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Supplying content to print, broadcast and online colleagues across the globe since 2000, we cover stories throughout the UK but concentrate largely on the news footprint of Central Scotland.
Our dedicated team of journalists and photographers cover everything from breaking news, politics and human interest stories to celebrity appearances, court reporting and sport.
Deadline News Suite 6, Bonnington Bond, 2 Anderson Place, Edinburgh, EH6 5NP
Deadline News is the leading independent news and picture agency in Scotland. Supplying content to print, broadcast and online colleagues across the globe since 2000, we cover stories throughout the UK but concentrate largely on the news footprint of Central Scotland. Our dedicated team of journalists and photographers cover everything from breaking news, politics and human interest stories to celebrity appearances, court reporting and sport. Agency & Services » Agency » News Coverage » Photography » Video » Public Relations » Student Placements Deadline News Suite 6, Bonnington Bond, 2 Anderson Place, Edinburgh, EH6 5NP 0131 516 3433 [email protected]
Supplying content to print, broadcast and online colleagues across the globe since 2000, we cover stories throughout the UK but concentrate largely on the news footprint of Central Scotland.
Our dedicated team of journalists and photographers cover everything from breaking news, politics and human interest stories to celebrity appearances, court reporting and sport.
Deadline News Suite 6, Bonnington Bond, 2 Anderson Place, Edinburgh, EH6 5NP
Medical gadgets are more advanced than ever before, allowing for earlier illness detection and more efficient treatment delivery, allowing people to live longer, healthier lives. Among the many technical innovations characterising 21st-century healthcare are battery-powered medical equipment, such as automated external defibrillators, surgical power instruments, pacemakers, robotic cameras, insulin pumps, and glucose monitors. They provide life-saving and life-sustaining functions while also providing convenience because they may be used both within and outside of healthcare institutions.
Manufacturers must stay current on the many criteria for medical equipment batteries, including those relating to performance, safety, and transportation, as Medtech innovation speeds up.
Historically, ventilators, infusion pumps, dialysis systems, and anaesthetic devices were powered by the main AC supply, with their internal battery serving only as a backup. This implies that the battery is frequently only discharged briefly before being charged again.
While today’s rechargeable batteries do not have the memory effect that was common with older technologies such as nickel-cadmium batteries — where the battery would lose capacity if it was not fully discharged before being charged again — modern batteries such as sealed lead acid and valve-regulated lead acid still have a failure mechanism; a gradual rise in internal resistance.
As internal resistance grows, any sudden requirement for power, especially from motor-driven equipment like dialysis machines and ventilators, can draw a lot of power, resulting in a voltage drop; not an ideal attribute of a medical battery.
The most common error we’ve seen equipment makers make when matching a battery to a device is failing to choose a battery with an internal resistance sufficient for the load. When the load current or pulses are significant, and the battery has a relatively high internal resistance, the voltage drop under load might be severe.
This will cause two issues. First, the battery will overheat and lose energy, and second, the battery will hit the device’s cut-off voltage much sooner than expected.
The internal resistance of a battery is composed of two components: electrical and ionic resistance. The resistivity of the materials used to construct individual cells, such as the cell cover, can, and current collectors, as well as the welded connective connections between cells and the battery-level elements, such as wiring, FETs, fuses, sense resistors, are all included in electronic resistance.
The resistance to current flow within cells caused by electrochemical parameters such as electrolyte conductivity, ion mobility, and electrode surface area is known as ionic resistance. The sum of these elements results in total effective resistance, which causes a voltage to decrease when the battery is loaded.
The effective internal resistance of a fully charged battery is normally determined by placing it under a modest current load, typically 0.2CmA, for 10 seconds. Following this, the current is quickly boosted to a higher level 1.0CmA and maintained for 1 second. The resistance is then calculated using Ohm’s law based on the differential between the two on-load voltages and currents.
Finally, batteries perform best at ambient temperature. A greater ambient temperature may enable improved short-term functioning by increasing the efficiency of the charge and discharge processes and, as a result, lowering internal resistance.
Sustained operation at high temperatures causes undesirable parasitic interactions between the electrodes and the electrolyte, as well as a breakdown of the cell structure, resulting in a long-term drop in performance.
The international standard IEC 60601-1, which defines the overall standards for fundamental safety and necessary performance, states that any part that a human can touch shall not be hotter than 43 degrees Celsius. Choosing a battery that overheats may cause non-compliance.
Temperature is also the reason for quick charging, and despite its benefits, is not good for the battery’s long-term health. It was reported in May 2017 that Tesla was restricting the charging rate for automobiles fuelled using its 120kW Superchargers to only 90kW if the vehicle had previously accrued too many DC fast-charge events. The business issued a statement clarifying the restriction.
After a significant number of high-rate charging sessions, the peak charging rate attainable in a lithium-ion battery will somewhat fall. This is caused by physical and chemical changes within the cells.
To preserve the safety and maximum range, we must slow down the charge rate when the cells are too cold, when the charge state is almost full, and when the cell’s conditions progressively change with age and usage.
It is ideal to charge a battery at the lowest current that a user can practically accept and then recharge it only when the remaining capacity has reduced to where there is insufficient capacity to give meaningful power.
This frequently results in a trade-off between the battery’s lifetime and the user’s demand. In medical settings where a portable dialysis machine must accompany the patient as they travel throughout a hospital, it is critical that the unit can be recharged fast without compromising the quality of treatment provided to the patient.
Lithium-ion batteries typically charge in two phases. The battery is charged at a steady current in stage one, and the voltage may grow. When the battery hits its maximum voltage limit (usually 4.2V per cell), the voltage is maintained constant while the current is permitted to gradually decrease to zero. Once the current has tapered to a certain level, the charge is discontinued.
The charging voltage must be never surpassed in this situation. Because lithium-ion batteries comprise multiple cells connected in series, it is best to utilise cell balancing circuitry to divert charge current away from cells that achieve their charging voltage first, enabling the others to catch up.
Monitoring individual cell voltages and draining energy away from the cells with the higher voltages is the most popular technique of cell balancing. The energy is lost as heat after being drained away by resistors. Neighbouring approaches, which squander less energy but are more difficult to implement, reroute cell energy to charge other cells.
While cell balancing will not transform a defective cell pack into a good one, it will maintain good cell balance, allowing the battery to be cycled hundreds, if not thousands, of times. Reduced charge voltage promotes longer cycle life, although at the expense of reduced capacity in each cycle.
According to Texas Instruments, some of the electricity that would charge the cell is redirected along a parallel channel.
Cell balancing occurs over a 50-ms nominal time. Voltage monitoring happens for roughly 10 ms of this interval, after which a balancing field-effect transistor inside the IC is turned on to provide a bypass channel for the remaining 40 ms. After the balancing time, the FET is turned off again to measure the cell voltage.
To stay up with the expansion and needs of the global medical device industry, design engineers must deliberate their battery selection, ensuring that mission-critical devices continue to perform in the most demanding of situations.
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