Power Distribution and Management

4 Big Benefits of Lithium Ion Batteries for UPS Systems – and 2 Key Challenges

A confluence of events is setting the stage for what may well be dramatic change in a key component of uninterruptible power supply (UPS) technology that really hasn’t changed much for 40 years or more.

I’m referring to the lead acid battery, the energy storage technology used in UPS systems, which remains much the same now as it did decades ago. But as the industry develops new types of batteries for devices ranging from smart phones to electric automobiles, we can clearly see the day when UPSs take advantage of these developments.

It’s coming at a good time, because customers are facing some difficult challenges with respect to UPSs, whether they’re for data centers, critical buildings, industrial processes or critical infrastructure. These challenges are driving the need for specific UPS requirements, including:

  • Reduced UPS footprint and weight to allow for a more effective, flexible use of space
  • Reduced cooling capacity
  • Increased energy storage availability and ability to predict UPS failures
  • Extended UPS life and reduced maintenance overhead

I believe lithium ion (Li-ion) batteries on Wikipedia hold great promise to address all of these challenges and requirements. In this post I’ll explain the four main reasons why.


First, Li-ion batteries provide multiple times the energy and power density as compared to valve-regulated lead-acid batteries (VRLA), which are the most common type currently used in UPS systems. As a result, UPSs built with Li-ion batteries take up only about one-third the space or less of a VRLA-based solution that delivers the same power.

That smaller footprint translates to reduced cooling requirements as well as about a two-thirds reduction in weight, at least. That means customers have more flexibility in terms of where they install the systems and can often avoid costly building modifications.

Li-ion batteries can also withstand a wider temperature range than VRLA batteries. The rule of thumb is that VRLA battery life is reduced by half for every 10°C (18°F) increase above 25°C (77° F) ambient temperature. Li-ion batteries when use at low discharge rate are far less sensitive to temperature fluctuations and can accept spikes in temperature with almost no effect on battery life. For very short run time and high discharge rates like in UPS application the Li-ion are still sensitive to temperature but to a lesser extent.

A third benefit is that Li-ion batteries always come with sophisticated battery monitoring systems (BMS) that provide a clear picture of battery runtime and health. It’s essentially the same technology that enables you to easily see how much battery life is left in your smart phone.

In contrast, VRLA batteries rely on chemistry that makes it hard to accurately predict when they’re going to fail. Think about your car battery: it may crank perfectly fine one day but the next it’s a little chilly and the battery fails, without warning. That won’t happen with Li-ion batteries.

Which leads to the final benefit of Li-ion batteries for UPSs: increased life expectancy. In theory, VRLA batteries used in UPS systems have a life expectancy of 10 years. But due to the constraints around being able to determine their actual health and life expectancy, in practice most customers replace them after 5 or 6 years.

In contrast, Li-ion batteries of the sort best suited for UPSs are expected to last for more than 10 years, reducing the burden and cost of battery replacements, as well as the risks of down time or load interruption during maintenance.

Of course no new technology comes without certain implementation challenges and Li-ion batteries are no different. First is the need to find the type of Li-ion battery that’s best suited for UPS applications. UPS requirements are quite different from those for, say, an electric car battery. Car batteries are designed to store lots of energy so the car can travel as many miles as possible before recharging. With UPS batteries, the concern is not length of run time so much as the need to deliver a lot of power quickly for a short period of time, usually just a few minutes until the backup generators kick in.

For a UPS we’re also not really interested in a battery that can cycle on and off thousands of times, because a UPS kicks in only occasionally. Rather, we need it to be highly reliable and safe, with a long life expectancy.

Secondly, we need a battery that can deliver a lower total cost of ownership (TCO) as compared to VRLA batteries. Li-ion batteries are already competitive on that front. They may cost more up front, but will last about twice as long as VRLA batteries. Li-ion batteries also have a far smaller footprint, which drives down both space and cooling requirements – delivering further cost savings.

I expect the TCO story to get even better in coming months and years, since Li-ion technology is still quite new with respect to UPSs. Prices should fall at a much faster rate than that for the mature VLRA technology.

