What voltage would you expect from a shore charger?

[davidej]

I am not convinced my shore charger is functioning properly. It is a Dolphin- French charger, French boat.

I disconnected it from the batteries and measured the voltage at the output. It seemed to be about 12.6-12.7. When the batteries are connected it reads 12.7. However when I leave the fridge on, the voltage drops surprisingly quickly as if there is no charge coming through from the charger.

On the other hand, when the motor is running, the batteries read about 13V. As an amateur this sounds about right to me and I would expect the shore charger to give a similar figure.

Could a fault reduce the output voltage? I would expect it either to be correct or not work at all.

Any advice would be welcome.

 

[PaulRainbow]

All of those readings are too low. I'd suspect your volt meter is incorrect.

 

[Refueler]

See if you can borrow a charger and check that against yours ........... that will then indicate whether your charger or meter ...

When my engine is running - my battery meter shows well over 13V ...

 

[VicS]

12.7 volts is about what you would expect a fully charged good battery to read after resting for 24 hrs with no load and and no further charge.
You need at least 13.8 ish volts for any meaningful charging to take place and more usually around 14.2 to 14.4..

Firstly check your voltage readings with a known good voltmeter or multimeter.

 

[reeac]

If it’s a smart charger then it will adjust its output voltage to suit the state of charge of the battery as indicated by the battery voltage. If the charger isn’t connected to a battery then it will have no reference voltage and will presumably get confused. Better to measure the battery voltage and then switch on the charger whilst still monitoring the battery voltage …which ought then to rise to 13.0 or more if the charger is working ok.