Power


The guide to effective battery maintenance


W


hile most car owners understand that properly maintaining brakes is one of the best ways to avoid


accidents, defective brakes are the most common cause of road accidents. Overlooking proper component maintenance isn’t exclusive to car owners however — it’s also true of battery-powered device users. Here, Neil Oliver, technical marketing manager at professional battery manufacturer Accutronics, explains how technical staff and device manufacturers can ensure batteries are safely maintained. Battery-powered devices are becoming


increasingly commonplace in sectors where failure is not an option. The continual shrinking of component sizes, alongside the advent of wireless technology and exponential increases in processing power, has meant that sectors such as medical are now condensing mission-critical equipment into smaller, portable forms. For example, mechanical ventilators have been decreasing in size in recent years and medical staff are increasingly using portable ventilators to treat patients in emergencies. These life-critical systems require a safe and reliable power supply, which means that the battery must be suitable for use and properly maintained. But how can technical staff ensure that batteries are properly maintained? While most original equipment manufacturers (OEMs) will supply rudimentary information for safe handling of the battery, there are three key considerations that are often neglected.


Storage


The first battery maintenance issue that many users neglect, but one that is easy to


38 February 2020


address, is that of improper storage. Some considerations are fairly obvious, such as how long a battery has been in storage, which can be managed by enforcing a strict first in, first out approach to stock control. Other considerations are less apparent, such as storage temperature. Every battery has an optimum operating temperature, which indicates the temperature range at which it can perform safely. Likewise, they also have an optimum storage range that must be adhered to. The reason for taking note of this storage temperature is two-fold. The first is that, by choosing a location that does not exceed the temperature, technical staff can ensure the battery will safely perform within operating temperature limits during next use. The second, is that it eliminates the risk of the battery losing capacity. The rate at which a battery loses capacity in storage varies depending on the battery chemistry. Most electronic medical devices, such as portable ventilators, use lithium-ion (Li-ion) batteries, which should not be stored in temperatures higher than 30 degrees Celsius to minimise capacity losses. An effective way of storing Li-ion batteries is in an open circuit condition in a dry, cool environment. Ideally, the storage area should be at or below room temperature. In addition to temperature, the state of charge (SoC) of a stored battery affects how well it operates after extended periods of storage. Due to transportation regulations, most Li-ion batteries are shipped at or below a 30 per cent SoC, which in most cases can allow for up to 12 months of storage without the battery incurring damage.


Components in Electronics Crucially, a battery should not be


stored at a fully charged state, as this may result in a higher level of irrecoverable capacity loss. As such, the safest approach in general is to aim for the 30 per cent. Depending on how long the battery will be in storage, technical staff will need to periodically recharge it in line with OEM guidelines.


Calibration Smart batteries are, in effect, two systems: the electrochemical battery, which provides the electrical energy, and the digital battery, which provides users with protection, charge control, performance data and SoC calculations based on discharge cycles. These two systems should complement each other perfectly, but the digital battery slowly loses precision as time passes and calibration is required to correct this. The latest smart batteries use fuel gauges that use both coulomb counting and impedance tracking to maintain a high degree of fuel gauge accuracy. However, in some applications, especially those where the battery is rarely discharged, the fuel gauge can become out of sync with the cells. These applications may require the battery to be periodically calibrated, either by forcing a deeper level of discharge or by using an external calibrator, such as the Inspired Energy CH5050X desktop dual-bay smart charger and calibrator. This exercises the battery over a full charge and discharge cycle to realign the digital and chemical batteries, allowing for accurate readings.


Conducting this calibration once every couple of months is enough to keep readings reliable and prevent any unexpected failures during use.


Transportation The final consideration is that of transporting batteries. Most device OEMs know about amendments to the dangerous goods regulations in 2016 that prohibit Li-ion batteries from being transported by air with more than a 30 per cent SoC, but technical staff may not be aware.


This is important to note because some specialist physicians may be required to travel by air to practice at different healthcare facilities. Technical staff should also be aware that the 30 per cent SoC limit does not affect batteries that are being transported with, or inside, equipment. By considering these three aspects, OEMs can include the best advice in technical guidelines to ensure that batteries in critical medical devices are handled properly and can operate effectively. This advice will be cascaded down to technical staff, who can then ensure ongoing device effectiveness. As with car brakes, keeping batteries


properly maintained is one of the best ways to avoid accidents. With an effective understanding of proper battery maintenance from both technical staff and OEMs alike, medical practitioners can avoid unexpected accidents and keep operations running smoothly.


accutronics.co.uk www.cieonline.co.uk


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