Why Cost Concerns Might Kill Off The Lead-Aid Battery – Even If Green Regulations Do Not
By Svend Culverhouse
EMEA Commercial Solutions Manager, Future Electronics
Read this to find out about:
- The environmental and economic pressures which are stifling demand for lead-acid batteries
- The performance and operating characteristics of the LFP battery chemistry, the favored technology for replacement of lead-acid batteries
- Considerations to take into account when specifying an LFP battery for commercial or industrial applications
Robust, cheap, and offering proven electrical and mechanical characteristics, rechargeable 12V lead-acid batteries are in use today as a back-up power source in tens of thousands of industrial and commercial systems (see Figure 1). The 12V lead-acid battery is also, of course, used to start the engine and back up the electrical system when the engine is turned off in cars and motorbikes. Indeed, the massive economies of scale created by the automotive industry explain both the low unit cost of lead-acid batteries, and their ready availability from commercial suppliers. The components of a lead-acid battery are simple and easily assembled.
Given all these factors in favour of the lead-acid battery, it might seem surprising that designers of industrial and commercial applications are seriously evaluating an alternative rechargeable battery technology. But in fact they have good reason: the prospect of the introduction of new European environmental regulations banning the use of batteries that contain lead is real in markets, such as emergency lighting, which today use lead-acid batteries as a back-up power supply. This coincides with a dramatic fall over the past two years in the cost of battery packs based on the chemistry most likely to replace the lead-acid battery: lithium iron phosphate (LiFePO4), also known as lithium ferrophosphate (LFP).
Fig. 1: a typical centralised power back-up system. These are Borri 100kW IP54 UPS units installed in a UK water treatment works. (Image credit: Borri, from www.borri.it)
In fact, it could be that design considerations will do more to accelerate the adoption of LFP battery packs than the prospect of new regulations: this article draws on experience of real-world installations to show how LFP battery packs offer performance, lifetime and cost advantages in industrial and commercial systems when used in place of lead-acid batteries.
A new regulatory environment
Lead is an extremely harmful element when released to the environment: lead contamination is associated with severely damaging effects on human health, and in particular to the central nervous system. The danger posed by lead in the environment induced governments around the world to ban the use of lead additives in gasoline fuel in the 1990s.
The lead in lead-acid batteries has not yet become the target of legal prohibition: unlike the lead additive in petrol, the lead in a lead-acid battery is not meant to be released into the environment as a consequence of its use. Nevertheless, some lead-acid batteries are bound to escape the proper channels for recycling at the end of their lives. Even for those which are recycled, the extraction of the lead component will often be incomplete. It is inevitable that some of the lead in discarded lead-acid batteries will find its way into the environment, and there is no level of lead contamination that is known to be safe.
For this reason, it is assumed in industry that lead-acid batteries will inevitably and progressively be eliminated by law from various applications.
This view is supported by the signs of progress made by standards-setting body the IEC in developing a technical standard for the use of LFP battery packs in emergency lighting (see Figure 2). The expected ratification of this standard will give the European Union the green light to introduce a ban on lead-acid batteries for back-up power in emergency lighting, since it will be able to mandate an officially validated replacement technology.
Fig. 2: emergency lighting (right) in a hallway in an office block in Aichi, Japan, with normal lighting shown on the left. (Image credit: Darklanlan under Creative Commons licence)
LFP gains most favored status
The lithium iron phosphate chemistry has gained favor because of a combination of electrical and commercial attributes which make it suitable as a replacement for lead-acid batteries. These include:
- Long operating lifetime. While a lead-acid battery might be specified for a lifetime of between one and three years, an LFP battery can last as long as ten years. Allied to this, an LFP battery can tolerate more charge-discharge cycles: up to 3,000 cycles, compared to the typical cycle life of a lead-acid battery of 200-1,000 cycles. Unlike a lead-acid battery, an LFP battery pack requires no maintenance.
- An LFP battery pack copes better with deep discharging: it can be discharged to 20% of capacity without long-term damage. By contrast, most lead-acid batteries lose capacity or cycle life if they are discharged to a state of charge lower than 50%.
- The lithium iron phosphate chemistry offers higher energy density than that of the lead-acid type. For a given energy capacity, therefore, an LFP battery pack will be smaller and lighter than a lead-acid battery.
- An LFP battery contains no lead, which makes it preferable from an environmental point of view.
