I Am a Motorcycle Battery

By John Urban, www.jurbanpower.com

I am your motorcycle battery and I would like you to know what you can do to make me happy.

Before I get into just what it is that I like, I would like to explain to you how my family of battery products work. If you know the basics of battery care and mix that with a bit of advanced battery knowledge, we may be together for a long time. My goal in this article is to have you treat me better than you have in the past. In return, I promise that I will start your bike consistently with an increased life payback so that you can spend your “every other year” battery allowance on other things, like a new set of driving gloves or possibly a new helmet lens, or helmet, or…..?

Let me begin by stating that what I am about to explain about myself is basically true for all of my Lead Acid brothers and sisters, this includes wet Lead Acid (historically used in motorcycles) as well as Valve Regulated Lead Acid (VRLA) or as many people call it: Maintenance Free, Gelled or Absorbed Glass Mat (AGM) batteries. Other rarely used battery types such as nickel zinc, or sealed nickel cadmium or others will not be covered in this article.

Safety First

My family of lead acid batteries are heavy for their size, have sulfuric acid in them, and produce hydrogen gas. Therefore use caution when lifting me even though most motorcycle batteries are not a weight threat to most people, I am heavier than I look. Under my cover

and while I am charging, I produce hydrogen gas along with other byproducts of charging. If you forget about me during a recharge, you could fill your garage with unwanted, EXPLOSIVE gas that could be ignited by any spark when not expected. Never put a source of flame or spark near me especially when charging. Sulfuric acid can cause severe burns. When working with me, always wear safety goggles with side protection to protect your eyes, and gloves to protect your hands. If you come in contact with the sulfuric acid, flush the effected area with water and get medical attention. 

This Is What I Am

As a lead acid battery I am an electro chemical storage device made of two dissimilar metallic plates immersed into a diluted solution of sulfuric acid (H2SO4). All of my plates are neatly packaged into three cell (6.0 volt nominal) or six cell (12 Volt nominal)  mono block, thermoplastic container that is made to keep the acid inside. My negative (Pb) plates and positive (Pb02) plates are paralleled then separated by a separator in each cell so that they don’t short circuit while you are riding, that way I can give you high motor starting current when needed. By using through the partition cell to cell connections under my battery cover, I can deliver three or six cells of power (2.0 volts per cell nominal) for your use.

I Love To Discharge

Now it is hard to believe, that while you are reading this article, I am in your bike doing what I do naturally, SULFATING. In a lead acid battery, sulfating is a chemical way to describe DISCHARGING.  That’s right, unless you have connected a voltage controlled float  / trickle charger on to me, I will sulfate. When you use me to start your bike or to listen to the radio while parked with no engine running, I am sulfating. It’s by the laws of physics that without a constant voltage controlled charger connected to me, or a running engine with a properly operating regulator, I discharge until I am useless. I sulfate much faster at higher temperatures in your summer garage.  When you store me for the winter months (for you cold and snowy climate people) I discharge slower and develop sulfate crystals that can be most damaging. When you combine the rate that I will naturally discharge and any key off load many bikes have with devices like clocks and ignition processor controllers, I can loose power quite fast. Further, depending on the alloy of my  plates, my self-discharge and water usage during our riding sessions could vary, even more as I age. If kept in freezing garages I might freeze and poke a hole through a plate separator and develop a short circuit path, again rendering me useless before my time. If I become too sulfated, your attempts to charge me will be met by the charger as two insulators in a tub of water. Remember, a battery is two dissimilar metal plates in an acid solution. When these plates are most dissimilar, I am better charged.  If you apply to much charge current to me for too long of time I will use a lot of water and overheat.  If you do your best to keep me properly charged, I will do my best to perform well.

I am not too hard to keep happy, but perhaps due to my forgettable disposition (usually under your seat) I am often abused by being forgotten. Most people forget about me needing water or during the cold season, to giving me a small amount of charge.  My brothers and sisters are not all alike. Some of them are made of different plate compositions that will determine how much water they will use during regular operation or effect the rate of discharge when just plain sitting (sulfating). If I am made with antimony plates my self-discharge is five to ten times greater than my cousin calcium plates especially when I get toward the end of my life.

