A few months in the past, spurred into motion by U.S. Home of Representatives passage of laws banning ongoing gross sales of DJI drones (and the still-unclear standing of corresponding laws within the Senate), together with aggressively-priced promotions on latest-generation merchandise (doubtless associated to the aforementioned legislative motion), I made a decision to splurge on an improve to the Mavic Air that I discussed again in October 2021 that I’d lately purchased.
Reality be informed, the Mavic Air was nonetheless holding its personal function set-wise, greater than six years after its January 2018 introduction. It helps, for instance, each entrance and rear collision avoidance and accompanying auto-navigation to dodge objects in its flight path (APAS, the Superior Pilot Help System), together with a downward-directed digital camera to help in takeoff and touchdown.
And its 3-axis gimbal-augmented entrance digital camera shoots video at as much as 4K decision at a 30-fps body fee with a 100-Mbps bitrate.
That every one stated, its diminutive picture sensor results in notable picture high quality shortcomings in low ambient mild settings, for instance. Newer drones additionally prolong collision avoidance capabilities to the edges, together with augmenting standard cameras with LiDAR. And different latest authorities regulatory motion, particulars of which I’ll save for a devoted writeup one other day, has compelled me to buy extra {hardware} so as proceed legally flying the Mavic Air in quite a lot of places, together with needing to formally register it with the FAA per its >249 g weight.
Nonetheless, I plan for the Mavic Air to stay in my aviation steady for a while to come back, alongside its newer sibling, particulars of which I’ll additionally save for a devoted writeup (or few) one other day (or few). In spite of everything, with better weight incessantly additionally comes better wind resistance. And as common readers already know, I’m loath to ditch completely good {hardware}. As such, after urgent “buy” on my new toy, I made a decision to drag the Mavic Air out of storage, mud it off and fireplace it up once more (I’d admittedly barely used it since buying it greater than three years again). On the time I purchased it, I’d additionally bought three factory-refurbished spare batteries (a key addition for lengthy working classes given its ~15 minute per-battery flight time) from a respected eBay supplier.
The unique battery put in within the drone nonetheless held a modicum of cost, I used to be fortunately stunned to see once I fired it up, and it additionally recharged again to “full” simply fantastic. Right here’s what it seems to be like:
Right here’s a closeup of these markings:
See: nonetheless alive!
And right here’s the place it suits within the drone physique cavity:
The three extra batteries, then again (educated readers are already shaking their heads in shared sorrow at this level)…useless as a doornail (or, should you choose, a parrot), all three of ‘em, with no LED illumination by any means in response to entrance button presses. And, for what it’s price, I’m not alone in my woe.
My subsequent analysis (PDF) knowledgeable me that per Battery Storage checklist entry #3, “the battery will enter hibernation mode if depleted and saved for an extended interval…go away the battery unattended for five minutes, after which…recharge the battery to carry it out of hibernation.” Sadly, that didn’t work for me, even after an hour’s price of charger tethering. Which led to Battery Storage checklist entry #2: “DO NOT retailer the battery for an prolonged interval after absolutely discharging it. Doing so could over-discharge the battery and trigger irreparable battery cell injury.” Readers of my latest publish on SLA and lithium-based batteries could also be feeling greater than a little bit of déjà vu at this level.
What I initially figured had occurred was one thing analogous to a scenario I’d identified greater than six years in the past, involving a wi-fi charging-capable battery case for my spouse’s iPhone that wasn’t in a position to recharge itself over Qi as a result of it its built-in battery cells had drained past the purpose the place they may even energy the charging circuitry itself. Actuality, it seems, was much more sophisticated than that as a result of DJI battery pack’s multi-cell construction and the ensuing want for an built-in battery administration system (BMS) analogous to, albeit considerably easier than, the one mentioned in a latest EDN writeup by one other writer.
