TX2 Battery Power Requirements

I am going to attempt to run my TX2 plus carrier board dev kit from an 8.4V LiPo Battery (1Ahr, 20C). Haven’t tried it yet but I am assuming it will work given the TX2 input voltage range (5.5-19.6V). Trying to get some information beforehand.

My questions are for anyone who has tried this before.

Is the input power for the TX2 constant? What I mean is, does the unit pull less current at higher voltage and more current at lower voltage? Or is the current draw more or less constant regardless of input voltage level?

At what voltage level will the module start to shutdown or go to sleep? From what I can tell, the module is controlled by a “Vin_PWR_BAD#” signal from the carrier. What is the threshold of this signal transition from high to low? And can it be changed?

Appreciate any assistance provided.

Once I get my module up and running, I will amend this post to show my results.

The input voltage level will not change as your battery’s power output capability is much higher than the maximum power consumption of TX2, and also the input voltage will go through some DC/DC to convert to appropriate constant level.

For the other info you mentioned, please refer to OEM DG, module datasheet and other doc in download center. https://developer.nvidia.com/embedded/downloads

The module and development board uses DC DC converters, which means they draw more current if the voltage is lower.

The module is specified as 5.5V minimum. I imagine that any conforming power control circuitry will assert power bad and shut down if the voltage goes below that.

If you’re using a LiPo straight into the Jetson, I suggest you use a “low battery alarm” to save the battery from over-discharge; LiPos discharged below 3.0V per cell are dangerous to recharge and dangerous to use after re-charge (and, in fact, if they over-discharge, you may not be able to re-charge them at all, even if you’re willing to live dangerously.)
For example: http://amzn.to/2rTx3ru

I’ll connect jetson tx2 with 11.1V LiPo(3S) Battery, and I’ll connect my jetson with orbitty carrier. I want to know the operation time of my kit…
I want to use at least 40minutes, but I’m not sure that the battery capacity is enough…
I’m look forward to get your reply for my work. Thanks.

The maximum work time depends on the work load and battery capacity. Measure the even power consumption during your work load running, then calculate the work time with it and battery capacity.

Of particular interest from the power design doc for TX2: “By default, the Jetson TX1 Developer Kit voltage and current monitor is configured for 19V input. If less than 19V input is used, the user must reconfigure the critical current limit of VDD_IN. If not set, unexpected CPU/GPU throttling and performance slowdown may occur.”

So it sounds like, while TX2 might work just fine with the voltage you’re supplying, you need to configure it, otherwise it will throttle. (Unless I’m reading it wrong?)

“I’ll connect jetson tx2 with 11.1V LiPo(3S) Battery”

The most important datum for battery lifetime is the energy content – measured in Watt-Hours.
Without telling us how many watt-hours the battery has, it’s impossible to calculate runtime.

If your battery has a certain number of amp-hours, then you can convert that to approximate Watt-hours by multiplying by the nominal voltage. So, if your battery is 1800 mAh, and 11.1V, then you’d get 1.8 Ampere-hours times 11.1 Volts equals about 19.98 Watt-hours.

A fully loaded GPU + CPU jetson, using the WiFi and other bits of the devkit board at full steam, may draw 25W or so. An idling system will draw less than 5W. For fully loaded, you’d get 6020/25 == 48 minutes of operating time from absolute full to absolute empty. For an idling system, you’d get 605/25 == 240 minutes, or about 4 hours.

All of these are of course approximate best-case numbers; you have to figure out the specifics of the battery and load you’re using, yourself. Easiest is to add a low-battery alarm, charge the battery full, turn on the Jetson with your workload, and then run a stopwatch until the low-battery alarm sounds. That’s your runtime. Make sure to disconnect the battery and re-charge it after the low-battery alarm!

Be forewarned that, while a 3S / 4S lipo might work with the devkit, not all carrier boards are created equal. If you’re using anything other than the devkit as a carrier board, it may have it’s own power requirements.