Battery Tutorial
Battery Tutorial
You have most likely heard the term K.I.S.S. (Keep It Simple, Stupid). I am going to attempt to explain how lead acid batteries work and what they need without burying you with a bunch of needless technical data. Actually I have found that battery manufacturers data will vary somewhat so I must generalize in some cases.
The commercial use of the lead acid battery is over 100 years old. The same chemical principal is being used to create energy that our great, great, grandparents may have used.
If you can grasp the basics you will have a lot less battery problems and will gain greater battery performance, reliability and longevity. I suggest you read the entire tutorial, however I have indexed all the information for a quick read and easy reference.
A battery is like a piggy bank, if you keep taking out, and putting nothing back, you soon will have nothing.
Present day chassis battery power requirements are huge. Look at a 1990s vehicle and all the electrical devices that must be supplied. Electronics require a source of reliable power. Poor battery condition can cause expensive electronic component failure. Did you know that the average auto has 11 pounds of wire in the electrical system? Look at RVs and boats with all the electrical gadgets that require power. I can remember when a trailer or motor home had a single 12-volt house battery. Today it is standard to have 2 or 4 house batteries powering inverters up to 4000 watts.
Average battery life has become shorter as energy requirements increase. Life span depends on usage; 6 months to 48 months, yet only 30% of all batteries actually reach the 48-month mark.
The Lead acid battery is made up of plates, lead and lead oxide (various other elements are used to change density, hardness, porosity, etc.) with a 35% sulfuric acid and 65% water solution. This solution is called electrolyte which causes a chemical reaction that produce electrons. When you test a battery with a hydrometer you are measuring the amount of sulfuric acid in the electrolyte. If your reading is low, that means the chemistry that makes electrons is lacking. So where did the sulfur go? It is stuck to the battery plates and when you recharge the battery the sulfur returns to the electrolyte.
2. Battery types, Deep Cycle and Starting
3. Wet Cell, Gel-Cell and Absorbed Glass Mat (AGM)
4. CCA, CA, AH and RC; what's that all about?
7. Selecting and Buying a New Battery
8. Battery Life and Performance
1. Well we must think safety when we are working around and with batteries. Remove all jewelry, after all you don't want to melt your watchband while you are wearing the watch. The hydrogen gas that batteries make when charging is very explosive, I have had 2 batteries blow up and drench me in sulfuric acid and that is no fun. This is a good time to use those safety goggles that are hanging on the wall. Sulfuric Acid eats up clothing and you may select Polyester clothing to wear, as it is naturally acid resistant. I just wear junk cloths, after all Polyester is so out of style. When doing electrical work on vehicles it is best to disconnect the ground cable. Just remember you are messing with corrosive acid, explosive gases and 100's amps of electrical current.
2. Basically there are two types of batteries, starting (cranking) and deep cycle (marine-golf cart). The starting battery is designed to deliver quick bursts of energy (such as starting engines) and have a greater plate count. The plates will also be thinner and have somewhat different material composition. The deep cycle battery has less instant energy but greater long-term energy delivery. Deep cycle batteries have thicker plate's design and can survive a number of discharge cycles. Starting batteries should not be used for deep cycle applications. The so-called Dual Purpose Battery is only a compromise between the 2 types of batteries.
3. Wet Cell (flooded), Gel Cell and Absorbed Glass Mat (AGM) these are various versions of the lead acid battery. The wet cell comes in 2 ways, serviceable and maintenance free, both are filled with electrolyte and I prefer one that I can add water and check the specific gravity of the electrolyte with a hydrometer. The Gel-Cell and the AGM batteries are specialty batteries that cost at least twice as much as a premium wet cell. However they store very well and do not tend to sulfate as easily as wet cell. There is no chance of a hydrogen gas explosion using these batteries. Some of these gel-cell and AGM batteries require special charging rate, especially the deep cycle models. I personally feel that in most applications they are not worth the investment.
4. CCA, CA, AH and RC what is that all about? Well these are the standards that most battery companies use to rate the output and capacity of a battery.
