AGM battery may boost micro-hybrids
Analysts are suggesting hybrids won’t be bridge between engines, EVS
Are micro-hybrids the missing link?
While electric motors might ultimately replace gasoline engines in the automobile of the future, it’s still a long step from here to there. The missing link in that transition may not be the hybrid, as is often assumed, but the micro-hybrid.
Micro-hybrids are exactly what the name implies: vehicles that incorporate just a small helping of hybrid technology. But they leverage that to achieve disproportionately large improvements in fuel economy.
For that reason, micro-hybrids are set to take over the automotive market, according to Kevin See, a research analyst at Lux Research Inc. , an international research firm that provides strategic advice and intelligence on emerging technologies.
See is the lead author of a recently published report called Every Last Drop: Micro- And Mild Hybrids Drive a Huge Market for Fuel-efficient Vehicles.
According to that report, “a low price premium, fuel savings of up to 10 per cent and a relatively easier manufacturing process will propel medium micro-hybrids to the top of the alternative auto market over the next five years.”
Micro-hybrids will account for 42 per cent of the overall light-duty vehicle market by 2017, the report concludes. Currently, in North America, all types of hybrid combined make up only about 2.5 per cent of the market.
Europe and China are expected to lead that sales surge as micro-hybrids are already well established in those markets — although perhaps not by that name.
They may just be identified as vehicles with automatic stop-start systems, which we have discussed previously in this column. In most cases, it is micro-hybrid technology that makes the auto stop-start function possible.
In its most basic form, a microhybrid system is composed of an energy storage device, typically a battery that is separate from the vehicle’s primary low-voltage electrical system, and a more robust starter motor that also serves as a generator. Those components, along with some sophisticated electronics, are all it takes to enable both an autostop-start system and regenerative braking, which we’ve also discussed previously in this column. Although General Motors doesn’t label it as such, the eassist versions of Buick’s Regal and Lacrosse are examples of micro-hybrids. In addition to supporting those two functions, eassist does provide some electric assist to the engine while the vehicle is in motion, although that is not always the case in a micro-hybrid. It also employs energy created by way of regenerative braking to power the radio, climate control and other accessories whenever the engine operates in auto-stop mode. The GM system employs a stateof-the-science, lithium-ion (Li-ion) battery pack located in the trunk. Lithium-ion batteries are typically used in plug-in hybrids and batteryelectric vehicles, while nickel-metal-hydride (NIMH) batteries are more common in conventional hybrids. Perhaps surprisingly, the Lux report suggests that neither of those will be the battery of choice for micro-hybrids as that market grows. “Absorbed glass mat (AGM), leadacid batteries will dominate the market for storage of micro-hybrids,” the report says.
Lead-acid batteries don’t seem suitable for hybrids
We’re all familiar with lead-acid batteries. They’ve been around for more than 100 years, in six- and 12-volt form, storing the energy used for automotive electrical systems. But they haven’t been considered suitable for hybrid systems. Too heavy and inefficient, as well as slow to charge. AGM construction addresses some of those concerns. Enough so, apparently, to make them worth considering for micro-hybrids, according to Lux. In conventional lead-acid batteries, positive and negative plates are submerged in a liquid bath (a weak sulphuric acid), known as the electrolyte. In an AGM battery, there is no liquid bath.
Rather, the plates are separated by, and in close proximity to, fibreglass-like mats in which the acid is absorbed. This construction enhances both the discharge and recharge efficiency of the battery.
It also frees the battery from its traditional box shape, in which maintaining separation of the plates within the liquid is vital. AGM battery cells can take other forms, including cylindrical.
According to battery manufacturer Exide, AGM technology is able to provide optimal performance in the extreme cycling applications encountered in micro-hybrids, with both high-charge acceptance and partial state-of-charge operations.
They exhibit three times the life cycle durability of a standard leadacid battery, the company says.
While more costly than conventional lead-acid batteries, they are typically be less expensive than their NIMH or Li-ion counterparts.
That cost advantage could be the major factor in their adoption for use in micro-hybrids. wheels@thestar.ca