I just want to ask how many volts of battery should I use to power my arduino project. I have 5 buttons, 2 DC motor, 2 servo motor, 2 HC-SR04 sensor and a bluetooth module if I want it to last for about 5-10hrs. Thank you!

  • You use the right voltage for the rating of your various components. You should be asking about current and capacity, not voltage. You know the voltages of all your components already.
    – Majenko
    Jun 3 at 12:41
  • Hi @Majenko thank you! So how many mAh and capacity should I use? I'm sorry I'm new to this Jun 3 at 12:46
  • That 100% entirely depends on the components you are using and what duty cycle each component is used for.
    – Majenko
    Jun 3 at 12:47
  • 1
    You need to work out the average current that your system requires (in mA), then multiply that by the number of hours you want it to run for. That gives you the minimum mAh you need.
    – Majenko
    Jun 3 at 12:48
  • 1
    Thank you so much @Majenko appreciate it! Jun 3 at 12:51

Just imagine your design needed a 1.5V battery. There are various sizes around, like AAA, AA, C, D and so on. They all provide 1.5V nominally. The difference is the amount of power they can provide, namely the number of mAh (milliamp hours).

Therefore the size of your battery depends on how many milliamps each device uses, and how many hours you want it to run.

How will I compute for the mAh my device uses?

Some devices will tell you on the device or on the datasheet. Otherwise you could measure it with a multimeter. Make sure you understand how to measure current with a meter. There will be many web pages with guides about that.

And by the way, it doesn't use mAh it uses mA.

Look, if you have a room heater that draws 1000W, then it draws 1000W while it is on. So, if you run the heater for an hour then it will use 1000Wh (1000 watts for one hour). That will use twice as much energy as running it for half an hour.

So, if your device takes 100 mA, and you want to run it for an hour, then you need a 100mAh battery. If you want to run it for two hours, then you need a 200mAh battery. Same mA from the device, but you are using it for longer.

  • Is there a "B" battery size? If not, why not?
    – Nick Gammon
    Jun 4 at 7:48
  • B for old bicycle lamps. discontinued 2001. P.S. mAh (at fixed V) is energy not power isn't it? Power (mWatts) is mA at nominal V. Jun 4 at 14:13
  • @RedGrittyBrick I always get those two mixed up. I think you're right. :)
    – Nick Gammon
    Jun 10 at 11:57
  • Hello @NickGammon sorry I just saw this now. How will I compute for the mAh my device uses Jun 10 at 14:49
  • @ThomasRaymondSantos - see my amended answer.
    – Nick Gammon
    Jun 11 at 7:51

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