I plan on using my Arduino Uno to cycle a battery that I made for a school project. Cycling a battery consists of charging and discharging it multiple times, and in my case, a thousand times. It's used to test the durability and consistency of batteries so it's most probable I will repeat this process multiple times until I find the right composition for the cathode and anode electrolytes.
The problem is that I don't know whether or not it will damage the Arduino.
I wonder if I would be better off trying to control an external power supply but I have no idea how to do it.
- Suggest you use a DPDT or SPDT relay to control charging then discharging of the battery.
The Arduino can control the timing of the cycle.
Thanks for your quick response ! I'm going to change it right away.
- Show us the schematic of the circuit you are changing.
I have got no schematic for this project. Which program do you advise me to use to make one ?
Pencil and paper works extremely well. Post a photo of your masterpiece.
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Maybe.
What is the battery voltage and chemistry?
I'm working on the schematic. I will add a picture of the electronics.
We are studying (at school project scale) iron/ air (Fe/O2) batteries.
We are still working on the cells, but based on our measurements, each cell is capable (at most) of delivering 1.2V and 10 to 20 mA.
I assume you meant 10-20mA, not mV.
Anyway, you could connect a 200Ω resistor in series with the battery and connect it directly to an Uno pin. The resistor will limit the current to a maximum of 25mA which is OK for an Uno output pin. Since the current is rather small it may take a long time to charge and discharge the battery but that all depends on the battery capacity.
You can try it and see
Indeed I meant 10-20 mA, but I think what LarryD suggested is not a bad idea (to use a SPDT relay to deliver the power and only control the timing with the Arduino) and I already have a L293D chip.
Take into account that batteries don't discharge at a constant current or voltage, so just measuring the time could be not a good indicator.
Instead of just a resistor would be better to use a constant current sink.
For discharging, something like this could work:
It will keep the current constant. And with the pot on the left, or with an Arduino, you could adjust the discharge current. In your case the power dissipated will be small, not a big concern.
Then measuring the time of each charge and discharge cycle you could know how much capacity it has, in mAh, how it degrades, etc.
Thanks for your interesting remark; I'm taking notes. However, I thought that as I was discharging through a resistor, I could deduce the current with Ohm's law and then the power, which would finally lead me to the approximate capacity of the battery cell.
In any case, I think you're right because, in almost every paper I read, the scientists were using constant current.
The problem is that the voltage of the battery is not constant.
I don't know these batteries, but for example could be that they go from 1.4V when full, down to 1.0V when empty. Then the current I=V/R, will go down as well. And not linearly.
If you don't need accuracy maybe it's ok jus with the resistor. You could take some average voltage as if it was constant, to have an approximation.
In the circuit above the trasnsistor works as a variable resistor, that adjust itself to keep the current constant regardless of the voltage. Anyway it will need some more adjustments for this small current, and more components if you want to automate and measure the cycles with an Arduino.
Here is the first version of the circuit's schematic. I'm still working on understanding how a current sink works before implementing it.
The SD card reader stores the data from the cycles, and the screen indicates how many cycles were carried out and checks the voltage readings.
From now on, I will be focusing on building the cell so I don't expect the system to be tested before next week.
PS : The AAA battery represents the cell we are going to test.
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