Displaying battery life?

Casey Gross

Im in the process of building an autonomous drone. I need to be able to tell how much battery life i have left in the battery. Whats is the best and cheapest way to do this?

Miles. k

i don't have much experience with this but, i do know that you can use a A/D converter to do what your trying to do. it might be worth looking into. they sell these on Parallax's web site.

Good luck,
Miles. K

Mike Green

Check out www.emesystems.com. If you click on the "app-notes" link at the bottom of the page you'll find some discussion on using the RCTIME statement to monitor battery voltage using very few parts. Estimating battery life is pretty difficult since rechargables like NiMH have a very shallow discharge curve. Their voltage drops only slightly until the cells are nearly exhausted.

SRLM

Best and cheapest often don't go hand in hand. Usually you have to choose somewhere along the continum. The best solution isn't cheap, and the cheap solution isn't best. This applies to all sorts of engineering problems. Anyway, sparkfun sells a nice current/voltage sensor board. www.sparkfun.com/commerce/product_info.php?products_id=9028. You can use this with an ADC to determine the current voltage and current drain history, and from that infer how much life you have. Such a solution would require some testing with the battery in question to get an accurate prediction.

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Colt

Your best bet is just do some testing.. Depending on the type battery you use and the specs available, you can get a good idea on how long you can run a load before you drain the batt..

The link for Sparkfun, that component is something I plan to order here real soon. Being able to sense both voltage and current will help you determine how long you can run your drone.

I've been working on a similar project, I did a small scale using a A/D to sense voltage, while having a solar panel charge the batt when called for, and a load running.. In order to go full scale I need the current/voltage sense breakout board since I'll be dealing with voltages above 5vdc ( actually around 14 or so ).. The project is for a diesel generator to maintain a bank of batteries, allowing it to operate in a start/stop mode.. So it's similar to what your doing, except I dont need to know battery life, just the voltage, the current being used by the loads, and charging current.

I was looking into current transducers, but the breakout board from Sparkfun is far more cost effective. With enough testing, and that board I think you'd be able to closely judge battery life..