How to Replace Corroded Battery Terminals

Got badly corroded battery cables? Here’s how to replace your car’s battery cable terminals with new ones in about an hour-and for less than $20.

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Replace Your Corroded Battery Terminals

Replace Your Corroded Battery Terminals

Corroded battery terminals can cause more problems than just poor starting. The “blooming” corrosion taking place on the battery terminals shown here is a pretty extreme example. But even minor corrosion can reduce alternator output by 30 per cent. That can stress your charging system and cause early failures.

On the starting side of things, the extra resistance causes slower cranking, overheated starter motor windings and premature starter failure (at about $400 each, including labour!). Prevent premature failures by replacing old corroded terminals. You just need a set of wrenches, a hacksaw and about an hour. The best part is, the whole job costs less than $20.

Required Tools and Materials for this Project:
Socket/ratchet set
Wire brush
Wrench set
Heat gun 
Plastic gloves
Battery cable terminals
Heat-shrink tubing
Neutralizing felt pads
Anti-corrosion spray

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Check the battery terminals and cables

Check the battery terminals and cables

If the battery terminals have minor corrosion, just remove them and clean them and the battery posts with a wire brush. Using the wire brush, neutralize the battery acid with a baking soda/water solution. Or buy a can of battery terminal spray cleaner. Dry off the battery with paper towels. Then apply acid neutralizing felt pads (about $3 a set) to the posts and connect the cleaned terminals.

Finish the job by coating each terminal with anti-corrosive spray. If the old plastic guards are damaged, install new ones (about $5 a set). But if either or both terminals don’t clamp tight or the corrosion is eating away at the metal, they should be replaced. And if you see any green corrosion on the copper cable going into the moulded lead terminals, it’s a goner.

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Buy the best terminals

Buy the best terminals

Every auto parts store sells cheap lead battery terminals. They work. But the clamp plate squashes the cable flat, so you only get partial electrical contact. Instead, get pro-style cast-copper compression terminals. A compression terminal is made from tinned copper and makes full 360-degree contact with the cable. Seal the entire connection with heat-shrink tubing to prevent corrosion. Buy QuickCable brand battery terminals at NAPA for $3 to $8 each, depending on the cable size. Also buy red and black heat-shrink tubing.

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Replace the battery terminals

Replace the battery terminals

Disconnect both battery terminals. With the battery terminals disconnected, use a slip-joint pliers to hold the terminal while you hacksaw it from the cable. Don’t saw it off while it’s still on the battery. Next, cut off about 1.25 cm of insulation from each cable. If the copper strands are green, clean them with a baking soda/water solution and a wire brush. Dry the cable with compressed air.

Slip the heat-shrink tubing over the cable and slide it down so it’s out of the way. Then insert the main cable and any smaller cables into the compression nut. Screw on the battery terminal and tighten until snug. Then slide the heat-shrink tubing over the connection and use a heat gun to shrink it.

Note: Always wear eye protection when working on car batteries, and don’t smoke.

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