Research Firm Tells EV BMS Makers to First Work on E-scooters

Huge number of cells in EVs makes battery management more complicated

Global sales of electric vehicles (EVs) have been falling short of expectations, despite governments in industrially advanced nations investing ever more resources to promote such environmentally-friendly transport, while makers work hard to develop newer and better options.

The same reasons remain hindrances to rising popularity of EVs, including relatively higher prices compared to gasoline-powered counterparts, inadequate cruise range, and recharging inconvenience under current infrastructure etc. Technologically and before clear advancement in lithium-ion battery technology is realized, there is still room for upgrading battery performance, whose enhancement hinges on BMS (battery management system).

Topology Research Institute (TRi), a private market-research firm in Taiwan, advises local players in the EV game to focus on niche segments, including designing and producing battery packs that satisfy real-world EV operations and upgrading their capability in developing better BMS. The research firm says that Taiwanese companies can first try to develop products for electric powered two-wheeler (PTWs), and then venture into four-wheel EVs.

Real-time Monitoring
A good BMS maximizes EV cruise range at minimized electrical consumption, while also protecting the battery pack simultaneously. Though different types of batteries have their own characteristics, TRi says, the basic functional requirements for BMS are basically the same, including monitoring, protecting, balancing, and gauging, or even vehicle safety surveillance.

Lithium-ion battery applications are quite common and mature in 3C (computer, communication, and consumer electronics) products, but their management becomes more complicated due to the vast array of cells on an EV.

In addition, EVs have to run outdoor under severe weather, with various kinds of road vibrations that may cause very high instability index for EV cells that work chemically. More importantly, any minor contact between hundreds or thousands of cells might lead to short circuit and safety problems. So inner-battery structure has to be carefully designed and laid out with proper insulation to avoid unwanted chain reactions. Supporting mechanisms for battery packs is also important, requiring firm connection to vehicle body, as well as minimal wiring/contact point designs to avoid battery safety problems from rising impedance.

TRi points out that the EV battery industry used to focus on power-cell testing and inspection and now on cell monitoring and charging balance, but still failing to pay enough attention to battery pack safety. So the research firm stresses pack monitoring to be a focus in future EV development.

Precision Required
The basic functions of a BMS include measuring, protecting, balancing and algorithm/analysis. The state of charge, or SOC, covers both measuring and algorithm/analysis as the core requirement for a BMS. TRi points out that SOC is not a new technology but has been applied in 3C products for a long time with greater inaccuracy allowed. Such inaccuracy would cause EVs to malfunction, so accuracy of SOC in EVs is much more important than that in 3C products.

To further upgrade SCO accuracy, TRi says, two issues must be addressed. The first is to upgrade accuracy of measuring techniques by including all variables into algorithm. The difficulties in upgrading accuracy include not only algorithmic complexity, but also measurement timing, location and method, TRi says, which require different players in to keep honing their game.

The second issue is higher precision level and readability of SOC data for an EV user. Currently, TRi says, most EVs adopt a five-scale meter to show SOC, leaving a 20% inaccuracy gap, which might meet the demand only from EVs with cruise range under 40 kilometers. Higher SOC accuracy means more controllable variables in EV operation, TRi says, to equal higher product value. Finally, the research firm says, SOC display will one day be digitized in conjunction with improved BMS capability.

E-Scooter
With thousands of power cells, TRi says, a four-wheel EV has too many variables to affect the normal operation of its battery packs, which also greatly lifts the technical threshold in designing a BMS meeting all requirements. So, TRi suggest that Taiwanese BMS developers and makers should first gain a more solid technical base in e-scooter BMS, and then gradually move into the four-wheel EV BMS market.

TRi says that Taiwan is ideal for EV BMS makers to sharpen their capability by starting from e-scooter applications, with e-scooters being more popular and affordable than four-wheel EVs on the island.