Questions about UPS Lithium Battery from Reddit
There were many similar questions on Reddit about using Lithium ion batteries for UPS, such as “UPS Lithium Battery suggestion”, “How to replace a UPS lead-acid battery with a UPS Lithium Battery”, “Lithium battery for UPS recommendation” etc. So here we are: the R&D Team of BAK Technologies to the rescue!
What is A UPS Lithium Battery and what is A Lithium Battery UPS
Let’s agree on the following terms: a UPS – is a device. It provides energy when the main power supply fails. Normally the amount of time a UPS can feed your equipment is quite limited. Just in case: UPS stands for Uninterruptible Power Supply.
- A UPS battery – is a part of a UPS. It’s basically the main component besides the IC.
- A lithium Battery UPS – is an UPS that uses Lithium Batteries.
- A UPS Lithium Battery – is a battery that is used in a lithium battery UPS.
What is a Lithium Battery UPS
It’s been a long-long time that UPS systems used lead-acid batteries. In the present days you still can see them everywhere because they are very cheap (there are exceptions, we will talk about them later). In “Top 10 lithium ion battery suppliers in 2024” we showed you how quickly the market of lithium-ion batteries grows. And where there were lead-acid battery UPS systems we more and more often observe implementation of UPS Lithium Batteries.
Today Lithium Battery UPS are used in data centers; to support medical equipment: for telecommunications; home or office backup.
Generally speaking the difference is only in the UPS battery. Instead of lead-acid ones there are lithium-ion batteries. Quite often a UPS battery is made of LiFePO4 due to its safe nature. We will talk about it later.
UPS Lithium Battery Specifications
For quite a long time the main cons of using lithium for UPS batteries was the cost and safety issues. But mainly the cost of the UPS battery. The problem with safety issues was mitigated when production of LiFePO4 batteries reached industrial level. And at the same time UPS lithium batteries became much more affordable for business.
Let’s have a look at Table 1, it will help us to compare a UPS lithium battery with a lead-acid alternative.
| Feature | Lithium-ion UPS Battery | Lead-acid UPS Battery |
| Lifespan | 8-15 years or ~2,000-5,000 charge cycles | 3-5 years or ~200-500 charge cycles |
| Charging Time | 1-2 hours for 100% charge | 8-16 hours for 100% charge |
| Energy Density | ~150-250 Wh/kg | ~30-50 Wh/kg |
| Weight | 30-50% lighter (e.g., 1 kWh battery ~10-15 kg) | Heavier (e.g., 1 kWh battery ~20-30 kg) |
| Maintenance | Low maintenance (typically no maintenance required) | Requires periodic maintenance, such as topping off electrolyte levels |
| Temperature Tolerance | Operates well between -20°C to 60°C (-4°F to 140°F) | Operates best between 0°C to 25°C (32°F to 77°F) |
| Cost (Upfront) | $400-$600 per kWh | $150-$200 per kWh |
| Cost per year range | $26.67 to $75 (based on the lifespan of 8-15 years and upfront cost of $400-$600 per kWh) | $30 to $66.67 (based on the lifespan of 3-5 years and upfront cost of $150-$200 per kWh) |
| Efficiency | 95-98% (less energy loss during charge/discharge) | 80-85% (higher energy loss) |
| Self-discharge Rate | ~2-3% per month | ~5-10% per month |
| Depth of Discharge (DoD) | Up to 80-90% (can use more of the battery capacity) | Typically 50-60% (can’t be deeply discharged often) |
| Safety | Safer with proper Battery Management System (BMS) but can be volatile if damaged | Generally stable, but risk of overheating or leaking electrolyte |
| Environmental Impact | Lower impact (longer life, fewer disposals, recyclable) | Higher impact (toxic materials like lead, more frequent disposals) |
| Applications | High-performance (data centers, hospitals, telecom) | General-purpose, cost-sensitive applications (home, small offices) |
Table 1. UPS lithium battery vs Lead-Acid Battery for UPS
Let’s Look at Those Questions about UPS Batteries from Reddit
Two of them are quite the same in their nature: “UPS Lithium Battery suggestion” and “Lithium battery for UPS recommendation”.
