Hey guys! Sorry about the delay... I keep waiting for an email notification that never comes and I end up forgetting about the topic. My bad. :sweat_smile:
It looks as though the average current is around 100mA, so you might expect about 20 hours battery life.
You could do a practical test, to find out. It will only take a day or two.
I was measuring the current drain using a Protek 506 (digital multimeter) connected on a USB port, but after almost 24h the multimeter's battery reaches the end (before my prototype) :(
Dimensional Analysis (aka canceling labels through division)
I believe a good idea would be to get some estimates on an upper and lower limit. However, it would be better to design around the assumption that you have maximum energy usage all the time.
If you have 6AA batteries in parallel, then your current capacity increases because your have more sources to sink current from. If they are in series you get no increase in current capacity. Your project is a little vague if they are in parallel or in series.
Anyway, in parallel you effectively have 2 Ahr * 6 = 12 Ahr. Assuming your maximum current draw of 0.15 amps 12Ahr / 0.15A = 80Hr. With the 0.07 A draw you could get 171 hours. I think you get the idea for doing the series one as its only 2Ahr total.
If you want to know for certain the best thing is to simply do a long term stability test. Hook up your project and devise a test to have it run at maximum capacity and minimum capacity and keep track of time before failure.
I'm using 6AA batterys in series. Each battery has 1.2V and I need more then this to feed everything. Thank you for your explanation, very helpfull. ;D
I got about 30 hours before Vcc dropped below 5V and close to 40 before the SD card wouldn't write anymore. The blue line was using a switching regulator substituted for the stock Arduino linear regulator. It is an obvious improvement. After this test I removed the linear regulator and glued the switching regulator into the same place on my Uno board. It is a Pololu
300mA 500mA 5V regulator and cost about $5.
Temperature has an effect and can markedly reduce life of alkaline batteries. Since I am anticipating somewhat cool conditions (down to ~0°C) I also tested lithium AA batteries. In addition to cold tolerance they also have about 30% greater capacity as compared to alkaline. With 6 of those my project ran for 78 hours before Vcc fell below 5V and 79 hours before the voltage dropped too low for the SD card to write.
My intention is to move every piece of code into an ESP8266, I'll be using an LD1117 regulator to feed my project with around 3.3V and a maximum current of 1A (ESP8266 drains a lot of current sometimes). Still don't know wich battery type I'll be using...
OP mentions 1.2volt AA. That could be NiMH rechargeables.
In my experience, the quality of those critters varies wildly.
I tested twelve 2500Ah brandless ones a while back. None of them were more than 700mAh, even after a few cycles.
Internal resistance is another problem that can make your Arduino reboot when the Wifi kicks in.
Field testing is the only option.
If battery life is important, do a "jboyton mod". A pololu micro buck converter (500mA).
In another post he has a picture of it.
Maybe he can post that here as well.
Well, brandless says it all. I've done the same experiment with Everyready NiMH 2500 mAh AA cells, and using a resistor with 100 mA initial draw as the load, got better than 24 hours or over 2000 mAh in every case.
Battery life is CRITICAL for my project. If I can't reduce battery consumption drasticaly (it needs to keep at least 2 years with the same battery) my hole project will be turned into nothing D: That's why I'll change to ESP8266. I'm also thinking in perform some duty-cycle optimizations to reach this bettery life of 2years.