# Zumo 32u4 higher voltage

So I tried to increase the voltage to my Zumo 32u4, I upped VBAT to 10.8 volts. I was thinking that 11V was the max for me to go, but I have subsequently re-read the documentation and see that 10V is the maximum for VBAT. I would like to understand what I did. After increasing the voltage, the robot still functions and runs the current program. When I connect the USB cable, the robot does detect that power and turns on, but the computer does not “see” the robot. I cannot get the computer to detect the port where it is plugged in. I don’t know if there may be any way to fix this. I also want to understand what I did so I don’t repeat the same mistake. I’m helping a Middle School class build a number of these and this was my (failed) prototype to increase the power. I’ve also been experimenting with bypassing the voltage divider, but I’ll post that question separately.

I’m working on a 32u4 robot. I wanted to get more power to the motors, so I snipped the A=VBAT/2 connector. Before I did this I measured the voltage across the batteries at 5.6V, and measured the voltage across the motors while running at about 2.8V. After I snipped the connector both of the voltages remained the same. I also increased VBAT to about 7V and the voltage across the motors measured ~3.5V. Shouldn’t I be seeing more voltage across the motors while their running after snipping this connector?

Hi.

I merged your two threads to make it easier to follow and respond since it seems they are related to the same robot.

The surface-mount jumper labeled “A1 = VBAT / 2” is used to disconnect pin A1 from the voltage divider that allows the robot to read its own battery voltage. It has nothing to do with what voltage gets supplied to the motors. If you are only seeing about half the battery voltage at the motors, I suspect you are not driving them at full speed. Is this the reason you increased th battery voltage? What kind of battery are you using now?

Sine you cut the VBAT / 2 jumper, it should be safe to apply up to 11V to the battery power input of the Zumo 32U4, but 10.8V is very close to that, and if that the nominal voltage of your battery, it will almost certainly be over 11V when fully charged.

Has the robot ever successfully connected to your computer? Have you programmed it before? Could you double check that you are using a USB cable that can transmit data rather than a charging cable? Could you try different cables, USB ports and if possible a different computer?

-Claire

Thanks Claire,

Your response certainly helped. My motors were running at about 50% power so that explains the difference. The main reason I want to increase voltage is just to have more power. My students are competing against robots that can weigh up to 1 kg, so we need all the help we can get. I use a combination of nominal and fully charged AA Nimh to get the 10.8 volts.

I thought I had fried two robots, but I did try various computers and cables and got one of them working. The other robot (luckily that was my robot) must have gotten shorted out when I was prototyping how to stack another set of batteries on. It has no response to the USB input (not even a power light) and the components between the Micro-B port and the power switch get really warm when the USB power is plugged in. I don’t know if that give a clue, but I am already swapping out the main board because I’m pretty confident it’s toast.

I am glad to hear one of your Zumos seems to be fine. Since the other is heating up with just USB power, I agree that it seems damaged. Since you are currently only running your robots at 50% speed, I recommend testing them at full speed and with added weight before messing with the battery voltage. Several engineers here have used segmented balance weights to get our Zumos to 500g for mini sumo competitions.

If you want to order a new Zumo or main board, you can send us an email with a reference to this thread and your order information and we might be able to help you out with a discount.

-Claire