Using Sparkfun Coulomb Counting Module to measure discharge profile

Components & Accessories Power
1

Hi everyone

I am currently performing few experiments (mostly discharge profiles, as my target applications are for wireless sensor networks where charging is not required). The aim is to monitor the discharge profiles of few batteries over different temperatures.

I have a simple circuit, where the sparkfun coulomb counting module draws current, which is read by arduino pro and later logged using CoolTerm on the PC.

To break it down, I will specify some of the experimental conditions and specifications.

  • Lithium-ion 1300 mAh battery

  • Sparkfun Coulomb Counter LTC4150

  • Sparfun Arduino Pro 3.3V

  • Operating temperature (30 C)

    • The equipment is working as intended and I am able to log all the readings, but, the biggest worry is the battery discharge time, as of now its been 18 hours and the battery State of Charge (SoC) is still at 84%. At this pace, it will take another 4 days to completely discharge the battery. As I have to experiment with 4 different battery types over different temperatures (-10C, 0C, 10C, 20C, 30C, 40C), so if my maths is correct

    Time for one experimental run = 5 days OR 120 Hours

    Time for one battery with 6 temperature variations = 30 experimental runs

    Total number of experimental runs of 4 batteries = 4 x 30 = 120 experimental runs

    Total number of hours = 120 x 120 = 1440 hours :cry:

    I am not sure what I’m missing here. I know I can buy additional boards and modules and run these experiments in parallel, but still it would cost me months.

    I am a little skeptical about the attached load on the batteries, as currently it is 50mA load (because my wireless sensor network draws almost that much load and I wanted to keep it close to it possible).

    This is my very first time working with batteries and I am unsure regarding the State of Charge (SoC) values , so I would like to ask the following questions:

  • Is it possible to add additional load?

  • If it is possible, can you suggest any DC load that can draw more current, let’s say close to 500 mA so that it drains the battery quickly

  • Will it effect the State-of-Charge values? What I mean to say is, whether SoC is dependent on load or not (will it disturb its profile?).

  • I know that adding more load should ideally drain the battery quicker, but I am unsure about its effect on discharge profile

    • So thankful for your time going through my query, any help or pointer is highly appreciated.

    cheers

    2

    Is it possible to add additional load? If it is possible, can you suggest any DC load that can draw more current, let’s say close to 500 mA so that it drains the battery quickly

    Yes, absolutely possible. A power resistor would work, roughly 9 ohms in parallel across your load would do the trick. You'd need a 2 watt or larger resistor to handle the power you're dissipating. Our [[power resistor kit](https://www.sparkfun.com/products/13053) would have what you need for a load.

    Will it effect the State-of-Charge values? What I mean to say is, whether SoC is dependent on load or not (will it disturb its profile?).

    State of charge is dependent on how many mAh's you've pulled out of the battery. If you raise the current flow, you're using more mAh's and the battery will run down quicker. A good analogy would be a bucket of water with a pencil sized hole in the bottom. If you make the hole bigger (more current) the bucket empties faster.

    I know that adding more load should ideally drain the battery quicker, but I am unsure about its effect on discharge profile

    That's something you will need to extrapolate out to get a profile but it may not be as accurate as only using your load and nothing else. (I'm assuming your load probably isn't a constant 50mA, it's probably going to vary a bit depending on what it's doing.)](https://www.sparkfun.com/products/13053)