Replacing Batteries? Do Your Homework First
New electricity-storage technology has introduced benefits—and issues—that you’ll want to weigh carefully when planning a refit or considering the purchase of a new boat. "Systems" from our February 2012 issue.
Because it’s been quite some time since Cruising World has taken a comprehensive look at the devices that make up an onboard direct-current power supply, we intend to do just that over the next few months. We’ll review what’s developed in the area of battery technology for cruisers and tell you what you should look for if you’re planning a simple replacement or an upgrade to the heart of your DC electrical system.
In Part II, we’ll dig into battery-charging systems and take a close look at what’s available in both engine-driven alternators and shore-power or generator-powered battery chargers for meeting the needs of the new types of batteries that are now available.
Finally, in Part III we’ll take stock of what’s new in the arena of alternative power generation. New solar panels and wind and water generators for the cruising sailor have made some pretty significant strides in the right direction over the last few years, so we’ll consider what’s available and tell you the things you’ll need to ponder if you plan to move in this direction with your boat.
Heart of the System
Batteries are at the heart of any DC electrical system. Your boat’s batteries are where any electrical power you generate gets stored for use on demand. This is an area of technology in which there’s been a huge amount of movement over the last 10 years, largely driven by interest in hybrid and full-on electric-propulsion systems in both the marine and automotive sectors.
“Green Tech,” as in electric propulsion, has been a prevailing phrase at every boat show I’ve attended for the last several years. New battery technology such as lithium-ion is one of the keys to making all of this hybrid “e-power” work for cars and boats. Eventually, proponents say, it will supplant “p-power” (as in petrofuels) for vehicles operating on land or in water. But are most sailors ready today for a new generation of battery technology?
And what about some of the interim battery types that are becoming increasingly popular, such as absorbed glass mat, gel-cell, and thin plate pure lead batteries? Let’s take a look at all of these so that you’ll be able to make an informed choice when you decide to replace or upgrade what you have or spec out a new boat.
The Lithium Option
Lithium-battery technology has been all the rage for several years, and for some compelling reasons. Lithium is one of the lightest of all metals and has an extremely high electro-chemical potential, which makes it a super-active ingredient for constructing batteries. We know that lithium batteries can easily achieve two to three times the current density of conventional batteries. But there are some really rough spots on this stretch of the technology superhighway.
Lithium-ion batteries must be controlled internally by electronic circuitry that keeps the cells in balance under all conditions.
Perhaps you’ve heard about lithium batteries in laptop computers overheating and burning people’s kneecaps. This is caused by a phenomenon known as “thermal-runaway,” and controlling, or rather, preventing it is one of the major factors on which hangs the success of this choice of chemical battery component.
To address these lithium-battery issues, manufacturers have embraced lithium-ion technology over pure lithium devices. Battery makers have also given closer scrutiny to the actual chemical compounds used within these batteries.
Manufacturers have moved away from using lithium cobalt in the kind of larger battery sets that we’re discussing here, and every vendor now has its own take on the specific compound to use in its product mix. Some use lithium iron phosphate (Mastervolt, Genasun); others use lithium manganese (Torqueedo); still others, like Valence Technology, use lithium iron magnesium. Each of these variations has strengths and weaknesses in terms of actual stability and current densities, but all are considered much safer than the cobalt formulations. The list of compounds seems to grow almost weekly as more and more players enter the game and researchers make new inroads. In the end, this all centers on design choices that factor in current density potential vs. chemical stability and, ultimately, safety.
If we’ve learned anything about lithium-battery technology in big-battery marine applications over the last five or six years, it’s that regardless of what brand you select, a carefully engineered battery-management system is an absolute must to ensure safety. This means a typical boat owner can’t simply go out and replace the existing battery bank with lithium-ion substitutes. Even in cases involving a specifically designed management system, we’re still hearing, in fact, about the occasional catastrophic fire on boats running at the bleeding edge of battery technology. A particular problem involves early adopters of this technology; their boats may be running, based on what we now know today, with less-than-adequate systems.
Lithium-ion batteries, meanwhile, aren’t cheap. Entry level with this technology is presently in the $2,500 range, and that’s only going to buy you around 100 to 150 amp-hours of capacity. Because this is roughly equivalent to a single Group 31 battery that in a traditional lead-acid/flooded-cell configuration can be bought for around $100, you have to wonder why anyone would pay more.