When developing new battery-operated devices, the decision regarding the type of power supply required is...
Renata develops and produces innovative, reasonably priced, environmentally friendly and high-quality battery solutions for industrial applications in close cooperation with its customers. The newly launched High Pulse silver-oxide batteries are particularly used for projects in the fields of medical wireless sensors.
Renata’s portfolio includes over 40 different silver-oxide batteries types, divided into High Drain, Low Drain and Improved High Drain (High Pulse) versions. Silver-oxide batteries are available in smallest form factors starting at a diameter of 4.8mm and a height of 1.25mm. Therefore, they are ideal for very compact and ergonomic application, such as Constant Glucose Monitoring (CGM) systems, smart patches and wearable sensors.
Renata has developed silver-oxide batteries that can support high current pulses of 10mA and even above for medical applications with radio transmissions. In addition, Renata is able to offer batteries with customised cell parameters, as well as assemblies consisting of several cells and / or tab configurations. The advantages of a multi-cell assembly in parallel-connected mode are higher capacity and pulse capability as well as lower internal resistance. In a serial connection of silver oxide batteries, a higher voltage level can be obtained (1cell = 1,55V, 2cells = 3,1V, 3cells = 4,65V).
Silver-oxide batteries have the big advantage that they are not classified as dangerous goods like lithium batteries. This fact makes them best suitable for example for medical sensors in terms of logistics and certifications.
At the beginning of every project, the requirements of the application and its usage should be defined precisely, as they are decisive for the choice of battery technology and its design.
The most important factors for primary coin cells are the maximum pulse current, the cut off voltage, the temperature exposure as well as the required life of the application. Each current pulse, no matter how short, will create a voltage drop depending on the batteries internal resistance. As the temperature has a major influence on this internal resistance, it must be ensured, that the maximum required pulse can be served safely even at lowest applicable temperatures and with batteries of a certain age. The pulse-load behaviour of the battery at higher temperatures is much better than at lower temperatures
The batteries lifetime calculation based on average load is possible for constant low current applications, but will certainly lead to a significant misjudgment in a pulse-loaded application.
The cut-off voltage of the application also limits the usable capacity of the battery. In concrete terms: the higher the cut-off voltage, the lower the usable portion of the total battery capacity.
The Self-Discharge-Rate (SDR) of batteries is typically defined and specified at room temperature. However, real SDR is heavily depending on the average ambient temperature. As a general rule of thumb: the self-discharge rate will double when the temperature rises by 10 K each time. So in case of a Silver Oxide Battery, which may have a specified self-discharge rate of 3% at room temperature, a usage at 30°C average will increase SDR to 6%, at 40°C average even to 12% and so on.
For storage, it is recommended, to keep the batteries in a cool and dry place. Condensation must be strictly avoided, as it can lead to short circuits and further damages.
Finally yet important, another key factor is the type of contact for the battery. It depends primarily on, whether it is a single-use solution or if the battery should be replaceable. For a replaceable option, a battery holder or a solution with cable connectors can be used. In case of a single-use battery, soldering tabs, which are welded to the battery, are the most common option. Alternatively, spring contacts can be integrated into the housing design.
An important point for a holder or spring solution is that the contacting is realised by spring force. Therefore, in case of a heavy mechanical impact or vibration, the electrical contact could be lost for a short time period, which could make the application to fail. Such points have to be verified and tested, if applicable.
The selection of the right battery and contacting solution requires much experience and expertise, which Renata can offer to its customer.
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