# How to calculate the battery usage of raspberry pi with 2 motor drives

We have a raspberry pi 4 with 2 12v motor drive L298, 5 ultrasonic sensors, and raspberry pi camera but we need to know how to calculate the battery usage of all these chips, could anyone help with this

• I can not see any relevance to the Raspberry Pi. Why don't you just buy a meter and measure consumption?
– joan
Dec 29, 2019 at 17:39
• That's what I was going to suggest. Dec 29, 2019 at 18:41
• Ah, let me see. If you worry your battery cannot last long, then you can check the motor current spec and battery capacity. Even toy motors can take over 1A, so if your battery is only 1000mAH, then it would last about an hour. Forget the little sensors, because they drink much much less than the big thirsty guy, I mean the motors. Dec 30, 2019 at 2:59

You can get wattage readers that plug to your wall and then you plug your devices to it. But if you don't want to get one this is how you do it.

Find out how any watts you use in total (Pi 4 is 5W, motors are 3W... you get the idea) then divide that by 5V. That'll be an estimate of how many amps you need an hour (assuming you are using a 5V battery pack).

Failing that, get a battery pack and run the system at full usage constantly until loss of power while recording it with a camera. The minutes from power on till power failure are what you need. Then use the rule of 3 to calculate the power usage. Example : You run your system with a 6A (6000mAh) battery pack. That means you can run at 6A for 60 min. Your system shuts down in 46 min. So if: 46 min = 6A

60 min = x

Multiply 60 min by 6Amps then divide by 46 min.

60min x 6A= 360

360/46=7.83A

You need a battery with 7830mAh per hour of operation of your device.

Now you only need to find a pack or packs capable of outputting that total amount of current and you are done.