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README.md

@@ -129,6 +129,33 @@ When heading to your Local Game Store (LGS), a friend's house, or a tournament,
 
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+### 🔋 Battery Life & Power Optimization (850 mAh LiPo)
+
+The MTG Companion is engineered for long tabletop sessions powered by a standard **850 mAh 3.7V LiPo** cell (~3.15 Wh).
+
+#### Expected Runtime
+
+| Play Style | Average Current | Expected Battery Life | Notes |
+| :--- | :---: | :---: | :--- |
+| **Typical Commander / FNM Session** | **~60 – 70 mA** | **10 – 12 hours** | Screen ON, tracking life, token spawning, occasional card scans, Wi-Fi modem sleep active |
+| **Offline Play (No Wi-Fi)** | **~50 – 60 mA** | **12 – 14 hours** | Wi-Fi idle/disconnected, all card art and Oracle data streamed from local LittleFS flash |
+| **Heavy Wi-Fi Setup / Card Pairing** | **~130 – 160 mA** | **4 – 5.5 hours** | Continuous SoftAP web portal active, bulk Scryfall art downloads, OTA updates |
+
+#### Firmware Power-Saving Features
+
+* **💤 Automatic Wi-Fi Modem Sleep (`WIFI_PS_MIN_MODEM`):**  
+  When connected to Wi-Fi but not actively transferring data (e.g. while tracking life or waiting for card taps), the Wi-Fi radio enters modem sleep between beacon intervals. This cuts ESP32 power consumption by **~30–40 mA**. The radio automatically boosts to full power (`WIFI_PS_NONE`) during active Scryfall downloads, OTA flashing, or SoftAP pairing mode.
+* **📡 125 ms RFID Carrier Duty Cycling:**  
+  The MFRC522 polling loop runs an RF carrier burst sweep every 125 ms instead of continuously pumping 13.56 MHz RF power. This reduces average RFID reader draw from 20 mA down to **~5 mA** without any perceptible tag detection latency.
+
+#### ⚠️ Hardware Tip: LDO Voltage Regulator Selection
+
+To extract the full capacity of a single-cell LiPo battery (discharging from 4.2V down to ~3.4V):
+* **Recommended LDOs:** Use ultra-low-dropout regulators such as **ME6211**, **AP2112K**, or **XC6206** (dropout voltage ~100–250 mV). These maintain a solid 3.3V rail down to ~3.45V battery level, utilizing **>90%** of the battery's energy.
+* **Avoid AMS1117-3.3:** The common AMS1117 has a large 1.1V–1.3V dropout. When powered from a 3.7V LiPo, it browns out before utilizing even 20% of the battery capacity.
+
+---
+
 ## 🛠️ Part 2: Technical Specifications & Build Guide
 
 ### Hardware Architecture