Solar Panel Connections on the Boat

  •  23/02/2019
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Charging ControlLers

A typical solar charger

Solar panels can output up to 19 VDC, large panels up to 40 VDC. Therefore, it is not right to connect directly to the batteries, they cause serious damage in a very short time.

Charge Control Lerers reduce voltage from the solar panel to levels that will fill the batteries in a healthy way. Charging control units typically have 6 clamps on them. two are for cables from solar panels, two to batteries. (Information about the third exit below)

Fuses: A fuse must be placed between the charger and the battery. (This is not about the solar system, every battery-bound cable should have insurance.) The insurance issue between the Charger and the solar panels is a little more ambigual. While many circuit drawings are not required, they suggest some resources.

PWM Units

Pulse Width Modulation, i.e. lowering the voltage by adjusting pulse ranges. These units reduce the incoming voltage by milliseconds to the desired level. As can be seen from the recipe, it is relatively inefficient because it breaks away the excess energy. However, it is still widely used because of the price advantage. For panels running at 18-19 volts, the loss may be acceptable, but the loss escalates seriously on panels running at 30+ volts.

MPPT Units

"Maximum Power Point Tracking," i.e. maximum power production point tracking. They work more like transformers, keeping the solar panel side at the ideal voltage/current level, while giving the desired voltage to the battery side at higher current values. They work with a higher efficiency. Naturally, the costs are higher. But the difference with PWMs is constantly falling.

In the chart on the right, you see the AKIM-VOLTAJ (IV) curve of a panel in orange and the POWER (Watt) curve in blue. While the PWM regulator can only transfer power between 10.5-15V to batteries (approximately 80W in the graph), the MPPT regulator can always capture the highest power point on the chart and deliver the maximum power that can be obtained from the panel (approximately 108W on the graph).

Who should use an MPPT regulator? Is that really what I need?

– Those who want to get a little higher efficiency from their classical systems.
– Those with a high panel output voltage (>20) (Some panels have an open circuit voltage of 44V or something..)
– Those who have grouped multiple panels serially parallel (we're not just talking about boat applications)
– Those with panels higher than 700-750W (PWMs support up to max 60A – 750W? Who are they ya!)
– Shading, less sun, etc. panel voltage decreases due to reasons
– Those who want to show off by saying that I use the latest technology "em pi pi tii"!

Which Battery Are We Going to Connect To?

The most frequently asked question about the solar panels to be connected to the boat's electrical system is which batteries or batteries to connect to. There's no absolute answer to that question, and it's very relevant to the way you use boats. First, the current charging system on the boat must be learned. If you have a Smart Relay system, just connect it to any battery group. It will combine intelligent relay batteries in case of charging.

For other occasions, it seems possible to charge two battery groups with insulation diodes, but the 0.7 volt drop on the diodes causes a very serious record. It's not just the power loss on the diode. The battery's charging acceptance rate is also dropping disastrously. When you give a battery 13.2 volts instead of 13.9, the charging speed goes down to a third! Such a loss in solar energy, which arrives for limited periods of time during the day, is unacceptable.

So what's normal is to connect the solar panels to the service battery. Anyway, even if there's no additional charge for days, the engine battery isn't a problem. In key and both switch solutions, the engine battery can be paralleled and filled from the solar system if desired. But when the sun goes out, don't forget to put the keys in the protective position!

Parallel Charging

One of the most frequently asked questions: What happens if multiple chargers are connected at the same time? Short answer: Nothing happens.

Actually, it was a question that should have happened before the solar panel. If the engine works while connected to the land charge, both the alternator and the redrector will create a parallel charging state. In these cases, each device continues to charge up to its capacity. The determining will be the capacity of the batteries to accept charge:

If the batteries are too hungry, they can receive the total current from all chargers. (There's a theoretical risk here. If the total capacity of our chargers is sufficient to damage the batteries, damage may occur. But who has that capacity?)

As the batteries are full, the charging current they can accept will decrease and the currents that the devices can give will decrease. Theoretically, even if they work at the same voltages, the small adjustment differences between them will determine who outweighs them. But the batteries will never encounter a high voltage, they will never be damaged.

A problem with some engines: if the solar panel system is already holding a high voltage, the alternator may not be activated. The engine's control circuit detects this and lights up the fault lamp on its own control panel. It doesn't hurt, but it's disturbing. Also, you get used to the fact that the fault on that panel is on fire, and a real malfunction detects late. He's like a lonesome shepherd.

Third Exit

The third output is intended for devices to be fed from batteries. Instead of connecting the devices directly to the batteries, it is foreseen that it will be connected to this output. (Don't just think about boat applications. These are designed to be used from the farmhouse to street lighting.)

The most important advantage is that when battery occupancy drops below a preset value, this output is automatically cut off and protected by batteries.

Normally, this third outlet is rarely used in boat installations. If you want to pass the entire distribution line through the Charge Control Unit, its capacity must be sufficient to meet the maximum load. However, we normally determine charge control units according to the capacity of solar panels. Our consumption capacity can be instantaneously higher than this.

This third exit on boats can be used for two different purposes:

Some devices such as televisions and computer chargers are connected to this output, enabling automatic shutdowns when the battery level drops. But a separate insurance group, etc. it's probably not worth the effort.

More interesting application; in most chargers, this output can be programmed as "only work at night". In this way, only the lamp that is asked to work at night, etc… can be automated. Or, by reversing with a relay, applications such as fans can only be made to work during the day.

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