Every type of VRLA battery will list a ‘design life’ on the Battery Specifications sheet. Design life can range from 8 years for a standard AGM battery or 20 years for a top-of-the-line Gel battery.
But does the design life refer to how long your battery will actually last? And what can you do to ensure you get the maximum service life from your batteries?
At Valen, we get asked these types of questions quite often. So in this blog post, we’ll explain design life and take a look at the factors that affect how many years you’ll get out of your batteries.
Firstly, what is design life?
The design life of a battery is determined through testing to a controlled environment. This controlled environment allows for optimal battery performance within a set temperature range and certain environmental factors. Full battery design life and the controlled environment range are usually listed on the Manufacturer Specifications (example shown below).
It’s important to note that the stated design life is not the guaranteed life expectancy of the battery. The actual life expectancy of a battery is determined by many factors including operating environment, temperature, maintenance and the number of discharge cycles.
So just because your battery has a design life of 8 years, you may only get 5 years of service life from it if the battery is over discharged repeatedly or not maintained correctly.
Let’s take a closer look at some of the factors that influence actual battery life expectancy.
Environment and Temperature
All types of batteries should ideally be stored in a secure, well ventilated box or storage space to ensure safety. Ventilation is especially required for VRLA batteries to minimise battery temperature variations and to reduce the build-up of potentially explosive hydrogen gas.
Operating temperature has a massive impact on a battery’s performance and life expectancy. In fact, every 8°C rise in ambient temperature above the recommended normal operating temperature will halve the design life of a battery.
For example, a VRLA battery with a design life of 10 years with a normal operating temperature of 25°C would only last for 5 years if placed in an operating environment of 33°C.
Storing batteries beyond their recommended temperatures for storage or usage, without charging, can further result in cell shorting, loss of capacity and loss of life.
Proper maintenance will ensure that your batteries are being correctly used, installed and will function immediately when needed. If you avoid conducting regular preventive maintenance, your battery will more than likely fail long before its specified design life.
General maintenance of the battery means keeping the battery and surrounding area clean and dry. VRLA batteries don’t require the addition of water or specific gravity checks for the life of the battery. The only required annual maintenance action is the re-torque of the battery connections.
Maintenance on your batteries should be conducted twice per year. The following should be recorded:
- Block float voltages
- String voltage
- Float current
- Ambient temperature
- Battery temperature
- Battery conditions
- String impedance cell/bloc
- Any unusual charges or discharges within the last 6 months.
Finally, always remember to ensure you use the correct testing equipment based on your battery technology, size and application.
Number of Discharge Cycles
Every battery technology can handle a specific number of cycles. A cycle is the process of charging and discharging a battery as required by the load.
The number of cycles for a rechargeable battery is specified with the design life. This indicates how many times it can undergo the process of complete charging and discharging until failure or its nominal capacity falls below 80% of its initial rated capacity.
Cycle life depends on the Depth of Discharge (DoD) and assumes that the battery is fully charged and discharged each cycle. If the battery is only partially discharged each cycle, then your battery will actually last for longer than the stated design life.
Average Number of Discharge Cycles by Battery Technology Type
|Lithium Phosphate Batteries|
|110 Heavy Cycles||400 Heavy Cycles||2000 Heavy Cycles|
Need further advice on battery design life?
The team at Valen are happy to answer your questions about design life and discuss ways you can get the maximum life expectancy possible from your batteries. If you’d like more information, please click here to get in touch with our expert team.