MotoMojo: Advanced Battery Designs

Dec 24, 2013 View Comments by

MotoMojo: Advanced Battery DesignsLightweight and powerful, advanced lithium-ion (Li-ion) battery designs are making their way from applications such as laptop computers and hybrid cars into motorcycling. They are far lighter and smaller, as well as maintenance free. In addition, they don’t contain toxic lead as conventional motorcycle batteries do.

Lithium-based batteries have been available for gasoline-fueled motorcycles for several years, and the new electric motorcycles now come with them. So it’s time to get acquainted.

Lithium is the lightest metal, and lithium batteries boast the highest energy to weight density that is currently available. Early research on lithium batteries actually started a century ago, and the first lithium batteries were sold in the 1970s. Most lithium metal batteries are non-rechargeable and are popular in film cameras.

MotoMojo: Advanced Battery DesignsLithium-ion Batteries
Due to lithium metal’s instability (particularly during charging), early rechargeable batteries were unsuccessful, so development progressed to non-metallic lithium-ion batteries. Lithium-ion (Li-ion) batteries have a slightly lower energy density than lithium metal, but they are more stable. In 1991, the first Li-ion batteries were sold.

Li-ion batteries are expensive, but they have no “memory effect,” are maintenance free, cause little environmental harm when disposed, and their self-discharge rates are slow. However, Li-ion batteries can have thermal-runaway problems; you may have heard about the theories that this caused fires on Boeing 787 aircraft. They don’t “like” high or low temperatures and require an elaborate voltage-controlling circuit to maintain safe operation.

Lithium Polymer
Lithium-polymer batteries, developed in the 1970s, use a solid, dry-polymer electrolyte, which makes them rugged, safe, and compact. However, they can’t provide the bursts of heavy current needed for starting vehicles. Gelled electrolyte versions were developed, which use a separator/electrolyte membrane of porous polyethylene or polypropylene filled with a polymer. However, cost and other considerations have kept them from being used in motorcycles.

Ballistic battery3Lithium Iron Phosphate Batteries
Lithium iron phosphate (LiFePO4) batteries, also dubbed LFP (for lithium ferro phosphate), are a recent offshoot of rechargeable lithium-ion technology that uses LiFePO4 as their cathode material. LiFePO4 was first used for cathodes in rechargeable batteries in 1996.

This type of battery construction is found in a number of recent motorcycle battery brands, including Ballistic, Braille, UPG’s Adventure Power Phantom, and Shorai.

These lightweight, high-performance batteries are designed to replace the heavy, corrosive, and high-maintenance lead-acid batteries used in motorcycles. They weigh approximately one fourth to one fifth of a standard lead-acid battery, have about twice the average service life, and can hold their charge for up to a year. There’s no water refilling, no acid venting or leaks, and the terminals don’t corrode as do lead-acid batteries. They are also non-toxic, have excellent thermal stability for improved safety, and have a high energy density.

LFP batteries have a very steady discharge voltage, unlike other Li-ion batteries. Voltage stays close to 3.2 per cell during discharge until the battery is exhausted, which allows full use of the battery’s capacity and reduces (or even eliminates) the need for voltage-control circuits. With their 3.2 volt nominal output, four cells can be connected in series for a voltage of 12.8V, which is close to the voltage of lead-acid batteries and is compatible with most existing charging systems.

MotoMojo: Advanced Battery DesignsUnlike lead-acid batteries, LFP batteries shouldn’t be kept at 100-percent charge during storage. When recharging an LFP battery, be sure to use a low-amperage charger without a desulfation mode. Shorai, for example, offers a special charger with a storage mode configured to maintain Shorai batteries at optimum levels during long-term storage. In “Store” mode, the charger brings the battery to 80-percent charge and allows it to dip to 60 percent, at which point it will charge back to 80 percent. The “Charge” mode of the Shorai charger will bring the battery level up to 100 percent.

LFP batteries don’t like parasitic draws when the bike is off. Clocks and computer memories should be OK during normal use, but cycles that aren’t ridden frequently and are loaded with accessories that draw current may be a problem. Never let an LFP battery get below 9.0 volts; this will damage it. If your bike has parasitic draws, such as alarms, disconnect the battery when not used for more than a few days. If an LFP battery becomes discharged, charge it immediately. Some LFP batteries come with an automatic shut-off circuit, which may help prevent deep discharges. LFP batteries also become weak when it’s very cold, but most motorcyclists don’t ride when it is below freezing.

Racers quickly adopted LFP batteries for their light weight, compact size, and because they won’t spill acid in a crash. Street riders, particularly sportbike enthusiasts, are also starting to convert to enjoy the same advantages. If you convert to LFP batteries, the most important thing to do is follow the battery manufacturer’s charging and care recommendations.

Text: Ken Freund

 

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