Why do old Li-ion batteries take so long to charge?
13 June 2018Editor's Choice
Power Electronics / Power Management
By Isidor Buchman, founder and CEO of Cadex Electronics.
Battery users often ask: “Why does an old Li-ion lake so long to charge?” Indeed, when Li-ion gets older, the battery takes its time to charge even if there is little to fill. We call this the ‘old-man syndrome.’ Figure 1 illustrates the charge time of a new Li-ion battery with a capacity of 100% versus an aged pack delivering only 82%. Both take roughly 150 minutes to charge.
Figure 1. New and aged Li-ion batteries are charged.
When charging Li-ion, the voltage shoots up, similar to lifting a weight with a rubber band. The new pack as demonstrated in Figure 2 is ‘hungrier’ and can take on more ‘food’ before reaching the 4,20 V/cell voltage limit compared to the aged Li-ion that hits V Limit in stage 1 after only about 60 minutes. In terms of a rubber band analogy, the new battery has less slack than the aged pack and can accept charge longer before going into saturation.
Figure 2. Observing charge times of a new and aged Li-ion battery in stage 1.
Figure 3 demonstrates the different saturation times in stage 2 as the current trails from the fully regulated current before triggering ready mode. The trailing on a good battery is short and is prolonged on an aged pack. This explains the longer charge time of an older Li-ion with less capacity. An analogy is a young athlete running a sprint with little or no slow-down towards the end, while the old man gets out of breath and begins walking, prolonging the time to reach the goal.
Figure 3. Observing saturation times of new and aged Li-ion battery in stage 2 before switching to ready.
A common ageing effect of Li-ion is loss of charge transfer capability. This is caused by the formation of passive materials on the electrodes, which inhibits the flow of free electrons. This reduces the porosity on the electrodes, decreases the surface area, lowers the lower ionic conductivity and raises migration resistance. The ageing phenomenon is permanent and cannot be reversed.
The health of a battery is based on these three fundamental attributes:
• Capacity, the ability to store energy. Capacity is the leading health indicator of a battery.
• Internal resistance, the ability to deliver current.
• Self-discharge, indicator of the mechanical integrity.
The charge signature reveals valuable health indicators of Li-ion. A good battery absorbs most of the charge in stage 1 before reaching 4,20 V/cell and the trailing in stage 2 is short. ‘Lack of hunger’ on a Li-ion can be attributed to a battery being partially charged; exceptionally long trailing times relate to a battery with low capacity, high internal resistance and/or elevated self-discharge.
Quality batteries are critical for IIoT Uniross Batteries
Power Electronics / Power Management
Batteries intended for use in industrial operations must indeed offer complete reliability under extreme environmental conditions, resistance to vibration and harsh environments.
Read more...Solving South African power problems with locally built intelligence
Editor's Choice Power Electronics / Power Management
Smart metering infrastructure in South Africa remains patchy. The rollout has been slow, coverage is inconsistent, and for the most part, granular per-unit measurement simply does not exist.
Read more...Lesley Havenga: Building partnerships for Africa’s electronics future
Editor's Choice News
As Würth Electronik expands its footprint across South Africa and the broader sub-Saharan region, Havenga’s blend of manufacturing expertise, supply chain knowledge, and people-centred leadership appears well suited to the task.
Read more...Generating negative voltages from a positive supply Altron Arrow
Editor's Choice Passive Components
It is common for IoT devices, industrial sensors, meters, and medical equipment to require both a positive and negative voltage, and this article explains the options available to produce a negative rail from a positive rail supply.
Read more...PEAK’s first automotive Ethernet solution Industrial Data Xchange (IDX)
Editor's Choice Telecoms, Datacoms, Wireless, IoT
The PAE-Media Converter is a robust and compact device designed to connect Automotive Ethernet (100BASE-T1 or 1000BASE-T1) with standard Ethernet (100BASE-TX or 1000BASE-T) networks.
Read more...Selecting primary batteries for maximum service life Uniross Batteries
Power Electronics / Power Management
Primary batteries play an important role in IoT applications. Designed for longevity, they have a high-energy capacity and are often used in standalone applications where charging is impractical or impossible.
Read more...EMC limits and levels Altron Arrow
Editor's Choice Circuit & System Protection
As soon as electronics and electrical systems started interfering with each other, the world had to come to some consensus. Considering physics is universal and does not care about what country electrical/electronic products are used in, it should be the same everywhere, right? It is nearly there, but not quite.
Read more...Sigfox SA powers smart connectivity
Editor's Choice Telecoms, Datacoms, Wireless, IoT
Sigfox South Africa is carving out a unique role, delivering low-power, wide-area network connectivity designed specifically for Internet of Things applications.
While every effort has been made to ensure the accuracy of the information contained herein, the publisher and its agents cannot be held responsible for any errors contained, or any loss incurred as a result. Articles published do not necessarily reflect the views of the publishers. The editor reserves the right to alter or cut copy. Articles submitted are deemed to have been cleared for publication. Advertisements and company contact details are published as provided by the advertiser. Technews Publishing (Pty) Ltd cannot be held responsible for the accuracy or veracity of supplied material.
printer friendly version