The charging system

Later E-Types use an alternator where the earliest cars carried a dynamo, and the checks differ a little, but the logic of diagnosis is the same: is the battery being charged, and where is the charge going.

Working through it

• The belt. A slipping alternator or water pump belt charges poorly and shows as a glaze, a squeal on load or dust in the engine bay.
• The charging voltage. With the engine running at a fast idle, a voltmeter across the battery should show a reading clearly above the battery's resting voltage. A reading that stays at resting voltage means the system is not charging; the precise healthy figures belong to the manual for your system.
• The warning light circuit. A failed ignition warning lamp or its wiring can stop an alternator charging at all on some systems.
• The drain. With everything off, a current meter in series with the battery shows what is being drawn at rest. A significant draw with the car asleep is a fault to find, not a battery to replace.

The battery itself

A battery that has been flattened repeatedly through storage or a drain loses capacity permanently, and no charging system will cure a battery that will no longer hold charge. Modern batteries of the right size and terminal layout fit without drama; period-looking cases exist for those who want them.

Replacing the battery

Battery location and hardware changed during the E-Type's life, so the first step is to identify what is in front of you rather than assume it matches a generic picture. The six-cylinder cars carry the battery in the engine bay, mounted on a tray or frame against the bulkhead or inner wing. The V12 cars moved the battery to the boot, partly to free space around the wider engine and partly to alter the weight distribution; it sits in its own tray with a hold-down rod and wing nut.

The awkward holding clips

The six-cylinder cars used a bakelite tray with a top frame or clamp held by short rods and wing nuts. Reproduction clamps and modern, slightly oversized batteries do not always agree, and owners often report that seating the frame squarely without the metalwork touching the terminals takes more patience than the job appears to deserve. The rods are short, the angles are tight, and the battery must finish upright with the vent tube still connected. It is worth test-fitting the new battery with the terminals covered before connecting anything.

The V12 boot installation swaps the frame for a single hold-down rod and a small wing nut, which is easy to drop into the boot trim. The battery has to be lifted in and held steady while the rod is threaded, and the boot floor and trim leave little room for fumbling.

What to check before buying a replacement

• Case size and terminal layout. Some markets used batteries with the positive and negative posts on opposite sides; the cable reach and clamp design must match.
• Capacity and cold-cranking output. The V12 in particular needs a battery that can turn the engine over reliably. Confirm the figures against the handbook or workshop manual for your car.
• The vent tube, especially on batteries mounted inside the boot or passenger compartment, where escaping gas needs a route outside.
• The earth or ground strap condition, because a new battery will still struggle if the return path is corroded.
• Tray corrosion or cracks. A loose battery will fail early and can damage the surrounding paintwork or wiring.

Once the battery is in place, the real test is that it stays put when the car accelerates, brakes and corners. If the clamp is loose or the case is the wrong size, it will work loose and the terminals will arc.

A note on upgrades

Dynamo-to-alternator conversions and uprated alternators are common and reversible. They are worth considering when a car has gained electric fans, pumps or other loads its original system was never asked to carry.