How did I find out about this quirk? Reluctant to simply toss the batteries and substitute them with (expensive) new(er) ones, I got here throughout somebody on-line who was providing a resurrection service. My eventual savior, who I’ve agreed to solely consult with by his first title Erik (and I’m referencing anonymously in any other case as a result of, in his personal phrases, “I don’t wish to carry any consideration to what I do as a result of I don’t wish to threat DJI unleashing their may upon me”), defined it this manner:
The cells have doubtless been discharged under the edge the place the BMS units a fault and retains you from charging them. I don’t understand how low they’ve drained till I open them up however, as a rule, they find yourself being simply fantastic after a pleasant balanced cost and some cost/discharge cycles earlier than the BMS is reprogrammed. There’s no design fault in these batteries. The BMS is fairly commonplace and the cells are literally very top quality.
Upfront, I paid $34.99 per battery (minus a modest amount low cost; additionally be aware that he gives a full per-battery charge refund for any batteries that he can’t repair), plus $9 for quantity-independent return delivery, together with $22.80 to ship the batteries to him within the first place. They arrived on a Friday, and he’d efficiently resuscitated, examined and shipped them again to me by the following Monday. Right here’s how he described the background and the method in his personal phrases (with solely light-touch enhancing by yours actually…be aware that he in-advance agreed that I may republish them):
All of them have been efficiently repaired, bench examined and test-flown.
Getting a little bit of the battery’s historical past and the issue doesn’t damage, however it’s pointless. The BMS shops all the knowledge I want. It’s like pulling codes out of your automotive with an OBD2 pc, and like repairing a automotive, it’s as much as the technician to interpret them.
When a battery arrives, I bodily examine it and ensure I didn’t get a battery that works fantastic. It’s occurred earlier than.
After that, I warmth the again cowl utilizing a heating mat to loosen up the glue that secures it. I exploit 40°C for 20 or half-hour. The quilt can be secured with a half dozen tabs that must be labored on. An X-Acto knife and a flat plastic spatula do the job. I attempt to use plastic instruments in an effort to not puncture the battery contents or short-circuit something.
As soon as it’s all opened, the cells must be examined. I made an adapter so I can join all three cells to a LiPo stability/charger, bypassing the circuit board. I exploit it to cycle the cells twice by charging them at 0.25C the primary time and 1C the second. Discharges are achieved at 1C the primary time and 4C the second time. I exploit 4C the second time as a result of it’s how a lot present the drone “pulls” whereas at flight. [Editor note: he’s referring here to the so-called C-rate]
If the cells try okay, I proceed to engaged on the BMS. I look to see if the cells stability accurately inside 0.2 – 0.3v and if there isn’t a lot voltage sag. These cells appear to be of excellent high quality and are due to this fact very resilient, however once more do not forget that your and others’ cells haven’t been cared for and aren’t model new, so I don’t anticipate them to work as in the event that they had been.
To attach, achieve entry, and talk with the BMS, I exploit the EV2400 from Texas Devices. Communication is finished through SMBus. That stated, any SMBus-capable interface adapter may conceivably be used.
Entry to the proprietary BMS is protected by passwords. You both have already got them or you might want to “break in” in an effort to achieve entry. I can’t let you know my passwords, however I do know of packages on the market that can “generate” codes and allow you to in.
I exploit BQStudio, additionally by Texas Devices, to tweak parameters and code as wanted to “erase” the everlasting faults (PF). Doing so permits the related MOSFETs to open or shut, thereby as soon as once more efficiently enabling fees and discharges.
After reprogramming it’s time to cost the battery, now utilizing the DJI charger, to see if it’s profitable. If it fees because it ought to, good!
Now, I put the battery within the drone and examine for firmware updates through the related DJI software.
Lastly, it’s time for the primary flight. I prefer to fly low and sluggish for the primary couple of minutes. After that, I fly usually and, if all of it checks out, I fly sufficient till the battery reaches 50 – 60% cost left. I prefer to ship these batteries at about 50% cost which is about 3.85 V per cell. That’s the producer’s really helpful storage voltage.
It’s additionally really helpful that these batteries be recharged each 4 or 6 months when not in use in order that the voltage doesn’t fall under the BMS’s threshold, which might trigger a PF flag to as soon as once more be set by the BMS. This goes for all “good batteries”, i.e., batteries with built-in BMSs.
Security is a should. Lithium batteries are flammable, so nice care have to be taken and customary sense have to be used when making an attempt to restore, cost, or use these batteries, they usually mustn’t ever be charged unattended. I’ve had two incidents occur, and it’s slightly scary. I didn’t get damage, however I had to purchase just a few new devices for my lab.