At this point the main quality we would like to mention is the type of UPS battery you should consider. We recommend LiFePO4 UPS batteries (Lithium Iron Phosphate or LFP). If you want to dig deeper in this topic, we already talked a lot about it.
Other potential options are: Lithium Nickel Manganese Cobalt Oxide (NMC) and Lithium Titanate (LTO) batteries. Obviously each UPS battery type has its strong sides and shortcomings. Let’s compare them, here is Table 2.
| Feature | Lithium Iron Phosphate (LiFePO4 or LFP) | Nickel Manganese Cobalt (NMC) | Lithium Titanate (LTO) |
| Average Weight of Batteries per kWh | ~8 kg | ~6 kg | ~11 kg |
| Lifespan (Cycles) | 2,000 to 5,000+ cycles | 1,000 to 2,000 cycles | 10,000 to 20,000+ cycles |
| Longevity in perfect conditions (Years) | 8-15 | 5-10 | 10-20 |
| Estimated Average Lifespan under Suboptimal Conditions (Years) | 6-8 years | 4-6 year | 8-12 years |
| Energy Density | ~90-120 Wh/kg | ~150-200 Wh/kg | ~50-80 Wh/kg |
| Disposal Costs per kWh | $16 – $32 | $30 – $42 | $33 – $55 |
| Disposal Cost per kg | $2 – $4 | $5 – $7 | $3 – $5 |
| Cost per kWh (including disposal) | $416 – $632 | $530 – $842 | $1,033 – $1,555 |
| Cost per year(based on the realistic average lifespans for each battery type) | $52 – $105.33 | $88.33 – $210.50(Higher due to better energy density) | $86.08 – $194.38(High due to advanced technology and longevity) |
| Temperature Tolerance | Excellent (-20°C to 60°C) | Good (0°C to 45°C) | Excellent (-30°C to 55°C) |
| Safety | Very safe, thermally stable, less prone to fire | Good safety, but more sensitive to high temperatures | Extremely safe, very thermally stable |
| Charging Time | 1-2 hours (moderate) | 1-3 hours (faster than LFP but not as fast as LTO) | 30 minutes to 1 hour (fastest charging) |
| Depth of Discharge (DoD) | 80-90% | 80-90% | 90-100% |
| Self-discharge Rate | Low (~2-3% per month) | Moderate (~3-5% per month) | Very low (~1-2% per month) |
| Weight | Moderate | Lighter (higher energy density) | Heaviest |
| Environmental Impact | Lower (safer chemistry, fewer toxic materials) | Higher due to cobalt content | Moderate, though very long lifespan reduces impact |
| Applications | Ideal for UPS systems needing long life and safety (Data centers, hospitals) | Common in high-performance applications requiring compact size | Used in special cases requiring extreme durability and fast charge/discharge (military, advanced industrial) |
| Total | The cheapest | The smallest and most compact | The safest and less demanding |
Table 2. Summary of LifePO4 UPS battery’s qualities vs other types of UPS lithium batteries.
We can roughly estimate the growth of expenses over the period of 24 years for each UPS battery type per kWh. For this model we set the lifespan of batteries 8, 6, and 12 years respectively. The initial cost is estimated based on Table 2, provided above, we also assumed that according to modern trends the cost of lithium batteries will decrease due to improved technologies of production (Plot 1).
It’s obvious that a LiFePO4 UPS battery is the most cost-effective choice. If we make a little step farther, and basing on open data estimate the average energy consumption of an ICU:
- Medical equipment (2-4 kWh per bed per hour),
- Lighting (0.5-1 kWh per bed per hour),
- HVAC (1-2 kWh per bed per hour)
for 300 people per hour, it will sum up to: 1,200kWh to 2,100kWh per hour.
