Batteries and Power Budgets

Every robot runs on a budget of watts. The average power decides how long the battery lasts. The peak power, mostly from motors starting or stalling, decides whether the battery and wiring can deliver enough current without the voltage dropping and the computer rebooting.

Single-board computer (6 W) AI compute module (15 W) 2D LiDAR (2.5 W) Depth camera (3.5 W) Microcontroller and sensors (1 W) Small arm with 4 servos (8 W average) Time spent driving Battery pack Capacity Max discharge (C rating) Converter efficiency

The budget

Electronics usually run through a voltage converter with efficiency $\eta$, while motors draw from the battery directly. With a pack of voltage $V$ and capacity $C_{Ah}$, using about 80 percent of it to protect the cells:

$$P_{\text{avg}} = \frac{P_{\text{electronics}}}{\eta} + D\,P_{\text{drive}} \qquad t_{\text{run}} \approx \frac{0.8\,V\,C_{Ah}}{P_{\text{avg}}}$$

A pack rated at $C$ can safely supply $I_{\max} = C \times C_{Ah}$. The peak current, when both motors stall, is $I_{\text{peak}} = P_{\text{peak}} / V$.

What to notice

Add the AI compute module and the runtime drops sharply, since it uses more power than the rest of the electronics combined. Motors may use the most energy, but they also set the peak current: two stalled motors can pull far more than everything else together. If the peak passes what the battery can supply, the voltage sags, and the computer may brown out and reboot. That is why robots often put the computer on its own regulator or battery.

The wattages here are typical round numbers, not measured values for any specific product. Check data sheets for the parts you use.