Harnessing Electrical Energy: Batteries and Battery Packs ExplainedBy Tom Bartley • Mar 5th, 2009 • Category: Battery Technology for Hybrid and Electric Cars
Ever wonder what battery packs really are? Here’s a little bit of an introduction to help ease the mind into the pondering of batteries with hopefully painless acquisition of the required jargon.
What is a Battery?
In general terms (not scientific), a battery is a hunk of something that has some stored energy that can be accessed to convert into some other energy. Energy can come in a variety of forms, such as gravitational, heat, light, sound, motion, pressure, and electromagnetic fields. For practical purposes Newtonian physics is all you need to understand the principles and operations of batteries. Energy cannot be destroyed, but can only be converted into some other form.
I can argue that a rock held up in the air, just like the water behind a dam is a battery with potential energy (gravitational) waiting to be converted into kinetic energy (motion). Similarly, a rotating flywheel or a moving vehicle has kinetic energy that can be converted into other energy forms. Even a wound up spring or a pulled back catapult could be thought of as a battery with stored energy.
In electric circuits energy is stored as an electric field in capacitors and as a magnetic field in inductors. Batteries, as commonly referred to, store and release electrical energy by a chemical reaction of compounds inside the batteries. Batteries are either primary (single use) or secondary (rechargeable).
Harnessing the Energy
In today’s society almost everyone is familiar with the small button, small flat module, and cylindrical shapes for batteries that power all kinds of electric gadgets including, toys, watches, phones, cameras, radios, flashlights, computers, and model vehicles (air, surface and water). Larger battery packs start and run cars, trucks, boats and airplanes. Even larger packs provide backup power for communications, control systems, buildings, and transportation systems, or in smoothing out load and generation power spikes.
Looking from a different perspective, batteries can be considered a time buffer between the generation and the eventual use of energy. A perfect example is solar and wind energy that may be collected and stored for energy load usage at a later time. Or hydrogen could be thought of as a battery (though somewhat inefficient). First hydrogen is separated out from water through the electrolysis using electrical power. Then the hydrogen can be used at a later time in a machine such as a fuel cell or engine-generator set to deliver power and energy.
So again, a battery is a hunk of something that has some stored energy that can be accessed to convert into some other energy. And since energy cannot be converted with 100% efficiency from one form to another, the final form of energy you get will always be less than what you started with. Obviously the more times you convert, the more losses you’ll have, and the less you’ll have left to use.
So What Are Car Batteries Then?
Car batteries are electrochemical batteries for cars and trucks. Primary batteries (single use) are out of the question for this application and are appropriately limited to devices like flashlights and toys.
In car batteries the energy is stored as electrochemical potential energy in the battery materials that make up the battery electrodes and the electrolyte that provides a path for electrically charged particles moving between the electrodes. We refer to this as “the battery chemistry.” A chemical reaction occurs to store energy and the reverse chemical reaction occurs to release that energy.
I have attended conferences where electrochemists speak a jargon all their own to describe combinations of new electrodes and electrolytes that have various voltage potentials and other characteristic tradeoffs. For car batteries, there are multitudes of desirable characteristics, many of which can conflict with one another. Here are a few:
- Light weight (high energy density, high power density),
- Quick charging,
- High power,
- Extended use (high energy storage capacity),
- Operation over a wide temperature range,
- Long shelf and operation cycle life,
- Easily manufactured, and
- Easily recycled.
This reminds me of something that I used to tell customers, “You want high quality, fast delivery, and cheap? Pick two!”
So what do you do when higher energy and/or power is needed? It’s actually pretty simple. Batteries can be assembled as multi-cell battery packs and packs of packs. In fact with all the buzz about hybrid and electric cars, battery packs are the hot devices (no pun intended) that currently propel the whole high-voltage, high-energy storage system industry. A battery pack manufacturer must follow an expensive process to bring its products to the consuming market. It has to spend time, money and effort in research, development, testing, production, distribution, charging, and salvaging/recycling. With many consumers still on the fence about buying hybrids and electric cars, the real question is, “where’s the money?”
If I’m thinking about buying a hybrid-electric vehicle (HEV) or electric vehicle (EV) what do I need to know about batteries? If I am converting a car or building a battery pack what else do I need to know? What is my current level of confusion? (Confusion is a prerequisite to understanding.)
All comments are welcome.
Tom Bartley is an industry veteran with 30 years of experience in general business, marketing, project and product management, and engineering research and development. Mr. Bartley provided executive management support including technical and business oversight to heavy-duty hybrid-electric prototype projects as they evolved into production. He developed cost models for energy storage and fuel savings, and power models for ultracapacitor packs. Mr. Bartley is well known throughout the industry of heavy-duty hybrid-electric buses and trucks, having delivered many papers and presentations since 2003. Mr. Bartley maintains a blog at TomBartleyIdeas.com. Follow twitter.com/TLBartley.
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