What Manufacturing Process Controls Are Important In Battery Factories

Nearly all the electronic products we have worked on include a battery. It is always a critical component since a failure of the battery means a failure of the whole product.

You may think batteries are very standard and mature products. And yet, even if you buy standard size battery packs, there is still a relatively high risk of experiencing quality issues.

In this article, we suggest a few important ways battery manufacturers need to control their processes in order to consistently make good products. (There are, of course, differences between types of battery technology, but the advice here holds true for most modern batteries.)

 

1. Preliminary concepts

You may want to watch an introduction about the reasons why battery manufacturing process control is so important:

 

2. Labeling

It is shocking how often some key inputs to the processes are not properly labeled… or, worse, mislabeled!

When the usual operators are not there, the likelihood of using the wrong material is pretty high, with disastrous consequences.

 

3. Controlled environment

Cell manufacturing is very sensitive to humidity. And extreme temperatures can impact quality all throughout production, as well as during storage of materials and finished goods.

If the factory has no way to control humidity and temperature where it should be kept within certain limits, we highly doubt their ability to make consistently good batteries!

 

4. Preventive maintenance of key equipment

Let’s take an example. When a pump delivers electrolyte into the cells, it is extremely important to ensure the pump works as expected.

If the pump is used until it obviously malfunctions, how many doses were improperly injected before that issue is noticed? That might impact hundreds of cells or more.

Preventive maintenance cannot be skipped on critical equipment.

 

5. Statistical monitoring of key dimensions

When electrodes are coated, is the coating thickness always within an optimal narrow band?

When the materials that will form that coating are mixed, are the amounts of certain solids monitored?

After the mixing and before the coating is applied, are certain properties (e.g. viscosity) checked?

These are a few of the variables that world-class factories follow up very closely, usually with statistical process control tools such as process behavior charts (a.k.a. control charts), capability indices (e.g. Ppk), and others.

 

6. Traceability

If some batteries are found unsafe, the whole batch should be contained (i.e. it has to be put aside and not be shipped to any customer) and the issue should be investigated carefully. That’s when traceability comes into play.

A good traceability system will provide information about what resources (materials, equipment, and people) were used for this batch. It also provides information on the in-process and intermediary records. That is critical information for such an investigation.

A very good traceability system will provide data for the whole batch but also at the individual battery level. It is sometimes available for the pack assembly operations.

 

7. Battery pack assembly

We have seen many instances of improper soldering. Whether it is done manually (with high variation from operator to operator) or automatically (with the risks of poor setting, deviation over time, etc.), it is a common source of issues.

In addition, the design of the packs should make it impossible for certain parts to come in contact (that’s how short-circuits and fires/explosions often happen).

 

8. Finished product testing

This article is about process controls, however, testing the finished products is a very important part of the quality system and it should give feedback to improve process controls. This step is not to be skipped.

We see many factories do a short ageing (a.k.a. burn-in) test. And checking only a few properties (e.g. voltage, capacity…). That might not be sufficient!

Here also statistical tools can be useful. There is usually no need to do in-depth testing on 100% of the pieces, however, a few pieces of each batch should be subjected to a serious reliability & safety testing program.

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These are just some of the ways things can go wrong, but you’ll find that these are the most frequently found sources of quality problems in batteries.


 

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The FAQs section is extremely detailed, including information about cell chemistries, information buyers need from their battery suppliers, how to calculate power supply, battery testing tips, and much, much more!

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Different Types Of Batteries For Electronic Products (Importer’s Guide)

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