Replace a Melted XT60 or Anderson Connector on a Low-Voltage Lead

Why this happens

Connectors melt when resistance at the contact creates more heat than the housing can shed. Common causes are a loose or worn contact, a poor solder or crimp joint, corrosion, or more current than the connector and wire are rated for. Simply fitting a new connector without fixing the cause leads to another melt, so the investigation matters as much as the repair.

What you need

Step by step

1. 1

   Decide whether this is a DIY job

   Only do this on a lead that can be completely separated from any battery, such as the controller side, an accessory lead or a lead on your bench project. If the melted connector is on the battery pack's own output lead, stop and take it to a service centre: working on a lead attached to a lithium battery risks a dead short you cannot switch off.

2. 2

   Disconnect and confirm zero voltage

   Unplug the battery from the lead and remove it from the work area. Wait a minute and measure across the lead's terminals with a multimeter to confirm zero volts, as controllers can hold charge in capacitors. Remove jewellery, work on a fire-safe mat, and use insulated tools.

3. 3

   Find out why it melted

   Inspect the old connector. Melting on one side only often means one contact was loose or badly soldered. General melting suggests too much current for the connector or wire size. Check the wire for heat damage further along, and note the current the lead actually carries. If the wire is discoloured or stiff, cut back to clean, flexible copper or replace the wire.

4. 4

   Choose the right replacement

   Fit a connector rated comfortably above the continuous current, from a reputable supplier, and matching the mating connector. If the old one was undersized for the load, upgrade both halves to a suitably rated type rather than repeating the mistake. Mark polarity clearly, and keep the polarity convention the same as the other half.

5. 5

   Cut and prepare the wires one at a time

   Cut and replace one wire at a time so the two conductors never have bare ends exposed together. Slide heat-shrink onto the wire first. Strip just enough insulation to fill the solder cup or crimp barrel without bare copper showing beyond it.

6. 6

   Solder an XT60 or crimp an Anderson contact

   For XT60, mate the connector with a spare half to hold the pins aligned while they heat, tin the wire and the cup, then join them with enough heat for the solder to flow smoothly. For Anderson-style contacts, crimp with the correct die and pull-test before pushing the contact into the housing until it clicks.

7. 7

   Insulate and check polarity

   Slide the heat-shrink over each joint and shrink it so no metal is visible. Use red for positive and black for negative if you can. Before connecting any power, check with the multimeter that there is no continuity between positive and negative and that each pin connects to the correct wire end.

8. 8

   Test under load and monitor

   Reconnect and run the circuit under its normal load for a few minutes. Check the connector temperature with an infrared thermometer and compare it with the wire next to it. They should be similar. Recheck after the first few uses; a connector warmer than its wire means a poor joint or an undersized part.

How to tell it worked

The new connector clicks firmly into its mate, polarity is correct, and after running under load it stays at about the same temperature as the wire either side.

Questions