Best way to treat rechargeable batteries

Discussion in 'Architecture & Engineering' started by Fraggle Rocker, Aug 15, 2011.

  1. Fraggle Rocker

    Fraggle Rocker Moderator

    There was a time when everyone told me that the way to get the longest service life out of (solid state) rechargeable batteries was to let them run all the way down frequently. Recharging them when they were only half down supposedly "trained" them not to use the rest of their charge.

    I don't know if this was ever true, but is it true now? I used to put the charger on my Kindle every night, and the battery wore out in three years. Would I be better off to let the new one run all the way down before recharging it?
  2. nietzschefan

    nietzschefan Thread Killer

    Certainly true for most batteries.

    When you keep it on the charge all the time...the top 5% of that battery is getting hammered and the rest unused. Slowly you lose max capacity in this manner until you are stuck with just the bottom dregs left with a charge capacity.

    Using the whole battery as much as possible, spreads the wear over the whole thing. It still wont last forever, but you will get a more accurate reading of when it's going to run out and be fairly safe from a sudden death of the battery.
  3. MacGyver1968

    MacGyver1968 Fixin' Shit that Ain't Broke

  4. quadraphonics

    quadraphonics Bloodthirsty Barbarian

    It depends on the type of battery you're using:

    Basically, nickel-based batteries should be fully discharged with some regularity (doesn't have to be every time, but they say at least once a month), whereas lithium-based batteries do better if you recharge them as frequently as possible, and will degrade if fully discharged.

    Most consumer electronics like phones and Kindles use lithium-based batteries, in which case you should charge them frequently (unless you are going to store them for a while; then try to leave them at half-charge). But you should double-check, because either type of battery will be harmed by subjecting it to the best practices for the other type. My current phone will do a forced power-down if the battery gets too low, exactly to prevent damage to the battery from full discharge.

    All that said, 3 years doesn't seem like a particularly short lifetime for the sorts of batteries in question (i.e., Kindle), so I'm not sure that is an issue of charging behavior. If the thing is getting used frequently (as in, every day), then I'm not sure I'd expect to get more than 3 years out of the battery. I tend to keep my devices (laptop, phone) plugged in whenever I'm at home or in the car, and only use the battery when I'm out and about and have no choice. The best way to prolong battery life, is to not use the battery :]
  5. cosmictraveler

    cosmictraveler Be kind to yourself always.

    My new Samsung Fascinate phone has a lith-ion and the techs at Verizon tell me that I should turn off my phone completely before recharging it not a "soft" shutdown. I found it drains fairly fast, so far about half a charge in 1.5 hours of constant voice use. The techs say that this phone has a built in device that allows a slower recharge doing it this way and is much easier on the battery.
  6. KilljoyKlown

    KilljoyKlown Whatever

    I don't know if all laptop's work the same way, but Gateway always works only on the battery and plugging it in only charges the battery. So if you are using while plugged in you are both drawing on the battery and charging it at the same time. It was used everyday and the battery only lasted about one year. I remember reading where using while charging wears the battery out much faster and because of my experience I believe it's true.
  7. wellwisher

    wellwisher Valued Senior Member

    Batteries will hold their charge longer if you recharge them after they are either fully discharge or close to full discharge.

    To understand why this is true, you only need to do is consider what a battery does. The battery works based on moving electrons from lower to higher potential during recharge. When we use the battery the electron energy is released as move back down in energy.

    When we fully discharge the battery, the battery atoms are at minimal potential. This means less potential for spontaneous change in ways that lower the potential but not as a battery.

    Say the battery is half charged when we charge it, this means half the atoms are always at higher energy, having more potential to change into a state of lower potential, that does not involve normal battery function. Or part of the battery's atoms changes their ability to be optimized for charge.
  8. Billy T

    Billy T Please use Sugar Cane Alcohol Fuel

    It is not possible that at same instant current is both flowing into and out of the battery.

