USB Power for Aircraft

With growing interest in using tablets and smart devices in aircraft cockpits, USB charging often gets confused with USB data — and there's a lot of myth around what current actually flows.

Connector Types

USB Type-A (legacy rectangular) vs. USB Type-C (smaller oval). Older iPads use Apple's proprietary Lightning port; newer ones are USB Type-C. Other tablets may have USB-micro-B or Type-C.

Power Delivery

USB-A chargers provide 5.0V, initially supplying a minimum 0.1A. The device and host then "negotiate" the operating current, with maximum availability set at either 1.5A (USB consortium spec) or 2.4A (Apple proprietary). The normal operating power of your device will be much less than the charging power available on the charger.

Battery Charging Behavior

When an iPad battery is low, the device draws maximum available current for rapid charging — which is why it warms up. Normal operating power is much lower. With a completely depleted battery, a small circuit draws <0.1A to initiate negotiation before accepting full charging power.

Installation Considerations

For your power budget, account for conversion inefficiencies: add 10% to 20% to the output amount. A dual-port 2.4A charger requires approximately 27.6 W once losses are included.