Four ways to improve alkaline battery performance in professional devices
Professional devices are placing new demands on batteries, requiring greater performance, reliability, safety and replacements available globally.
Selecting the right battery to match the power needs of your device can make batteries last longer. This guest blog from Procell explores four ways this is achieved.
1. How to get greater alkaline delivered capacity
Alkaline cell capacity is usually expressed in milli Ampere-hours. The theoretical or rated capacity of a cell is usually measured during a low drain continuous discharge at room temperature to an end point voltage of 0.8V. However the delivered capacity is the capacity that is delivered from the cell in a specific application. The theoretical capacity of the cell is constant however the delivered capacity of the cell varies greatly depending on discharge load magnitude, load type, endpoint voltage, temperature, continuous/intermittent discharge and battery design characteristics such as rate of increase of polarization during discharge. The cutoff voltage also impacts the battery capacity. The higher cutoff voltage applications will see less delivered capacity than lower cutoff voltage applications.
Many of today’s applications require high drain pulses and have a high cutoff voltage. In this case the cell with lowest internal impedance will demonstrate a lower voltage drop and will last longer before hitting the device cutoff voltage. Procell Intense batteries were designed for these applications as they provide more delivered capacity due to lower internal impedance.
2. How to get greater alkaline temperature performance:
The recommended temperature for alkaline-manganese dioxide system is -20°C to 54°C. However, the cell performance can still be impacted by the temperatures within the above range. The performance of the cell is critically dependent on the mobility/movement of ions within the cell. As alkaline electrolyte contains water, the lower temperature limit is determined by the temperature at the electrolyte freezes. As the temperature decreases the mobility of ions decreases there by decreasing the overall performance. The decrease in mobility also increases the internal impedance which also increases the battery voltage drop. Hence the high drain applications will be impacted more by the low temperatures than low drain applications because of the increased voltage drop in high drain applications. It is important to note that the cell capacity is not lost in low temperatures, rather it becomes harder to access the capacity because of the decreased mobility of the ions. On the contrary, increased temperatures increases the mobility of ions. This can cause an increase in self discharge of the cell there by decreasing the shelf life of the cell.
3.How to get better performance when using multiple cells
IEC primary alkaline cell longevity tests discharge individual cells under specific load and duty cycle conditions to prescribed cutoff voltages. However, market research studies* (Conducted in the US) indicate that greater than 90% of battery-driven devices: (in the US) require more than 1 cell to function.
Focusing on AA size batteries, multiple cells discharged in series configuration may demonstrate lower cell performance vs single cells discharged under similar load and duty cycle conditions. The magnitude of decrease in performance is highly related to the cell-cell performance variability, efficiency of multi cell connection (Contact resistance offered by the cavity). In series combination: cell-cell variability may force the device to perform only as best as the weakest battery in the series combination. This can cause the device to have premature failures or lesser run times. In a parallel configuration: significant cell–cell variability may cause non uniform loading between the cells and might cause the weakest cell to be over discharged and eventually leak.
Procell batteries have been designed to have reduced cell-cell variability to increase multi-cell performance in series configurations and reduce non-uniform loading in parallel configurations.
*Reference: https://iopscience.iop.org/article/10.1149/MA2018-02/1/72/meta
4. How to predict run-times accurately
Technical datasheets often show the cell performance at continuous discharges. However, in real life situations, most of the applications are intermittent usage. The rest time/duty cycle used in the cell discharge can significantly impact delivered capacity. An application with enough rest time allows the battery voltage to recover there by extending the longevity versus a continuous drain application with no rest time. The lesser the duty cycle (On time / (ON time + OFF time)), the more time battery has, to recover. Recovery is a process of the migration of active materials within the battery into the reaction area which otherwise would be occupied by depleted materials and reaction byproducts. The magnitude of increased capacity or longevity depends on the load current magnitude, load current pulse duration, duty cycle, cutoff voltage and the temperature. Procell Intense is specifically made to have an increased ion mobility to withstand any changes in discharge pattern and to efficiently deliver capacity even in high frequent device usage cases.
Procell engineers, using smart technologies, have developed the world’s first dual portfolio of professional alkaline batteries, Procell Intense and Procell General Purpose. These new device-specific batteries, each with unique power profiles, are designed to deliver optimum performance in both high and low-drain devices. Procell can also offer lifetime analysis on your product. Email our battery specialists to request a test or to discuss how you can optimise your designs with alkaline batteries.
