12VNominal voltage
50AhCapacity, 20-hour rate (C20)
815AStarting power (EN)
Summary: Built for boats and motorhomes, the Optima BTSLI-4.2 carries the rating 50Ah 12V 815A. Get the size and terminal side right and you are most of the way there.
Optima BTSLI-4.2 data sheet
Using it day to day: practical tips
Rough passages give boat batteries a beating that a car battery never sees. Keep a battery monitor reset after fitting new batteries. Charging on the wrong programme quietly shortens battery life.
Alternatives that fit the same space
Cannot find the Optima BTSLI-4.2 you want? These share the same size and terminal layout.
Optima BTDC-4.2Optima YTS-4.2Optima YTU-4.2
Why choose the Optima BTSLI-4.2
Narrowboats and fishing boats sometimes carry a Optima BTSLI-4.2 too. Ratings of 50Ah 12V 815A give a starting point for sizing a service bank. Ordering from baterias.online takes minutes once the code and chemistry line up.
Small and light at 50Ah, ideal where space is short. 815A beats many larger batteries for cranking.
Frequently asked questions
Should I charge a stored battery before use?
Store it fully charged, away from heat and frost, and give it a refresh charge before installation.
Will the Optima BTSLI-4.2 fit my battery space?
The case measures 254 × 175 × 200 mm and the battery weighs 18.4 kg. Check both against your tray and the hold-down before ordering, and lift it with care.
What do 50Ah and 815A mean for this battery?
It stores 50Ah and delivers 815A of cold cranking current under the EN test. Choose a battery that matches or slightly exceeds the figures of the original.
Check before ordering
- ✓ Size check: 254 × 175 × 200 mm. A battery even slightly taller than the original can touch the bonnet or the seat base.
- ✓ Plus pole position: positive on the left-hand side. Mixing up orientation is the most common reason a battery of the right size will not connect.
- ✓ 50Ah sets how long the battery can power things with the engine off.
See also
Finished comparing? Placing your order online takes a couple of minutes. Recycling the old battery is easy at most tips and garages.
spiral-cell AGM: how it works
Pressure inside the cylinders keeps the plates firm. Spiral batteries power winches and lights well. Secure spiral batteries with proper brackets.
