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Home > Suggestions on designing Lithium battery packs
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- When designing a lithium battery pack for your device, you must have two levels of protection. The primary protection should be from the device for charge and discharge of the battery. The secondary protection is from the battery's protection circuit board which protects batteries from over-charge, over-discharge and short circuit. You must not rely on battery's PCB/PCM protection only. Let's use Lithium-ion cells as an example:
- Primary protection: When designing protection on device, the charge circuit should be cut off at 4.2V/cell and discharge circuit should be cut off at 2.5V -3V/cell (please refer to cell's specification).
- Secondary protection: When designing a protection circuit board (PCB/PCM), the over-charge threshold voltage should not exceed 4.35V/cell and the over-discharge threshold voltage should not below 2.3V/cell.
- Please also consider using a thermistor to monitor the temperature, thermostat to cut off at high temperature and polyswitch to limit the current when necessary.
- Please always check the cell's specification to determine the cut off voltage and charge/discharge current.
- Design of enclosure: The battery should be attached to enclosure firmly. Due to the nature of polymer cell, it might swollen over time. Please leave at least 5mm or 10% more (whichever is bigger) space to allow the cell to expand.
- For medical device, we strongly recommend use brand name cylindrical cell, like LG, Sony, Panasonic and Samsung, 18650 cells.
- Suggest to replace the battery pack once every two years, used or not used.
- Certifications: For Lithium batteries, you will need UN38.3 for shipping, also you might need IEC62133 or UL2054. Those 3 tests need cell to pass UN38.3/IEC62133/UL1642 accordingly first before the packs to get UN38.3/IEC62133/UL2054 test. We suggest you check the following links when selecting cells. If there is any cell meet your requirement, you will save around $10K when you decided to get pack's certification later.
- Batteryspace.com is NOT liable for any mis-use due to using PCB/PCM from other venders.
Updated on 3/3/2016 |
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