Because electric vehicles have so few moving parts many claim there are low maintanence requirements and they are more reliable. While it’s true you don’t have to change the oil every 3000 miles or perform other required maintanence at regular intervals there are many things which can break and which have specific maintanence requirements. One of these is proper battery management, properly charging the batteries, and preventing damage to the battery pack. Batteries are by nature chemical and the chemicals inside a battery can pretty easily go bad ruining the battery. With todays lithium batteries a ruined pack is a very expensive proposition.
AeroVironment, Inc. has been granted a patent (no. 7,444,192) for technology that facilitates the optimal charging, management, control and maintenance of battery packs, chargers and electric vehicles. The patent describes a monitoring system that collects data from the battery pack, from the “smart grid”, the history of the battery pack, and perhaps the phase of the moon. It is able to facilitate longer life of the battery pack and also adjust the pack charging rate based on the condition of the overall power grid. The patent covers technology Aerovironment developed for their PosiNET system.
Such a system has to involve per-battery monitoring of voltage and other characteristics during charge and discharge. For example the only way to detect a weak battery cell is to observe the voltage during discharge (during use). A battery at rest may appear fine but under discharge the voltage of a weak cell will dip much lower than the other cells in the pack. Further if a battery pack has a weak cell in it this will affect the lifetime of the rest of the pack, because the other cells must work harder to provide the power not supplied by the weak cell.
The patent shows a system which, given historical data about the battery pack, can send alerts to a maintanence crew to replace individual cells in the pack or perhaps replace the whole pack. The illustrations in the patent only talk about maintanence issues for lead acid battery packs. Lithium battery pack maintanence has other considerations than for lead acid, because the chemistry characteristics are different. Presumably AeroVironment has also studied lithium battery pack issues and have programmed them into their PosiNET system.
Because battery pack management requires specialized knowledge, a big advantage to a system like this is to embed that specialized knowledge in a system that aids maintanence workers to know what to do. Battery pack management is not something best left to untrained individual car owners, especially as this requires attention on essentially every charge cycle. For daily use by typical drivers it is best for battery management to be embedded in an automated system.
In the near future when electric vehicles are more common, and your vehicle informs you that battery maintanence is required, pay attention. Pay more attention than the “check engine” light, or the oil pressure light, or other routinely ignored warning lights. Batteries can be very expensive to replace and can be quickly damaged by neglect.
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