    Over heating is very hard on a battery, any type, so I tend not to trust the overcharge controls. Thus usually I operate my lap top on the AC line, with the Li-ion battery removed, but at end of the day, when shutting computer down, I plug it back in, and turn off the charger. I.e. for the minute or two it is logically turning off, it is running on battery. (I don't like to wait around for that to finish.)

    The next day normally I put the battery back into the computer and turn on charger. I typically notice the yellow "I'm charging the battery" for up to a minute and then it switches to be green, indicating full charge, so when I notice that, the battery comes out again. Sometimes I forget to turn the charger on in the morning so may run on battery even 10 minutes before turning the charger on for the day.

    I know li-ion batteries do not have the same "memory effect" that Ni based battery do but they too do have sections of the electrodes with very slightly different open circuit potentials. The higher potential parts are first to supply discharge currents; however, unlike the Ni battery the lower potential parts do not become "poisoned" and useless without occasional deep discharges. Occasionally (every few months) I do use most of the battery capacity and get warning that I only have five minutes remaining battery life.

    My battery was in the discontinued floor model computer - last one best buy sold and I got a deep discount early in July 2007. It still seems to have its full deep discharge capacity, but I only test that about once per year. It probably is more than 4 years old and still "like new."

    I suspect your battery died after a year because it got too hot. I never operate computer on anything but a hard surface so air flow is unrestricted, none the less, the exhaust air is quite warm. If your battery was switching between charge and discharge several times each minute because, for example, some internal charge regulator needed help form the battery when writing a big file to disk, then there was significant heat being generated in the battery by this cycling as well as by the computer. That "inadequate" AC to DC supply / regulator could be why you must keep the battery in at all times. The maker may have saved a dollar or so with weak AC to DC supply, not up to the peak DC load, but cost you much more if this battery cycling heating is what did your battery in.
    Last edited: Aug 16, 2011
  9. quadraphonics

    quadraphonics Bloodthirsty Barbarian

    Interesting data point. However I'm quite certain that my own laptop uses AC power directly when plugged in - it explicitly switches into a "hi performance AC power" mode. Various of the other laptops I use these days exhibit similar features - when plugged in, they charge the battery and run the machine off of AC power. In fact I'd go so far as to suggest that any laptop that doesn't behave that way is really poorly designed. Which would not surprise me one bit in a Gateway (or Dell) machine.

    My experience with both Gateway and Dell laptops is that they make cheap crap, and in particular use crap-quality batteries that are unreliable. My wife's Dell laptop's battery barely lasted one year - and so now can only run if connected to AC power (gives a literal meaning to "desktop replacement"). They seem to operate by selling computers that look like a good deal, superficially, but tend to malfunction and die fairly rapidly. Although, I've never used any of their higher-end models - if you're going to pay that kind of money, might as well get a respectable brand like Lenovo or Asus or Acer (or, at the very least, HP).
  10. Read-Only

    Read-Only Valued Senior Member

    Yep, that original weakness was limited to a specific generation of NiCad batteries and first came to light with a problem in Skylab in 1979. :)

    It's orbit was decaying and they were attempting to re-aim it to bring it down safely in a deserted area. Even though the solar cells were working, the on-board NiCads would not hold enough charge to make the needed course correction.

    After a bit of hurried research, they finally forced the batteries to a near-depleted state and then were able to recharge them to a level considerably higher than before.

    Also, as has already been noted, heat is THE battery's worst enemy. Keeping it as cool as possible during use and recharge can extend it's useful life by a very noticeable amount.
  11. KilljoyKlown

    KilljoyKlown Whatever

    I'm inclined to go with what you just said. That Gateway wouldn't work at all without a good battery plugged in. It was a real bitch because it failed right after the warranty expired. A replacement battery cost $80.00. I would never buy another Gateway laptop and I've never liked Dell.
  12. quadraphonics

    quadraphonics Bloodthirsty Barbarian

    I have some electronics with the same issue (shaver, inflatable mattress pump): they only run on battery power, and plugging them in is only useful for charging the battery. It seems that what happened is they saved money by not installing a robust power system on the AC end - only a small one that is capable of (slowly) charging the battery, but not actually running the machine directly. The only part that has a robust power subsystem is the output of the battery, so unless you've got a charged battery you can't use them. And they take much longer to charge, than to discharge through use, which is why I can tell there isn't a high-output power supply coming from the AC end.

