Battery Safeguards Protection Circuits from Battery University

Protection Circuits

Batteries can release high power, and most packs include protection to safeguard against malfunction. The most basic safety device in a battery is a fuse that opens on high current. Some devices open permanently and render the battery useless; others are more forgiving and reset. The Polyswitch™ is such a re-settable device. It creates a high resistance on excess current and reverts back to the low ON position when the condition normalizes. A third method is a solid-state switch that measures the current and disconnects on excessive load conditions. All switching devices have a residual resistance during normal operation, which causes a slight increase in overall battery resistance and a subsequent voltage drop.

Intrinsically Safe Batteries

Intrinsically safe (IS) batteries contain protection circuits that prevent the formation of high currents, which could lead to excess heat, sparks and explosion. Authorities mandate IS batteries for two-way radios, gas detectors and other electronic instruments operating in hazardous areas such as oil refineries, chemical plants and grain elevators. There are several levels of intrinsic safety, each serving a specific hazard level, and the requirements vary from country to country. The provisions are in addition to the protection circuit for lithium-ion, and the approval standards are rigorous. This results in a high price for the battery.

Making Lithium-ion Safe

Battery packs for laptops and other portable devices contain many levels of protection to assure safety under (almost) all circumstances when in the hands of the public. The safety begins with the battery cell, which includes: [1] a built-in temperature switch called PTC that protects against high current surges, [2] a circuit interrupt device (CID) that opens the electrical path if an over-charge raises the internal cell pressure to 1000 kPa (145psi), and [3]a safety vent that releases gas in the event of a rapid increase in cell pressure.

In addition to these internal safeguards, an external electronic protection circuit prevents the charge voltage of any cell from exceeding 4.30V. Furthermore, a fuse cuts the current if the skin temperature of any cell approaches 90°C (194°F). To prevent the battery from over-discharging, a control circuit cuts off the current path at about 2.20V/cell.

Each cell in a string needs independent voltage monitoring. The higher the cell count, the more complex the protection circuit becomes. Four cells in series had been the practical limit for consumer applications. Today, new chips accommodate 5–7, 7–10 and 13 cells in series. For specialty applications, such as the hybrid or electric vehicle delivering several hundred volts, specialty protection circuits are made, which sharply increases the overall cost of the battery. Monitoring two or more cells in parallel to get higher current is less critical than controlling voltages in a string configuration.

Battery Safeguards; Protection Circuits – Battery University.

Fast and Ultra-fast Chargers – Battery University

Fast and Ultra-fast Chargers

Nowhere is fast-charging in higher demand than with the electric car. Recharging an EV in minutes replicates the convenience of filling up 50 liters (13 gallons) of gasoline into a tank that is capable of delivering 600kWh of energy. Such large storage of energy in an electrochemical system is difficult to fathom and a battery holding this capacity would weigh 6 tons. However, electric energy from a battery delivers far more efficient and cleaner propulsion than the internal combustion engine.

Charging an EV will always take longer than filling a tank with liquid fuel, and the battery will always deliver less energy per weight than fossil fuel. This ratio with current battery technology is roughly 1:100 in favor of fossil fuel. Read more about Net Calorific Value. Breaking the rule and forcing ultra-fast charging would cause undue stress to the battery and strain the power grid by dimming the city. When talking about ultra-fast charging we must remember that the battery is an electrochemical device that is sluggish and loses performance with use and aging. Charging a battery cannot be compared to filling a tank with fuel that contains 12,000Wh of calorific value per liter. Furthermore, while a fuel tank keeps its volumetric dimensions, a battery begins to fade by the time it leaves the factory.

Fast and Ultra-fast Chargers – Battery University.


Wednesday 20th March to Sunday 24th March 2013

A New Format has always been the guiding principle for both the Automobile Club de Monaco and its New Energy Rally organising committee.

The next event, which is held from 20th to 24th March 2013, has been completely rethought. A new stage format will give competitors a greater number of regularity tests than in previous years.

Meanwhile, a packed schedule allows constructors an opportunity to showcase progress made in their latest generation of vehicles.

Finally, the Zero Emission No Noise Rally (ZENN) will make its debut, replacing the Urban Electric Challenge. Purely electric vehicles, with a range of less than 150 km, are eligible to take part. ZENN will comprise several regularity tests, sharing some with the Rally competitors, and will straddle Friday 22nd and Saturday 23rd March.

Scrutineering and administrative checks will be held on Wednesday 20th March 2013 in the three traditional starting cities: Lugano, Clermont Ferrand and Annecy le Vieux; ZENN competitors will have these checks on 21st March in Monaco.

The Concentration Run, where competitors converge on Monaco from their starting cities, is held on 21st March. Once in the Principality, competitors drive to the end-of-stage parc fermé on Quai Albert 1er.

The Monaco – Aix en Provence leg starts on the following day, Friday 22nd March and comprises 4 regularity sections.
The second leg (Aix en Provence – Monaco) is on Saturday 23rd March when competitors will drive 2 regularity tests before reaching Monaco.
In the evening, all competitors leave on the night-time final leg, which is a Monaco – Monaco stage, split into two tests before a return to Monaco.

On Sunday 24th March 10.00 am, the Timed Manoeuvrability Event is held in the Port Hercule – Darse Sud , followed at 12.30 am by the Prize Giving Ceremony.

23 boulevard Albert 1er
98000 MONACO
Tél. (+377) 93 15 26 00
Fax : (+377) 93 25 80 08
info @


Build Your Own Electric Vehicle

The definitive handbook on DIY electric vehicle design and construction — now completely revised and expanded to cover the latest technologies and enhanced with exclusive online content

Custom-built for environmentalists, engineers, students, hobbyists, and mechanics, Build Your Own Electric Vehicle, Third Edition is the guide to making or retrofitting an electric vehicle. Written by one of today’s top authorities on EVs, and featuring contributions from an internationally recognized team of engineers and educators, this new edition details all the latest breakthroughs in electric vehicle (EV) technologies, including AC propulsion and regenerative braking systems, intelligent controllers, batteries, and charging technologies—all presented in simple, clear, and easy-to-understand language. A new web feature provides online supplier and dealer lists, which the author will continue to update throughout the life of the book.

Features automatic conversions instead of complex mathematical equations
Expansion on global electric car information, with data from the Electric Auto Association of Europe, which was begun in July, 2008, and specific information from around the world, particularly from Australia, England, India, Korea, Japan, and South Africa
Equal coverage of AC and DC systems
Electric Vehicle Benefits; Electric Vehicle History; Drive Systems, Chassis, and Designs; Sources, Parts, Conversion Companies, and Experts; Calculating Torque Curves; Electric Motors; Controllers; Batteries; Chargers; AC/DC Drive and Controller Packages; Visions for Future Electric Cars and Electric Car Conversions
About the Author
Seth Leitman is the Managing Member for ETS Energy Store, LLC, a green living and renewable energy consulting company. Prior to this, he worked for the State of New York where he was instrumental in adding more than 3,500 alternative-fueled vehicles and buses to fleets statewide. Leitman also served as the Market Development and Policy Specialist for the New York Power Authority, where he helped create, roll out, and run electric and hybrid vehicle programs serving the New York City metropolitan area. He has a large following on his blog,, Discovery’s, Mother Earth News, and other media

Build Your Own Electric Vehicle