Photovoltaics – maritime applications

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Aktualisiert – November 14, 2025

Photovoltaics can also be used for maritime applications, i.e. on motor boats and sailing yachts, even sea kayaks, because electricity can be used anytime and anywhere.

Special, walk-in and flexible solar modules were developed for marine purposes. Due to comparatively lower production quantities, they are unfortunately characterized by a higher price than conventional modules such as those used on mobile homes, etc.

You should stay away from supposedly particularly cheap offers, because you usually pay twice, especially if you have to replace the modules due to a defect. This is a major nuisance, especially with modules that are glued over the entire surface.

You would be well advised to pay attention to the marine application specification and limit yourself to well-known manufacturers when it comes to other components. Despite higher production numbers, these are more expensive than the super special offer around the corner, but offer solid quality and service on almost all continents of the world.

Performance needs determination

Which service ultimately meets your own needs is very individual. The more power-hungry technology is, the less you spend most of your time in sunny areas, the higher the required module performance as the number of modules increases.

Since many leisure captains have already thought about this, there is no need to reinvent the demand “wheel” and you can, for example, use the following list, which covers the majority of possible consumers and, updated with the actual consumption data, outputs the daily requirements .

The fields highlighted in yellow can be edited. Your own consumers and data are entered here. You can usually find the required consumption data on the nameplates of the respective devices or the associated manuals under “Technical data”.

Please those first On-board voltage by clicking on the “24" choose. A selection between 12 and 24 volts appears.

Then the consumer data (watts, number and average Operating hours) register.

In the lower section, the x entries can be overwritten with your own consumer names and the associated data can be recorded.

All performance data is added up in the green line at the top and displayed in Ah. This value represents the determined daily power requirement.

If necessary, the table can be saved as a PDF or printed using the following two buttons.

Determination of space requirements – PV modules

Depending on the space available, the first thing to do is to find surfaces that are as flat as possible on which the flexible, walk-in PV modules can be installed.

The attribute “walkable” should not be taken literally here, as scratches caused by dust leave marks on the surface of the modules, which ultimately lead to a reduction in performance and durability.

This means that areas that are not subject to foot traffic are usually preferred, as they ensure predominantly vertical sunlight and - of course - are as free as possible from frequent shading. Sails also naturally lead to shading effects.

When choosing the future mounting surfaces for the PV modules, the cable routing to the MPPT controllers and the associated necessary cable bushings must also be taken into account.

Determination of space requirements – technology

The voltage supplied by the PV modules of (individually) around 20 V, or 24 V connected in series, is adapted to the 12 or 24 volt on-board voltage via MPPT controllers.

MPPT controllers can partially compensate for shading, but can never fully compensate for it. The use of multiple MPPT controllers is, in addition to the redundancy it provides, a more expensive approach, but all the more effective.
A shaded panel, as a “consumer”, does not reduce the performance of the panel that is still illuminated by the sun - connected to the same MPPT controller.

The MPPT controller from Victron SmartSolar MPPT 75/10 - at around 80 euros - has an output of 145 W at 12 V (290 W at 24 V) with very small dimensions of only 100 (H) x 113 (W) x 40 (D) mm and is for a PV module with up to 120 W is predestined. The type SmartSolar MPPT 100/15 With identical dimensions, it is even designed for outputs of up to 220 W at 12 V (440 W at 24 V) and is also very affordable at around 100 euros.

Execution SmartSolar already includes Bluetooth connectivity, which allows all performance data to be displayed and graphically visualized on the associated mobile phone app. BlueSolar-Variants have NO BT functionality!

12V or 24V?

Whether 12 V or 24 V MPPT controllers are required is determined by the existing on-board network or the connection of the PV modules (in series or parallel).

However, with 24 V MPPT controllers you will not reach the starting voltage with a single PV module.

A module that supplies 19.8 V correlates with the necessary input voltage of a 12 V MPPT regulator (V_Batt + 5V = 17 V), but not with that of a 24 V MPPT regulator, which requires at least 24 +5 = 29 V to start working.

When using a 24 V MPPT controller, two PV modules supplying 19.8 V must be connected in series in order to start the MPPT controller with 19.8 + 19.8 = 39.6 V.

Battery types

There is usually an AGM battery on board, which is charged by the alternator when the engine is running. MPPT controllers have the ability to be adapted to different battery types.

LiFePo4 batteries are characterized by very high charging density and constant voltage output until shortly before the end-of-discharge voltage. However, they require different charging characteristics compared to AGM batteries, which is why they cannot be connected directly to an alternator.

