Power distribution

Submitted by CaptainPi on Thu, 06/29/2017 - 03:14

Forums:

I'm just curious about how much power I need for the thunderborg. I've got 2 12v dc motors so do I need a 12v battery or is the power halved between them so that'll need two batteries. So will each motor get 12v or will each only get 6v and how much power will be given to my raspberrypi. I'm also wondering how far off until it will be ready for market. There's no rush but an idea would be helpful. Thanks guys :)

piborg's picture

piborg

Thu, 06/29/2017 - 10:54

Both motors will get the full battery voltage at 100% output, which would be 12V from a 12V battery. What will happen is that the current drain on the battery will be doubled. The net result is the battery will last for about half as long running two motors as it would for running a single motor.

As long as the battery can keep up with the current drain from both motors and the 5V DC/DC at the same time then the ThunderBorg will be able to provide full power to both the Raspberry Pi and the motors at the same time. Good quality rechargeable batteries should not have any problem with this.

Our MonsterBorgs used in the Formula Pi races use four 12V motors (two in parallel per output) with a 10x rechargeable AA (~12V) battery pack and a Raspberry Pi 3 powered by a ThunderBorg. This works well even with all motors at 100% output :)

ThunderBorg will be released within a week, so keep your eyes peeled :)

piborg's picture

piborg

Fri, 06/30/2017 - 15:58

You can now order ThunderBorgs from our brand new store site: https://shop.piborg.org/products/thunderborg

CaptainPi

Tue, 08/08/2017 - 06:30

I was thinking about using the rechargeable 18v batteries from power drills with 12v motors by using a buck converter. However I've had trouble finding one that doesn't keep it at a stable current (eg 2A). This will be an issue won't it. Eg with both motors on they will be at half power plus I don't want to damage anything. Or do you have another suggestion of how to do this.
Cheers guys

piborg's picture

piborg

Tue, 08/08/2017 - 11:29

You can use your 18V batteries with the ThunderBorg without needing any 12V regulator. All you need to do is limit the output from the ThunderBorg to a 12V maximum.

In your case to get 12V output to the motors from a 18V battery the maximum power output should be:

12V ÷ 18V = 0.667

which is 66.7 %

Most of our examples for ThunderBorg already have a calculation to figure out the maximum allowed power. All you would need to do is find this section in each example:

# Power settings
voltageIn = 12.0                        # Total battery voltage to the ThunderBorg
voltageOut = 12.0                       # Maximum motor voltage

and change the two voltages to match your battery and the motors. The script will then calculate a maxPower value which it will use for full speed :)

CaptainPi

Tue, 08/08/2017 - 23:55

That's great to hear and exactly what I was hoping for.
Cheers guys.

Subscribe to Comments for "Power distribution"