Getting a jump on battery maintenance

Coach batteries usually work so well, we often forget about them. But from time to time, they give us trouble, and the simplest of problems can pose confusing challenges. That's why it's important to understand, evaluate and care for your battery. To that end, we offer a few tips.

Nothing that we know of can make battery maintenance entertaining or fun. But neither is it difficult. It's mostly a matter of just rolling up your sleeves and doing it. As with any preventative maintenance, your best bet is to be preemptive. There is a lot more information on this subject available, but this is a starting point (pun intended), so don't let your studies end here. Otherwise your learning curve might accelerate in some cold parking lot late on a Saturday night.

Safety First

Always have large amounts of water (a garden hose) and lots of baking soda around when working near batteries. Always wear face and eye protection. Needless to say, battery acid on your body can be very destructive. Counteract any exposure with water and baking soda immediately. If it gets in your eyes, flush with large amounts of water, and get medical help quickly. Never put your face directly over a battery when jumpstarting or moving cables around. The old wives tale about batteries blowing up is not fiction. Sparks can ignite hydrogen gas in battery cells and cause a violent explosion. This writer has experienced it.

Taking Charge of the Situation

First, just take a quick look at your batteries once every several days, being on the lookout for any corroded connections so you can clean things up at your convenience before they fail. Dirty batteries will actually discharge themselves, as the "fuzzy" accumulation on the battery case will act as a conductor between the positive and negative posts and actually draw current from the battery. Keep them clean.

Second, check for strong acid smells, wet spots around the battery filler caps, and a swollen (bulged out) battery case. These are sure signs of overcharging or other imbalance (equalizer), and if the electrolyte level drops below the top of the plates, a battery's life expectancy can drop quickly. If all the cells on just one battery are spitting acid or repeatedly low, it may be due to battery equalizer problems. If both batteries look like this, check the charging system voltage. Generally anything over 28.5 volts (with engine on fast idle) spells trouble. If only one cell is spouting electrolyte (most easily observed when cranking the engine), that cell is shorted and the battery should be scrapped. Make sure that all the members of your team have been instructed on how to fill the cells properly (not tap water), without overfilling.

Here are two surefire battery killers that you need to avoid at any cost unless your best friend makes his living selling bus batteries.

  1. Fully discharging the battery until it has no charge left
    This hurts a new battery quite badly and usually totally ruins an older one. Consider this a death sentence for any battery, new or old. As a cell discharges, the sulfur from the sulfuric acid (electrolyte) gets absorbed into the lead plates of the cell. Once totally saturated, the lead cannot release all of this back into the electrolyte during the normal charging process. The result is a weakened chemical reaction that produces less of the electrical energy we need from the battery. If your battery goes "dead" in normal service, find out why and fix the problem quickly so that you don't also wreck the new ones (plural), since batteries should always be replaced in pairs. And by the way, late night wash crews are notorious battery killers. Not on purpose, but in addition to leaving coach interior lights on for extended periods, an overly enthusiastic wash crew can drive soap solution into the battery cells. Use the battery charger or in-station lighting, if possible, and be careful when washing the battery area.
  2. Letting a battery run dry
    As mentioned earlier, keep electrolyte levels above the tops of the plates. An empty battery is a dead, damaged battery. Any section of the lead plates left exposed to the air is shot. The lower the level, the worse the damage. When the plates are exposed, the lead dries out and flakes off, falling into the bottom of the cell. Enough lead buildup in the bottom of a cell will create a short circuit between two plates, resulting in what is commonly referred to as a dead cell. Charging system voltage and hot weather will affect water usage, so check and fill batteries regularly. We recommend distilled water for your batteries, since tap water often has metals in it that can harm the plates. Distilled water isn't hard to come by; however, any water (the cleaner the better) is better letting the battery go dry. Repeat: Any water is better than no water at all!

Enough of the negative. How do you get the best new battery for your money?

It's common sense that a smaller, low-capacity battery works harder than a high-capacity battery under a given set of circumstances. The harder a battery works, the sooner it fails. The less it works, the longer it will last. The upshot? Buy the battery with the most capacity that you can fit into your vehicle. There will be some compromises, but it's a sure bet that a low-capacity, inexpensive battery is not going to be your best value in the long run. MCI recommends at least 1350 cold cranking amps (CCA) per battery — not simply cranking amps.

Cold cranking amps is a quick convenient way to judge a battery's capacity under adverse conditions. Use this specification to judge the general merits of a given battery. Buyers beware: Less expensive often also means cheaper! Make sure that the spec that you are looking at is for "COLD Cranking Amps." Some cut-rate batteries are sold with the specification showing only "Cranking Amps." It's not the same thing. Cranking Amps denotes testing done at warmer temperatures when chemical activity in the battery is much greater. Any reputable battery will also show a spec for Cold Cranking Amps. Use this figure for your comparisons, and accept nothing less.

Getting Specific

Before load-testing any battery, the technician needs to know if the battery is even able to be tested. A "Specific Gravity" test will indicate not only the state of charge that a battery is holding, but also the condition of each cell by testing the electrolyte in them. The electrolyte solution in a battery cell will be heavier than pure water, depending upon the exact amount of sulfuric acid in solution Using water as a base line of 1.000, a hydrometer can measure the specific gravity of the solution. The reading can then be referenced on a battery testing chart to determine the state of charge. In addition, all cells should be within 0.050 points of each other, with no more than 0.050 from highest to lowest readings. If a battery specific gravity test shows any cell below @ 80% charge, it should be charged before load testing. If, after charging, any cell does not respond to the charge cycle, then the battery should be considered unusable and be replaced. Always replace batteries in complete sets.

Getting the LOAD out

"Load Testing" checks a batteries ability to provide power during use. The term "power" is actually a combination of two electrical properties: voltage and amperage. While amperage (current, measured in amps) actually performs the work in a circuit, voltage (measured in volts) is responsible for pushing the current through the circuit. Once it has been determined that a battery is ready to load-test, the technician needs a way of placing a high electrical load or draw on the battery, normally half of the CCA rating of the battery. With the load still applied to the battery, voltage is measured at about the 15-second mark, and once again compared to the performance chart. Failure to pass the chart's recommended points will once again require replacement of the battery set.


While test result charts are used throughout the industry, they are generally intended as a guideline, and have to average many different test methods, test equipment, and specific manufacturers' components. ALWAYS CONSULT YOUR MANUFACTURER'S EXACT RECOMMENDATIONS AND PROCEDURES.

That's enough of the basics to get you started and keep you on the positive (pun intended) side of the battery curve.

Happy motoring!

Please download a printable battery testing chart here.

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