BMS and EVs

An EV is a shortened acronym for an electric vehicle. EVs are vehicles that are either partially or fully powered on electric power. They operate on an electric motor instead of an internal combustion engine that tends to generate power by burning a mixture of fuels and gases. Over the years, EVs have been gaining prominence in the automotive sector slowly and steadily. They have shown the world that they are at least equitable if not mostly superior in performance to their ICE engine counterparts. Now it's time to bust everyone's myth that EVs are more susceptible to damage, ancillary components affect the range of the electric car, etc.

What is a Battery Management System?

A Battery Management System is an analog and/or digital electronic hardware device complemented with specific software added to a battery system.

In electric vehicles, the Battery Management unit is a part of a system that stores and converts energy into motion and vice versa. To prevent battery failure and mitigate potential hazardous situations, there is a need for a supervising system that ensures that batteries function properly in the final application. This supervising system is referred to as Battery Management System (BMS). Electrification will have a profound impact on the vehicle's electrical system. As many systems are traditionally based on hydraulics which is now driven by electric motors in the world of battery-operated products and especially in electric vehicles, battery management is perhaps the most important aspect of the product.

Why is this, an article published in the WALL STREET JOURNAL in 2019 provides some insight which identifies the battery as quoted, the big obstacle on the road to electric vehicles?

The battery system is the most expensive component comprising the bill of materials. For this reason, the batteries must be able to impact performance and functionality in a big way!!! Commensurate with its relative cost. So, the care and feeding of the battery pack is a big focus to ensure that it delivers the performance and longevity that justifies its cost. Several factors go into the design of a battery pack as well as the battery management unit. Ideally, the battery pack should outlast the service life of the vehicle itself and it must do so safely and efficiently, accomplishing this; means monitoring and controlling certain operational parameters.

at some of the nuances of

Now, let's look at some of the nuances of battery management in an electric vehicle. Battery management implemented in electric vehicles is quite different from something like a mobile phone. A mobile phone battery system is optimized for two primary factors that are cost and talk time; longevity of the battery is not a concern as mobile phones are typically upgraded every two years. By contrast, the electric vehicle battery pack should ideally last for the service life of the vehicle. To do this the pack is typically sized for a larger capacity than the desired target range based on the efficiency of the vehicle platform. So, the BMS and new vehicle charges and discharges the pack to something significantly less than full capacity as a vehicle battery packages the capacity is diminished and the BMS charges and discharges the pack over a broader range. Thus overall, the perceived vehicle performance is retained over a longer period, even though the capacity of the battery pack is diminished.

Minimal Requirements for a BMS: -

While there is no unique definition of a BMS, the world does seem to agree that it should be designed with a minimal set of requirements.

It must measure individual cell voltages.
It must measure temperatures at different points as close as possible to the battery.
It must measure currents flowing through it.
It should communicate information to control units and undertake action to ensure the battery will be operated within safety limits.
It should balance battery cells passively or actively.
It should provide thermal management.
It should be able to detect and isolate faults.
It should protect against short circuits.

The chart above lists a few of the methods of gauging battery capacity and performance as well as some pros and cons of each approach. Intuitively monitoring cell voltage to track charge and discharge and hence capacity seems like the simplest approach to implement. However, there are potential pitfalls which can turn to be the biggest roadblocks in the course of development to EVs:

Mid charge lithium-ion discharge curves are relatively flat. This necessitates the use of a very high-resolution signal path.
Cell voltage is impacted by load current as well as temperature variation.
Fuel gauging in lithium cells suggests that the battery be unloaded for a long time before cell voltages are sampled, and even some aspects of cell voltage monitoring are impractical for EB applications.

Structural Battery = Massless Battery?

In ground-breaking new research, Swedish scientists have made a structural battery 10 times better than in any previous experiment. Previous attempts to make structural batteries have resulted in cells with either good mechanical properties, or good electrical properties. But now, using carbon fibre, scientists have succeeded in designing a structural battery with both competitive energy storage capacity and rigidity.

You think science is badass. So do we. Let's nerd out over it together!

In this environmentally conscious world, fossil fuels are being shunned in favour of renewables for electricity generation and transportation. Due to their periodic nature, excess energy generated by renewables is frequently stored in batteries. However, these often add extra weight to the cars and consumer electronics they power. Batteries in future electric vehicles, smartphones, electric planes, and other devices can become conditionally weightless without losing energy storage properties. There is no aabra ka daabra over here. If the battery is made an integral part of the case or other structural part of the structure, then its weight can simply be ignored. This approach will eliminate the need for a separate battery in the device, making the product lighter and smaller. And this is not fiction.

ONCE A DREAM, BAKED WITH HARDWORK AND PERSEVERANCE, AND FINALLY THE TASTE OF REALITY IS OBTAINED.

Due to their multifunctionality, structural battery composites are often referred to as ‘massless energy storage’ and have the potential to revolutionize the future design of electric vehicles and devices. Both electrode materials – carbon fibre at the negative, and a lithium-iron-phosphate-coated aluminium foil at the positive electrode - contribute to the mechanical properties of the structural battery. The carbon fibre serves as a host for lithium and stores energy, and, because it also conducts electrons, it helps to reduce weight by negating the need for copper and silver conductors. The battery has an energy density of 24 Wh/kg, around 20% capacity compared to lithium-ion batteries currently available, but because the weight of the vehicle is significantly reduced, less energy will be required. The lower energy density also makes the vehicle safer, and with a stiffness of 25 GPa, the structure is comparable to other commonly used construction materials. But the best is yet to come ....

The next-generation structural battery has fantastic potential. Further improvement in the field of structural batteries can be achieved. Carbon fibre will replace the aluminum foil as a load-bearing material at the positive electrode, providing greater stiffness and energy density. The fiberglass separator will be also swapped with an ultra-thin variant to yield a greater effect and faster-charging cycles. A battery with an energy density of 75 Wh/kg and stiffness of 75 GPa could be achieved, making it about as strong as aluminium, but comparatively, much lighter.

In the longer term, the work could result in electric cars, electric aircraft, and satellites designed with and powered by structural batteries.

DON'T PREDICT YOUR FUTURE, JUST CREATE IT !!

AIM TO MAXIMISE HUMAN POTENTIAL !!

AND THEN U WILL SURELY REQUIRE SUNGLASSES TO SEE YOUR BRIGHT FUTURE

SOURCES :

KCT BLOG | Battery Management System for E-Vehicle - KCT BLOG

Big Breakthrough for “Massless” Energy Storage: Structural Battery That Performs 10x Better Than All Previous Versions (scitechdaily.com)

"Massless" carbon fiber battery doubles as a structural component (newatlas.com)

IMAGES:

1-(322) Battery Management in Electric Vehicles - YouTube

Written By - Anshika