Its All In The Numbers

Now for the bit of advanced battery knowledge previously mentioned. At 77 degrees F. (lead acid battery performance standard temperature) each of my cells are nominally 2.0 volts DC. The problem is they are never exactly 2.0000 volts but for a moment when my sulfating or loading decays me to low voltage values.  My cells are usually between 1.98 and 2.15 when I am just sitting around waiting to do work for you (open circuit slight key off load). If I am below 1.98 – 2.02 volts per cell charge me or I might let you down when I am needed. I work on a sulfuric acid specific gravity point drop range, designed to give me orders to perform for a designed length of time at a given discharge rate. Being that voltage measurements can be confusing depending on what condition your are measuring me, loaded, charging, or static, I thought that I would share with you a lead acid battery constant to calculate my state of charge. The magic number is .84. That’s right .84. If you subtract .84 from the “at rest” per cell voltage, the result is the specific gravity or density of the sulfuric acid in my cells. The higher the specific gravity of my acid, the higher state of charge that I am in.  Here’s an example: A 12 volt battery has 6 cells. If the total terminal voltage is measured at 12.8 volts, divide 12.8 by the number of cells (6) and you get 2.133. If you subtract .84 from 2.133 you get 1.293. Are you with me so far? Now the magic begins. Water has a specific gravity of 1.000, most motorcycle batteries have a full charge sulfuric acid specific gravity of 1.265 -1.300 and a “out of gas” specific gravity of 1.100. The difference between those two figures is 165- 200, that’s up to 200 points of designed performance range mentioned above. In our example 1.300 is really called thirteen hundred specific gravity in the battery business, and that is a fully charged battery! Playing with acid is not fun, it is messy and is a safety risk. VRLA batteries are sealed with a pressure relief valve so as to force the recombination of oxygen and hydrogen to re-hydrate me so you could not confirm the state of charge by acid measurements if you wanted to. By using the .84 rule, you can benefit by knowing if you are half way discharged or three quarters fully charged. Remember the voltage reading to do this math must be taken when I am at rest, no load and no charger connected. It’s another tool to analyze what condition that I am in… or should I say that you have left me in?  And you don’t have to play with the acid. Be aware that shorted cells can skew the per cell numbers but basically this exercise can work fine when determining when to charge me. Below eleven eighty (1.180) specific gravity… give me a charge.

Vintage Motorcycle Charging Systems

Today we have extremely small microprocessors running proven algorithms that calculate my rate of charge, rate of discharge, and voltage level many times per second to optimize the conditions that help me to remain happy for a long life. But that was not always the case. Many 1960 series Japanese bikes had absolutely no means of voltage regulation for the load bus except for me and my counter voltage to a charge. The basic components of the charging system were: 1) a dynamo, generating an AC output voltage, 2) rectifier, half or full wave type and 3) me, a battery. It could be said that I was the sacrificial lamb to the system because in most cases I was the only limit to the increasing system voltage due to unregulated dynamo output. The faster the engine RPM the higher the AC/DC output, when I would reach critically high voltage limits because of the uncontrolled output and prolonged high RPM, I would overheat, use the water in my electrolyte and dry out. If left in this condition I would fail open circuit whereby there would be absolutely no (in my absence) voltage regulation causing exceedingly high voltages (sometimes as high as16-22 volts) where it was common to pop light bulbs as if they were old camera flash bulbs. Early Japanese bike designers attempted to calculate the additional headlight / taillight load by using a switch in the headlight bucket that added windings of the generator for the added load output, but usually this method either left me undercharged or overcharged. To make matters worse, if the AC generator output was rectifier by a half wave rectifier, the AC ripple voltage/current measured at the battery posts would serve to over heat me until I would just plain stop working for you. Thank goodness that most solid state regulators entered the picture by the late 60’s. Early bikes used for prolonged, high RPM trips were battery eaters and would migrate sulfuric acid out of the vent tube usually causing a mess, while low RPM night time runs tended to undercharge me. 

Conclusion

I know that I can be fussy at times and you don’t even know it. When I am not charged you don’t know, when I’m overcharged, you don’t know, when I need water, you don’t know and to make matters worse, I have no way of telling you other than just plain failing, and then it’s too late. So if you pay more attention to me and apply some of the things you have learned from this article, I will hold true to my opening promise. I will last longer and be more dependable thus giving you a better return on your investment in me. Who knows, with the money you save year after year, you might buy your wife a vintage motorcycle as a project, a project that you can help her with!

END

About the author:

John Urban owns J. Urban Power, LLC,  a DC power consulting company that distributes DC power equipment and services. He started as a battery technician with EXIDE battery in 1978 and has contributed to IEEE battery VRLA maintenance standards as well as conducted many battery industrial training seminars in the Midwest. His education has spanned many years with studies at Milwaukee Area Technical College, University of Wisconsin – Milwaukee, and Marquette University - Milwaukee.  He currently enjoys vintage motorcycles and has restored, to one degree or another, (3) Vintage Japanese motorcycles: 1967 Honda CL 77, 1975 Honda CB 750, and 1977 Kawasaki KZ 1000A1. John and his wife Jan cruise with their 2003 Honda GL 1800.