It’s the batteries...
The three leisure batteries on our recently purchased boat are not holding a good charge for very long. After a day’s cruise they seem reasonable but, 24 hours later, the Eberspächer heating gives an ‘insufficient battery voltage’ fault. The 12v fridge doesn’t last long before the compressor stops cutting in, but is fine with the engine running. I assume one or more of the leisure batteries needs replacing, but do you think I might also have a problem with the alternator – perhaps a voltage regulator?
Qwebsite TONY REPLIES... To be absolutely sure I need voltage figures and hydrometer readings. Twelve volt compressor fridges have a safety cut-out that shuts them down if the
Avoltage under starting load drops below about 11.5 volts, so you have both fridge and Eberspächer telling you that you have flat batteries.
To be sure of what is going on I would need a battery voltage reading just before you start up in the morning and again about half an hour after you shut down at the end of the day’s cruise. I would also require the charging amps at first start up and just before you shut down at the end of the day, plus the alternator’s rated output.