What You Need to Know About Motorcycle Batteries

A battery of questions answered

The day breaks warm and sunny. You're at the annual Billy Bob's Billet Bike Bonanza, cruising through town on your 18-cylinder Bus Hussy XS Glide. The bike's in third gear with the engine just ticking over and the 100-watt stereo is cranking. Your 10-bulb light bar's ablaze and a Sharper Image radar detector blinks furiously atop your instrument panel. You fiddle with the electrically adjustable windshield and remote trunk cooler. Pulling over after a few miles, you duck inside a café for a mochaccino.

You've been making this same run for the last five days of your pilgrimage, but today is different. When you exit the java joint, saddle up and thumb the starter, you hear only a deathly ominous, "click." You hurl a battery of expletives at your brand-new, unruly battery. It's a current model motorcycle! It's perfect weather! What the hell's going on??!!

Battery tips
Knowing the components of your battery and what affects it can help increase the battery's life.Cruiser

Stuck In The Middle With You
You know there's a positive and negative terminal in a battery. You know accessories are battery-driven. You know how to connect the battery and forget about it until it's too late. Do you really know the special needs of your battery? We rang up John Driscoll, Director of Marketing at Yuasa, Inc. for insight into the riddle, and came away with a quick refresher course on the care and feeding of batteries.

A battery is an easily overlooked component of motorcycles, though things have changed since the days of bump-starting your scoot every week because your battery couldn’t hold a charge. Back then, most of the juice for your ride came from a conventional flooded acid battery. Nowadays, bikers can debate about two basic types: the aforementioned flooded battery, and the AGM (absorbed glass mat) battery, offered on many bikes. Driscoll is quick to point out that the AGM battery is also commonly known as a sealed, maintenance-free, dry or gel battery, but the terms often are misused. He hopes the industry adopts a standardized name of AGM to refer to a maintenance-free battery, to clear up misconceptions.

Simply put, a battery is an electrochemical device that converts chemical energy to electrical energy. It’s made up of individual cells that produce between 2.11 and 2.20 volts each; a 12-volt battery will thus have six cells that may actually produce more than 13 volts. The cells are composed of alternately charged negative and positive lead plates stacked inside—negative, positive, negative, etc. In your basic conventional, or flooded battery, insulators are placed between the cells. The current increases as the plate surface area increases—the more plates in a cell, the more current (flow of electricity) and energy capacity (amp hours). Each cell’s groups of plates are then connected to those in the next cell, and the whole shebang is added to a solution of sulfuric acid and distilled water—the electrolyte. The fun begins when the reaction between lead plates and electrolyte sets off a chemical change, creating an electrical charge. Both AGM and conventional batteries are lead-acid types; the AGM type differs from its more traditional flooded cousin in its choice of electrolyte. The AGM’s solution is maintained in a glass mat and doesn’t slop around as it would in a flooded battery.

Know Thine Enemy
Now that you know how a battery works, it's probably a good idea to learn what'll bring the whole sizzling metal chunk to its knees. Simply stated, a battery's most common natural enemies are:

  • Heat. Excessive heat is one of the worst enemies of a battery's life. Battery temperatures exceeding 130 degrees Fahrenheit will dramatically reduce longevity. A battery stored at 95 degrees will discharge twice as fast as a battery stored at 75 degrees. (As temperatures rise, so does the rate of discharge.) Heat can virtually destroy your battery.
  • Vibration. It is the next most com­mon battery killer after heat. A rattling battery is an unhealthy one. Take the time to inspect the mounting hardware and let your battery live longer. Installing rubber supports and bumpers in your battery box can't hurt.
  • Sulfation. This happens because of continuous discharging or low electrolyte levels. Excessive discharge turns lead plates into lead sulfate crystals, which blossom into sulfation. It's usually not a problem if the battery is properly charged, and electro­lyte levels are maintained.
  • Freezing. This shouldn't bother you unless your battery is inadequately charged. Electrolyte acid becomes water as discharge occurs, and water freezes at 32 degrees Fahrenheit. Freezing can also crack the case and buckle the plates. If it freezes, chuck the battery. A fully charged battery, on the other hand, can be stored at sub-freezing temps with almost no fear of damage.
  • Not concrete floors. That old wives' tale about not keeping your battery on concrete floors for long periods of time? It was true when old wives were storing batteries with Bakelite cases, but no longer.

It's clear that many battery killers are overrepresented in the cruiser genre, with our bikes' V-twin vibration and our preference for warm-weather trolling. Add to this the fact that short trips at low rpm and multiple accessories deplete a battery's power quickly, and you have the recipe for a dead battery (our opening scenario). It illustrates Driscoll's concern with the type of riding many cruiser enthusiasts tend to do. We amass an array of parasitic electrical accessories, putt around our bikes for short distances at engine speeds too low to provide enough charging output (much less excess charge) for all that current draw in a sweltering desert. And then we wonder why the bike won't crank over. Cruiser riders should monitor their batteries' effective power diligently, and check the electrolyte levels at least once a month. Checking with a voltmeter is the surest way to know. (An AGM battery can only be tested with a voltmeter, but tends to have a longer shelf life and resists vibration better.)

For You? No Charge
If it looks weak and you need to charge your battery, Driscoll recommends a 12-volt, 1.0-amp trickle charger or taper or maintenance charger—available from Yuasa or Deltran—to meet most rider's needs. The drawback to a trickle (which has a fixed rate of charge) or taper charger (which has a variable rate of charge) is speed, or lack thereof. It can take more than a day to bring a fully discharged battery back to 100 percent. But remember that a charge greater than 2.0 to 2.5 amps can easily cook a small-engine battery. And a poorly discharged battery might not ever accept a charge from a standard charger, at which point it's probably not worth saving.

From Driscoll, though, a man well-positioned in the battery trade, comes the juiciest tip of all: “The best battery charger in the world? It’s your motorcycle! If you ride your bike, your battery will always be charged.” We’ll have no argument with that. In fact, we’ll just go charge our bikes right now.