Why does the charger "Pap" when I connect it to the battery?

That little “pop / snap / pap” when you plug a 72V charger into a 72V battery is almost always inrush current. Totally normal in high-voltage EV / e-bike / pit bike systems, but worth understanding.

⚡ What’s causing the “pap”

Inside your charger (and sometimes inside the battery/BMS) are large capacitors.

When you plug in:

• Your battery is sitting at ~75–84V (depending on charge)

• The charger’s capacitors are at 0V

• The instant you connect → the battery dumps current into those empty caps

• That creates a huge split-second surge

That surge =
💥 tiny arc at the connector = “pap”

It’s literally a micro lightning bolt.

🔧 Why it’s more noticeable on 72V systems

At 72V nominal, you’re really dealing with:

• ~84V full

• High current capability

• Low internal resistance

So:

Higher voltage + high current = more visible arc.

That’s why you don’t really hear this on 36V scooters, but you do on Sur-Ron / Talaria / E&C RTR / etc.

⚠️ Is it bad?

Short term:
👉 Usually no, if it’s occasional and small.

Long term:
👉 Sort of, you may see some black soot on the copper connectors. Simply clean with isopropyl alcohol and a cotton swab

“Pre-Charge” Manually

Plug in slowly until you feel first contact, wait 1 second, then seat fully.

That tiny touch charges the caps before full contact.

Works surprisingly well.

Plug Order Matters

If your charger has AC input:

Best sequence:

1. Plug charger into wall first

2. Let it power up

3. Then plug into battery

This way the charger caps are already charged.

Reduces pap.

🚩 When to worry

Not normal if:

• Loud crack

• Visible big spark

• Connector getting hot

• Burn marks

• Charger stops working

• Plug feels loose

If you see those, stop immediately and submit a support ticket