Batteries are a vital element on a boat, yet they’re often neglected — right up until the moment they stop working. Suddenly the lighting, bilge pump, electronics and engine starting system won’t work. You’re stuck, hopefully not in the middle of the bay. What do you do now?
The key to preventing battery failure is to look after them. Here are five of the most common ways that marine batteries meet their end — and how to avoid them.
1) Use the wrong kind of battery
The surest way to quickly kill a marine battery is to use the wrong kind. Marine batteries are manufactured in a variety of types and for different applications, so choosing the right one is vital.
Due to their lower cost, the most common type of marine batteries are the flooded lead acid type (e.g. wet cell batteries). There are also gel batteries, Absorbent Glass Mat (AGM) batteries and spiral-wound battery derivatives; and lithium-ion marine batteries, although they tend to be more expensive.
Marine batteries are made to meet two applications. Starting batteries, also known as cranking batteries, provide a large jolt of amperes. As the names implies, they are typically used to start a marine engine and are built to recharge quickly.
Deep cycle batteries are designed to provide fewer amperes but are intended to operate for longer. They run the various electronics components on a boat and are meant to recharge more slowly. ‘Pure’ deep cycle batteries aren’t designed to be fully discharged. Instead, they have an ideal operating range (typically around 60 per cent) and shouldn’t be discharged below this level.
Dual-purpose batteries are also very common. Sometimes referred to as just marine batteries, they provide a balance between starting and deep cycle use.
A cranking battery repeatedly used for deep cycling can degrade in a matter of weeks, and vice versa, so choose the right one.
2) Overcharge and undercharge
Batteries need to be properly maintained in order to last. Essential to marine battery maintenance is proper charging so always use a charger that meets the manufacturer’s recommendations.
Regularly under-charging a battery erodes its performance and reduces its life due to a phenomenon called sulfation. This occurs when lead sulfate crystals form on the negative plates, impeding performance and reducing the battery’s ability to charge. Eventually this can render it unusable.
Excessive or incorrect overcharging can be equally damaging, particularly with AGM and gel batteries. Doing so can ‘cook’ a battery so it is essential to follow the manufacturer’s charging recommendations.
Thankfully, many readily available tools and accessories are available to keep your batteries in running order. For example, charging and maintaining a battery over long idle periods (like winter) using a multistage charger like SmartCharge will prolong its life.