Battery is the most misunderstood product. Its performance is judged by its electrical parameters, where as it lies in its electro-chemistry. Judging a battery by its discharge current or its end cell voltage is a mistake and results in millions of batteries being replaced or junked, causing a massive financial and environmental impact.
Proper understanding of the battery behaviour and timely implementation of remedial measures can avoid millions of batteries getting scrapped and avoid environmental damage. The current new sale vs. replacement ratio for industrial/ domestic/UPS batteries is 60:40, that means a large chunk of supplies go towards replacement market is proportional stress on the environment. Replacement decisions are devoid of environmental and economic prudence.
Research shows that 90 per cent batteries get replaced due to capacity degradation caused by suphation of its plates. Battery plates are prone to hard lead sulphate crystal deposits, increasing its internal resistance, is the cause of sudden shut down of your backup system.
These sulphate deposits can be treated electronically with high frequency low energy pulses riding over the charging current. The sulphate deposits are forced to detach from the plates and dissolve back in the electrolyte, slowly recovering the battery capacity back to original. If this regeneration process is adopted by the industry a major cause of environmental degradation is avoided.
Even a partially sulphated battery is bad for any application. Increased internal resistance of a battery increases energy losses by square of the charging/discharging currents, is a dormant burden. Identifying and treating a sulphated battery at an early stage is ideal and promises a much longer battery life.
An individual sick battery in a battery bank infects other batteries in a battery bank by interfering in the charge discharge cycle. Timely identification of the sick cell is the key to avoid a complete shutdown and a hectic decision to replace the entire set. While battery suppliers limit their scope to the warranty clause and UPS or charger vendors do not generally cover the battery in AMC. Routine battery maintenance ensures a much longer service life. Like an old saying, “stich in time, saves nine”.
Prevention is a good cure
- Use of battery management systems to keep a watch on battery cell performance under charge and discharge cycles. Battery end cell voltage and Temperature parameters are logged. Minute changes in the battery behaviour are logged or reported. Alarm Thresholds are user defined.
- Do not install batteries in high temperature environment.
- While installing a new battery set, do at least two charge – discharge cycles. Ensure individual cell voltages in the Battery Bank remains within 0.05 volt during charge and discharge cycles. Ensure that cells belong to the same batch of manufacture and have same IR.
- Give cooling delay between charge and discharge tests. Ensure full battery capacity recovery. Monitor temperature of individual cells. A heated cell/battery indicates higher IR.
- Repeat a full charge – discharge – charge cycle every six months followed. Find out cells that are differing from their original voltage levels.
- Plan for a scheduled battery test and locate the weaker cell for treatment.
- Using the battery beyond its discharge rating has a damaging effect, with temperature rising square times the discharge current.
- In solar, high temperature, applications use only flooded tubular batteries. They can last up to 20 years if maintained well.
A few applications which heavily depend upon battery
Fork Lifts
Fork lifts run purely on battery power, it’s a cyclic application i.e. the batteries have on an average a 24-hour charge/discharge cycle and are highly investment intensive. Average battery life recovered from a given battery set is 3 years against a design life of over 12 years. Batteries often remain idle for a long time and suffer misuse. Timely corrective intervention can increase its life. A typical 48V, 300 Ah battery bank costs Rs. 1 lakh if replaced after three years the service life vs capital cost is Rs. 33,000.00 per annum. Assuming that the regeneration process is adopted by the user @ 35 per cent of the capital cost and achieved 5 years’ service life. Thus, the service life vs capital cost comes to Rs. 27,000.00 or less, add interest on the postponed repurchase capital investment, is a win-win case. A long-term approach to battery health management simply prevents investment pressure and generation of hazardous waste.
Telecom
Battery regeneration is akin to health insurance for humans. Early detection and or prevention saves cost saves life. Service industries carrying performance pressure need to be convinced about the need for a proactive preventive maintenance for the batteries. It is wrong to assume that the maintenance free batteries need no maintenance. Scientific studies suggest otherwise.
UPS Systems
UPS is a typical service critical item, installed by various users in various environments. It is a known fact that batteries installed in air-conditioned environments last longer and as much as 8 years, and even this can be extended as under cooler environs, the battery aging process is slowed down. Batteries are not dehydrated. If subjected to routine maintenance can lead to meeting its design life of 10 years.
Design Life
Battery life also needs to be viewed in terms of its design life and is often proportional to the warranty period offered by the manufacturer. Ni-Cd batteries are known for their long service life, but not in a maintenance-free regime. If maintained well, one can expect service life of more than 20 years. Similarly lead acid flooded tubular 2V cells bear a design life of 20 years, and sealed lead acid maintenance free batteries 8 -10 years.
Battery chemistry is extremely sensitive to changes in temperature, humidity, discharge derating and charging voltage and current limitations. Other than end cell voltage, internal resistance of the battery is the key indicator of its health and it varies with temperature and charge conditions. A new battery has IR or the order of a few milliohm where as an old sulphated battery have IR greater than 30 milli-ohm. Higher IR means higher losses and greater chances of battery failure.
Case Studies
A number of case studies indicate that the batteries, lifted from the junkyard were treated for de-sulphation and fitted back into the same application. De-sulphation is not a new idea. Researchers all over the world were working on discovering the most efficient ways to de-sulphate the battery for the past 50 years. Now that some international companies have commercialised and patented their technologies, the idea of battery life extension is gathering acceptability.
Author
Ajay Sabharwal, Director
Everon Energy Systems Pvt. Ltd.
Email: asabharwal@everon.in
www.everon.in
