Battery Drains Overnight
Step 4 of 4
"Bike worked last night. Now it's dead again. Something's drawing power."
The Vampire Drain
Parasitic drain happens when something continues to draw current while the bike is OFF — often aftermarket accessories or a faulty relay.
A small drain is normal (clock, alarm, ECU memory), but anything over 30mA (0.03A) will eventually drain your battery if the bike sits for a few days.
🎙️ Listen to Explanation
🛠️ Diagnostic Steps:
- Set multimeter to current mode → connect in series
- Watch for amp draw (>0.03A is a problem)
- Pull fuses one-by-one to isolate the draw
In this lesson, you'll learn:
- How to diagnose parasitic battery drain
- Common causes of overnight battery drain
- How to use a multimeter to measure current draw
- How to isolate the circuit causing the drain
🧩 Parasitic Drain Simulation
Diagnose the parasitic drain by disconnecting accessories and checking relays.
12V
🔌
⚡
Current Draw (Key OFF)0.12A
0A0.03A (Max Normal)0.2A
Diagnosis
The USB charger is drawing power even when the bike is off! This is draining your battery overnight.
❓ Quiz
What can cause parasitic battery drain?