Boat batteries at a glance

  • 1. Installation battery boat
  • 2. Usage Notice for Batteries
  • 3. Security and case
  • 4. BMS boat battery
  • 5. Monitoring and control of the battery
  • 6. Charger fore battery on the boat

Do you want to buy a battery for the boat or inquire which battery is the most suitable? We would be happy to help you with the topic of batteries, enjoy reading!

  • 1. Installation

  • 2. Security

  • 3. Battery Management System

  • 5. Charger

  • 4. Monitoring and control

Installation battery boat

There are a few basic things to keep in mind when installing your battery system. The most important is the information from the manufacturer! If you observe the following 10 points, almost nothing can go wrong!

When installing the battery, make sure that:

  • 1. Stands safely or is fixed in the boat

  • 2. Is protected against water as much as possible or has an appropriately waterproof housing

  • 3. Adequate air circulation is possible

  • 4. The contacts of the batteries are protected

  • 5. The connection cables are securely attached

  • 6. Only compatible cables with sufficient cross-section can be used

  • 7. The correct circuit is observed / poles are observed

  • 8. A BMS is used with lithium (LiFePo4) batteries

  • 9. A battery balancer is available if connected in series

  • 10. The cables are neither damaged nor too long to avoid the loss

The determination of the capacity of your battery on the boat can be found in our advisor article. Just make sure you stop by!

Construction of a battery system with circuits

We recommend that you use a battery if possible. In addition to increased installation effort, circuits also have other technical disadvantages. An important prerequisite for the circuit is the manufacturer's information about the suitability of the battery.

When you combine batteries, you can increase the voltage or capacity of the battery system. When connected in series, the voltage increases. You can combine two identical batteries with a nominal voltage of 12 V in a series connection to form a 24 V battery system. With a parallel connection, the capacity would double from 100 Ah / 12 V to 200 Ah / 12 V.

Construction of a battery system with circuits

Disadvantages of series connection

A series connection of several batteries is only as strong as your weakest link. Different charge levels lead to reduced capacity and lifespan of a battery system, which is prevented by a balancer. Chargers cannot compensate for this!

Disadvantages of parallel connection

Failure of a single cell can damage the entire parallel connection until cell death. The cause is high equalizing currents between the batteries. Again, use fuses or balancers so that a single, defective battery cell does not damage all others within the battery system.


With the lithium battery, the balancing of the cells is carried out by the BMS, so that small differences can be compensated for. Cell balancing can be active or passive. Active balancers transfer the energy from cells with a higher charge to cells with a lower charge. In contrast, passive balancers function like a charge limitation, so that all cells are charged to the same extent.

Usage Notice for Batteries

You should have read these instructions before operating:

  • 1. Be sure to follow the manufacturer's safety instructions! Please also consider the safety of others here!

  • 2. Make sure that you use a suitable charger to charge the battery

  • 3. Recharge the battery as soon as possible after use (otherwise, there is a risk of loss of capacity!)

  • 4. Make sure that your lithium-ion battery is protected by a BMS!

  • 5. Pay attention to a suitable installation location or a safe stand for your battery

  • 6. Use only suitable cables for the connection and attach them carefully

  • 7. Carry out a charge equalization between the batteries as regularly as possible if you use a circuit made up of several batteries

  • 8. If possible, only use batteries of the same model, age and state of charge in a battery circuit

  • 9. Pay attention to the correct storage and wintering of your battery

Security and case

Battery safety

We only offer lithium-ion batteries or VLRA batteries. Both are maintenance-free and leak-proof. This means that the batteries can be installed anywhere. These batteries are very safe compared to other open battery types or petrol.

You should always follow the manufacturer's safety instructions. Security risks mainly arise from improper handling or gross negligence. This can e.g. incorrect installation, incorrect charging, violence, open fire or a short circuit.

Incorrect installation or charging with an unsuitable charger will damage the electric motor and the battery. Excessive currents of the charger lead to the battery heating up and reducing the service life. In an emergency, this can lead to fire or explosion. Pay attention to compatible components when buying to avoid certain risks.

Battery safety

Battery Case on Boats

The housing protects battery cells from environmental influences. For boats, the housing should at least be splash-proof or waterproof. The standard material for battery housings is ABS plastic with a low weight. This is robust, weather and aging resistant, so ideally suited. Some manufacturers of particularly high-quality battery systems, some with high capacity, use stainless steel or aluminum alloys.

Batteries that are not primarily designed for the boat sector often do not have a high IP protection class. Compared to boat batteries, solar storage systems are neither particularly dust-protected nor water-protected. If you want to use these batteries, they must be installed in a water-protected place. Alternatively, you can use a battery case.

