Fast charging

04Dec 2020

When it comes to electric vehicles, there is an understanding that the battery is a fundamental component to the vehicle’s utility. Yet, there is also a false expectation that the battery can deliver all what drivers expect from an EV.  Often underestimated is the role of battery management systems (BMS) in delivering critical performance and safety, in particular, extended driving range, very fast charging, long warranties and utmost safety. I will explore this topic in more detail in a series of blogs. 

In this first part, let’s define what battery management is and does. BMS historically included the electronics (hardware) that measure voltage, current and temperature, protect the battery from current or voltage spikes, and distribute charge evenly across different cells (called cell balancing). There is a basic layer of software that computes how much charge is stored in the battery.

Generally, these are electrical systems with very little intelligence related to the chemical operation of the lithium-ion battery. There are many suppliers of such basic BMS systems, spanning smaller companies to incumbent automotive Tier-1 and Tier-2 suppliers, and some of the battery manufacturers. Most electric vehicles on the road, whether you own a Tesla, a Nissan Leaf, a BMW i3, have one of these basic BMS on board.

Future EVs demand far more performance than what present BMS are providing. Specifically:

  1. Very fast charging: Newer EVs must be able to fully charge the battery in under 20 minutes without degrading the battery. This is strictly the role of more intelligent BMS.  If you try to fast charge your EV today at a DC-fast-charging-station, you likely will not do much better than 35 minutes. The vehicle’s manufacturer will also throttle your charge if you try to DC-fast-charge too many times in a row — in order to preserve the battery’s health. An intelligent BMS should be able to lift such restrictions!
  1. Maximum driving range: Car manufacturers reduce the available charge from the battery (and the driving range) in order to guarantee the battery’s longevity. It is one of the key tradeoffs between available charge capacity, fast charging, and battery longevity (hence warranty). This, again, is the role of a more intelligent BMS.
  1. Extended battery warranty: EVs have traditionally offered 100,000 miles of warranty. But, if you look closely, the fine print warrants that only 70% of the original driving range remains after 100,000 miles. So if your EV has a nominal driving range of 300 miles, the warranty covers you only if the driving range drops below 210 miles after 100,000 miles. Not ok! Yes, you guessed it, it’s the BMS function.

Fast charging, maximum driving range, and battery warranty form a triangle of tradeoffs. An EV maker must balance these three conflicting parameters. If they add more fast charging, then they must sacrifice warranty or driving range….and vice versa. This game of whack-a-mole makes today’s EVs fall short of market expectations. Next-generation of EVs must include intelligent BMS that are able to break this limitation. The technology exists.

The intelligent BMS diagnoses the battery in real time, assesses the likely degradation mechanisms and the battery’s health at that moment in time, then dynamically makes the necessary adjustments to optimize the operation of the battery. It is “computation” meets “chemistry.” 

In part 2, I will cover the suppliers of BMS and their integration into the EV.

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12Aug 2020

Three factors contribute to the mass penetration of electric vehicles:

  • Driving range that eliminates range anxiety;
  • Lower cost batteries for affordable vehicles;
  • Availability of fast charging.

A common denominator is the battery’s energy density: it is the amount of electrical energy per unit volume (or per unit weight) that a rechargeable battery can store. Energy is measured in units of kWh. Hence energy density is in units of Wh per liter (Wh/l), or Wh per kg (Wh/kg). State-of-the-art energy density figures for lithium-ion batteries stand today near 700 Wh/l and 300 Wh/kg.

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31Mar 2020

While the current situation has put us all in unfamiliar territory, one bright spot has been the willingness of so many people and organizations to offer advice and assistance. With hundreds of millions of us isolated in our homes, making especially intensive and important use of our phones and computers, it seems like an opportune moment to share four battery-specific recommendations that can help ensure your personal safety and extend the lifespans of all our devices as we adjust to this period of uncertainty, and WFH normalcy.

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09Mar 2020

Is it true that electric vehicles (EV) need 800-V battery packs for ultrafast charging? Is it true that the Porsche Taycan uses 800-V packs to enable ultrafast charging? Why did GM announce that its new battery platform will support 800 V? Let’s find out.

Let’s start with two essential ingredients required for ultrafast charging:

1. A charging station that is capable of providing a lot of electric power;

2. The ability for the battery to accept the extra charging power without being damaged or degraded.

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30Dec 2019

Whether related to the stock market, presidential elections or climate, December is the month to make predictions for the coming year and decade. So what battery trends should we expect for the upcoming 2020-2030 decade?

1.Lithium-ion batteries will power more applications — electrification of everything:  The 2019 Nobel Prize in Chemistry highlights the progress lithium-ion batteries achieved in the past four decades. From a laboratory experiment in the 1970s, they are now ubiquitous in consumer devices. Increasingly, they are making inroads in transportation and grid storage applications. 

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