Not all batteries are created equal, even if they sometimes look the same. At BCL Power, we often come across central battery systems fitted with the wrong type of battery. In some cases, it’s a well-meaning attempt to save money. In others, it’s the result of poor advice from non-specialist contractors. Either way, the consequences can be serious: reduced runtime, premature failure, or complete loss of backup during a power outage.
Here, we outline some examples of battery adaptations and errors we’ve seen, and the impacts on wider systems they can cause.
Same Size, Wrong Battery
Although the physical size and terminals are the same, there is a big difference between a regular 12v (5 to 10Ah) battery (typically used for renewable energy or electrical toys) and a High-Rate Performance UPS 12v (5 to 10Ah) battery. This is the same for larger Telecoms batteries.
Appearances can be misleading. UPS batteries are designed for high-rate discharge, specifically to support the demands of a UPS system under load. Swapping it out for a battery that looks the same but isn’t rated for this type of performance will cause major problems, especially during a power outage when you need the UPS to perform.
A Dangerous Shortcut: Car Batteries in Telecoms UPS Central Battery Systems
We’ve even come across telecoms installations where car batteries have been fitted into UPS systems. Whoever installed a setup of this type might have thought it was a clever workaround, but really this kind of mismatch is a ticking time bomb.
Car batteries are engineered for one purpose: to provide a burst of power to start a vehicle, followed by immediate recharging. They’re not designed for deep discharge or sustained load. By contrast, UPS batteries must deliver reliable, continuous power when the mains supply fails, and they need to recover from repeated charge and discharge cycles. Using the wrong type, like a car battery, leads to rapid degradation, limited backup time, and increased risk of failure under pressure.
UPS Battery Mismatches That Lead to Premature Failure, Shutdowns, and Safety Risks
These aren’t rare “one-off” cases; we routinely find UPS systems compromised by improper battery installations, often done by contractors unfamiliar with the strict performance and safety requirements of central battery systems. With the wrong battery in the wrong application, that’s just setting you up to fail.
Some examples include:
Lithium batteries in a legacy UPS without proper BMS (battery management system) integration can open the door to several serious consequences:
- Overcharging and Overdischarging – Legacy UPS charging profiles are designed for lead-acid batteries, not lithium chemistry, which can push cells beyond safe voltage limits.
- Thermal Runaway Risk – Without BMS protection, lithium cells can overheat, leading to venting, fire, or even explosion.
- Unreliable Runtime – The UPS may misread the battery’s state of charge, causing unexpected shutdowns during power loss.
- Accelerated Battery Degradation – Lithium cells age much faster without proper charge balancing and protection controls.
- Warranty Voidance and Compliance Issues – Manufacturers may void warranties, and installations can breach safety regulations or insurance requirements.
Replacing one failed cell in a string with a different model or brand is something that should be avoided, or else risk things like:
- Electrical Imbalance – Cells with different internal resistance, capacity, or voltage curves will charge and discharge unevenly.
- Premature Failure of the Entire String – The weakest or mismatched cell limits overall capacity, causing other cells to overwork and fail sooner.
- Reduced Runtime – The UPS will cut off earlier because the mismatched cell hits its voltage limit first.
- Heat Build-Up in the Mismatched Cell – Higher stress on the odd cell can lead to overheating and potential venting.
- Inaccurate Monitoring & Maintenance Data – Battery monitoring systems may misinterpret the string’s health, masking early warning signs.
- Increased Risk of Sudden Shutdown – One cell dropping out can instantly collapse the string voltage, forcing the UPS offline.
Incompatible batteries in high-temperature environments without thermal design considerations can also have serious negative consequences to your central battery system, including:
- Accelerated Capacity Loss – Every 10 °C rise above the design temperature can halve a battery’s service life.
- Thermal Runaway Risk – Heat buildup can cause uncontrolled chemical reactions, leading to venting, fire, or explosion.
- Severe Voltage Drop Under Load – High heat increases internal resistance, causing the UPS to shut down prematurely during discharge.
- Uneven Cell Ageing – Hot spots within the battery bank cause some cells to degrade faster, leading to imbalance and early failure.
- Increased Maintenance Frequency & Costs – Elevated operating temperatures accelerate failure rates, forcing more frequent replacements.
- Possible Safety & Compliance Breaches – Exceeding the manufacturer’s specified temperature range can void warranties and breach regulatory requirements.
UPS central battery systems exists to protect business continuity instantly. With the wrong battery in the wrong system, you’re risking performance and building in failure from day one.
Why Specialist Knowledge of Central Battery Systems Matters
More than voltage or physical size, choosing the right central battery system is about selecting a solution that suits the application, environment, load profile, and backup time requirements. That’s where BCL Power’s UPS battery professionals come in.
We assess your needs, apply over 30 years of industry expertise, and supply batteries specifically designed for your system, whether that’s VRLA, lithium-ion, or another deep-cycle solution. And we back it up with ongoing UPS maintenance and support to keep your systems compliant, resilient, and ready.
Unsure What’s Powering Your UPS?
If a general contractor has maintained your UPS, or you’re unsure about the batteries currently installed, we strongly recommend a UPS system audit. Our specialist technicians will verify battery suitability, check for signs of degradation, and provide honest, practical advice on next steps.
Get in touch today to arrange a battery check or speak with one of our experts. The right battery is the foundation of reliable backup power.