As we all know by now, the Samsung Galaxy Note 7 phone has a pretty big design flaw in it that makes the batteries extra-flammable. The phone is totally recalled and permanently off the market now, an expensive debacle for Samsung. But how, one might wonder, does a flaw that big actually escape notice during testing? Was there even testing?

There was, in fact, testing! But as the Wall Street Journal reports, all of Samsung’s battery testing is done in-house, instead of by third party labs, and that may have contributed to the company’s ability to miss the problem.

There are standards for phone battery testing and certification in the U.S. Those standards are maintained by the CTIA, now known as the Wireless Association. Here at Consumerist central we usually hear the name in the context of some piece of lobbying or another lawsuit against the FCC, but as a major industry trade group it actually also does more than that.

In fact, the CTIA certifies certain hardware-spec testing labs for U.S. wireless carriers. Those labs allow “operators and their suppliers” — i.e. anyone who makes the phones — to make sure the lithium ion batteries inside the devices meet IEEE standards, among other things.

The industry created and imposed the program about a decade ago, as cellphones began to proliferate and cheap, poorly-made, knockoff batteries began to hit the market in their wake. That’s bad for everyone — consumers, carriers, manufacturers and brand-holders —

There are many CTIA-certified labs worldwide, with several battery-testing ones across the U.S. and Asia. Any company that wants to have its phone sold by one of the major U.S. carriers needs to test their phone’s battery at one of those certified labs first.

But Samsung, the WSJ reports, only ever tested their Note 7 batteries in their in-house lab. While that lab is CTIA-certified, testing a product in-house obviously has more potential for a conflict of interest to arise — or even for an internal blind spot to simply continue being overlooked — than third-party testing does.

You might assume that having the in-house certified lab do all the testing is standard practice but actually, it’s not quite. Samsung is the only major manufacturer doing 100% of its battery testing in-house, as far as the WSJ could determine.

Apple told the WSJ that it uses third-party CTIA-certified labs to test its batteries. Motorola (Lenovo) and Nokia (Microsoft) have operated their own certified testing labs in the past, the CTIA told the WSJ, but both are closing down.

Motorola told the Journal that it tests its batteries in-house but uses third-party labs additionally to make sure parts get CTIA certification; neither Huawei nor Microsoft provided the WSJ with comment.

Manufacturers like Samsung probably keep as much testing as possible in-house to protect their trade secrets, an expert told the WSJ, which is understandable in a highly competitive market like phone design. But Samsung still hasn’t been able to identify the actual problem inside the Note 7 battery.

With all their continued testing in-house only, there are fewer eyes on the problem — and less shared information out there to prevent others from making the same design mistake. One battery expert who owns a lab told the WSJ he wants Samsung to release details ASAP so everyone else can determine if their own battery testing procedures need to be improved, saying, “They have to tell us what happened so we can fix it.”

Samsung Self-Tested Batteries in Galaxy Note 7 Phone [Wall Street Journal]

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