It is also important to note that the LiFePO4 chemistry is different from that used to make the lithium-ion batteries in consumer devices such as laptop computers and smartphones. Unlike these consumer batteries LiFePO4 has markedly less risk of thermal run-away. With the application of mandatory protection circuitry to prevent conditions such as over-temperature, over-current or over-voltage, the LiFePO4 chemistry is safe for use in industrial or commercial equipment.
An LFP battery pack, which supplies a nominal 3.2V output when fully charged, is best suited to a Constant Current/Constant Voltage (CC/CV) cycling regime which maintains a 100% state of charge – a charging method which is compatible with use as a back-up power supply. LiFePO4 cells are typically supplied in a standard 26650 or 18650 cylinder format: a battery pack consists of multiple cells alongside protection circuitry and a battery management system on a PCB assembled inside an enclosure. Commercial off-the-shelf LiFePO4 battery packs matching the form factor of 12V lead-acid battery products are available.
Competitive total cost of ownership
The prospect of future regulation requiring the elimination of lead-acid batteries from systems such as emergency lighting drives many OEMs to first consider an LFP replacement. But when they compare whole-of-life costs, the commercial advantages of LFP often assume greater importance.
These commercial advantages have emerged over the past two years as the unit price per Watt-hour (Wh) of LFP battery packs has fallen steeply. This is the result of increasing adoption of LFP technology, which has induced LFP cell manufacturers to ramp up automated production lines. Automation has led to a large fall in production costs, while enabling manufacturers to maintain a consistently high level of quality.
The lower initial purchase cost/Wh of an LFP battery pack changes users’ calculation of lifetime costs. In a typical application such as emergency lighting, the service life of the system is often specified as ten years. Over this period, the user could expect to replace a lead-acid battery-based back-up power supply once or twice. But an LFP battery pack, used in place of the lead-acid battery, can be expected to last for the entire ten years of service life without replacement. Unlike the lead-acid battery, the LFP battery also needs no routine inspection and maintenance.
A recent feasibility study carried out by Future Electronics used detailed operating data provided by a customer, a manufacturer of centralised emergency lighting systems. Future Electronics’ calculations revealed that the cost-per-charging-cycle of a back-up power supply based on a lead-acid battery would be between €0.50 and €0.88, including the cost of maintenance and replacement. The cost for the same system with the same energy capacity provided by an LFP battery pack was €0.27 per cycle.
LFP battery implementation issues
While LFP battery packs are available today in a choice of standard formats for drop-in replacement of a 12V lead-acid battery, it is important to note that an LFP’s chemistry means that its use requires some considerations to be taken into account.
Most important, the battery pack needs to be properly protected by fail-safe circuitry ensuring that it is not vulnerable to electrical or thermal abuse. Like any lithium battery type, an LFP battery also requires a correctly regulated CC/CV charging profile and cell balancing. For most OEMs, the surest way to implement a new LFP battery-based power supply is to specify a complete, assembled battery pack, including protection circuitry and a battery management system, from a specialist LFP battery manufacturer such as Grepow or BST Power.
OEMs also need to consider the supply chain through which they will procure their LFP battery. While 12V lead-acid batteries are available from a wide range of non-specialist distributors and even from retail outlets, LFP batteries are produced in much smaller numbers, and supply is limited. A knowledgeable distributor such as Future Electronics, which has a direct franchise relationship with LFP battery pack manufacturers, can provide sound and reliable guidance on important supply-chain issues such as security of supply, lead time, second sourcing and quality.
Finally, lithium batteries are subject to special safety regulations governing transit and storage. Whether an LFP battery pack is shipped by air, land or sea, its owner has to comply with strict labelling, packaging and handling rules. Customers of a distributor such as Future Electronics need pay no attention to these regulations, since compliance is the responsibility of the distributor, not the buyer, until the packs are delivered to the OEM’s premises.
Distribution customers which benefit from a just-in-time supply arrangement such as Future Electronics’ Bonded Inventory Management scheme can even avoid the need for large-scale storage precautions on their own site, since they will only ever be stocking 1-3 days’ worth of inventory.
With the backing of a strong distributor assuring security of supply of high-quality assembled LFP battery packs, manufacturers of industrial and commercial systems can now confidently evaluate the LiFePO4 chemistry as a replacement for lead-acid, and discover the cost and performance benefits to be gained.