MotoMojo: Lithium-Ion Batteries for Motorcycles

Mar 06, 2020 View Comments by

Lithium-Ion Batteries for MotorcyclesRechargeable lithium-ion batteries are used in all sorts of common portable devices, including cordless power tools, cell phones, laptops, and tablets. Lithium-ion cells have made nickel-cadmium and nickel-metal hydride batteries outmoded, and lithium-ion batteries are making inroads into the motorcycle market. The safest lithium-ion battery chemistry used for starting engines is lithium ferrous phosphate (LiFePO4), sometimes also known as lithium iron phosphate or LiFe/LFP 4-cell batteries.

There are a number of reasons why they’ve become so popular. LiFe/LFP batteries are light (lithium is the lightest metal known) and have high storage capacity (energy density) for their size. They also have little memory effect (tendency to lose capacity due to improper charging regimens) and their self-discharge rates are low. When stored and not connected to circuitry, they typically lose 1% to 3% of their charge each month. By comparison, lead-acid batteries typically self-discharge at around 5% per month.

The charging systems of most motorcycles produce voltages compatible with LiFe/LFP batteries. A LiFe/LFP cell’s nominal voltage, depending on the electrode materials, is between 3.2 and 3.3 volts. So with four cells in series (for a “12-volt” battery) that’s 12.8 to 13.2 volts, compared with 12 volts (6 x 2 V cells) for a lead-acid battery. You need a charging system/regulator that keeps the voltage between 13.8 and 14.5 volts. If it’s higher than 14.5, you will run into problems, as LiFe/LFP batteries, just like any lithium-ion type of battery, do not tolerate overcharging. Lithium-ion batteries overheat when overcharged. At 15 volts and above you will run into serious problems: The battery will swell, overheat, and could melt down. Tip: Make sure your vehicle’s charging system is working in that zone of 13.8 to 14.5 volts before considering a LiFe/LFP battery.

For storage and deep (low volt) recharging, special chargers are recommended for LiFe/LFP batteries. Unlike lead-acids that should be kept fully charged at all times to avoid the battery losing capacity, LiFe/LFP batteries last longest if kept somewhere between 70% and 90% (13.3 to 13.6 volts) when the motorcycle is stored.

LiFe/LFP batteries work best near room temperature and can be fast-charged within the temperature range of 32 F to 113 F (0 C to 45 C). Charging should be performed within this temperature range. From -4 F to 32 F (-20 C to 0 C), charging current should be reduced. When temperatures get near freezing, the batteries may need to be warmed up before use. This may be done by turning on the lights for a couple minutes until the battery “wakes up.”

Certain lithium-ion batteries have been known to catch fire when used or charged improperly, but the LiFe/LFP (lithium iron phosphate) chemistry used in motorcycle lithium batteries is far more stable, with a higher runaway temperature of 518 F / 270 C, almost 1 ½ times higher than what’s used in a smartphone. (Runaway temperature is that critical temperature when it will start to self-consume, heat itself, and catch fire). However, a lithium-ion battery’s temperature increases during use and during normal charging. Tip: If you’ve been riding all day in hot weather, only hook up the maintenance charger once your bike has cooled. By that time the LiFe/LFP battery would have cooled as well.

Battery life varies greatly, depending on operating conditions. Lead-acid batteries typically last one to three years, while some owners report lithium-ion battery life spans of about five years. As a result, most LiFe/LFP motorcycle batteries have longer warranties, often three years, while lead-acid batteries typically have shorter warranties of one year or less. LiFe/LFP batteries are light, with a typical weight savings of 75% to 80%. In addition to having a low self-discharge rate, LiFe/LFP batteries deliver higher cranking amps for a quicker engine start. Lead-acid batteries shouldn’t be discharged deeper than a 50% state of charge. Lithium-ion batteries will produce full cranking power until they’re almost completely discharged, even down to 10%. Lithium-ion cells don’t contain toxic lead and sulfuric acid. They also can be mounted in any position and can’t leak acid.

While LiFe/LFP batteries have advantages, they may not be right for everyone. They cost substantially more than lead-acids. They also should be used with a special charger, thus adding to the cost.

Many lithium-ion batteries designed for motorcycles now come with a protection circuit module/board (PCM or PCB) that prevents the battery from being overcharged, overdrained, and overdischarged.

How should you dispose of them when they fail? According to the U.S. government, lithium-ion batteries are classified as nonhazardous waste, but it’s strongly recommended to return old batteries to a dealer to ensure they are disposed of properly.

Lithium-ion batteries are best suited for folks who want a light, compact battery that lasts longer, despite the cost. For those who ride in cold weather, a lithium-ion battery may work, but it could prove to be an annoyance due to the warm-up procedure. We’ve found that for heavy cruisers and touring machines where a few pounds of extra weight aren’t noticeable, a sealed absorbed glass mat (AGM) battery works well.

Martin Human, CEO of battery charger brand OptiMate, strongly recommends using only chargers designed for LiFe/LFP batteries. Human says it’s especially necessary when that battery is deep discharged below 9 volts; a slow controlled charge is needed to bring the battery safely back to full charge. Human says LiFe/LFP batteries are best suited for sport bikes, particularly those used on race tracks, and on dirt bikes and dual sports, where weight and resistance to vibration are important considerations. Parasitic draws from accessories such as alarms are harder on LiFe/LFP batteries than on lead-acid batteries due to having less amp-hour capacity, so if your bike has various power draws or you run systems (such as sound) when the engine is not running, stay with lead-acid batteries.



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