Solar panel is stopping alternator from charging...

[casper ghost]

My brother has fitted a 40watt solar panel, which is connected directly to his 2 domestic batteries. It appears that the solar panel is stopping the alternator from charging at the same time, as the alternator charge light stays on and only goes out when we cover the solar panel? We've turned the battery switch to just charge the starting battery (which is not connected to the solar panel) with the alternator and this works fine?

As it stands he would have to cover the panel to get any charge whilst cruising the boat...

We've checked with an avo, The solar panel is producing 15.8 volts, with panel covered the alternator is 14.5 volts. We tried reading the volts from the alternator with the panel uncovered but the avo only registered the 15.8 from the panel. The battery with no charge to it is at 13.4 volts. I do believe however that this avo is not very accurate and reading a bit high all the time.

Any ideas?

Casp'

[the grinch]

you need to fit a relay of some sort to stop the solar charge backtracking into the alternator as prolonged operating will damage the alternator

[Gibbo]

My brother has fitted a 40watt solar panel, which is connected directly to his 2 domestic batteries. It appears that the solar panel is stopping the alternator from charging at the same time, as the alternator charge light stays on and only goes out when we cover the solar panel? We've turned the battery switch to just charge the starting battery (which is not connected to the solar panel) with the alternator and this works fine?

As it stands he would have to cover the panel to get any charge whilst cruising the boat...

We've checked with an avo, The solar panel is producing 15.8 volts, with panel covered the alternator is 14.5 volts. We tried reading the volts from the alternator with the panel uncovered but the avo only registered the 15.8 from the panel. The battery with no charge to it is at 13.4 volts. I do believe however that this avo is not very accurate and reading a bit high all the time.

Any ideas?

Casp'

 

The batteries are fully charged. The solar panel is holding the voltage above the alternator regulator voltage so the alternator shuts down completely. If the batteries were not fully charged, this wouldn't be happening. Stopping it happening will not achieve anything, it won't make the alternator put any power into the batteries because they are already full.

 

The ony issue is the nuisance value of the warning light being on (and perhaps no tacho).

 

However you do need to find a way to reduce that voltage. Extended charging at that level will boil away all the electrolyte.

 

you need to fit a relay of some sort to stop the solar charge backtracking into the alternator as prolonged operating will damage the alternator

 

No it won't.

[casper ghost]

The batteries are fully charged. (snipped)

 

However you do need to find a way to reduce that voltage. Extended charging at that level will boil away all the electrolyte.

Thanks. He has decided to fit a solar panel controller, I expect that will reduce the voltage to a better level.

Casp'