How To Charge A Traction Boat LiFePO4 Battery?

Traction batteries are used for stable power supply of the boat electric motor and other volatile devices on board. Unlike starter batteries, automotive and not only, they operate in a cyclic mode. Charged from the mains, traction batteries give off the accumulated energy for several hours – during the operation of the electric motor and related equipment.

In order not to shorten the battery life, you must strictly follow the rules for its operation. Boat batteries of the latest generation are not afraid of shaking and vibrations, are resistant to external influences and temperature fluctuations. They come in a sealed housing, are maintenance-free and work efficiently in any position. Therefore, the main requirement for their correct operation comes down to proper charging.

Traction LiFePO4 Batteries

Today, the best traction batteries for use on boats and other small boats remain lithium iron phosphate batteries – LiFePO4 or LFP for short. They are:

  • Adapted to harsh working conditions;
  • Resistant to deep discharges – unlike batteries with other types of chemistry, they are less prone to irreversible processes and the destruction of the internal structure during a critical voltage drop;
  • Provide consistently high current output;
  • Do not ignite even with mechanical damage and depressurization;
  • Retain the original (replenished when charging) capacity reserve for 2000 operating cycles;
  • Allow fast recharging with high currents;
  • Work perfectly in a wide temperature range (from -20 to +60 ° C);
  • Have 70% less weight than lead-acid batteries with absorbed or gel-like electrolyte (at the same power-to-weight ratio).

How To Protect Lithium Batteries From Premature Wear?

Although LFP batteries are the best at resisting chemical degradation, this feature should not be abused. If the voltage on the batteries drops below 2 V per cell, slow but irreversible processes will begin to occur in their structure. If you regularly discharge the battery “to zero”, the value of the replenished capacity will gradually decrease and the battery will last less than it could serve with more careful use.

Therefore, you need:

  1. Follow the LiFePo4 battery manufacturer‘s recommendations.
  2. Put the battery on charge with a residual charge level of at least 10%.
  3. Do not store it in a discharged state.
  4. Use chargers that work according to the CC / CV scheme. They first charge the cells with direct current, and when the voltage reaches 3.65 V, the remaining 5–10% of the capacity is added to the cell at a minimum charging current. As a result, the cells receive full capacity replenishment without the risk of overcharging.
  5. Ideally, use smart memory. They are able to check the state of the cells with the help of short voltage pulses and charge them according to the optimal algorithm.
  6. Use a battery with a capacity reserve – at least 20% compared to the calculated value. Such a battery will easily deliver the necessary discharge currents – without critical load, wear and tear and resource reduction.

3 Approaches: Fanatical, Lazy And Optimal

3 approaches are common among users on how to charge a traction boat battery . The first approach is to maintain the maximum charge level, bringing it to 100% after each use of the battery, even for a short time. In this case, the manufacturer’s recommendation to store batteries with ≈50% charge level is violated. This is not critical, but periodically you need to let the battery discharge to 10-30%.

The other extreme is the systematic use of batteries to a deep discharge, followed by a fast charge with high currents. Although LFP batteries survive these tests, even with this approach, performance and life are reduced.

Therefore, it is best to use the battery in the charge range from 10–20% to 90–100%, and leave about half charged before long-term storage. To balance the parallels, it is enough to leave the battery connected to the charger 1 time out of 4 charges after indicating the end of the charging process.

Charging Algorithm

To properly charge the boat battery for an electric motor, it is enough:

  1. Remove the battery from the boat and take it to a dry room with positive temperature. Keep away from sources of fire and heating appliances.
  2. If the battery was used in the cold, keep it indoors for a couple of hours.
  3. Take a memory device that works according to the CC / CV principle. Connect it to the charging port on the battery and connect it to the 220V mains.
  4. Make sure that the red light on the indicator lights up.
  5. When the indication color changes to green, disconnect the battery – unplug the charger from the socket, and then disconnect the connector from the battery.

It is strictly forbidden to cover the battery and the charger during charging, charge the battery in the cold (if it is not equipped with a heating system) and use the charger with unsuitable charging current values. For LFP batteries, the charge current can reach 10C. But under normal conditions, when the time is not strictly limited, it is better to use a charge current from 1C to 5C.

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