Optima BTDC-4.2 leisure and marine battery, rated 55Ah 12V 765A

At a glance: Built for boats and motorhomes, the Optima BTDC-4.2 carries the rating 55Ah 12V 765A. Technology matters here: it is a spiral-cell AGM battery.

Why choose the Optima BTDC-4.2

Cruising yachts and touring motorhomes often share the same battery code: Optima BTDC-4.2. Polarity is positive on the left-hand side, which keeps the cable run unchanged in most lockers. Matching a whole bank is easier at baterias.online, where each model keeps its exact code.

With 55Ah, it suits smaller engines and machines with few accessories. 765A gives more starting power than most batteries of similar dimensions.

Technical figures at a glance

Optima BTDC-4.2 in everyday use

Weekend sailors often find the engine battery fine and the domestic bank flat. Set the mains charger, the solar regulator and any B2B charger to the spiral-cell AGM profile. Swollen cases or a smell of acid in the locker call for immediate attention.

How spiral-cell AGM batteries work and how to look after them

Rolled plates offer a large surface in a compact space. Off-road vehicles love spiral cells for vibration resistance. Recharge after heavy accessory use.

Quick compatibility checklist

• ✓ The capacity rating, 55Ah, should suit the consumers you run. Lots of electrical equipment calls for the higher end.
• ✓ For winter starts, 765A should at least match the old battery.
• ✓ Terminal check: 1 & 21. Spade widths and post diameters vary, so match the type exactly.

Answers before you buy

Batteries with the same format

If you prefer another make, these fit the same space with the same terminal side.

Optima YTS-4.2Optima YTU-4.2Optima BTSLI-4.2

See also

Finished comparing? Placing your order online takes a couple of minutes. Bookmark this page if you want the data sheet to hand while fitting.

• Other batteries for boats and motorhomes
• See every Optima reference