Maintenance Q&A
Beyond the batteries

By Paul Abelson, senior technical editor

Q. In 2009, I bought a 2006 Volvo VN. I love the truck, but I’ve had battery problems. After the first year I had it, I had trouble starting the truck. My dealer replaced the batteries. He even saved me some money and weight by suggesting I get three 900-CCA (cold-cranking amps) batteries in place of the four 625-CCA ones that came with the truck. It ran fine after that.

Last year I was in a snowstorm and a wreck happened ahead of me. Traffic was at a standstill for a few hours until they were able to clear the road. Since we could move at about 5 mph every few minutes, I kept the truck idling. After I got past the wreck, I pulled into the next truck stop for some coffee and to stretch my legs. I figured I’d be there only about a half-hour, so I shut down the engine.

When I came out about 45 minutes later, the truck wouldn’t start. The guys in the shop wanted to sell me a new set of batteries, but I was able to get a jump start from another truck and make it back to my yard. I dropped my trailer and bobtailed to my local dealer where I bought the truck. He sold me three new batteries, and even gave me a discount price.

This year, something similar happened. It wasn’t a wreck this time. I was caught in a snowstorm. The traffic averaged less than 20 mph for several hours. Again, it wouldn’t start and the truck stop wanted to sell me new batteries. This doesn’t seem right. Is there something else I should do?

A. I can understand replacing batteries after four years. Your model year 2006 truck may have been built in 2005, and by 2010 your four-year-plus-old batteries were due for replacement. I agree with his suggestion – and your decision – to go with fewer but stronger batteries. You gained an added 200 cold-cranking amps while saving weight. Last year, your batteries were a little over two years old. There may have been a pro-rated warranty remaining, and that could have figured into the “discount” you got.

You didn’t mention anything about load testing the batteries or checking the charging and starting circuits. At the Technology and Maintenance Council, many fleet consultants have discussed having a large number of batteries waiting to be picked up for recycling. When charged and load tested, they were found acceptable and functional. At TMC, we’re taught to look for causes in addition to repairing symptoms. If you just replace a part, the part will likely fail again. If you correct the cause, it won’t fail.

When most people experience electrical problems, the first thing they do is voltage-test the batteries. Naturally, they test low because they are discharged. New batteries run well for a while because they are new and fully charged.

Fleets do load testing and examine the charging circuits. I had a personal situation driving in a blizzard. After going only 26 miles in two and a half hours, I stopped for fuel. The engine would not restart. For the entire time, the heater and defroster fan were turned way up, the mirror heaters were on, the seat heaters were on high, and my lights were on. What I did not know was that the fan belt was glazed and slipping and, at virtually idle speed, the alternator wasn’t turning fast enough to create a charging current. Meanwhile, all the accessories were draining the batteries. The result was inevitable.

Before buying a new battery, here’s what you should do. Load test your batteries. Start by checking the electrolyte’s specific gravity. Most testers today are direct-reading so you don’t need to do any interpretation. Float-type testers may be as much as 15 percent off. The most accurate testers are optical refractometers. They measure the way the specific gravity of the electrolyte bends light through a prism. Using just a drop, they will give a precise measurement of the electrolyte. They can also be used to measure protection from both ethylene glycol and propylene glycol coolants.

Proper readings and temperature correction tables are in TMC Recommended Practice RP132-B, Battery Charging, Testing, and Handling. According to the RP, batteries do not have to be fully charged to be tested. One can be as low as 75 percent, or at a 1.225 specific gravity reading. Pure water is 1.000, and acid is heavier. Specific gravity accurately measures the acid content of the electrolyte. A fully charged battery reads 1.265. A battery is considered fully discharged at 1.120.

A carbon pile load tester measures battery voltage at rest, then puts a load on the battery (150 amps) or bank of batteries (300 amps) for 10 seconds to draw off any surface charge. Then a test load, sometimes 300 to 500 amps, is put on the batteries. Each battery’s test load is on the label or an instruction molded onto the battery case. Use a thermometer to measure electrolyte temperature. At room temperature (70 degrees), there should be 9.6 volts minimum after 15 seconds of load.

If the battery is good, your problem is likely in the charging system. Detailed procedures are in RP129A, Heavy Duty Vehicle Cranking and Charging Troubleshooting: 12-volt Systems. Check cables from the battery to the alternator. If there are any signs of corrosion on terminals or in the cables themselves, replace them. Corrosion increases electrical resistance and could lower available amps below what is needed to start your truck.

Check your fan belts and belt tension. Even an automatic tensioner used with multi-V belts can wear out. That can cause belt slippage leading to low alternator output. If batteries, cables and drive belts are all good, hook up test equipment as indicated in the schematics in RP129A. If alternator output is good, test the starter and its control circuits.

Electrical problems are not always due to battery failure. In fact, problems often lie elsewhere. LL

July Digital Edition