Now the question arises as to whether the AGM (starter) battery should not only be used for starting and the rest of the on-board technology should be supplied with additional LiFePo4 batteries. This would ensure that the starter battery is always in a charged state (e.g. charged by the PV batteries' own Victron Orion-Tr Smart DCDC charging booster*).
Conversely, the LiFePo4 battery can also be charged using an additional charging booster via the alternator.

In addition, LiFePo4 batteries are a good third lighter and more compact than comparable AGM batteries, especially in terms of capacity, but more expensive. Still, it's worth considering...

More on this topic is in this Contribution described in detail.

Charging from battery to battery*

A DCDC charging booster (galvanically isolated / isolated) - allows the input side to connect any voltage source (e.g. alternator or battery, e.g. LiFePo4) to a different type of battery (e.g. AGM) in order to charge it.

In addition to the pure charging function, a charging booster compensates for voltage losses on the input side. Accordingly, it should be installed close to the battery(s) to be charged in order to keep cable losses on the output side as low as possible.

The output voltage of a charging booster can be adjusted in a wider range (10 .. 15 or 20 .. 30 V).

cabling

The cables of common Flex PV modules are 4 mm² executed. One cable for plus and one for minus must be connected to the input of an MPPT controller. They are flexible, but not highly flexible like measuring cables, for example, but still allow relatively narrow laying radii and a direct connection of stripped cable ends to the screw terminals of an MPPT controller.
Anyone who donates wire end sleeves will be rewarded with a particularly secure connection and a more visually appealing connection pattern.

A DCDC charging booster is more demanding in terms of cable cross-sections: with up to 60 A short-circuit current, the cross-section should be at least 10 mm² be. In the table above, the DC column is relevant here. The cross sections were calculated for 12 V. With 24 V systems, the currents are half, i.e. only 6 mm².

Here you can calculate the required cross-section of copper cables for DC applications, as well as the voltage drop. The yellow fields are editable. Please ensure correct spelling: enter 2.5 instead of 2.5!

The thicker the cable, the lower the losses. So it never hurts to lay thicker cables than necessary. Because, over time, the load is usually expanded and the load that is still determined to be moderate can quickly give way to a significantly higher one. And who wants to reinstall the basic cabling just because the currents are suddenly tight?!

Cable lugs are mandatory for higher currents in order to effectively counteract loose contacts and uneven current transmission at connection points. Yes, the costs of the necessary crimping tools also need to be taken into account if you cannot ask your trusted electrician to lend one or two tools.

Screw connections must always be TIGHT to prevent increased resistance, resulting heating of the contact point and possible cause of fire.
Tightening torques are sometimes noted on devices. These can be maintained using suitable torque wrenches.

Circuit example for 12 V and 24 V

Hier werden beispielhaft zwei PV-Module beliebiger Leistung über je einen eigenen MPPT-Regler zur Ladung der (größeren) Aufbaubatterie rechts in der Abbildung genutzt. Die (kleinere) Starterbatterie links im Bild wird wie üblich über die Lichtmaschine geladen.

Ein zusätzlicher Lade-Booster sorgt für eine zum Laden der Aufbau-Batterie geeignete (adaptierte) Spannung, indem Spannungsverluste auf dem Kabelweg von der Lichtmaschine zum Eingang des Lade-Boosters ausgeglichen werden, um die erforderliche Ladespannung zur Verfügung zu stellen.

Sicherungen in den jeweiligen Plus-Leitungen sind in passender Dimensionierung zu wählen,

Here is the schematic representation of an installation for 12 V:

bzw. für 24 V Bordnetz – hier werden zwei PV-Module in Reihe geschaltet, wodurch sich die Spannungen addieren und mittels 24 V MPPT-Regler und 24V Lade-Booster die 24 V Aufbaubatterie geladen wird. Eingangsseitig arbeitet der Lade-Booster mit 12 V, entsprechend der normalen Bordspannung von Starter-Batterie und Lichtmaschine:

Battery choice

After the consumers and loads are shown in the table above, the required minimum capacity of the batteries is now known and it is important to find batteries that are of good quality and have a high number of charging cycles.

On relevant portals you can initially find offers from Far Eastern direct suppliers that initially appear to be inexpensive. It should be noted here that warranty claims will be more difficult to enforce than against domestic providers. Some very high shipping costs and customs fees also need to be taken into account.

So far it has always proven to be more cost-effective to purchase from local dealers.

It is important to choose batteries from a manufacturer that has been on the market for many years, produces large quantities and has a high staff density. EVE batteries appear to offer the best value for money at the moment.

The number of cycles already mentioned is always based on a discharge percentage. So 6,000 cycles with 60 % discharge depth are worse than 6,000 cycles with 80 %. It is advisable to study the data sheets carefully. If this information is missing, the dealer should be contacted and asked for the relevant data sheets.

ps If you need personal support in the implementation for a fee, you are welcome to Ticketing make!