I’ll increase Erik’s sensible phrases with two extra quotes from the earlier referenced DJI documentation:
Discharge the battery to 40%-65% if it’s going to NOT be used for 10 days or extra. This will significantly prolong the battery life. The battery robotically discharges to under 65% when it’s idle for greater than 10 days to forestall it from swelling. It takes roughly at some point to discharge the battery to 65%. It’s regular that you could be really feel reasonable warmth emitting from the battery throughout the discharge course of.
and
Totally cost and discharge the battery at the least as soon as each 3 months to keep up battery well being.
Seemingly unsurprisingly to a lot of you from what you’ve already learn, Erik additionally famous in a subsequent message:
The elements on the [battery] board are off-the-shelf. Each the system chip and microcontroller are from Texas Devices.
And Erik even shared some photographs with me, to subsequently reshare with all of you, of the varied disassembly, rejuvenation and reassembly steps:
As talked about upfront, I’m not the one one who’s been struck by “useless DJI battery” lightning. And, because it seems, Erik’s not the one one who’s found out how one can revive ‘em. Try, for instance, this chronologically ordered sequence of movies from an outfit in New Zealand who focuses on such providers (amongst different drone-related issues):
In one of many movies, the technician even makes use of TI’s EV2400; the others, to Erik’s feedback that “any SMBus-capable interface adapter may conceivably be used,” showcase an cheap USB-to-SMBus bridge board primarily based on Silicon Labs’ CP2112 IC. And so far as software program goes, the commonest method leverages a freeware utility known as “DJI Battery Killer”. The device’s lineage is unknown, though it appears to have initially come from Ukraine, and it’s seemingly disappeared from websites that initially hosted it (though in at the least one case, I occur to know that it’s nonetheless downloadable through the Web Archive Wayback Machine middleman), so take into account your self duly warned, and no, I’m not going to supply any direct hyperlinks. I’ll solely be aware that the utility’s documentation (which, sure, I now have a replica of) particularly mentions that it helps a number of battery administration controllers: the BQ30Z55, BQ40Z50 and BQ40Z307 (BQ9003).
In closing, I’ll repeat for emphasis one phrase from Erik’s earlier in-depth commentary:
It’s additionally really helpful that these batteries be recharged each 4 or 6 months when not in use in order that the voltage doesn’t fall under the BMS’s threshold, which might trigger a PF flag to as soon as once more be set by the BMS. This goes for all “good batteries”, i.e., batteries with built-in BMSs.
That last-sentence actuality examine is each validating and deeply disturbing. To my proper as I kind these phrases, along with numerous drones’ batteries, is my costly set of multi-cell D-Faucet video batteries that I discussed on the finish of final yr and once more a month later, together with quite a lot of cameras and proprietary batteries for them. In entrance of me, in fact, is my built-in multi-cell battery-based laptop computer pc. And to my left are a number of wi-fi headphone units. Extra usually, scattered round the home (together with in long-term storage) are any variety of units that run on Li-ion, LiPo and different battery chemistries, with most of these cells absolutely built-in and difficult-to-impossible to switch.
All of them, it appears primarily based on this and previous experiences, are basically ticking time bombs, simply sitting there ready to die in the event that they’re not usually topped off. Whereas I’m not so cynical as to knee-jerk label all of them as examples of “obsolescence by design”, I’m additionally not a Pollyanna inclined to fully low cost this chance in all circumstances. No matter whether or not it’s an upfront intention or simply an unlucky facet impact of at this time’s dominant energy supply know-how, it’s a sooner-or-later supply of shock for customers, to not point out a root cause for untimely, extreme landfill donations. I welcome others’ views, together with insights into up-and-coming battery applied sciences and implementation methods that don’t exhibit this Achilles heel, within the feedback.
—Brian Dipert is the Editor-in-Chief of the Edge AI and Imaginative and prescient Alliance, and a Senior Analyst at BDTI and Editor-in-Chief of InsideDSP, the corporate’s on-line publication.
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- Battery life administration: the software program assistant
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