2.3 Instructions for use of batteries

The correct handling of batteries is at first glance an art in itself. There are many important points to consider so that your battery system lasts as long as possible. If handled improperly, the system can already lose a lot of power in just one season.

To prevent this, we will show you the most important tips you should know when dealing with batteries. You will see that most of the points are basic and already when buying well compatible components you avoid many risks.

1. Be sure to follow the safety instructions of the manufacturer!
2. Be sure to use a suitable charger to charge the battery.
3. Charge the battery again as soon as possible after use.
4. Be sure that your lithium-ion battery is protected by a BMS!
5. Be sure to use a suitable installation location or a safe stand for your battery.
6. Use only suitable cables for connection and attach them carefully.
7. If possible, regularly perform a charge equalization between the multiple batteries, if you use a circuit of multiple batteries.
8. If possible, use only batteries of the same model, age and state of charge in a battery circuit.
9. Attention to the proper storage and winterization of your battery.
10. Monitor regularly the characteristic values of your battery.

Of course, the safety and usage instructions should always be followed. This is important not only because of your own safety, but also for the safety of others. If used incorrectly, you may have no or only limited warranty claims against the manufacturer.

You can find the instructions and conditions on the individual detail pages of the batteries.

Use only chargers that are suitable for your battery and the appropriate connection. If a port power connection is not designed for it, the fuse will come. If you charge lithium-ion batteries with the wrong device, this can lead to capacity loss!

Much more dangerous, however, is if you charge a lead-acid battery incorrectly. If the charging currents are too high, the battery can heat up strongly and more hydrogen is formed in the battery. This leads in extreme cases to a high risk of fire and explosion, not to mention the loss of capacity of the battery.

Lithium-ion batteries cannot tolerate permanent deep discharge because this can irreparably destroy the battery cells. Therefore, the lithium-ion batteries are also protected against deep discharge by a BMS. The BMS ensures that a little residual energy always remains in the battery and you are on the safe side.

Do not wait several weeks or even months in a deeply discharged state (over 90% discharge), otherwise there may be a loss of capacity. AGM batteries they can safely charge completely full. The lithium batteries feel comfortable between 50 to 80% charge state. 

Lithium-ion batteries must be protected by a battery management system (BMS) in any case, otherwise they quickly lose capacity or safety risks arise. The batteries we recommend always have a BMS integrated.

Lithium-ion cells are particularly susceptible to overcharging and deep discharging. If the voltage range specified by the manufacturer is left, this can very quickly lead to total failure of the individual cell. Deep discharging a cell below 1.5 V, for example, causes copper bridges to form. When recharged, these lead to a short circuit and thus to the destruction of the cell.

Another important function of the BMS is the balancing of the cell voltages. A temperature monitoring and a load limitation ensure that the current is interrupted in an emergency. The battery can thus take no damage and dangers, such as fires or explosions, are prevented.

The cables should have a sufficiently large cross-section for the application. It is best to use cables directly from the motor/battery manufacturer. These should usually be included in the scope of delivery. Of course, you should not use damaged cables.

Further, it is important that you use cables with the same cross-section and identical length, especially in a parallel connection. Different cables have an influence on the resistance, which can result in a reduced lifetime or lower capacity.

AGM, gel and lithium-ion batteries can usually overwinter in the boat, since the cold temperatures in Germany do not harm them. Only below -20 ° C the batteries could be damaged, because at some point the electrolytes freeze.

Batteries do not tolerate permanent heat. Low temperatures, on the other hand, are fine, as long as you are above -20°C, as this will reduce self-discharge.

AGM and gel batteries should be stored in a fully charged state if possible. You should always disconnect the batteries and if possible connect to a charger with trickle charge. The battery is thus fully charged at regular intervals again and again.

If this is not possible, it is recommended after 2-3 months to check the charge level of the battery and charge if necessary. Observe thereby best the recommended discharge voltage of the manufacturer. If the discharge is only small, it can be waived in the future or the intervals of the check be increased.

Lithium-ion batteries are best not stored in a fully charged state. A charge level of 50-80% is best. Lithium-ion batteries should also be disconnected, but in no case connected to a charger with trickle charge.

Because of the very low self-discharge per month, the battery should survive the entire winter. However, you can check the charge level of your battery after a few months to avoid a deep discharge. It is best to follow the recommended discharge voltage of the manufacturer.

If low temperatures below -20 ° C, the battery should be removed from board if possible, because the electrolytes can freeze.

A display on the engine or a separate battery monitor shows you the state of charge of the battery. The values are measured via the voltage and are sufficient, even if it is somewhat inaccurate. Depending on the manufacturer and model, the monitors are even integrated into battery or into the electric motor.

You as a user have the advantage that you can be much safer while driving. No uncertainty about the current battery level and no unexpected lying down. 

The voltage is probably the most important characteristic value of a battery. The voltage can be used to determine the charge level. If the battery is fully charged, then the measurable voltage is above the nominal voltage, namely at the end-of-charge voltage. If the battery is "empty", then only the discharge end voltage is present.

The monitoring of the voltage of a battery and the monitoring of the charge level are always closely related. 

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

You should always make sure that the battery also tolerates the charging current. If not, it can come from capacity losses to the destruction of the battery. The same also applies to the discharge current. This can be monitored either at the consumer directly, or by means of shunt and a battery monitor or on-board computer.

The remaining drive time can be calculated relatively easily. If you measure the current power consumption and know the remaining capacity of the battery, you can calculate the remaining driving time using a simple rule of three. The remaining range can also be calculated based on the current speed and the remaining driving time. 

The temperature must not exceed a certain value (about 55 ° C) when charging, so that the battery is not damaged. The danger is usually only with fast chargers or if the charging currents are too high for the battery or the ambient temperature is very high.

The temperature of the battery in operation should also be neither too high nor too low. A temperature of 20° C is ideal. With some lithium-ion batteries, the BMS provides overheating protection. If the temperature is exceeded, the voltage outputs are switched off and an error signal is displayed. The battery cannot be restarted until a non-critical battery temperature is reached. The same applies to a too low temperature. 

AGM and gel batteries actually never have this integrated. You can of course extend this by means of a temperature sensor and a circuit for automatic shutdown when a critical temperature is reached. 

If several batteries are connected in series or parallel, it must be ensured that the voltage or capacity in the individual batteries remain the same. Furthermore, only the same battery models should be used for a circuit.

With different batteries, it can quickly lead to problems, depending on how much the batteries differ from each other. In any case, but the life of the batteries decreases.

If possible, use only batteries of the same model, age and state of charge. In all the above cases, there may be a strong loss of capacity and life, depending on how large the differences between the batteries are.

The cause is that batteries are loaded differently. If you want to be on the safe side, you should not dare to experiment here.