The Sealegs smart charger plus its plug, which makes connecting easy. They cost less than $200 and using a smart charger like this extends your boat’s battery life.
As the weekends turn sunnier, our lives in the Coastguard Hibiscus unit are growing busier. And the number-one reason for callouts? Flat batteries.
Think about it: the sea is an electrics-hostile environment, unlike the cosy engine bay of your garaged car. Batteries don’t hibernate well if uncared for, especially if they’re more than a couple years old. That’s why, particularly in spring, we find many boaties stranded at sea, having found just enough juice to spark up the motor and take them out to a fishing spot – but too little to get them home. So what’s really happening inside your battery?
Marine batteries are usually of the traditional lead–acid type. They contain a series of interleaved lead plates bathed in electrolyte, typically sulphuric acid (H2SO4). One group of plates (lead) attaches to the positive, another group (lead dioxide) to the negative. That, at least, is the situation in a fully charged battery. When discharged, both the positive and negative groups become lead sulphate (PbSO4) and the electrolyte is mostly water. By charging a battery, you restore it to the original state. If you overcharge it, you ‘cook’ it, and it vents oxygen and hydrogen (which is explosive) and the electrolyte diminishes – which is why you have to top the cells up from time to time with distilled water. If you allow it to discharge too often, it may become permanently ‘sulphated’ – dead.
In boats that have both a house battery (for lights, instruments, and so on) and a start battery (for the motor/s), the plot thickens. A house battery is typically a deep-cycle unit, with fewer, thicker lead plates, delivering a high capacity but a low current. The start battery, by contrast, has very many thin plates, delivering a massive, brief wallop of power, but it’s easily exhausted and will suffer permanent damage if you discharge it too often. Not all batteries are lead-acid, either: in some the acid is suspended in absorbent glass mat, or a silica gel, and while these types are more spill-proof they usually require careful charging.
A battery won’t last forever, but if you want to extend its life, look after it by following a few simple tips:
• Charge it regularly, ideally with a smart device. The CTEK chargers on our Coastguard vessels, for example, automatically cycle the batteries.
• Keep it clean: wipe the outside with a high-pH paste (e.g. baking soda) to remove any greasy film that might cause a short-circuit.
• Keep cells topped up (with distilled water, not plain tap).
• lightly grease the terminals.
My thanks to our unit maintenance officer, Raymond Greenfield, for his expertise on batteries and electrics.