I’d love to hear your thoughts on Li-ion technology and whether you think it could help address your own UPS challenges and requirements. Please let me know what you think using the comments below.

37 Responses
  1. Ian

    If size and weight is the major factor, yes, Lithium it is. However, VRLA technology is also improving with the advent of additives like carbon that makes it behave like Li-Ion in terms of charge acceptance rate and capacity. The price challenge is VRLA is also being addressed on new manufacturing technology like automation. So maybe we will continue to see the two types of batteries a little longer if VRLA technology continues to evolve.

    • Avatar photo Patrick Brouhon

      Hi Ian, thank you for your comment… Yes I agree, VRLA batteries remain cheaper (in CAPEX), and will continue to evolve, and will stay around in large UPSs for the foreseeable future. Yet, Li-ion batteries are becoming more competitive for customers concerned about the TCO (total cost of ownership), and have more potential for further improvements and optimization.

  2. Luke

    One issue I have seen in the past is the restriction on Li-ion in shipping. They have had several accidents with fire which has caused several shipping entities to not allow you to more than a certain amount. This would become an issue depending on the size and scope of their use.

    • Avatar photo Patrick Brouhon

      Hi Luke thanks for your comment. Yes, there has been some uncertainties and challenges regarding logistics aspects for large Li-ion configurations. My understanding is that new, clearer rules are going to help address those logistics challenges in a structured way. As the end-user benefits are there, I believe this should not prevent or slow adoption.

  3. Hans

    Good article, and I agree that Li-ion is only going to grow more competitive and attractive to UPS users. A couple of things that went through my mind when reading this. The reasoning given is mostly applicable to commercial and light industrial UPS systems. True industrial UPS systems with external batteries are still commonly using flooded lead acid battery technology due mainly to the cost and reliability. Industrial systems do also use 20 year VRLA and NiCad batteries. In the industrial world, the on battery time is more of an issue, with a typical system being required to backup a load for 30 minutes to 8 hours. I don’t think Li-ion will become attractive to anyone in the power generation segment (for UPS applications) for quite some time, as usually there is plenty of space available, and cost and reliability are king. In the oil and gas segment, especially offshore applications, I could see the adoption of Li-ion much sooner, as weight and size is a very large issue. With the recent news of the Tesla Powerpack, the future looks good for Li-ion.

    • Avatar photo Patrick Brouhon

      Hi Hans, thanks for your insights on these industrial segments.

  4. kevin

    It is a good idea for lion-battery, the battery can install in 19″ rack, more power capacity and better BMU, but the key point is the cost, the lion- battery cost is 2x-3x time than lead battery. I hope Schneider can find a balance point for the lion- battery.

    • Martin Winlow

      Sure the up-front cost is cheaper but there is absolutely no doubt that modern Li-based battery technology has a far superior operating life, the best of which are several times as long. In my opinion, UPS makers stick with lead-acid for the same reason people stick with fossil-fuel cars; reluctance to change and relatively low up-front cost. The other huge advantage of li cells is that they do not self discharge. In a UPS situation this is unlikely to be a regular issue as, by definition, they should always be powered by the mains once installed. However, if you do have to un-install them for any significant period of time, lead-acid batteries have a nasty habit of expiring after a few months requiring replacement. Lithium cells – if disconnected – will keep their charge for years.

      • Avatar photo Patrick Brouhon

        Hi Martin, thanks for your note. Yes I agree and that’s the point of this blog, and why we have brought li-ion support on our range of UPS with a very positive market reaction. Initially we target our largest UPS’s but plan to extend the range.

      • Francis ukennah

        Well there are now silicon oxide electrolyte alum and epsom and other additives version that one can consider for cost and performance

  5. Daniel

    Hi Patrick

    Great article! I’ve been curiously following Elon Musk’s ambitions to drive down the Li-Ion cost. Hopefully we will see something happening when his new factory comes online.

