Talk:1872: Backup Batteries

Explain xkcd: It's 'cause you're dumb.
Revision as of 14:02, 6 August 2017 by (talk) (made a ridiculously long comment drawing out several interpretations of the joke in the title text in order to justify my explanation of the joke in the article.)
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This actually sounds like the classic provisioning situation. How many spares do you require, and when do you require additional spares. One of the things that he doesn't mention is whether he carries a USB cord for his phone and USB power supplies for auto and wall outlet use. ( For iPhones, you need one cord for charging the phone and a different cord for charging the power pack.) I have three power packs in my bag normally. When one of the power packs is low on power, I plug it into an electrical outlet while using the phone. I also plug the phone into an electrical outlet when available to prevent the battery from running down. If at home or a hotel room, I can also have one or two power packs charging while I travel with the phone and the third power pack. I also charge the phone overnight. Having multiple power packs doesn't do any good without a means of maintaining them in a charged state. I typically start the day carrying a charged phone and three charged power packs, which is enough to let me use the phone all day. At night, I plug all of the devices into electric power. If I really wanted 24 hour usage or a lot of gaming (games use up the batter faster), I could use six power packs but only carry three with me at a time. The other three would be charging at a base location.

Having too many redundant backup devices can actually reduce the up time of the system. This was seen at the Superbowl in New Orleans. It is also very dangerous to assume that your backups are adequate and that you don't have to watch the log files. If somebody had been reading the logs, they would have seen the message that essentially said: "I have reported two power surges and you haven't told me what to do. Although these are not individually dangerous, one more power surge before somebody talks to me and I shut down the entire stadium."

What if the backup batteries are actual removable batteries? 05:03, 6 August 2017 (UTC) An optimist states that the water glass is half full, while a pessimist states that the water glass is half empty. What an engineer really does is find out where the water faucet is so that he can refill the glass as needed. (The original joke says that the engineer states that the glass is twice as large as needed. This is ridiculous unless he knows how much water is needed and how much is available at the faucet. The size of this glass is irrelevant unless it is too large to be handled easily or too small to transport water at the required rate.)

BradleyRoss (talk) 17:21, 4 August 2017 (UTC)

Assuming he charges the batteries in series (i.e. the second backup charges the first backup which charges the phone, etc.) I wonder how many batteries he'd be able to go through, before the charging/discharging inefficiency (heat generation etc.) meant none of the original power would get to the phone? Also I can relate to this comic, when traveling I may bring 2-3 batteries, even though in practice I rarely need more than one ๐Ÿ˜๐Ÿ˜‚. 18:58, 4 August 2017 (UTC) (talk) (please sign your comments with ~~~~)

EDIT: Replying to below comments, I have a power bank that allows simultaneous discharging and charging. Also I really meant to say it as them being charged/drained in sequence, rather than all simultaneously. (talk) (please sign your comments with ~~~~)

Maybe the bag turns red when it falls below 20% batteries...Jamgard (talk) 19:20, 4 August 2017 (UTC)

Judging by and a number of similar entries, charging and discharging a metal hydride battery at the same time seems to be highly undesirable. Remember that these batteries have a bad habit of exploding if the charging and discharging rates aren't correct. If there were two batteries in series as you discuss, I believe that my best approach would be to be in another building and have the fire department on speed dial. BradleyRoss (talk) 22:00, 4 August 2017 (UTC)

The phone itself is constructed in way which allow it to run while being charged - likely by operating directly from external power instead of from battery. It would be theoretically possible for the backup batteries to be constructed the same way - although unlikely, as it's not something people would normally do. Also note that those backup batteries might be really just backup batteries (to be switched with device battery), not power banks (capable of charging the device). -- Hkmaly (talk) 03:14, 5 August 2017 (UTC)

I bet Cueball carries recursive battery backpacks as well, as well as recursive battery backpack backpacks, and recursive battery backpack backpack backpacks, and recursive battery backpack backpack backpack backpacks, and recursive battery backpack backpack backpack backpack backpacks, and recursive battery backpack backpack backpack backpack backpack backpacks, and... OriginalName (talk) 18:17, 5 August 2017 (UTC)

I think the 20% full doesn't mean the energy capacity of the backpack, but the actual contents of the backpack. If it is less than 20% (charged) backup battery, he panics. Physicalattraction (talk) 11:04, 6 August 2017 (UTC)

That version of the joke with the bag blinking at "20% batteries" is also in another comment. Sure, that could be it, since a percentage of batteries is mentioned in the comic proper. However, it is ambiguous. The bag starts out at 90% batteries. So would the bag start blinking when charged batteries occupy 20% of the initial amount, such as in phones โ€” which is 18% of the space of the bag โ€” or would it start blinking when they occupy 20% of the total space in the bag, which is 22% of the initial amount? Besides, batteries are not removed from the bag when emptied, as they still have to be carried. If the bag is 80% uncharged batteries, I think the bag is still just as "full" of batteries, as worded in the title text. Furthermore, even if you decide that it refers to "charged batteries", a battery may be stored while partially charged, which makes it unclear whether it counts as a charged or uncharged battery. If it counts as charged, then it provides less energy than indicated by its count, and if it counts as uncharged, it provides *more* energy than indicated by its count, and may not be picked up by Cueball when he's looking for a charged battery and doesn't known which of his backups he just put back in there without fully using. If it counts as a partial battery, say, 50% of a battery if it's 50% full, then all you're doing is counting the energy capacity of the backpack, which is what in the article because it makes sense, but with the added ambiguity of whether you have started from the total amount of batteries the backpack is capable of carrying, or simply the amount it started with. Therefore the title text must be referring to energy, which makes the most sense given all of these considerations, and which would most easily allow an actual such bag to be built, if it all the batteries were somehow plugged into some machine inside which would flash red lights when at 20% of the total capacity. Now, while writing this I notice that "energy capacity" is also slightly ambiguous as technically a backpack may have the "capacity" to carry more batteries than are in it, which may be said to be the "energy capacity", however I still believe the term is easily understood by article readers as the energy-carrying capacity of the total of batteries inside the backpack when summed. Lastly, I warn that you do not confuse "capacity" with "capacitance", as that word sprung to mind in this context. 14:02, 6 August 2017 (UTC)