    So, yeah, it's worth paying for a quality battery (and AC power subsystem to boot) - a laptop becomes way less useful without it, so a few bucks spent up-front can prolong the usable lifetime of your purchase substantially. It's one of these hidden issues that's hard to discern from the spec sheets, so you kind of have to go by the brand's reputation unless you can find really detailed user reviews of the particular model you're interested in. Even then, these kinds of issues won't pop up for 1+ years so the reviews will still be of limited value.

    Another good thing to do when it comes to batteries in mobile electronics is to load them only with what you need. Instead of that super high-power workstation laptop with the big processor and tons of memory and stupid graphics card and crazy-powerful screen and ultra high-speed DVD/bluRay drive, consider getting a netbook with none of that stuff, and a lot of intelligent power management capabilities and low-power core components instead. This way, you put way less load on the battery, and so the battery can be smaller, and so you can get a quality reliable battery for a reasonable price, etc. Usage time between recharges will also go up (at least, on a per-dollar basis). Moore's Law has driven computer performance to the point where the lion's share of users don't need anything like the top-end performance. So, resist the urge to drool over impressive specs, and instead get a machine with suitable performance and very high build/component quality. The thing about those high-spec machines is that there's a huge incentive to cut corners to keep costs down, and this invariably means compromises with "under-the-hood" things that aren't apparent on the spec sheet: long-term battery reliability, well-integrated power management, long-lasting touch interface, resistance to general wear-and-tear, etc. If you decide you really need the high-spec machine, be prepared to pay for it or compromise in some other way (get a desktop instead of a laptop, typically).
    Last edited: Aug 17, 2011
  13. Asguard

    Asguard Kiss my dark side

    lithium batters have about a 3 year lifespan. Even if its left sitting on shelf unused it will still be rooted after about 3 years
  14. KilljoyKlown

    KilljoyKlown Whatever

    That really sounds bad for those expensive electric lithium car batteries. Don't know if I could come up with an extra $5000 every 3 years.
  15. Asguard

    Asguard Kiss my dark side

    dont know if car batteries are any different, the guy who was talking about this was talking about small ectronics (like the batteries in a PS3 controler or an ipod)
  16. KilljoyKlown

    KilljoyKlown Whatever

    That's the best advice I've heard in a long time. One thing I would like to see getting cheaper is the solid state drives for lap tops and if they get big enough maybe even for desk tops. But nothing beats having a battery that's good for a whole day before needing charging. Your comments about the AC are well taken. I remember going over the specs with a fine tooth comb and there was nothing about the way the AC was constructed and installed. Had I known that, I would not have bought that lap top. To me that company lied by omission and not only did they lose a customer they gained an unhappy ex-customer that's willing to talk lot's of shit about them.
  17. KilljoyKlown

    KilljoyKlown Whatever

    They are leading people to believe the car batteries will last about 10 years, but if it turns out they don't, there will be a lot of very surprised unhappy customers. But even if they by chance do hold up for ten years and you want to sell and buy a new car in 8 or 9 years. How much would you expect to get for it? As a used car buyer I wouldn't be very happy thinking I might have to cough up another $5000 in a year or two.
  18. Repo Man

    Repo Man Valued Senior Member

  19. KilljoyKlown

    KilljoyKlown Whatever

    Sad maybe but not out of your price range.:D
  20. Repo Man

    Repo Man Valued Senior Member

    It was back then.

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