If your car battery keeps going flat overnight, even after you replaced it, you may be dealing with parasitic draw.

Many car owners in Nigeria assume the battery is bad. Some replace the alternator. Others keep jump-starting every morning. But the real issue might be something silently draining power while your vehicle is parked.

In this guide, we’ll explain:

• What parasitic battery drain is
• What causes parasitic draw
• How to test it properly
• Normal vs abnormal amp readings
• How to fix it permanently

---

What Is Parasitic Draw?

Parasitic draw (also called parasitic battery drain) happens when electrical components continue to consume power after the vehicle has been switched off.

Every modern vehicle has a small normal draw to keep memory functions active — such as:

• Radio memory
• Clock
• ECU memory
• Security system

But when something malfunctions, the battery drains faster than it should.

---

What Is a Normal Parasitic Draw?

For most vehicles:

• ✅ 20mA – 50mA (0.02A – 0.05A) = Normal
• ⚠️ Above 80mA = Suspicious
• ❌ 0.3A (300mA) and above = Problem
• 🚨 1 Amp and above = Severe battery drain

If your meter shows 0.93A, 3A, or 5A, your battery will drain overnight.

For example:

A 75Ah battery with a 1A draw can be completely weak within 24–48 hours.

---

Common Causes of Parasitic Battery Drain

Here are the most common causes we see in workshops:

1. Faulty Infotainment System

Modern vehicles like:

• Toyota Highlander
• Lexus RX 350
• Mercedes-Benz C300

Often develop radio modules that refuse to sleep.

Symptoms:

• Battery dies overnight
• Screen sometimes stays on
• Draw drops when radio fuse is removed

---

2. Body Control Module (BCM) Not Sleeping

The BCM controls:

• Interior lights
• Door locks
• Immobilizer
• Alarm

If the BCM fails to enter sleep mode, it can maintain a 0.5A–2A drain.

---

3. Trunk or Bonnet Light Staying On

A faulty switch can cause the bonnet or boot light to remain on even when closed.

Many drivers don’t notice this.

---

4. Stuck Relays

Fuel pump relays or cooling fan relays sometimes stick internally.

This causes continuous power flow even with ignition off.

---

5. Aftermarket Installations

Poorly installed:

• Tracking devices
• Amplifiers
• Reverse cameras
• Alarm systems

Are major causes of parasitic battery drain in Nigeria.

 

---

How to Prevent Parasitic Battery Drain

• Avoid cheap electrical installations
• Fix dashboard warning lights immediately
• Use proper diagnostic equipment
• Ensure doors/bonnet switches work
• Disconnect battery if vehicle will sit for weeks

---

Final Thoughts

Parasitic draw is one of the most misdiagnosed automotive electrical problems.

If your battery:

• Dies overnight
• Dies after 1–2 days parked
• Is new but still going flat

You likely have an electrical drain issue.

Proper diagnosis saves money and prevents repeated breakdowns.

---

Need Professional Diagnosis in Lagos?

If you’re experiencing battery drain or electrical faults, expert diagnosis is critical.

Visit Carmedis – Auto Repair By The Best Mechanics in Lagos
🌐 www.carmedis.com
📱 WhatsApp: +234 803 898 5410

We use advanced diagnostic tools to trace electrical drains accurately and fix them permanently.

•