Best practice IQC for LiPo batteries?

[raj-thomas]

Hi all,

My company develop a device which uses a 3.7V LiPo battery as a power source. We currently source it through our contract manufacturer but we've seen a few failures in use, and so we want to get them to do some more IQC on the parts when they're delivered from the sub-supplier.

The only problem is that I'm a mechanical engineer, not a battery specialist - so I have no idea about best practice for things like this! Could someone point me to the kind of tests that are available in this sort of situation, and the best practice for IQC of such parts?

Any more information required, please let me know - but for context we are manufacturing in China and using about 20k of these per year.

Thanks in advance!

 

[Miner]

You said that you see failures "in use." Do these failures occur in the field after the product has been used for a period of time? Would these even be detectable at IQC? My initial feel based on your wording is that you have a reliability issue that must be addressed through design and the supplier, and that IQC will be of little benefit.

Added: I do see that there are storage requirements for temperature and humidity. You could require that the supplier add max temperature indicators and humidity indicators if you feel they are warranted then check for that at IQC.

 

[raj-thomas]

Hi Miner thanks for your quick reply. In answer to your question, the definition of "in use" varies - sometimes we see failures straight out of the box, other times it is after a period of use. Thanks for the suggestion of max temperature and humidity indicators. I will speak to the supplier about this.

You are definitely correct that a lack of IQC is not the whole reason for these failures; my intention is not to totally fix the issue but rather to make sure that we are not missing some obvious best practice that might help to improve things or detect reliability issues before the parts are assembled. Our supplier is good at making PCBAs but not so experienced with box building, so don't have any expertise in this area, but are willing to accommodate us if we have specific inspection requirements - I'm just trying to establish what these "should" be in an industry standard sense.

 

[Miner]

I would start by analyzing the out-of-box failures for the top defects and see how those may link back to the supplier. I don't know how similar LiPo batteries are to the Lithium Ion batteries, but one of the top failure modes for the latter was mechanical damage. You mentioned box building. Is mechanical damage one of the out-of-box failure modes? You can easily inspect for external packaging damage at IQC. You should also do a short-term study on a number of containers by unpacking and inspecting for product damage. It is possible that the internal packing is inadequate to protect product from other product. The supplier may also have inadequate material handling containers at their manufacturing location.