Best way to treat rechargeable batteries

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

1. Fraggle RockerStaff Member

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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?

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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.

5. MacGyver1968Fixin' Shit that Ain't BrokeValued Senior Member

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

http://en.wikipedia.org/wiki/Battery_charger#Prolonging_battery_life

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 :]

8. cosmictravelerBe kind to yourself always.Valued Senior Member

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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.

9. KilljoyKlownWhateverValued Senior Member

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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.

10. wellwisher

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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.

11. Billy TUse Sugar Cane Alcohol car FuelValued Senior Member

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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 by a moderator: Aug 16, 2011

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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).

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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.

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18. AsguardKiss my dark sideValued Senior Member

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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)

19. KilljoyKlownWhateverValued Senior Member

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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.

20. KilljoyKlownWhateverValued Senior Member

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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.

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