Did connectivity sunsetting kill your embedded-system battery?

July 18, 2025

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Did connectivity sunsetting kill your embedded-system battery?

You’re doubtless acquainted with the idea of “sunsetting,” the place a connectivity normal or utility is scheduled to be phased out, such that customers who depend upon it are sometimes merely “out of luck.” It’s irritating, as it may render a longtime working system that’s doing its job correctly both partially or completely ineffective. The business usually rationalizes sunsetting as an inevitable consequence of the progress and new requirements not solely superseding previous ones however making them out of date.

Sunsetting can depart unintended or unknowing victims, nevertheless it goes far past simply lack of connectivity, and I’m talking from current expertise. My 2019 ICE Subaru Outback wouldn’t begin regardless of its pretty new battery; it was completely lifeless as if the battery was lacking. I jumped the battery and recharged it by operating the automobile for about half-hour, nevertheless it was lifeless once more the following morning. I assumed it was both a faulty charging system or a low- or medium-resistance brief circuit someplace.

(As an added punch to the intestine, with the battery lifeless, there was no solution to electronically unlock the doorways or get to the inner hood launch, so it appeared it must be towed. Luckily, the digital key fob has a tiny “secret” steel key that can be utilized in its old style, back-up mechanical door lock only for such conditions.)

I jump-started it once more and drove on to the seller, who verified the battery and charging system have been good. Then the service technician pulled a technical rabbit out of his hat—apparently, this downside was no shock to the service staff.

The vampire (drain) did it—however not the standard method

The explanation for the battery being drained is delicate however completely avoidable. It was an aggravated case of parasitic battery drain (typically known as “vampire drain” or “standby energy”; I want the previous) the place the numerous small features within the automobile nonetheless drain a number of milliamps every as their keep-alive present. The combination vampire energy drawn by the numerous features within the automobile, even when the automobile is purportedly “off,” can kill the battery.

Subaru used 3G connectivity to hyperlink the automobile to their primary Starlink Security and Safety emergency system, a free function even in case you don’t pay for its many add-on subscription features (I don’t). Nevertheless, 3G mobile service is being phased out or “sunsetted” in business parlance. Regardless of this sunsetting, the automobile’s 3G transponder, formally known as a Telematics Knowledge Communication Module (TDCM or DCM), simply stored attempting, thus killing the battery.

The seller was apologetic and changed the 3G unit for gratis with a 4G-compatible unit that they conveniently had in inventory. I think they have been ready for this incidence all alongside and have been hoping to maintain it quiet. There have been some class-action fits and settlements on this problem, however the submitting deadline had handed, so I used to be out of luck on that.

An open-market alternative DCM unit is on the market for round $500. Whereas the seller pays much less, it’s nonetheless not low cost, and swapping them is difficult and time-consuming. It takes a minimum of an hour for bodily entry, setup, software program initialization, and check-out—if you understand what you might be doing. There are lots of caveats within the 12-page instruction DCM part for removing and alternative of the module (Determine 1) in addition to within the companion 14-page information for the choice Knowledge Communication Module (DCM) Bypass Field (Determine 2), which particulars some tough wire-harness “fixing.”
Determine 1 The offending unit is behind the console (dashboard) and takes a while to take away after which exchange. Supply: Subaru through NHTSA

Determine 2 There are additionally some cable and connector problems with which the service technician should be conscious and use care. Supply: Subaru through NHTSA

Whereas automakers impose strict limits on the related standby drain present for every perform, it nonetheless provides up and might kill the battery of a automobile parked and unused for wherever from a number of days to a month. The interval relies on the magnitude of the drain and the battery’s situation. I strongly suspect that the 3G hyperlink transponder makes use of much more energy than any of the opposite features, so it’s a extra worrisome vampire.

Sunsetting + vampire drain = hassle

What’s the issue right here? Though 3G was being sunsetted, that was not the true downside; discontinuing a regular is inevitable sooner or later. Additional, there may be many different causes for not having the ability to join, even when 3G was nonetheless out there, corresponding to being parked in a concrete storage. In any case, each short- and long-term hyperlink issues ought to be anticipated.

No, the issue is a short-sighted design that allowed a secondary, non-core perform over which you may have little or no management (right here, the viability of the hyperlink) to turn into a precedence and single-handedly drain energy and deplete the battery. Take into account that the automobile is completely secure to make use of with out this connectivity function being out there.

There’s no message to the automobile’s proprietor that one thing is unsuitable; it simply retains chugging away, making an attempt to meet its mission, no matter the truth that it depletes the automobile’s battery. It has a mission goal and nothing will cease it from attempting to finish it, considerably just like the relentless title character within the basic 1984 movie The Terminator.

A correctly vetted design would come with a path that claims if connectivity is misplaced for any purpose, preserve attempting for some time after which go to a a lot decrease checking price, and maybe ultimately cease.

This embedded design downside is not only a difficulty for automobiles. What if the 3G or different hyperlink was a part of a hard-to-reach, long-term data-collection system that was periodically reporting, but in addition had inner reminiscence to retailer the information? Or maybe it was a part of a closed-loop measurement and management that might perform autonomously, no matter reporting performance?

Constantly attempting to attach regardless of the fee in energy is a case of the connectivity tail not solely wagging the core-function canine but in addition beating it to demise. It isn’t a case of an utility going dangerous attributable to compelled “upgrades” resulting in incompatibilities (you in all probability have your individual record of such tales). As an alternative, it’s a design oversight of permitting a secondary, non-core perform to take over the ability funds (in some circumstances, additionally the CPU), thus disabling all of the performance.

Have you ever ever been concerned with a design the place a non-critical perform was inadvertently allowed to demand and get extreme system assets? Have you ever ever been concerned with a debug problem or product-design evaluate the place this disagreeable truth had initially been missed, however was caught in time?

No matter occurs, I’ll preserve checking to see how lengthy 4G is on the market in my space. The assorted business “consultants” say 10 to fifteen years, however these consultants are sometimes unsuitable! Will 4G connectivity sundown earlier than my automobile does? Abd if it does, will the automobile’s module preserve attempting to attach and, as soon as once more, kill the battery? That is still to be seen!

Invoice Schweber is an EE who has written three textbooks, lots of of technical articles, opinion columns, and product options.

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