CCA is cold cranking amps is a measurement of the number amps a battery can deliver at 0 degrees F for 30 seconds and not drop below 7.2 volts. So a high CCA battery rating is good especially in cold weather.
CA is cranking amps measured at 32 degrees F this rating is also called MCA marine cranking amps. HCA hot cranking amps is seldom used any longer but is measured at 80 degrees F.
RC Reserve Capacity is a very important rating. This is the number minutes a fully charged battery at 80 degrees F will discharge 25 amps until the battery drops below 10.5 volts.
AH amp hours a rating usually found on deep cycle batteries. If a battery is rated at 100 amp hours it should deliver 5 amps for 20 hours, 20 amps for 5 hours, etc.
5. Battery Maintenance is an important issue. The battery should be clean. Use baking soda and water mix. Cable connection needs to be clean and tightened. Many battery problems are caused by dirty and loose connections. Serviceable battery needs to have the fluid level checked. Use only mineral free water, distilled water is best. Don't overfill battery cells especially in warmer weather. The natural fluid expansion in hot weather will push excess electrolytes from the battery. To prevent corrosion of cables on top post batteries, use a small bead of silicon sealer at the base of the post and place a felt battery washer over it. Coat the washer with high temperature grease or petroleum jelly (Vaseline). Then place cable on post and tighten, coat the exposed cable end with the grease. Most folks don't know that just the gases from the battery condensing on metal parts cause most corrosion.
6. Battery Testing can be done in more than one way. The most popular is measurement of specific gravity and battery voltage. To measure specific gravity buy a temperature compensating hydrometer at an auto parts store. To measure voltage, use a digital D.C. Voltmeter.
You must first have the battery fully charged. The surface charge must be removed before testing. If the battery has been setting at least several hours (I prefer at least 12 hours) you may begin testing. To remove surface charge the battery must experience a load of 20 amps for 3 plus minutes. Turning on the headlights (high beam) will do the trick. After turning off the lights you are ready to test the battery.
State of Charge Specific Gravity Voltage
100%
*75%
50%
25%
Discharged
1.265
1.225
1.190
1.155
1.120
12V
12.7
12.4
12.2
12.0
11.96V
6.3
6.2
6.1
6.0
6.0
*Sulfation of Batteries starts when specific gravity falls below 1.225 or voltage measures less than 12.4 (12v Battery) or 6.2 (6 volt battery). Sulfation hardens the battery plates reducing and eventually destroying the ability of the battery to generate Volts and Amps.Load testing is yet another way of testing a battery. Load test removes amps from a battery much like starting an engine would. A load tester can be purchased at most auto parts stores. Some battery companies label their battery with the amp load for testing. This number is usually 1/2 of the CCA rating. For instance, a 500CCA battery would load test at 250 amps for 15 seconds. A load test can only be performed if the battery is near or at full charge.
The results of your testing should be as follows.
Hydrometer readings should not vary more than .05 difference between cells.
Digital Voltmeters should read as the voltage is shown in this document. The sealed AGM and Gel-Cell battery voltage (full charged) will be slightly higher in the 12.8 to 12.9 ranges. If you have voltage readings in the 10.5 volts range on a charged battery, that indicates a shorted cell.
If you have maintenance free wet cell, the only ways to test are voltmeter and load test. Most of the maintenance free batteries have a built in hydrometer that tells you the condition of 1 cell of 6. You may get a good reading from 1 cell but have a problem with other cells in the battery.
When in doubt about battery testing, call the battery manufacture. Many batteries sold today have a toll free number to call for help.
7. Selecting a Battery, when buying a new battery I suggest you purchase a battery with the greatest reserve capacity or amp hour rating possible. Of course the physical size cable hook up and terminal type must be a consideration. You may want to consider a Gel-Cell or an Absorbed Glass Mat (AGM) rather than a Wet Cell. If the application is harsher environment and the battery is not going to receive regular maintenance and charging, as it should. This is a hard call, because there is very little that substitutes for maintenance.
