2 Ohm will be about only 0.5A In most cases that is less than 0.5C (C – capacity), its safe. Ofcorse everything ruin NiMH/Cd battery life, slov charging, fast charging, slow discharging (this hapens when battery is not used for some time).

By: tj

tj — Thu, 12 Nov 2009 12:48:31 +0000

This is probably the first Arduino project I’ve taken seriously in a while. It actually shows an effort and practicality.

urlax pointed out a good refinement for it too

By: TNW

TNW — Thu, 12 Nov 2009 08:26:17 +0000

Therian,

A lot of people have started using microcontrollers using Arduino hardware because it’s easy and straightforward. Many people don’t even know about programmers and bootloaders and their functions because that’s not required to mess around with platforms such as Arduino.

By: therian

therian — Thu, 12 Nov 2009 05:52:53 +0000

The biggest mystery, why he use arduino bootloader. The only arduino advantage over uC is no programmer requirement, and it very arguable one(you always cab build programmer with less than 2 resistor).

By: therian

therian — Thu, 12 Nov 2009 05:34:00 +0000

Im afraid this method with so low impedance not valuable for making measurement instead this is great way to ruin battery life quickly.

By: Thomascpp

Thomascpp — Thu, 12 Nov 2009 04:25:47 +0000

Whats the point of using a bootloader if you already have a programing tool.

By: Haku

Haku — Thu, 12 Nov 2009 01:53:09 +0000

Now that’s a hack! :)

I’m impressed, the cherry on top would be circuitry+code to be able to peak charge the battery in question, then you can start doing fancy stuff like ‘rejuvination’ by running the battery through some charge/discharge cycles to get it’s capacity back up to a better level. Much like this one which I highly reccomend – http://www.batterylogic.co.uk/technoline/technoline-BL700.asp

By: gyro_john

gyro_john — Thu, 12 Nov 2009 01:46:49 +0000

My LaCrosse BC-900 is also good for this. It charges, exercises and/or tests the capacities of 1 to 4 NiCd or NiMH AA and AAA independently and simultaneously.

I modified it so I can also work with the sub-C cells found in cordless drills.

Very handy to be able to easily put numbers to the capacity of rechargeable cells.

By: urlax

urlax — Thu, 12 Nov 2009 00:12:11 +0000

I think he’s made a mistake. because current is measured in mA and not mAh. mAh = I (in mA) * time (in hour)

so he uses the 2 ADC’s because he measures on the side which is charged. so the voltage across the battery is not constant, and thus he needs to measure the voltage before, and after the 2,2Ohm resistor. (ADC2 is equal to Vcharger, which may variate during charging)

GND)—(-BAT+)–(FET)-(ADC1)-(2,2OHM)-(ADC2)–(VCharger)

if he moved the circuit, he might save one ADC

GND)-(ADC1)-(2,2OHM)-(ADC2)–(FET)–(-BAT+)–(VCharger)

(ADC1 will now always be 0)

By: ThanhTran

ThanhTran — Wed, 11 Nov 2009 20:17:08 +0000

The 2 ADC are to measure the voltages across the 2.2 ohm resistor. The purpose is too measure the current running through it. The voltage should be used to decide when to stop the discharge process. The current measurement would tell the capacity of the battery (mAh or Ah)

By: Jancans

Jancans — Wed, 11 Nov 2009 19:25:16 +0000

Vondering, why he use 2 ADC for measuring voltage. A mosfet is used in switch mode, or to control current (that probably would explain why 2 ADC)?

By: St.Jimmy

St.Jimmy — Wed, 11 Nov 2009 19:11:37 +0000

this is how you use an arduino. congrats