TECHNICAL RECYCLING BATTERIES
Batteries are in many ways anathema to sailors. They are heavy, finicky things, whose performance wanes with time, requiring an elaborate system to keep them in good shape. They are also, when you get down to the level of individual cells, thoroughly analogue – even if a host of clever digital battery management systems have grown up around them.
As consumables, they need regular replacement – perhaps as often as every five years, depending on how kind you are to them and how much they are used. So in one sense, at least, sailing is the process of turning a steady flow of new batteries into waste, which, like all waste, has to be dealt with.
It is something of a dark art to know when your lead-acid batteries need replacing. But the most basic way is to measure the voltage after a full charge and a period of settling. A voltage below 12V indicates total failure, while 12.20V-12.35V indicates around 50% state of charge (it varies slightly according to whether your battery is wet-cell, gel or AGM). A healthy battery should measure 12.70-12.85V. You could also measure the specific gravity of the electrolyte after a full charge, which equally tells you how much capacity remains.
How much capacity is enough? Well, that