Now let’s have a look at the cost of such energy support to let a healthcare institution survive a 3 hour blackout at this scale. We need to consider DoD (Depth of Discharge) of UPS batteries. For the LiFePO4 UPS and an NMC UPS lithium battery it’s about 90%. Lithium Titanate UPS batteries can be discharged up to 100%.
Also let’s compare it with lead-acid batteries (DoD is 50%). The reference battery cost per kWh we will take from Table 2. Here are our final calculations (Table 3):
| Battery Type | Energy Needed per Hour | Total Energy for 3 Hours (kWh) | Cost per kWh (USD) | DoD (Depth of Discharge) | Final Cost Range (USD) |
| LiFePO4 (LFP) | 1,200 to 2,100 kWh | 3,600 to 6,300 kWh | $416 to $632 | 90% | $1,664,000 to $4,424,000 |
| Nickel Manganese Cobalt (NMC) | $530 to $842 | 90% | $2,120,000 to $5,894,000 | ||
| Lithium Titanate (LTO) | $1,033 to $1,555 | 100% | $3,718,800 to $9,796,500 | ||
| Lead-Acid | $150 to $200 | 50% | $1,080,000 to $2,520,000 |
Table 3. UPS expenses of an ICU estimated to survive a 3 hour blackout.
This estimation clearly shows that at industrial scale none of UPS lithium batteries options can compete with lead-acid UPS batteries due to high cost-efficiency of later ones. Nevertheless there are scenarios where lifepo4 UPS are still relevant even at the industrial scale.
Lithium UPS at Industrial Scale Scenarios
Expensive and limited area
Lithium-ion batteries are smaller and lighter by 50-70%, it plays out when they need to be located at expensive premium areas of modern business buildings, where the floor space and weight capacity are limited. For example Data Centers (owned by Equinix and other giants) have begun adopting LiFePO4 UPS solutions specifically due to these limitations.
Frequent Cycling
Another example is Energy Storages for Microgrids. In renewable energy microgrids (solar power, wind power), the system needs to be charged and discharged daily, sometimes several times a day. If we take a look at Table 1 again, we can see, that cycle life of a lead-acid battery is only 200-500 cycles, where a UPS Lithium Battery can offer 2000 – 5000 cycles (LiFePO4 UPS) or even up to 20000 cycles (LTO UPS Battery). Where LTO can offer a 100 longer life cycle for only x3-4 increase of the price. And we know such examples: Tesla Powerwall systems are used in small-scale microgrids, and residential microgrids.
This example doesn’t describe the “UPS use-case scenario”, but shows how at industrial level other qualities of a powersource become significant for the economy of the project.
UPS Replacement Battery
Replace a Lead-Acid Battery With a UPS LIthium Battery
Hold on! Not all UPS systems are designed to support lithium-ion batteries as a UPS replacement battery. Lead-acid and LiFePO4 batteries have different voltage characteristics, charging requirements, and different discharge profiles. Simply replacing one battery with another one may not work, and in the worst case be dangerous.
What shall I do? First check whether your UPS is a hybrid type and supports lithium batteries.
My UPS supports lithium replacement battery
Some modern UPS can digest both: lead-acid and LiFePO4 UPS batteries. In this case a lithium one can be a good new UPS replacement battery.
If you’re a lucky one, and your system supports lithium UPS batteries, then the next step is to contact the vendor and check the exact specifications for the battery type you want to use as a UPS replacement battery.
My UPS doesn’t support a Lithium Replacement battery
If your UPS doesn’t support it, but you understand a LiFePO4 UPS is what you need, we can offer you our BAKTH-UPS Energy Storage System, 48V, 100Ah, 4800Wh. We believe it’s a powerful and versatile solution, especially when you need a reliable backup.
Use case
This would suit home energy storage, small office setups, or even small industrial applications where moderate energy demand is required during blackouts. And 4.8kWh capacity at 48V is ideal for many backups because it can easily handle power outages for several hours (depending on the load of course).
