Effect of Solar panel on engine alternator ??

[Vronsky]

Hi All,
I'm planning to install a 50W solar panel on the roof of my pilothouse motorboat to maintain the 74Ah starter battery (charge controller will be a Victron BlueSolar MPPT 75/15).
I'm now wondering about what effect this solar panel & controller will have on the functioning of the engine's alternator ??

As I understand it, the alternator stops charging when it senses sufficient battery voltage. With a solar panel attached and permanently charging, it would appear the voltage of the battery will always be high, so shutting down the engine's alternator (when engines runs).

If this will indeed be the case: is this harmfull to the alternator. or perhaps harmful in some other way ??

THANKS,
V.

 

[omega2]

DISCONNECT IT, before starting, reconnect when leaving boat, thats what we do.

 

[Hurricane]

I just connected my 600w solar panels (via the MPPT controller) across the battery - just like the battery charger.
Used MCBs instead of fuses and the controller was one of the Victron MPPT ones.

That said, our panels are connected to a "house" battery bank. Engine start batteries are not in this circuit but the alternators do charge the "house" bank.

However - make sure that your solar panel is capable of producing a voltage of 5v more than the battery bank.
The Victron MPPT controller needs 5volts mote than the battery voltage before it starts working.
For example if your battery is 12v (13.8 when full), you will need your solar panel to produce a voltage of (at least) 17volts (18.3 when full) before the Victron controller will start charging.
All this is in the Victron manual.

Also it is well worth the extra Bluetooth interface for the Victron MPPT controller - so that you can see how well the solar panel is performing.

Good luck.

 

[simonfraser]

DISCONNECT IT, before starting, reconnect when leaving boat, thats what we do.

why would you need to do that ?

 

[Vronsky]

I just connected my 600w solar panels (via the MPPT controller) across the battery - just like the battery charger.
Used MCBs instead of fuses and the controller was one of the Victron MPPT ones.

That said, our panels are connected to a "house" battery bank. Engine start batteries are not in this circuit but the alternators do charge the "house" bank.

However - make sure that your solar panel is capable of producing a voltage of 5v more than the battery bank.
The Victron MPPT controller needs 5volts mote than the battery voltage before it starts working.
For example if your battery is 12v (13.8 when full), you will need your solar panel to produce a voltage of (at least) 17volts (18.3 when full) before the Victron controller will start charging.
All this is in the Victron manual.

Also it is well worth the extra Bluetooth interface for the Victron MPPT controller - so that you can see how well the solar panel is performing.

Good luck.

Thanks !
The manual says this about the 5V >

"The PV voltage must exceed Vbat + 5V for the controller to start.
Thereafter the minimum PV voltage is Vbat + 1V"

Seems the MPPT needs +5V to get started, and then proceed with just +1V
My 50W panel has Voc 23.4, and Vmp 19.8 > seems okay I guess.

No need for this bluetooth tool: will simple check out the LEDs flashing, once in a while...

 

[BruceK]

MCB is a good idea and I was wondering if a relay connected to the ignition (that would break contact when ignition was on) might round that off nicely if indeed there is any mileage in the assumption that the alternator may not excite.

 

[omega2]

No idea!

 

[peteK]

Never had any problems with having solar panel connected. As you say the alternater senses the voltage and cuts the output its only when you switch a load on and the voltage drops that it starts outputting again.