Contributed Commentary By Ilyas Ayub, Inventus Power
August 27, 2018 | Let’s be clear, the Lead-Acid (Pb) battery is still the mainstay of many battery applications such as starting your car, backing up a server-farm or telephone system, maintaining an alarm system – the list is long. But Lithium-ion (Li-ion), the mainstay for portable devices, such as cell phones and laptops, is continuing to expand into new markets and applications – even those where Pb is king.
Pb offers many advantages for non-portable devices where size or weight are not critical factors. While it has low energy density, it features great power density at a very low cost. However, the maintenance and replacement costs of Pb are starting to become a hindrance to Pb’s continued dominance.
Lithium is more than twice the cost of Pb, but it has improved power capability and low-maintenance such that is has become more popular for in-rack backup for server functions such as memory storage. The reduced space, better heat tolerance, and high-power discharge capability out-weigh the added costs in mission critical computing uses. Additionally, due to the recent push for electric vehicles around the world, the price point for Li-ion is starting to decrease.
For low-cost, but critical applications, such as starting your car, Pb-Acid will certainly remain the battery of choice. Sealed Lead-Acid (SLA) or Valve-Regulated Lead-Acid (VRLA) still command the majority of server and telecom backup systems along with flooded Lead-Acid, which can last up to 20 years when properly maintained.
As more devices become portable via the continued advancement of low-power electronics, Li-ion will continue to enable new applications. For truly portable devices, Li-ion has ruled for laptops and cell phones for many years, but is now expanding into “larger” portable devices such as lawn and garden tools. Soon enough, Li-ion will be seen more within the outdoor power equipment segment that includes mowers, chain-saws, etc.
Why Is Li-ion Continuing To Expand Into New Market Applications?
Li-ion enables new opportunities due to its benefits such as low weight, high energy and high power density. Just 10 years ago, the power tool market was dominated by Nickel-Cadmium (NiCd) batteries due to low cost and high-power delivery. Li-ion was a very expensive alternative such that many thought it would never be viable for power tools—particularly ones at consumer price points. But Li-ion enabled a new type of power tool: one which took advantage of a more efficient and more powerful motor at a higher voltage. Previous NiCd designs did not exceed 18V due to the weight of the battery, but Li-ion enabled 36V (and now higher) designs. Higher motor voltages are more efficient and more powerful such that now portable power tools could do things previously reserved for only plug-in AC-powered tools. DeWalt 36V and Milwaukee 28V started the trend which has continued to even higher voltages and more capable devices.
A similar trend is occurring with Li-ion in mid-size Pb-Acid “motive” applications. The 48V limit of Pb in small motive utility vehicles is no longer a constraint. Li can easily achieve 60V and 72V to enable smaller, more efficient electric-drive utility vehicles from floor cleaners to excavators. This may expand further into the material handling fork-lift market which already has Li-ion replacement options for 24V, 36V, and 48V Pb-acid batteries, but can provide even more benefit for lift-trucks designed around Li-ion’s size, weight, power & energy benefits. Additionally, Li-ion provides an option for much faster charging which can improve up-time utilization of lift-truck vehicle operations.
In “stationary” battery applications—server, telecom, or similar backup systems—Pb-Acid maintains a large presence that will remain dominant. Large installations of flooded Pb battery systems often last 20 years with regular maintenance. But these large uninterruptible power systems (UPS) do require space and continual monitoring to maintain their backup capability which can last from a few minutes (until a fuel-powered generator can start-up) or a few hours (for a telecom system). Often such heavy batteries have limitations in where they can be located and mounted due to their weight and risk of spillage or leakage. New fire regulations also limit their location in mixed use buildings.
The benefit of these large systems is that they provide backup for all the equipment in the building. However, the drawback is that only a portion of the equipment may need full backup. For example, in a server environment, it may make sense to only provide power for the memory systems to finish storing the last transactions and operational state and then shut-down gracefully – often in less than a few minutes. The battery requirement for such a backup would be reduced and could be easily co-located with the equipment it serves. Li-ion is particularly well suited for this use due to its high energy density, low weight, long life, and better tolerance of warmer temperatures than Pb-acid.
Pb-acid has a huge advantage in recyclability – almost 98% of all Pb-Acid batteries are fully recyclable. You cannot buy a replacement car battery without returning your old one. The same is true for the larger Pb batteries in fork-lifts, uninterruptible power supplies (UPS) and telecom backup. And the other benefit is that the industry has the infrastructure to support the return and recycling of Pb, whereas Li-ion is just starting to develop such a system.
While Li-ion has a 3 to 5x life advantage over certain types of Pb batteries, it will still need to be replaced and returned or recycled. The industry is addressing this need, but it remains in its infancy. The added feature of Li-ion degradation is that an “old” battery still has 70 to 80% of its original capacity which could be re-purposed for a different application – i.e. an electric vehicle battery could easily be re-used as a back-up power system.
So, What’s The Verdict?
Lead is not dead. Pb-Acid is still the king for many applications – there are still more Pb batteries sold than any other type – by dollars or unit volume. But Lithium is getting better, cheaper, and more cost-effective for many applications that previously were considered “out of reach” for Li-ion.
As Senior Director of Application and Project Engineering at Inventus Power, Ilyas Ayub is responsible for new product development for batteries, chargers and power supplies. He has over 12 years of power electronics experience including battery development and power control modules from companies such as Baxter and Motorola. Mr. Ayub holds a master’s degree in electrical engineering and bachelor’s degree in computer engineering from the University of Illinois Champaign-Urbana and holds several patents. He can be reached at IAyub@inventuspower.com.