Learn about low-capacity cells, cell matching, balancing, shorted cells and loss of electrolyte
The three main battery defects are low capacity, high internal resistance and elevated self-discharge. Capacity fade occurs naturally with use and time; resistance increase is common with nickel-based batteries; and elevated self-discharge reflects possible stresses endured in the field. Capacity loss can often be reversed with NiCd and NiMH; lead acid with sulfation can sometimes also be improved.
Battery defects include low capacity, high internal resistance and elevated self-discharge. Capacity fade occurs naturally with use and time; resistance increase is common with nickel-based batteries; and elevated self-discharge reflects stress. Capacity loss can be reversed on nickel-based batteries affected by memory; some lead acid with sulfation can also be improved.
Batteries can be classified into portable, wheeled mobility, starter and stationary systems. Not all batteries are worth servicing but there are jewels among the rubbish. To turn a profit, some basic battery knowledge will be needed, such as familiarity with chemistries and understanding voltage, Ah, charge methods and C-rate. Above all, you must have a knack to spot what to touch and what to pass. Knowing the former life and how the end-of-battery life is determined will play a large role in how well these discarded batteries can be redeployed.
Store clerks replace mobile phone batteries on the slightest customer complaint without testing the pack. Installing a new battery satisfies the customer but this often does not solve the perceived problem of short runtime and the customer may return. There are also batteries that go to sleep due to over-discharge. These seemingly dead lithium-ion packs cannot be recharged with a regular charger but there is a way to boost them back to life. (See BU-808a, How to Awaken Sleeping Li-ion)
Many mobile phone batteries are discarded. They fill large boxes under service counters with nowhere to go. Meanwhile, service providers have discovered that nine out of ten replaced packs are good and can be restored. A recent study estimates the cost of frivolous battery replacement to over $650 million per year in the USA alone.
Ingenious entrepreneurs have discovered an opportunity to re-circulate these abandoned batteries. Service centers sprung up in the USA, UK and Israel that purchase surplus batteries by the ton and check them with battery analyzers capable of performing rapid-testing. (See BU-907: Testing Lithium-based Batteries.) Some service centers handle as many as 400,000 batteries per month and the refurbished packs are redistributed as B-grade to stores. Studies show that these B-grade batteries perform as well as a new pack as there is no reported difference in the failure rate.
Not all smartphones allow battery replacement, but this does not eliminate the need to test them. Not being able to replace the batteries has affected the business model as there are fewer available packs to test and recirculate.
Healthcare is a large user of portable batteries. In the absence of battery maintenance, device manufacturers recommend replacing the packs according to a date-stamp. This helps rotate inventory but it adds an unnecessary time restrictions as battery-wear is mostly attributed to usage and less on idle time. A heavily used battery could fail within the allotted date-stamp period and to compensate for this eventuality, device manufacturers mandate a tight replacement policy of 2–3-years. Fabrication-to-destination can cause delays and a battery could be one year old when it enters service.
Batteries have improved and live longer; they also carry a higher price tag. Lead and nickel-based batteries are good for about three-years of service, Li-ion typically last for five years. (See BU-501: Basics About Discharging.)
Under-usage is more common in healthcare that over-usage and this leads to discarding a large pool of good batteries. A manager of the Energy Storage Research Program at DOE visited a recycling plant in the USA and discovered that “every year roughly one million usable lithium-ion batteries are sent in for recycling with most having a capacity of up to 80 percent.” A medical technician in a large USA hospital in Michigan reuses spent batteries from patient heart pumps to cut the grass at home with his electric lawn mower. This makes green energy even greener.
Biomedical Technicians are aware of frivolous battery replacements and a whistle-blower at a mid-sized US hospital said: “Batteries are the most abused components in hospitals. Staff care little about them and only do the bare minimum. Recommendations for battery maintenance are vague and hidden deep inside service manuals.”
Restoring spent batteries lends itself to several business models. One is collecting and testing batteries from organizations that would otherwise discard them. The in-house analysis includes checking the capacity by applying a full discharge/charge cycle with suitable battery test equipment. Capacity is the leading health indicator and should read between 80 and 100 percent. Lower thresholds may be acceptable for less critical applications.
When testing a battery pack, also observe the internal resistance. The resistance of lead and lithium-based batteries stays low until the end of life. Although an ohmic reading cannot predict the capacity, a high measurement could indicate anomalies, such as corrosion.
Battery validation should also include a self-discharge test by observing the voltage loss of a fully charged battery over 24 hours or longer. A stable voltage assures that the cell or pack had not been undue stress. A voltage difference of +/-5mV per cell after 24 hours is a go. If all requirements are met, the battery can be re-certified and sold at reduced cost.
A smart battery may not only fail because of capacity fade but by a deliberate end-of-life setting. This can be a set cycle count, calendar date, exceeding the Max Error level on a SMBus pack or inability to communicate. Such errors cannot be corrected digitally but the cells may still be good. Salvage involves cracking the pack open and utilizing the naked cells.
The cells can be checked individually or left intact as a family by observing capacity, internal resistance and self-discharge. When building a pack, pay attention to cell matching. Only use cells of the same model number and equal performance to build a pack. It is not recommended to utilize cells that were designated for single-cell use for multi-cell packs as the performance may vary. (See also BU-910: How to Repair a Battery Pack.)
Batteries made for the electric powertrain are designed to last longer than those in consumer products. Experts predict that these rugged industrial batteries should still have up to 70 percent capacity after 10 years of service or 160,000km (1000,000 miles) of driving on electric propulsion. (See BU-1002: Electric Powertrain, HEV, PHEV.) If such a long life can be expected, then it will make sense to test and re-purposing the batteries for a less demanding application. Several companies, including GM and ABB, are taking advantage of this business opportunity.
Large-scale batteries are divided into smaller modules that are connected in series and parallel. These units do not need cell-level checking but must meet state-of-health requirements as a module that includes capacity, internal resistance and self-discharge. Modules with similar performance levels can then be grouped together and used for solar and other systems. (See BU-901: Difficulties with Testing Batteries.)
Also known as starter, lighting ignition (SLI), these batteries are commonly checked with a load test or a device that reads CCA (cold cranking amp). A battery that cranks can be sold for money but a CCA measurement alone does not reveal the capacity, the leading health indicator. CCA refers to the internal resistance that stays low through most of the battery’s life while capacity gradually fades with use and time. A battery that is only tested with CCA is a gamble, adding capacity measurement commands a higher resale value. (See BU-904: How to Measure Capacity.)
Stationary batteries are mostly lead acid. There is no easy way to test the capacity other than applying a full discharge/charge. These batteries are commonly replaced after 5–10 years of service; more frequently in hot climates. (See BU-806a: How Heat and Loading affect Battery Life.) Battery failures tend to be permanent, but sulfation–related failures can be corrected if caught in time. Sulfation often occurs on a solar system when the battery never receives a fully saturated charge. This is also common on electric wheelchairs that may only get an eight-hour charge overnight.
Adding additives to fix a faded lead acid battery is often not worth the effort. The active materials of an old battery are exhausted and the plates are corroded. (More on BU-804a: Corrosion, Shedding and Internal short.) Guys who claim success in restoring these old-timers echo what Thomas Edison said: “Just as soon as a man gets working on the secondary battery, it brings out his latent capacity for lying.” As with all products, the importance of reducing waste is in respecting battery, caring for them, and only discarding them after their useful life has been spent and no salvage is possible.
Last updated 2016-01-17
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