Don’t Buy Any Lithium BatteryUntil You’ve Read This

First of all, it depends on the generation of cells and their design chemistry. Normally, a manufacturer specifies this in the documentation. In the "Cruiser" battery series, we use the latest generation of lithium-iron-phosphate (LiFePO4) EVE A-Grade cells with 8,000 cycles before degradation.  But this is only a physical test of the cell, under ideal laboratory conditions, and many parameters reduce this number during real operation as part of an assembled battery. The tests are carried out at a temperature of 25 degrees Celsius, and increasing the temperature dramatically reduces the number of cycles. For example, an average cell on the market (designed for 6000 cycles at a temperature of 25 degrees) will show a result of only 2500-3000 cycles at a temperature of 45 degrees Celsius. Many users operate batteries in the tropics and subtropics, where ambient temperatures are 30+°C. A marine battery typically has a sealed, moisture-proof enclosure with a waterproof rating of at least IP65. As a result, the temperature inside the battery case is always significantly higher than the ambient environment. Voltage drop in the wires generates heat. The only way to minimize this temperature increase is to reduce the internal resistance of all battery components, such as the BMS and wires. That's why we use internal wires with a cross-section of at least 64-75 mm² and a 300-amp BMS with low internal resistance. However, thick copper wires and powerful BMS systems are expensive, so most manufacturers use the minimum cross-section and smaller BMS without considering voltage drop and the generation of additional heat. Wire thickness and internal resistance matter for Marine Grade batteries! During manufacturer tests, prismatic cells are compressed. If compression is not used, the number of cycles decreases, sometimes by 20-30%. Compression is especially important at high currents close to 0.5C and above. We often see such currents in marine applications because we typically use 12-volt systems and are limited by space for battery installation: small total capacity and high current mean a high C-rate. In the Cruiser battery series, the cells are compressed and fixed in the module. However, most manufacturers skip compression to save costs. Compression matters for marine applications!