BMS boat battery

A battery management system (BMS) protects the lithium batteries against dangers and damage, as well as other safety risks. For this reason, we always recommend using a BMS for lithium batteries. Lithium-ion cells are particularly susceptible to over- and deep discharge.

Damage and dangers of batteries

Leaving the voltage range recommended by the manufacturer can lead to a short circuit and destruction of the cell. Another important function is the balancing of the cell voltages. Temperature monitoring and load limitation ensure that the electricity is interrupted in an emergency. The battery cannot be damaged and hazards such as fires or explosions are prevented.

Other functions of a BMS can be:

  • 1. Deep Discharge Protection

  • 2. Overload Protection

  • 3. Temperature Monitoring

  • 4. Balancing the Cells

  • 5. Short Circuit Protection

  • 6. Load Limitation against excessive currents

  • 7. History Record (important for warranty)

  • 8. Communication between battery cells and on-board computer

What batteries do we recommend?

Therefore, when choosing the latest lithium technology, make sure that the battery is protected by a BMS. The lithium-ion batteries without BMS are a rare exception anyway. We separately point out exceptions.

What batteries do we recommend?

Monitoring and control of the battery

Important parameters that are monitored:

  • 1. State of charge of the battery

  • 2. Battery voltage (charge and operation)

  • 3. Charge and discharge currents

  • 4. Battery temperature when charging

  • 5. Battery temperature in operation

State of charge of the battery

It is usually important to be able to read the remaining capacity of the battery and to have certainty about the remaining range. An LED indicator is often attached to the electric outboard. This is usually not very precise but is usually sufficient. A battery monitor shows you the state of charge in more detail.

Battery Voltage

The voltage is the most important parameter because the charge level can be determined from it. Many displays show the relevant charge level directly and not the battery voltage. For battery monitors or on-board computers, the voltage is a standard value. With chargers, the battery voltage is always displayed during charging.

Charge and discharge current

The charging current is controlled by the charger. Many chargers offer the possibility of displaying the current charging current. The charging power can also be determined on the basis of the charging current and the charging voltage (V * Ah = Wh). The higher the charging current, the higher the charging and charging speed of the battery

You should always make sure that the battery can handle the charging current. If not, it can result in loss of capacity or even the destruction of the battery. The same applies to the discharge current. The remaining driving time can be calculated on the basis of the discharge current and the charge level.

Display of the remaining driving time

The remaining driving time can be calculated relatively easily. If you measure the current power consumption and know the usable capacity of the battery, you can calculate the remaining driving time. The remaining range can also be calculated based on the current speed and the remaining driving time. Since both values cannot be measured directly, they are not displayed by engine displays and on-board computers by default.

The temperature when charging the battery

A frequently monitored characteristic value is the temperature of the battery when charging. The temperature must not exceed about 55 ° C, otherwise, it will be damaged. The danger is usually only with fast chargers or excessive charging currents. We therefore always recommend a suitable charger.

Operating Temperature

The temperature of the battery during operation should also not be too high or too low. A temperature of 20 ° C is ideal. Overheating protection is by no means standard for batteries. As long as you use your battery properly and use a suitable charger, this will probably never be relevant.

Operating Temperature and storage

Storage and wintering of the battery

The best way to store or hibernate the battery varies slightly depending on the type of battery. AGM, gel and lithium batteries can usually hibernate on the boat. Cold temperatures do not harm them thanks to their low self-discharge. The batteries could only be damaged below -20 ° C, as the electrolytes will freeze at some point.

Storage and wintering of lead-acid batteries

Lead batteries (AGM and gel batteries) should, if possible, be stored in a fully charged state. You should disconnect the batteries and if possible connect them to a charger with trickle charging. If this is not possible, we recommend checking the charge level of the battery and charging if necessary. It is best to observe the manufacturer's recommended final discharge voltage.

Storage and wintering of lithium-ion batteries

Lithium-ion beverages are best stored in a charge level of 50-75%. Lithium-ion beverages will also be disconnected, but under no circumstances will they be a trickle charger. Due to the very personal self-discharge, the battery should survive the entire winter. You can charge your battery after a few months to include a deep discharge.

Charger fore battery on the boat

The battery chargers must be connected to the charging process, the voltage range, and the charging power. In theory, all different charging methods have the same purpose and can be used for all types of batteries. Since these have different properties, not all charging methods are ideally heard for all types of batteries. There is a different risk in that the charging power is too high and the battery temperature rises sharply.

Charger fore battery on the boat

Always a compatible battery charger!

We therefore only recommend compatible chargers for your battery system. So you have a long time from your battery! Do you want to charge your battery on the boat and don't know how? Take a look at our article You can find the capacity of your battery on the boat in our article In 4 steps to the perfect electric drive!

Always a compatible battery charger!
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