Charging:
The current (0.2C standard and 1.0C maximum) can do both: standard and fast charging.
Discharging:
Standard DR (0.5C) and Max DR (1.0C) will support your high-power loads continuously.
Conditions:
Yes, a lithium UPS replacement battery can survive in rough conditions (charge 0°C to 55°C, discharge -20°C to 60°C) but it comes at a cost of shorter life span, the longest your battery can last will happen if you take good care and keep it within 20°C to 30°C. Not too hot and not too cold. And your little battery will be happy for a long-long time.
My UPS doesn’t support a Lithium Replacement Battery, but I feel crafty
On the other hand, if you have an old-fashioned UPS, that doesn’t support a Lithium replacement battery, but you are an engineer, you are 100% sure about every little detail of what you are going to do, and safety especially (your safety concerns us the most) remember:
Charging profile differences.
Replace the charger or adjust the charger settings (if possible)? Because lead-acid batteries require a CC/CV profile, and LiFePO4 UPS replacement battery (we assume you are going to use this type) prefers a different voltage cutoff (around 14.6V for a 12V battery).
Battery Management System (BMS)
Just make sure your lithium UPS Replacement battery has a built in BMS, if it doesn’t – get one (even from us – BAK Technologies). And it’s very important to make sure in advance that your UPS and your battery’s BMS are compatible (can properly communicate).
Voltage Differences
Your brand new LiFePO4 UPS replacement battery will normally operate at a higher nominal voltage compared to your old lead-acid battery. Per cell LiFePO4 operates at 3.2V, and lead-acid is around 2V. It means that for a typical 12V system your lithium battery will operate at about 12.8V.
Capacity Matching and Runtime
For Lithium UPS Replacement Battery the DoD is almost twice bigger than for a lead-acid one. Speaking roughly it’s 90% vs 50%, and that’s nice, because you need fewer Ah to achieve the same runtime. Remember to save your money and recalculate the capacity. If your old lead-acid battery had 150-200 Ah, then your new LiFePO4 UPS replacement battery will provide the same runtime with only 100Ah.
Our UPS Lithium Batteries
And if you need some LiFePO4 batteries, here is what BAK TECHNOLOGIES (it’s in caps because we are shouting) has for you!
BAKTH-LiFePO4 12.8V 24Ah, 307.2 Wh
Optimal for 💡
Tailored for compact applications like home electronics backup—WiFi routers, small LED lighting, and low-consumption devices. 🏠 Runtime of this battery excels with lightweight demands, effortlessly powering a 100W device for approximately 3 hours. 🌟 Recommended for low-power devices requiring uninterrupted operation during brief power disruptions. ⚡
BAKTH-LiFePO4 12.8V 54Ah, 691.2 Wh
Optimal for 🔋
Ideal for mid-level UPS applications, including home office environments with laptops, routers, and small monitors. 💼 Runtime: Efficiently supports a 200W device for about 3 to 3.5 hours, offering robust backup for moderate power requirements. ⚙️ Recommended for home offices or critical small systems needing reliable performance during power outages. ⚡
BAKTH-LiFePO4 12.8V 100Ah, 1280 Wh
Ideal for 💼
Engineered for substantial UPS applications—computers, security systems, and medical equipment. 🔋 Capable of sustaining a 300W load for about 4 hours or a lower load for extended durations. 🚀 We recommend this for home entertainment setups, small server rooms, or office spaces requiring dependable power backup. ⚙️
BAKTH-LiFePO4 48V 30Ah, 1440 Wh
Optimal for 🏭
Designed for industrial or heavy-duty UPS systems demanding elevated voltage and power capacity. ⚡ Perfect for supporting high-wattage equipment, efficiently running a 400W load for approximately 3 to 3.5 hours. 🔧 We recommend for small data centers, telecom infrastructure, or industrial control systems where robust power supply is critical. 🔌