Some points raised so far. Evey time you discharge the battery to any extent you convert lead oxide (can,t remember which oxide)into lead sulphate and when you charge again you convert the lead sulphate back into lead oxide. You can do this at 13.8 volts but it will take a long time.
Time is the problem with lead sulphate because the longer it is left the "harder" it becomes and this in turn requires higher and higher voltages to reconvert it. Eventually the voltage required will be so high it will destroy the cells. This means that we need to reconvert the lead sulphate back to lead oxide as fast as we can. To do this we need the highest charging voltage that is compatible with optimum battery life and water use. This is where the 14.4 volts comes into the question. It is about the voltage where using energy to split the water into H & O starts to rise and this reduce the amount being used to convert the sulphate. It is also known as the gassing voltage. Because converting the last 10 to 20% of the sulphate takes an inordinate amount of time and trying to shorten this by raising the voltage only results in more heat and gassing it follows that engine charging will not be on for long enough to reconvert the sulphate so we are left with some ever hardening sulphate on the plates. Equalisation charging will convert some of this but its primary purpose is to mitigate the acid stratification found on batteries that are kept on float charge for long periods - like standby batteries. Typically it should not be required on a boat that is in daily use, but it will make a difference to the sulphation,but how much is open to question. If your alternator's voltage regulator is set for 14.4 volts it is now considered that any additional controllers or regulators are not required, save to overcome installation faults that make battery sensing of charging voltage valuable. If it is set for less (13.8 for very old ones or about 14 to 14.2 for more modern ones)may benefit from an addition for a controller. Until the pulsed anti-sulphation devices can be proven to do what is claimed then the only way to minimise (note - I did not say prevent) sulphation is to provide a charge for long enough to convert most of that last 10 to 20% of sulphate. Tony Brooks
