Proper care for a backup electronic device
October 17, 2020 1:04 PM   Subscribe

My "holy grail" totally unique electronic device was discontinued so to ward off my extreme anxiety about mine breaking/dying, I bought a backup. Would it be better to alternate between the two devices, use it once to make sure it's not a dud then wait until my old one breaks, or not turn it on and just hope for the best?

This is a sort of USB-charged bluetooth speaker, made by an extremely reputable company, if it matters. And I bought it straight from the manufacturer.
posted by acidic to Technology (7 answers total) 3 users marked this as a favorite
 
I can't imagine any reason not to fire it up and use it once, as long as you're confident you won't return or resell it. Is there a particular risk you have in mind there?
posted by nebulawindphone at 1:39 PM on October 17


Lithium batteries seem to have better longevity overall when they are stored around 50% charged. I'd use it for a couple full charge cycles (100% full, down to "charge me now," and back) and then use it down to 60% power and turn it as "off" as it goes. I'd be curious how much power it consumes when it's "off" (it may never truly be off) but on their own the batteries should have very low self-discharge. Check it about once a month, and maybe repeat the full charge cycle thing once a year.
posted by fedward at 1:52 PM on October 17 [1 favorite]


I agree with fedward batteries, even rechargable ones, are a consumable part. Depending on the chemistry and quality they could last ten years, or be nearly useless in two, so keeping it at 40% is a good idea to prolong storage life. I would still expect that in 5-10 years battery capacity will be less than new, so maybe invest in another charger.

Next up is probably the Electrolytic Capacitors, which tend to dry out and have a lifetime of 6-10 years. But sometimes they fail much earlier. I have opened up audio equipment that suddenly stopped working after about 4 years and found bits of exploded capacitor spread throughout the case. The best thing to stave this off would be to keep the temperature low.

Semiconductors like the amplifier and logic chips tend to fail at the very beginning of their life, or last a very long time and fail at end of life, with minimum random failures in the middle. This results in a rate of failure over time curve that looks like a smile. I'd say 10-20 years for modern semiconductors.

Lastly, speakers have moving/vibrating parts and the flexible surrounds (where moving part transitions to stationary part) sometimes become brittle and break, and need to be replaced. This was particularly bad with speakers in the 80's that used very light, flexible foam surrounds that did not last long. Every modern compact bluetooth speaker that I have taken apart has more durable rubber surrounds. If this part fails the odds of finding a replacement kit for the very small custom made drivers in a blutooth set are basically zero, so that's the end of it.

So my recommendation is to use both devices for about a month to discover if any of the components fail early. Then charge the backup device about 40% battery capacity, put it back in the box, and store it in a cool dry location. Maybe use it once a year to drain and recharge.
posted by sol at 2:30 PM on October 17 [3 favorites]


> Lithium batteries seem to have better longevity overall when they are stored around 50% charged. I'd use it for a couple full charge cycles (100% full, down to "charge me now," and back) and then use it down to 60% power and turn it as "off" as it goes.

Do not do this with Lithium Ion batteries. (Also, lithium batteries are not the same thing as lithium-ion batteries.)

"Avoid completely discharging lithium-ion batteries [...] For extended storage, discharge a lithium-ion battery to about 40 percent and store it in a cool place" [source]

"The smaller the discharge (low DoD), the longer the battery will last. If at all possible, avoid full discharges and charge the battery more often between uses. Partial discharge on Li-ion is fine. There is no memory and the battery does not need periodic full discharge cycles to prolong life." [source]
posted by ardgedee at 4:27 PM on October 17


Do not do this with Lithium Ion batteries. (Also, lithium batteries are not the same thing as lithium-ion batteries.)

The advice fedward and sol gave is fine for lithium-ion batteries. Discharging the battery to near-empty isn't required, but it also isn't going to do any harm.

The advice you linked about "depth of discharge" is talking about long-term degradation of the battery. Basically, a lithium-ion battery's capacity slowly degrades with repeated charging and discharging cycles. And the more deeply you discharge the battery each time, the stronger the effect -- that is, discharging twice to 50% causes much less wear and tear than discharging once to 0%. But either way, the effect is cumulative and only starts to matter after hundreds of cycles, as the graphs on that page illustrate; one or two deep cycles is really no big deal.

The important thing is that the battery should not be left near-empty or near-full for long periods of time in storage, and since it will slowly lose charge over time (at a rate that depends on temperature and all sorts of other things) you should check on it and recharge it if necessary every 6 months or so. Anything in the approximate vicinity of 50% is fine.
posted by teraflop at 5:12 PM on October 17 [1 favorite]


Lithium-ion batteries are indeed not the same as lithium batteries; if your device charges from USB it is certainly the former. Never fully discharge lithium ion (or nickel-cadmium, or lithium iron oxide) batteries. However, charge controllers know this, and short of total incompetence, "charge me now" is must closer to 40% than it is to full discharge.

Even with a magical golden charge controller and all the loving care in the world, batteries are a consumable. They need periodic inspection and testing (like, every 6 months minimum) lest they swell and wreck stuff (Li-ion) and/or leak and wreck stuff (other chemistries).

For truly long-term storage with no opportunity for (or if you don't trust yourself to do) maintenance, I'd remove the battery and pack the device with silica gel packets in a sealed container with dry inert gas (argon or nitrogen).

Electrolytic caps have gotten much better over time, but yeah.. that and any rubber parts will be ravaged by time.

In your place, I'd alternate every few weeks.
posted by sourcequench at 5:25 PM on October 17


The point of my advice about running the battery down was not about memory effect, which I wasn't trying to imply was a thing with lithium or lithium ion batteries. I was thinking more along the lines of making sure the battery really ran as long as it's supposed to, so you don't waste effort on carefully preserving a battery that wasn't good to begin with. And I assumed, based on it being from an "extremely reputable company," that the device's low battery warning would happen well before the depletion level that would damage its battery. I'd expect going all the way to the low battery warning to be safe and non-battery destroying in any new device from a legitimate company with a reputation for quality. Beyond the low battery warning, IME devices like that will not even power on when the battery is so low it could be damaged by further depletion. The safety factor tends to be designed in these days.
posted by fedward at 6:00 AM on October 18


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