Electronics > Projects, Designs, and Technical Stuff

My Battery Discharge Analyser Project

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andyg:
This is my first post on the forums, I've watched all the awesome videos, and funny after watching the last post about the batteries, is that I am actually working on a open source project about analysing battery discharge curves. So I thought I'd post this and show it off :)

A while ago, I thought I'd make my own battery discharge analyser, something that can discharge a battery and log the voltage curve. So I built my own based on the Arduino. I made one on prototype board with the Atmega chip in it, a MOSFET on a old fan cooled computer CPU heatsink, it works okay, theres a few issues to iron out, but in general it does what I want it to do.

This is my first "real" project other than flashing LEDs etc, I do have a slight engineering education but I now work as a professional photographer and do some work in electronics manufacturing (assembly). But I like to tinker around a bit with electronics as a hobby.

Heres some photos of the prototype:




As part of my work in manufacturing, I have the pleasure of being able to use Altium Designer also, so I have made a SMD board of the project, that I might get made. I don't know how much interest there would be out there, so I was wondering if anyone out there had any input on whether this might be worth forking out the dollars for a real board etc, as-in, would anyone buy it? Is there a market potential here in the maker, hobbyist area?

Heres a 3D render of the board:




The PCB isn't ready yet, its just a preview of work in progress. Theres a few more things that need to be done (e.g double checking everything, cleaning up silkscreen, LCD mounting holes etc)

Thanks!

Andy

andyg:
I forgot to add, what its suppose to do :)

- Programmable battery discharge analyser
- Analyses batteries 1V to 15V
- Discharges 0-2500mA (about 10mA resolution)
- Programmable termination by voltage, time, capacity, or dV/dt.
- Logging of data (capacity, voltage etc) to SD card, to CSV file
- Uses Arduino libraries for easy modification of firmware by hobbyists
- Spare I/O ports broken out so users can add custom features
- USB port access (via FT232RL chip), can be left empty if no USB required
- TTL-UART terminals for serial interface (when built without USB)
- Discharge in constant current, constant resistance, constant power modes
- Internal resistance test (by multiple constant current discharge steps)
- 16x2 LCD display showing current status
- 4-way key pad navigation
- Stand-alone operation, no need to connect to computer
- Can be powered by USB or external DC jack
- Calibration via serial port terminal
- MOSFET mounted externally, using appropriate heatsink for battery voltage and current discharge. This is so the user can customise their own mounting options.

Mechatrommer:
man! thats the 1D battery, you dont have to hide. nice project! with SD Card capable. care to tell what chip do you use to read/write the card? i have maha charger with discharge capability telling it can improve/restore dead battery, i just say it a crap! my dead battery is still dead! face it! i ended up discharging battery the normal way... using it. so what promise can this device make? if it want to go to niche? to be specific, what we can save by using this product?

andyg:
Good recognition :) I originally decided to make this to test my third party battery packs for my 1Ds. As I believed I may have gotten a few dodgy ones from eBay and wanted to test its discharge characteristic.

Unlike the Maha C9000 AA/AAA charger, it does not do any charging, only discharge. So it doesn't do cycling etc. I did think about this, and to do it would add considerable cost to it. I have one of those Maha chargers too! But I think the Maha charger is pretty good.

I guess the people its targeted to, are people who rely on batteries a lot and need to check its condition regularly. Such as people using cameras, the RC crowd and their toys, hobbyists wanting to see a visual graph of the discharge characteristic. I doubt it has any real general-population commercial use.

It would be nice to have a computer program to see the plot without having to import the files to Excel etc, but I couldn't write a Windows GUI program (e.g .NET, VB, etc) to save my life!

So if I open source it, maybe some enthusiastic person could build on it.

It uses an AVR Atmega328 chip, the SD read/write code is done using Arduino sdfatlib. I originally tried writing straight AVR code using Chan's FatFs and i couldn't get it working. PetitFS worked okay, but wasn't really suitable for writing data in a practical way. So to sdfatlib for Arduino it was. The output from the MCU (5V) is level converted to 3.3V and drives the SD card.

On a practical note, I did use it and found some battery packs with a out of balance cell, which was discharging to zero (falling off the wall) before the rest and managed to improve it signficantly by doing a few cycles (charging manually 16hrs 0.1C, discharge 0.1C).

tyblu:
Nice project! I like it.
Note: forum seems to be screwing my youtube embed.

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