2.4 Chargers for boat batteries

What to look for in chargers on the boat. Are there different chargers? How long does the charger charge until the battery is full? What do I have to pay attention to when using it? 

The speed of charging depends on many factors, so it is not possible to make a statement applicable to all batteries. The most important factors are the capacity of the battery, the maximum charging power of the charger, the charging method used and the battery type.

It is important that the charger is well suited to the battery. Most batteries can not be charged arbitrarily fast, especially lead-acid batteries are not suitable for fast charging. Generally, a slower charge will preserve the battery. Lithium-ion batteries can tolerate higher currents and can sometimes be fully recharged in under 2 hours. 

As you can see, a concrete specification is difficult. You can get an approximate guide value by dividing the battery capacity by the charging power. However, since the charger can not charge at full power for the entire charging time, the practical charging time is longer. In order not to damage the battery, chargers work at the beginning and end of the charge with lower voltage and lower charging current, respectively.

In particular, when charging lithium-ion batteries, this is important. Therefore, many manufacturers also specify the charging time to 80%, as the remaining 20% is charged much slower. This phenomenon can also be observed very well on your own smartphone: From about 90% battery level, it only charges very slowly. Nevertheless, we give you a concrete charging time, because we calculate with an additional factor that takes the charging delay into account. 

The chargers differ based on the charging methods, the voltage range and the charging power. Theoretically, all different charging methods serve the same purpose and can be used for all battery types.

Because they have different properties, however, not all charging methods are ideally suited for all battery types. A particular risk is too high a charging power and a subsequent sharp rise in the temperature of the battery.

Furthermore, lead-acid and lithium-ion batteries differ in their charging voltages. With permanent use of a charger with unfavorable properties for their battery, this will not have a particularly long life.

We therefore recommend only compatible chargers for your battery system. So you have long something from your battery and can strive carefree to the weekend and a pleasant day on the water.

When charging a battery, you can do a lot wrong. If you pay attention to a compatible charger when buying your battery, then you have already avoided most of the mistakes. We always suggest you a compatible charger. We pay particular attention to the charging currents.

It is important that you quickly recharge the batteries after use, especially in the case of deep discharge. Especially lead-acid batteries lose life if they are stored for a long time in a deep-discharged state. Lithium batteries also do not like permanent deep discharge below 20%.

Lithium-ion batteries also do not tolerate a permanent deep discharge. Since the cells can be irreparably destroyed. Therefore, most lithium-ion batteries are also protected by a BMS against deep discharge, so that always a little residual energy remains in the battery and you are on the safe side.

Also here it is important to charge the battery again relatively quickly. The batteries should not be several days, weeks or even months in a deeply discharged (over 90%) state, because it can lead to a loss of capacity.

If the voltage of a cell drops below 1.5 V, the battery should no longer be used, because then probably already copper bridges have formed, which could trigger a short circuit, creating a fire hazard.

When discharging lead-acid batteries, sulfation of the batteries occurs. If the battery is now heavily discharged and not recharged, so this leads to the fact that further lead sulfate is formed and at some point can no longer be degraded and the battery performance permanently decreases.

For this reason, you should recharge your batteries as soon as possible after use. If you do this, less lead sulfate is produced and the chemical reaction can be reversed. As a result, you have longer what from your battery.