Charge It!
Electrical loads on highway trucks are dictating a need for a more versatile battery — or a complete rethink of the electrical storage system.
Steve Sturgess
Senior Editor
Batteries are second only to tires when it comes to breakdown calls. The frequency of dead batteries and call outs for jumps or snatch tows costs fleets thousands of dollars each year.
Yet by the application of new battery and electrical technologies, much of this unscheduled downtime and expense can be eliminated. New-technology storage batteries are available that package the plates and electrolyte in revolutionary designs that greatly extend battery life, functionality and cranking power. And now there's the asymmetric ultra capacitor, a new electrical storage medium that can actually start a truck with an effectively dead battery, pulling it up by its own bootstraps.
While we have had maintenance-free batteries for years — a major boon to fleet operations — the type 31 battery found throughout heavy-duty applications is still basically a conventional battery with lead plates and sulfuric acid electrolyte. In its most basic form, the battery is faced with competing needs in a modern, over-the-road truck: high current for starting and deep-cycling for what are becoming known as the "hotel" loads of the sleeper.
Some of the newest batteries feature changes to the plates and plate supporting grids that improve performance while also extending battery life in the typical high-vibration, severe service of a truck application. The DayStarter MX grid technology, for instance, provides a rigid base to allow for a lead/tin plate that is claimed to outperform batteries with a lead-calcium alloy. According to DayStarter, the grids allow for significantly higher current for good cold-cranking amps with the ability to deep cycle the battery for current draws in excess of 20% of the battery's capacity.
RoadGang batteries are part of the Road Gang heavy-duty system by DelcoRemy. The company recommends not only the deep cycle batteries for a reliable system, but using them with a low-voltage disconnect switch. Along the same lines, Kenworth announced earlier this year it will make LVDs standard on certain sleeper models.
Some of the newer premium lead acid batteries introduce a new feature: an absorbent glass-mat (AGM) electrolyte containment that means there's no free sulfuric acid sloshing around inside, as is the case with the conventional flooded battery. Examples include the Delphi Freedom and Freedom Extra and the Guardian by Douglas Battery. Then there's the revolutionary-looking and, to an significant extent, revolutionary designed Optima, recently acquired by Johnson Controls' and sold under its own name or through Interstate Battery. Because the electrolyte is contained in the glass mat, the AGM storage batteries can also be mounted in virtually any position and orientation because they are leak-proof, said Pankaj Dhingra, business line executive for Delphi's Freedom. An alternative electrolyte containment uses a gel, as in the Deka batteries by East Penn Manufacturing. In both cases, electrolyte leakage is prevented - even if the battery is punctured.
The glass-mat construction brings other major advantages, said Dhingra. Delphi's Freedom has more than twice the cycle life of a conventional flooded battery. And the assembly is under pressure so the plates are much more resistant to vibration - the No. 1 killer of truck batteries.
The vibration resistance comes from the added mechanical strength of the mat that provides additional support to the lead alloy in the battery's plates. This is important in a truck, especially one with the battery box cantilevered off the frame rail.
In the Optima battery, the plate-support concept is taken even further. This battery looks most like a big yellow or red soda six-pack. Each of the cells has large sheets of almost pure lead with the electrolyte-loaded mat sandwiched between them. These are then rolled into a spiral and inserted under pressure into the case. The nearly pure lead and the minimal interior connections allow the battery to deliver an especially high cranking current while being able to sustain deep cycling. And with its unique construction, the Optima is claimed to be as much as 15 times more resistant to vibration and shock loads without the plates separating.
According to Jay Kedia, commercial market manager for Optima, the very low internal resistance from the few internal connections means the batteries will hold a charge for considerable periods - twice as long as a conventional batteries. And this translates to a long shelf life in storage, too.
A completely different electrical storage medium to the conventional — and even these unconventional-lead-acid batteries — is the ultra capacitor. The technology is being introduced to North America markets through consolidated efforts by cold-start experts KBi, headquartered in Lake in the Hills, IL., and a Russian producer/ supplier company that is also the technology proprietor.
With the lead-acid battery, electrical energy is stored by performing a reversible chemical reaction inside the battery. It is forced one way by applying a voltage, and it gives up its energy when a current is drawn. Even in the very latest designs, the reaction takes time to complete and it has an inefficiency that generates heat. The battery also has an internal resistance, so even without an external load, it eventually runs down over time. And while the new designs are extremely good at providing good cranking current, it takes a top-of-the-line battery to optimize for the two competing requirements on a truck: a good cranking battery and a good deep cycle battery to run sleeper loads. And, however good, a conventional battery wears out.
In the capacitor, the electrical energy is stored physically as charges on two minutely separated plates; the more area, the more energy. Capacitor self-discharge is very low, so the capacitor will hold its energy for months and months. It's no good for sustained current and won't run sleeper loads but it's great as a starter source because it doesn't have to wait for a chemical reaction to give up its charge. The ultra capacitor can deliver a huge current instantly—and can be dangerous because of this. And it can pick up that charge from an almost exhausted conventional battery. One way to think of it would be as an electrical equivalent of an air starter.
Like the air starter, the ultra capacitor is potentially best used in a combination installation with deep-cycle lead-acid batteries. And a big plus: Based on the work performed by KBi's Russian partners, the ultra capacitor has the potential to outlast the vehicle.
As well as the elimination of problems with run-down batteries that fail to crank over an engine, the ultra capacitor can bring a number of additional maintenance benefits, says KBi. Potentially, it can replace several of those conventional lead-acid batteries, saving weight. The capacitor can be cycled 300,000 plus times — outlasting the truck — and at the same time protect the conventional vehicle battery, giving it a much longer life. In fact, long after a lead-acid battery can no longer crank an engine, it can satisfactorily provide for the electrical loads on the vehicle, enormously extending its useful life.
Because vehicle system voltage is maintained during capacitor engine cranking, starters last longer. And using an ultra capacitor in the electrical system acts as a major filter, smoothing voltage spikes to give a longer life to electrical components such as alternators and headlights.
Today, the ultra capacitor has one big drawback — cost. But even that is changing (see below). It may well be the truck electrical storage system of the future will be a combination of new technology batteries and an ultra capacitor.
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