Charging engine battery

[B27]

My personal choice setup would be to have en engine battery with a 1 way VSR to also charge the domestic bank when the engine is running. A mains powered battery charger connected just to the domestic bank and an emergency parallel switch to allow the domestics to start the engine if the engine battery went flat for any reason. I have rarely ever seen the need to charge the engine start battery from a mains battery charger unless the boat gets left unused for very extended periods.

I think that's a good approach.
But I can remember the days before cheap solar panels with no shore power.
There did seem to be a recurrent theme of taking batteries home to charge.
And batteries having short lives.
Affordable solar to keep the engine battery topped up through Autumn and Winter was a major improvement.
With shore power, a small maintenance charger for the engine battery can make sense.

 

[Graham376]

My personal choice setup would be to have en engine battery with a 1 way VSR to also charge the domestic bank when the engine is running. A mains powered battery charger connected just to the domestic bank and an emergency parallel switch to allow the domestics to start the engine if the engine battery went flat for any reason. I have rarely ever seen the need to charge the engine start battery from a mains battery charger unless the boat gets left unused for very extended periods.

That's my setup, the VSR is connected to the engine side of the engine battery isolator. My Trojans charge at 14.82 via solar and I don't want the sealed engine battery charging for extended periods at that voltage. Engine battery still starts the engine after 2-3 months off charge but can parallel if needed. We're mooring based so only use mains charger occasionally if we're in yard in winter.

 

[William_H]

That's my setup, the VSR is connected to the engine side of the engine battery isolator. My Trojans charge at 14.82 via solar and I don't want the sealed engine battery charging for extended periods at that voltage. Engine battery still starts the engine after 2-3 months off charge but can parallel if needed. We're mooring based so only use mains charger occasionally if we're in yard in winter.

"My Trojans charge at 14.82 volts via solar" My guess is that is just optimistic claim from controller data. Unless you ave enormous solar capability small batteries, much sunshine and measure at the end of bulk charge cycle then charge volts will be lower. The regime is a maximum voltage for that stage (bulk) not a guarantee. Even with MPPT technology which raises voltage to that desired it can't raise the voltage if charge current effectively uses all the power available. Solar is not like a mains charger or laternator controller with staged charge regime where input power is effectively unlimited. While solar power is limited by power, orientation and sunshine. ol'will Not wanting to criticize but help newbies understand the stepped charge regime specs on solar controllers.

 

[Graham376]

"My Trojans charge at 14.82 volts via solar" My guess is that is just optimistic claim from controller data. Unless you ave enormous solar capability small batteries, much sunshine and measure at the end of bulk charge cycle then charge volts will be lower. The regime is a maximum voltage for that stage (bulk) not a guarantee. Even with MPPT technology which raises voltage to that desired it can't raise the voltage if charge current effectively uses all the power available. Solar is not like a mains charger or laternator controller with staged charge regime where input power is effectively unlimited. While solar power is limited by power, orientation and sunshine. ol'will Not wanting to criticize but help newbies understand the stepped charge regime specs on solar controllers.

We get around 300 days of sun per annum, with 320w of solar and 450AH of Trojans +engine battery, Victron graph shows max battery voltage between 14.74 and 14.81 so not far from expected.

 

[William_H]

We get around 300 days of sun per annum, with 320w of solar and 450AH of Trojans +engine battery, Victron graph shows max battery voltage between 14.74 and 14.81 so not far from expected.

Roger that and well done. I do suspect yours might be more an exception (I do not know where your boat is based from place names) ol'will

 

[Graham376]

Roger that and well done. I do suspect yours might be more an exception (I do not know where your boat is based from place names) ol'will

Algarve, southern Portugal.

 

[Buck Turgidson]

"My Trojans charge at 14.82 volts via solar" My guess is that is just optimistic claim from controller data. Unless you ave enormous solar capability small batteries, much sunshine and measure at the end of bulk charge cycle then charge volts will be lower. The regime is a maximum voltage for that stage (bulk) not a guarantee. Even with MPPT technology which raises voltage to that desired it can't raise the voltage if charge current effectively uses all the power available. Solar is not like a mains charger or laternator controller with staged charge regime where input power is effectively unlimited. While solar power is limited by power, orientation and sunshine. ol'will Not wanting to criticize but help newbies understand the stepped charge regime specs on solar controllers.

It's exactly what I would expect. I get the same from my 90w panel. I set the voltage to 14.8 and I get 14.75 measured.