    Are there also some environmental benefits of using Li, in terms of raw material production, production of the batteries them selves , EoL disposal and lower auto-discharge? How much could that weigh in on the “pro” side?

    In my experience with Li Batt’s. they are great at holding their charge for extended periods without any significant auto-discharge, but they seem to loose life expectancy when kept fully charged for any extended time (such as the time between typical power events) Would that be a problem in a UPS application or are there already Li-ion types out there, that are more resilient to full-charge storage than those we normally see?

    • Avatar photo Patrick Brouhon

      Hi Daniel, thank you for your interest and insights. From an environmental standpoint, Li-ion batteries do not contain harmful material. Regarding EoL recycling, the industry is still not as mature as for existing professional VRLA batteries for which the vast majority of batteries are recycled today. But this will evolve of course as Li-ion batteries become more popular. Also, we do not expect issues maintaining full charge batteries working with UPS systems.

  6. Rusdy

    “With UPS batteries, the concern is not length of run time so much as the need to deliver a lot of power quickly for a short period of time, usually just a few minutes until the backup generators kick in.”

    Even more reason to use Lithium (high C rate for charge and discharge). My take on this is simply “if it works, why change” within the manufacturer (and market).

    I myself wonder to this date why manufacturer is seems too slow to adopt lithium batteries in UPS. They are far superior, lighter (which reduces logistic cost), etc etc (too numerous benefit which I won’t repeat).

    By using LFP type, the size is not much different either (and safe). It’s a no brainer really.

    That brings to your second challenge, i.e. cost. Most big end-consumer see cost in capital cost, and don’t really much look into the TCO. When the project team handover to operation, see you, bye, move to another project, and let the operation team takes care the maintenance cost.

    Very rarely big companies look the holistic cost, especially when the UPS is just a very small pie of the total project cost. Less incentive from the big users to see the benefit of using lithium.

    Sad news really. Since I really wish big users encourage suppliers to use Lithium as their battery, hence, the benefit trickles down to small consumer, i.e. myself. Lead acid is dead, but the market is too slow to response.

    • Avatar photo Patrick Brouhon

      Hi Rusdy, thanks for your insights. Yes I agree on the many benefits. And I do think there is more of a tendency now for companies, even large ones, to consider full lifecycle cost which will make this technology more attractive and adopted.

    • Francis ukennah

      I dont believe lead acid is dead because they still have some advantage over lithium and with better electrolyte the can cost less and perform better and last longer so they cant be dead after all they ve done for us in the bygone centuries with the added fact that the lithium is still radio active and unstable

      • Avatar photo Patrick Brouhon

        Hi Francis, thanks for your comment. We are not claiming that lead acid technology is dead, and with increased li-ion competition, new ways to improve lead-acid batteries are being proposed. However, benefits of Li-ion are so significant that we see strong interest and a definite shift since this blog was published and we released this solution. Also, all occurring lithium isotopes (6Li and 7Li) are stable from a radiological point of view and are not radioactive. There is no lithium metal in a lithium-ion cell, since all the lithium is present as a lithium salt in a solvent – thereby the name “lithium-ion”.

  7. Andrew

    In terms of safety – Lithium Ion technologies still have a problem with overcharging, which makes them less than ideal for standby or float service applications.
    They are a great technology and show massive potential, but that potential so far hasn’t been tailored to the UPS market.
    In addition, calendar lifespan of Lithium batteries has not yet reached the level of VRLA or NiCad technologies – Roughly 5+ years for Lithium, versus 10-12 for VRLA and up to 25 for NiCad.
    They also have a limited discharge ‘cap’ – roughly 2 x the Nameplate rating – which means they are not ideal for fault clearing downstream of the UPS itself.
    I think – and stress the think – that the major manufacturers have concentrated on the high volume small cell packages – 3 Volt cells – and current larger Lithium Ion blocks are basically stacks of these small cells. That means that the construction properties most valuable in high volume low cost cells are propagated to the larger blocks.



