AGM Battery 12 V 225 Ah (Group 8D)

AGM (Absorbent Glass Mat) technology means the electrolyte is fully absorbed in glass fiber mats. Its main advantages are:

A completely maintenance-free design (no water or acid topping up).No gas release during normal use, making it very safe.A very low internal resistance allowing high current delivery.

This Mastervolt battery (8D group model) provides a nominal voltage of 12 V and a capacity of 225 Ah (measured over 20 hours, C20). It is suitable for high-capacity service battery banks or for starting large engines.

This standard "group 8D" model has the following dimensions: 522 x 240 x 224 mm (Length x Width x Height, including handles). Its weight is 63.5 kg. Due to its significant weight, it is recommended to use appropriate handling equipment during installation.

Yes, absolutely. Thanks to its AGM design, it can deliver very high discharge currents. It has a cold cranking amperage (CCA) of 1080 A (SAE standard) and 680 A (DIN standard). It is therefore perfectly suited for starting large marine engines or powering bow thrusters.

The battery should be installed in the upright (vertical) position. Ensure it is securely fastened to prevent movement caused by the boat's roll or pitch.

If you install a bank of multiple batteries, you must leave a space of at least 1 cm between each unit. This allows for adequate heat dissipation and prevents overheating of the bank.

The battery is maintenance-free in terms of electrolyte: never open it or add distilled water or acid.

Check the tightness and condition of the terminals every three months. Keep the battery clean and dry using a soft, damp cloth (never use solvents or abrasive products).

Under normal use, the AGM battery does not emit any gas. However, in the event of accidental overcharging, a safety valve may release a gaseous mixture (hydrogen). It is therefore recommended to provide adequate natural ventilation if the battery is installed in a locker or confined space.

You must use exclusively a battery charger with an IUoUo charge curve (3-stage charging: Bulk, Absorption, Float). Using an unsuitable charger may irreparably damage the battery.

The maximum charging current accepted by this AGM 12/225 battery is 63 A. It is important to properly size your shore power charger or alternator to avoid exceeding this value.

For a reference temperature of 25°C, the voltage settings must be as follows:

Absorption voltage: 14.25 V (for a maximum of 5 hours). Float voltage: 13.80 V. It is strongly recommended to use a charger equipped with a temperature probe to compensate for charging (-30 mV/°C).

To maximize the lifespan of your AGM battery, avoid deep discharges. It is recommended not to regularly discharge the battery beyond 50% of its rated capacity. Always recharge the battery immediately after a discharge.

Yes, you can connect these batteries in series (e.g. for 24V) or in parallel (to increase capacity in Ah). However, all batteries in the bank must be of the same brand, same type, same capacity, and have the same state of charge. Never mix new batteries with used ones.

This battery is fitted with M8 terminals (type A). These terminals are removable, allowing you to either attach eyelet terminals directly or use adapters to make it compatible with all standard automotive battery terminals.

The battery can operate within a temperature range from -20°C to 55°C. However, the ideal nominal operating temperature is between 5°C and 35°C (25°C being optimal). Note that each 10°C increase above 25°C halves the battery’s lifespan.

To ensure optimal electrical contact and prevent overheating, the recommended torque for these battery screw connections is between 14.7 and 19.6 Nm.

Leaving a discharged lead-acid battery causes irreversible sulfation that destroys its capacity. The battery must be recharged to 100% immediately after use. Even during winter storage, it must be fully recharged at least once per month or maintained under float charge.

To achieve the best possible conductivity and minimize losses, it is recommended to directly mount eyelet terminals (cables) on the M8 threaded poles of the battery. To do this, first remove any conical pole adapters if they are installed.

Absolutely. It is in fact an excellent upgrade. A Mastervolt AGM battery delivers starting power equivalent to a flooded lead-acid battery with nearly double the capacity. Furthermore, it eliminates maintenance requirements (water levels) and the risk of acid leaks.

Yes, for obvious safety reasons. During installation and connection of the battery, all electrical consumers (loads) and chargers must be turned off. Always connect the negative cable (minus) last to prevent accidental short circuits with your tools.