Vintage Tractor Engineer

Fitting battery leads to your tractor.

When fitting screw clamp type battery terminals to the leads it is important to get a good contact between the terminal and the lead. The problem is that when the clamp screws are tightened, the wires tend to spread out which results in a poor electrical connection and hence an inefficient transfer of power when under starting load.

An improved connection can be achieved by running solder into the wires before the terminal is fitted, as shown in the photo below. This will make the end of the cables rigid, allowing the clamp screws to take a firm hold. If this has not been done, then the connection is more likely to deteriorate and could be the cause of poor starting performance.

Care is needed during the soldering to make sure that the insulation is not damaged. The correct flux should also be used. Beware, due to the conductivity of copper, the heat will travel quickly and a long way along the cable.

When the new cables and terminals are fitted, anti-corrosion gel should be applied to the exposed metalic surfaces around the battery terminals to prevent corrosion.

Remember, many battery terminal clamps need a spanner size of 5/16ths Whitworth. This is indicated when both 1/2in AF and 13mm spanners are too small, whereas 9/16in AF and 14mm spanners are too large. There is no need to overtighten the clamp bolt if all the surfaces have been cleaned before connecting. Do not clean the battery posts using a wire brush as this can cause sparks and thus an explosion of the hydrogen gas in the battery.

Other areas to check on the leads are the insulation on both leads and the integrity of the terminals on the starter motor and earthing point.

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