Be sure to purchase the correct type of battery for the job it must do. Remember an engine starting battery and deep cycle batteries are different. Freshness of a new battery is very important. The longer a battery sits and is not re-charged the more damaging sulfation build up on the plates. Most batteries have a date of manufacture code on them. The month is indicated by a letter 'A' being January and a number '9' being 1999. The letter "i" is not used because it can be confused with #1, so, C8 would tell us the battery was manufactured in March 1998. Remember the fresher the better.
Battery warranties are figured in the favor of battery manufactures. Let's say you buy a 60-month warranty battery and it lives 41 months. The warranty is pro-rated so when taking the months used against the full retail price of the battery you end up paying about the same money as if you purchased the battery at the sale price. This makes the manufacturer happy, what makes me happy is to exceed the warranty. Let me assure you it can be done.
8. Battery life and performance, average battery life has become shorter as energy requirements increase. Two most phrases I hear most often are "my battery won't take a charge and my battery won't hold a charge". Only 30% of batteries sold today reach the 48-month mark. In fact 80% of all battery failure is related to sulfation build-up. This build up occurs when the sulfur molecules in the electrolyte (battery acid) becomes so deeply discharged that they begin to coat the batteries lead plates. Before long the plates become so coated the battery dies. The causes of sulfation are numerous, let me list some for you.
Batteries sit too long between charges. As little as 24 hours in hot weather and several days in cooler weather.
Battery storage, leaving a battery sits without some type of energy input.
Deep cycling engine start battery, remember these batteries can't stand deep discharge.
Undercharging of battery, to charger a battery lets say 90% of capacity will allow sulfation of battery using the 10% of battery chemistry not reactivated by the incomplete charging cycle.
Heat of 100 plus F., increases internal discharge. As temperatures increase so does internal discharge. A new fully charged battery left sitting 24 hours a day at 110 degrees F for 30 days would most likely not start an engine.
Low electrolyte level, battery plates exposed to air will immediately sulfate.
Incorrect charging levels and settings. Most cheap battery chargers can do more damage than help. See the section on battery charging.
Cold weather is hard on the battery the chemistry does not make the same amount of energy as a warm battery. A deeply discharged battery can freeze solid in sub zero weather.
9. BatteryCharging, remember you must put back the energy you use immediately, if you don't the battery sulfates and that affects performance and longevity. The alternator is a battery charger. It works well if the battery is not deeply discharged. The alternator tends to overcharge batteries that are very low and the overcharge can damage batteries. In fact an engine starting battery on average has only about 10 deep cycles available when recharged by an alternator. Batteries like to be charged in a certain way, especially when they have been deeply discharged. This type of charging is called 3 step regulated charging. Please note that only special SMART CHARGERS using computer technology can perform 3 steps charging techniques. You don't find these types of chargers in parts stores and Wal-Marts. The first step is bulk charging where up to 80% of the battery energy capacity is replaced by the charger at the maximum voltage and current amp rating of the charger. When the battery voltage reaches 14.4 volts this begins the absorption charge step. This is where the voltage is held at a constant 14.4 volts and the current (amps) decline until the battery is 98% charged. Next comes the Float Step, this is a regulated voltage of not more than 13.4 volts and usually less than 1 amp of current. This in time will bring the battery to 100% charged or close to it. The float charge will not boil or heat batteries but will maintain the batteries at 100% readiness and prevent cycling during long term inactivity. Some get cell and AGM batteries may require special settings or chargers.
10. Battery Do's
Think Safety First.
Do read entire tutorial
Do regular inspection and maintenance especially if hot weather.
Do recharge batteries immediately after discharge.
Do buy the highest RC reserve capacity or AH amp hour battery that will fit your configuration.
11. Battery Don'ts
Don't forget safety first.
Don't add new electrolyte (acid).
Don't use unregulated high output battery charger to charge batteries.
Don't place your equipment and toys into storage without some type of device to keep the battery charged.
Don't disconnect battery cables while engine is running your battery acts as a filter.
Don't put off recharging batteries.
Don't add tap water as it may contain minerals that will contaminate the electrolyte.
Don't discharge a battery any deeper than you possibly have to.
Don't let a battery get hot to the touch and boil violently when charging.
Don't mix size and types of batteries.
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