Why it is so difficult to answer this simple question: "How many Cycles can I expect from my battery?" There are many factors involved in predicting the cycle life of a battery pack. Cell manufactures usually only provide cycle life under very narrow defined conditions. However, as you may know, rarely are those conditions encountered in real applications of batteries. Visit http://www.epectec.com/batteries/ to learn more about custom battery packs.

1.  DELIVERING QUALITY SINCE 1952.
Why Is It So Difficult To Answer
This Simple Question:
“How Many Cycles Can I Expect From My Battery?”
10.14.15
Special thanks to our strategic partner Texas Instruments for the
charts and graphs contained in the in this presentation.

2. 2
Expected Number of Cycles
 There are many factors involved in predicting cycle life of a
battery pack.
– Chemistry selected/used
– Amount of time the battery is exposed to temperature extremes.
– Average charge state the battery is in.
• Charge voltage
– High discharge and charge rates (localized internal heating)
– Pack design and construction
• High current path routes / cells exposed to same load
• Inner cells and thermal management
– Number of series cells and parallel cells
• Cell balancing

3. 3
Expected Number of Cycles
 Chemistry Selected/Used
– The core chemistry plays a large role in the cycle life of the battery. There
are always tradeoffs, however.
• 20 to 50 cycles, Li-Sulfur
• 300 to 500 cycles, Li-Ion
• 1000 to 3000 cycles, LiFePO4
• 20000 cycles Li-Titanate, Li4Ti5O12

4. 4
Expected Number of Cycles
 Amount of time the battery is exposed to temperature extremes.

5. 5
Expected Number of Cycles
 Charge Voltage Affects Battery Service Life
– The higher the voltage, the higher the initial capacity
– Overcharging shortens battery cycle life

6. 6
Expected Number of Cycles
 Charge Current versus Battery Degradation
– Charge Current:
• Limited to 1C rate to prevent overheating that can accelerate degradation
– Some new cells can handle higher-rate

7. 7
Expected Number of Cycles
 Pack Design and Construction
– High current path routes / cells exposed to same load
– Internal Cells and thermal gradients

8. 8
Expected Number of Cycles
 Series Cells, Full Pack Limited by Cell Imbalance
Cell misbalance can cause significant degradation to battery pack performance and cycle
life
– When the first cell becomes full, charge must stop
– When first cell becomes empty, discharge must stop
– Weak cells will age faster than strong cells
– Weakest cell ultimately limits pack usable energy (weakest link)
– Systematic temperature gradients in the pack weaken cells running at
higher average temperature
– Without balancing, at every cycle the voltage difference between the
weakest and strongest cell increases
– Eventually one cell will always be near the
maximum voltage and another cell near
the minimum voltage => can not
charge or discharge pack

9. 9
Expected Number of Cycles
 Capacitive current redistribution – more
complex implementation, no energy loss.
Low balancing rate. Moderate size
requirements.
 Inductive current redistribution – most
complex implementation, no energy loss.
High balancing rate can be supported.
Highest size requirements
 Current bypass (Passive) – simplest method,
but some energy loss. Both high and low rates
can be implemented. Easy to integrate, small
size and cost.
Cell Balancing

10. 10
 In Summary the primary factors that affect cycle life are:
– Chemistry selected/used
– Amount of time the battery is exposed to
temperature extremes.
– Average charge state the battery is in.
• Charge voltage
– High discharge and charge rates (localized internal heating)
– Pack design and construction
• High current path routes / cells exposed to
same load
• Inner cells and thermal management
– Number of series cells and parallel cells
• Cell balancing
Summary

11. 11
Our Products
Battery Packs Flex & Rigid-Flex PCB’s User Interfaces
Fans & Motors Cable Assemblies Printed Circuit Boards

12. 12
Design Centers & Technical Support
 Battery Pack & Power Management – Denver, CO
 User Interfaces – Largo, FL
 Fans & Motors – Wales, UK
 PCB’s – New Bedford, MA & Shenzhen, China
 Flex & Rigid Flex – Toronto, Canada
 Cable Assemblies – New Bedford, MA
 Our Engineering and Design teams are ready to help
our customers create world class and cost effective
product solutions.

13. 13
Q&A
 Questions?
– Enter any questions you may have
in the Control Panel
– If we don’t have time to get to it, we
will reply via email

14. 14
Thank You
Check out our previous webinars at www.epectec.com.
For more information email sales@epectec.com.
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