Update third_scale.md

docs/third_scale.md

@@ -19,6 +19,20 @@ Since the last two measurements corroborate each other, the torque specification
 ### Motor Mounts
 
 ## Power and Electrical
-
+* The stock motor pulls 16A at 24V, leading to 16*24= **384W**
+* The Docyne motor (throttle) is 5A at 18V --> 5*18 = **90W**
+* The Docyne motor (brake) is also **90W** (although used much less frequently)
+* The On Board Computer (OBC) uses **65W**
+* The NVIDIA Orin + ZED cameras use roughly **100W** (?check this empirically?)
+
+The third-scale vehicle's battery is selected based on the above power requirements, which **sum to 729W** (Watts). If we select a 44.4V (volts) battery, the current draw is 729/44.4 = 16.4A (amps). Thus a 16Ah = 16000mAh battery would last one hour of operation and a 32Ah battery would last roughly 2 hours.
+
+The choice of battery voltage is informed by the ability to have step-down DC-DC converters from [48V>>24V (rated up to 16A)](https://www.amazon.com/Victron-Energy-Orion-Tr-380-Watt-Converter/dp/B07DPZ9G7M) and [48V>>12V (rated up to 30A)](https://www.amazon.com/Victron-Orion-TR-DC-DC-Converter-Isolated/dp/B07DQ5H3T2).
+* The [motor controller board](https://trampaboards.com/vesc-100v-250a-in-cnc-t6-silicone-sealed-aluminum-box--p-28113.html) accepts voltages between 14-100V.
+* The [On Board Computer (OBC)](https://www.onlogic.com/k804/) accepts voltages between 12-48V (so this sets the upper limit on voltage, unless we wanted to use another step-down converter to 45V).
+* The [Docyne motor](https://www.docyke.com/products/servo-motor) accepts voltages between 12-24V.
+* The NVIDIA Orin accepts voltages between 7-20V.
+* The LIDAR operates on PoE sourced from the OBC.
+* The ZED cameras operate on GMSL connections from the NVIDIA Orin.
 
 ## Sensor Mounts