Solar panels & diode splitter

[Gwylan]

We have a diode splitter that shares the charge from the alternator to our 3 banks of batteries.

I know the part of this question about the sun shining might be a bit academic but I just want the pedants to approach the question in a rational and objective manner. Though looking at some of the recent posts these two properties are rarer than sunshine.

Anyway,
If I install solar panels can I wire them all in parallel, via a controller, to the splitter?

What might happen when the engine is on and the sun is shining?

When the engine is off but the sun us shining will the energy be used to heat up the alternator rather than charge the batteries?

Or should I just wire an appropriate number of panels via a controller to each battery bank separately?

 

[pampas]

Connect your solar output to the splitter diode and forget about the alternator, Does it get hot with power to the engine? No only when running so dont worry.

 

[GrahamM376]

Diodes not a good idea as they drop the voltage so batteries won't get fully charged, unless you've converted to battery sensing with Sterling, Adverc or similar.

All my panels (200W) are in parallel into two regulators, one to each domestic bank, I don't bother charging the engine battery. Again, diodes after regulator is not a good idea plus, I'm not sure if the regulators would work properly - depends on how they sense battery voltage.

Whether you connect the panels direct or via regulators, it won't have any effect on your alternator when the engine is running or not.

 

[Maine Sail]

We have a diode splitter that shares the charge from the alternator to our 3 banks of batteries.

I know the part of this question about the sun shining might be a bit academic but I just want the pedants to approach the question in a rational and objective manner. Though looking at some of the recent posts these two properties are rarer than sunshine.

Anyway,
If I install solar panels can I wire them all in parallel, via a controller, to the splitter?

What might happen when the engine is on and the sun is shining?

When the engine is off but the sun us shining will the energy be used to heat up the alternator rather than charge the batteries?

Or should I just wire an appropriate number of panels via a controller to each battery bank separately?

No issue with the alt but many if not most solar controllers won't turn on when connected to a diode splitter. They need to sense battery voltage to turn on. Happens with many modern battery chargers too. Kind of a catch 22 with a diode splitter. This on top of the other issues with diode splitters means you'll be better to direct wire or use a product like the Sterling Pro-Latch R to charge both banks from the same panel.

 

[William_H]

Diode splitters

As I am sure you have been told these drop about .7 volt regardless of current so presumably your alternator has been set up ton generate more voltage to allow for this drop. (battery sensing is the usual way)
Now if you run a solar panel into a controller the controller will ensure that only 14volts comes out. The voltage that ensures the battery will not be overcharged. If you then feed this into the batteries via diodes either the existing diodes or additional diodes you will still lose .7 volt meaning the most the solar system ca deliver is 13.3 volts. This voltage means that into batteries will diminish and cut off when the battery reaches 13.3 volts.Which is actually a small degree of charge. You need 14v to get a good charge.
You can solve this problem by feeding the solar to only the domestic batteries as most people do.
Or buy a controller with 2 outputs for 2 isolated batteries.
Or you can feed the solar to your existing diodes then to batteries without a controller. The solar panel produces up to 20v so diode volt drop is not a problem. However this last option while giving you max charge from solar may leave batteries susceptible to overcharge. Perhaps not a problem with large batteries small solar power or winter. good luck olewill

 

[pampas]

If your diode splitter has Schotty diodes no problem. mine supplies 3 batterys doing it this way. dom and bow thruster stand at 14 ish and eng batt at 13.5. when out and frig in use I switch to dom. batt only.

 

[Gwylan]

Another forum triumph

Thanks for the quality and clarity of the replies.

I now have a clear idea what to do.
I will wire panels via controllers direct to the batteries. Might try and look at a multiple battery controller to simplify the wiring.

For the record we do have an Adverc system, which I cannot praise too much. The system is excellent, we just want to extend range especially on the fridge with solar panels.

 

[nigelmercier]

Might try and look at a multiple battery controller to simplify the wiring...

Good plan.

 

[GrahamM376]

Thanks for the quality and clarity of the replies.

I now have a clear idea what to do.
I will wire panels via controllers direct to the batteries. Might try and look at a multiple battery controller to simplify the wiring.

For the record we do have an Adverc system, which I cannot praise too much. The system is excellent, we just want to extend range especially on the fridge with solar panels.

Agree with proposed solution but, something to watch for if you decide to go for the two controller option. Some models will allow backfeed and I found both battery banks to be balanced by morning. Had to put a split charge diode in the feed from the panels. 0.5v drop on 20+ volts not a noticeable problem there.

Would prefer a dual output unit but most won't handle the potential current to one bank if the other is fully charged. i.e a unit advertised as 16A is only 8A per bank.

 

[Gwylan]

Thanks for the warning on the controllers. Seems hard to find anything over 20A, or 2x10