    • Avatar photo Patrick Brouhon

      Hi Andrew . Thank you for your answers and comments. As you point out, Li-ion is a great technology with massive potential, but, until now, has not been the ideal fit to the UPS application. However, (1) as you certainly know, there is not one, but a large number of various technologies and implementations within Li-ion, with very different characteristics and (2) this is precisely what we have been investigating -and what is becoming available: the right cells and system-level implementation for the UPS market.
      In terms of safety, we are considering cells that are aimed for the float application segment, and multiple levels of monitoring are implemented. Regarding lifetime, this heavily depends on the battery chemistry. We are considering technlogies that provide much superior lifetime vs. VRLA (in the order or 2 times better, or more),in similar useage conditions. Fault clearing downstream is always an issue in battery operation – this is due to many factors, but mainly to the design of the inverter in the UPS and less to battery itself. The impedance of the VRLA battery and the Lithium Ion battery are similar for similar sized batteries. Finally, regarding cell sizes, we are considering large prismatic cell from leading vendor(s). This cell size is well suited for large systems, and, in any case, the system level design should and will be suited around the deployment within a UPS environment. Thank you again for your comments!

  8. Rob

    My premise uses avg 95kWh per day. I have 16 x 280 amp hr agm batteries (1180 amp hr) in 48v system with 12,000w inverter – runs (large extended family) household including 2x air con, pool, septic etc all day every day and up to about 9 or 10pm at night when 5 yr old batteries are down to about 55% then cuts over to grid. When the batteries finally do give up i’ll be looking for large cycled storage capacity – maybe 3 or 4 10kw Li batteries or something possibly on commerical scale to run through whole night.

  9. Thomas Fischel

    I was just checking Li replacement batteries for several UPS’s we have in our home. Several are available….seemingly a Direct Replacement for SLA batteries in a UPS, however, at bottom of description it specifically has a Warning: Do Not Charge with a Lead Acid Charger….so, does the On-Board PCB circuit that supposed to protect the Li batteries compensate for that….or just how do we use the Li bats for replacing SLA bats in out current model UPS units?

    • Avatar photo Patrick Brouhon

      Hi Thomas, thanks for your comment. My article refers specifically to large facility-scale UPS, and for those we definitely need to ensure voltage and firmware compatibility for each concerned UPS to support a given type of li-ion batteries (there are many options). For large 3-phase UPS we are coming up with a specific li-ion offer for selected ranges. This is true in general, we do not and cannot support batteries that we have not tested and do not recommend this, there is a number of factors to consider to ensure safe and reliable performance.

  10. Prageeth

    These statements are not true:
    Car batteries are designed to store lots of energy so the car can travel as many miles as possible before recharging. With UPS batteries, the concern is not length of run time so much as the need to deliver a lot of power quickly for a short period of time, usually just a few minutes until the backup generators kick in.

    • Prageeth

      Oops, they are true when you talk about electric automobiles! Sorry!

      • Avatar photo Patrick Brouhon

        Yes Prageeth, exactly that is what I was referring to. Thanks for your interest!

  11. J1mbo

    It seems very difficult to find a small, light, efficient UPS to power a small rack e.g. concentration point for IP CCTV or other small infrastructure requirement. Li-ION seems ideal for this – just a couple of laptop batteries could support 24 cameras and PoE switch for an hour.

    Currently APC still sell the antiquated HS 500 which could surely be replaced with such a product (and I hope a more recent SoC).

    • Kristen Larsen

      Apologies for the delay. We do in fact have a small li-ion UPS, the BG500 ( https://www.apc.com/shop/us/en/products/APC-Back-UPS-Pro-500-Lithium-Ion-UPS/P-BG500?isCurrentSite=true ) , that should be a good fit for this application depending on runtime requirements.

      The BG500 is a 500VA, 300W lithium-ion UPS that is remotely manageable via a web browser. Unique qualities include the “watchdog” feature, which reboots hung networking equipment automatically, and “smart outlets” which are remotely manageable. The UPS sends out an email when it detects a power outage, and the li-ion battery lasts 8 to 10 years (versus the standard 3 to 5 of a lead acid battery).

