Learn about low-capacity cells, cell matching, balancing, shorted cells and loss of electrolyte.
Battery users and entrepreneurs often ask, “Can batteries be restored?” The answer is: “It depends.” A battery failure does not always mean end of battery life. Rather than discarding a pack, ingenious entrepreneurs are discovering business models to grant retired batteries a second life. Considering the growing number of batteries that are being discarded, such business opportunities can only grow.
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.
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.
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 (100,000 miles) of driving on electric propulsion. If such a long life can be expected, then it will make sense to test and re-purpose 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.
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.
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. 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 8-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. 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 the battery, caring for them, and only discarding them after their useful life has been spent and no salvage is possible.