Solar Kit Installation

[Phoenix]

Hi All, I have a solar kit to fit. The boat has a split charge relay fitted, so my question is,  do i fit the solar cables just to the starter battery. I believe that i should as it will then split the charge to the 2 x leisure batteries.  Just want a second opinion to confirm i am right.

 

Thanks All :-)

[JanetAnne]

Excellent question! I shall look forward to a definitive answer.

My thought is that the split charge relay is only activated when the engine is running otherwise your engine battery would discharge along with the domestic bank when the engine is off. 

[WherryNice]

I think it depends on the exact set up and type of the split charge system fitted to your boat. There are different types of relay and ways of connecting them up. Janet Anne is right about a traditional relay only energising when engine is running(or more likely when ignition is on) but there are other types which engerise when they sense a high enough voltage and also diode splitters which are just passive and work at all times. 

The way your current system is wired up will also have a bearing on where you would need to connect the solar panels to in order to make it all work, just going straight to the starter battery might not be effective.

When I fit a solar panel to my boat I will likely just connect to the domestic bank as my starter battery has nothing draining it unless it's cranking the engine but that may not be the case on all boats.

[Vaughan]

10 hours ago, Phoenix said:

I believe that i should as it will then split the charge to the 2 x leisure batteries. 

I think that would be going in the opposite direction.  Imagine how the alternator is wired and the solar panels, which are also providing a charge, would be wired the same way.

Except. . . . 

There is only a small amount of current, around 5 or 7 amps, so not worth splitting.

It is normal to wire the panels, and also the 220v shore power charger, to the domestic batteries only, on the basis that the starter battery is fully charged at all times.  The only things wired to the starter battery are those, such as wipers, that you are only using when the engine is running.

[Oddfellow]

I assume your kit contains a solar charge controller?  If it doesn't, get one. Don't connect a solar panel directly to the batteries. 
 

Other than that, what Vaughan said. 

 

[Vaughan]

48 minutes ago, Vaughan said:

I think that would be going in the opposite direction.

Just to explain, charge splitters have blocking diodes (or something similar) to separate the batteries and prevent them from remaining connected in parallel when they are not on charge. Otherwise there would be no point in splitting the charge, or having separate battery banks.

You don't need an electronic "intelligent" splitter just to separate the charge, it can be done very effectively with a simple relay, such as a Lucas 33RA.

[Oddfellow]

3 hours ago, Vaughan said:

Just to explain, charge splitters have blocking diodes (or something similar) to separate the batteries and prevent them from remaining connected in parallel when they are not on charge. Otherwise there would be no point in splitting the charge, or having separate battery banks.

You don't need an electronic "intelligent" splitter just to separate the charge, it can be done very effectively with a simple relay, such as a Lucas 33RA.

This is true, but by using a relay such as the Lucas 33A, the batteries are COMBINED during the charging phase. There are downsides of this, especially if you have mismatched battery banks.  

By using a splitting diode, they remain separate and thus charge separately BUT at a lower voltage as the diode will eat some millivolts and whilst a millivolt or two doesn't sound like much, it's enough to increase charging time and also ensure that the alternator cannot fully charge batteries as there's never enough voltage at the battery terminals to achieve this. 

The best way to charge batteries in the Domestic / Starter bank environment from the engine is to use an intelligent charging system that properly separates the battery banks and monitors each, ensuring that they both get the full charge they need. 

 

[annv]

Hi Get a double outlet controller and connect direct to battery's it will then chose the lowest voltage battery to charge along with keeping your battery's fully charged when moored so there longevity is increased, dont go through diodes as they have internal losses. John

[Phoenix]

On 12/07/2021 at 06:35, Vaughan said:

I think that would be going in the opposite direction.  Imagine how the alternator is wired and the solar panels, which are also providing a charge, would be wired the same way.

Except. . . . 

There is only a small amount of current, around 5 or 7 amps, so not worth splitting.

It is normal to wire the panels, and also the 220v shore power charger, to the domestic batteries only, on the basis that the starter battery is fully charged at all times.  The only things wired to the starter battery are those, such as wipers, that you are only using when the engine is running.

Thank you, makes sense:-)