      Assuming the power consumption of the DVR & cameras are well within 300 watts (rule of thumb typically 75 to 240 watts), the BG500 should be a strong product solution for this application.

      Hope this helps! Thanks for reading our blog and reaching out.

  12. Thomas Scherrer

    Great article,
    I Work with backup systems at the moment, Lead Acid, Li-Ion and LiFePo4 cells are in my experiments.
    I do not like LI-PO since they are just in a thin plastic bag, and connections always a pain to connect to.
    Anyways, you dont address the long time affects by keeping the different LI types, fully charged and ready for action, a typical UPS application would do exactly that,
    some Experts claim LI cells will suffer from this, like higher impedance and lower capacity, how long time, and temperature they dont really reveal, so I have to perform own experiments, takes a long time..

    • Avatar photo Patrick Brouhon

      Thanks Thomas for your comments. Regarding the long term effect of keeping li-ion battery charged, be rested that this is part of the work that we do in terms of battery selection and integration with our UPS battery charging system, to ensure no negative effect on the great lifetime offered by li-ion batteries

  13. Gene

    While I don’t have the technical expertise of most on this forum, as an average consumer looking for a safe and cost effective UPS option my primary concern is safety.
    With phones catching fire, hover boards erupting in flames and my neighbors house near burning down as a result of a lithium ion battery charger in his garage…..well frankly I can’t see using one inside my home yet. I wish I could because I really like the technology. I’m just not there yet.

    • Avatar photo Patrick Brouhon

      Hi Gene, thanks for your message. Be assured this aspect has been a key element of our choice of technology for these lithium batteries, some technologies (chemistries) and systems (battery monitoring…) being a lot safer than others.

  14. Dylan Turner

    Another issue is that unlike a regular lead acid based ups,the ups would have to support an on-board li-on battery safety check system,i use a starter ecig,a kangertek topbox mini,and when it you insert the battery into the mod,it checks for shorts during boot,if it detects it,the the coil is locked by the firmware from firing and it powers down to prevent a fire(aka short circuit protection) also either the battery itself would need the chip that regulates and monitors the energy output to prevent a fire or the ups(lithium ion batteres become electically unstable without the regulation/ monitoring circuitry either installed in the batt. Itself or on the device as without it your its outputing the max energy density/max discharge current beyond what can safely be discharged due to the fact that the li-ion plates are essentially overheating and can melt shorting the + and- plates out)i dont believe a current lead acid based ups would be able do a hot swap with to a lithium ion based chemistry battery (cross compatibility)as it would be a fire hazard/ explosive hazard and would cost too much to design.also the battery would have to prevent water mosture from getting inside as we all know how highly and chemically untable lithium becomes when it mixes with water but would still require a vent incase of a short(the vent would have to prevent water based moisture from getting in while venting any electrolytic gasses should a critical failure/short occure within the batt it self.i do see li-on batteries increasing the runtime and max load due tue its high current output(high drain energy density),i have a ecig high drain 18650 Li-NiMn INR batt with advanced battery chemistry that is rated at 3.7 volts with a max current output of40.6 A,from ohm tech,my mod has a max wattage output of 70 watts,and i keep it on 24 watts min and 30 watts max,residential/ retail ups’s equiped with this tech Would certainly be helpful.

  15. jacob

    Great Article.
    Three more factors to consider when evaluating cost for Lithium vs VRLA.
    1) Labor. Hauling a set of VRLA’s to each rack can be time intensive – network gear isn’t always super accessible. Lithium makes it faster and less frequent.
    2) Depth of Discharge. VRLA’s can be killed by one major discharge below 50% capacity. Lithium units can be fully discharged and still recover
    3) Storage. You can’t store an VRLA without maintaining it. Lithium cells can sit for very long time without significant discharge.

  16. Rochan

    Yes Jacob, I agree with you. But incase lithium pack, they should be away from fire or hot things else it will catch fire very easily. Future is with who have wide scope for improvement that may be batteries or Human beings.