INTRODUCTION TO THE NEXT GENERATION OF BATTERIES

INTRODUCTION TO THE NEXT GENERATION OF BATTERIES
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Digital Battery Management Systems

Battery History:

It is believed that the first battery ever created was sometime around 200BC, two full millennia before Alessandro Volta’s first electrochemical cell in 1800. The ancient batteries were found around 1940 in Iraq. A simple copper sheet formed into a cylinder with an iron rod suspended in a clay pot full of vinegar to produce an electrical reaction that was most likely used for electro-plating jewelry. This early battery produced about 2V. The battery was named the Baghdad Battery.  

Modern lead acid technology has not changed much. The use of stronger acid and lead has improved voltage characteristics, stability and reliability and helped form the modern world. 

Used in everything from cars to flashlights, batteries have helped shape our lives for over 200 years. Keeping in mind that primary batteries are a throw-away type like AAA and AA and used to power small electronics. Secondary batteries are rechargeable large format typically seen in electric vehicles and power standby solutions. The secondary battery market expects exponential growth in the next 5-10 years. This growth will be fueled by the automotive and high-tech industry needs for backup power that cannot be achieved with existing lead or standby generator systems.

The Future of Secondary Batteries:

The demand for smaller, lighter, more powerful and longer-life secondary batteries is pushing a whole new frontier of battery development. With “Molten Sodium”, “Carbon Nano”, “Graphene”, “Super-Capacitors” and other types of exotic battery technology on the fringe of development a whole new approach to power and power management is closer than just talk. 

The aim of new battery development is:

• Improved Power Density (smaller & lighter)
• Faster Recharge Time
• Higher Rates of Discharge
• Longer life (number of charge cycles)
• Lower Environmental Impact
• Less Expensive to Produce

The ability to charge a tablet computer or phone in seconds and drive an affordable all electric vehicle for 500+ miles is probably less than 10 years away. In the meantime, what can we do to improve and continue to build on the existing technologies at hand?

The “Real World” Battery:

New technology development-time-to-market has improved, but at present there is limited technology available for “real world” manufacturing. The greatest commercialized battery development in the past 40 years was the development of the lithium battery.

At approximately one quarter the weight and nearly half the volume of lead systems, lithium also has a cycle life in the thousands rather than the hundreds as today's lead batteries. Several commercial variants of lithium chemistry are on today’s production market. Some of these variants include the addition of exotic metals to improve energy storage or cycle life. Lithium Cobalt Oxide (LiCoO2) and Lithium Iron Phosphate (LiFePO4) are two notable examples.

Lithium Cobalt Oxide has superior power to weight performance but has had a history of instability when charged incorrectly or damaged. This instability has led to fires or damage to equipment. Lithium Cobalt Oxide battery cores were utilized in the highly publicized Boeing battery fires. This light weight high power battery system is also popular with electric vehicle manufacturers.

Lithium Iron Phosphate has less energy density than Lithium Cobalt Oxide but is more tolerant to abuse. Lithium Iron Phosphate is considered to be the safest of the lithium class batteries by several industry developers. This battery chemistry has over 10 years of commercial service and is utilized by at least 10 major manufacturers worldwide.

Secondary Battery of Today:

At present there are several lithium battery core systems manufactured today that provide enough improvement over lead acid systems to begin making significant market inroads into various industries:

• Transportation
• Grid Stabilization
• Communications
• Power Backup
• Energy Storage
• DOD (Military)

Lithium battery manufacturers produce the battery cells in 3.2V nominal units. These cells can be assembled in combinations of series or parallel to boost voltage or amp hour capacity. For example, four 100Ah cells in series would give a 12.8V nominal battery pack. The same four cells in parallel would give a 400Ah pack at 3.2V nominal. By optimizing technology available today, a better and more efficient battery is available now.

Battery of Tomorrow:

The key to optimizing lithium battery systems is battery management system (BMS) technology. Lithium batteries are especially sensitive to damage nearing fully-charged status and when near end of discharge (empty). This sensitivity drives special handling needs of lithium batteries. 

At present the battery industry utilizes several systems for managing lithium batteries. One method - the most inefficient yet widest used - is to not use a battery management system at all, but rather uses the mid voltage range of the lithium cell. This system only uses the middle 60% of the battery pack. This means designers must add 40% more battery than needed to get 100% energy storage. This method only charges the battery to 80% and only discharges it to 20% meaning that the battery system has to be oversized by 40% in size, weight and cost.

Another method presently used in the industry is “by-pass” battery management. This BMS allows the battery to charge to 100% by intercepting power from cells that fill up first. The intercepted power is then bled off through a bypass resistor while the cells still needing charge continue to absorb charge. This type of BMS produces heat and requires external control of the charging system that is not compatible with existing charging systems already in place to support lead systems. 

Digital BMS technology is presently under development and may finally bridge the technological gap between existing charging systems and new lithium batteries. Digital BMS technology allows the lithium battery to act independently from the charging system that it is hooked up to. This means existing lead chargers can now be used to safely charge lithium batteries with Digital BMS technology. When the battery is nearly full the BMS takes over and regulates the power into each cell of the battery allowing the safe charge to 100% capacity with lower heat, less wasted energy, no strain on full cells waiting for lagging cells to fill and allows for a full charge 20 times faster than existing technologies presently available. Digital BMS technology also allows for instantaneous high power control in switching between charge, discharge and standby modes.

The Future for Digital BMS Lithium Batteries:

At present rechargeable lithium battery production has begun to pull ahead of traditional lead acid on a worldwide market. It is expected that the stationary lead acid and deep cycle markets will be overtaken by lithium systems in the next 5-10 years. With the development of less costly and more dependable lithium batteries it is expected that 50% of the starter battery market could fall to the lithium systems as well.

The Final Frontier:

A digital control BMS technology that is safe, self-protecting, adaptable, dependable and has a low production cost would make lithium a “true” market competitor to lead battery systems.

Improved battery technology will provide stable power from solar and wind farms by storing excess power to be released over time as needed. Storage battery systems will stabilize and reduce costs in the power grid by charging batteries in homes and business during off-peak hours allowing the batteries to take the peak loads off the grid when needed. California has already launched a battery rebate program similar to the solar rebates seen in several other states. Batteries that run cooler will reduce the cost and damage to our environment caused by cooling needs as required by existing battery systems.

Regardless of the battery core chemistry or design, a flexible management system that allows for cost-effective commercialization will still be needed by industry.

Imagine, as battery core technology improves, being able to change out the battery in an electric car or existing power system for a fraction of the cost of replacing the car or power system, and enjoy the features of the newest batteries. Digital BMS technologies can make this a reality.