Why does my solar node keep dying at night?

Diagnosing Night Drain

If your solar node runs fine during daylight but goes offline overnight, you have one of three problems: undersized battery, incorrect charge controller settings, or excessive power draw.

Step 1: Verify Actual Battery Capacity

First, measure what you actually have. LiPo and LiFePO4 batteries are frequently sold at optimistic ratings. A "5000 mAh" LiPo from an unknown manufacturer may test at 3000-3500 mAh in practice.

Test: Fully charge the battery, disconnect solar, and measure how long the node runs. Node runtime (hours) × current draw (mA) = actual battery capacity (mAh).

Step 2: Calculate Required Overnight Capacity

In winter at high latitudes, "night" can mean 16+ hours of darkness. Your battery must cover: hours of darkness × node current draw.

Example: 14 hours dark, 12 mA draw = 168 mAh minimum. Even a small 1000 mAh battery covers this with margin. If your node dies overnight, either the battery is not fully charging during the day or the current draw is much higher than expected.

Step 3: Verify the Battery is Actually Charging

Check the charge controller status LED or voltage output during the day. Common issues:

• Panel undersized for the season - A panel just barely adequate in summer may not fully recharge the battery on short winter days. The battery reaches discharge before it can recover overnight.
• Panel partially shaded - Even partial shading (one corner of the panel) can reduce output by 50-80%. Inspect during the time of day the sun is lowest (winter morning/afternoon).
• LVD set too high - If the charge controller's Low Voltage Disconnect threshold is set above the battery's actual minimum, it cuts power while charge still remains. For LiFePO4: LVD = 3.0V/cell (12.0V for 4S). For LiPo: LVD = 3.0-3.2V/cell.
• Charge controller in wrong battery mode - A controller configured for lead acid will overcharge LiPo or undercharge LiFePO4. Verify the battery type setting matches your battery chemistry.

Step 4: Reduce Power Draw

If the battery and panel are correctly sized but the node still dies, attack the power draw:

• Disable OLED display (save 15-20 mA)
• Disable Bluetooth (save 5-15 mA on ESP32)
• Switch from ESP32 to nRF52840 board (save 30-50 mA average)
• Reduce TX power to minimum needed (each 3 dB reduction in TX power roughly halves transmit current)