I’ve seen conflicting info over the years on whether it is better to charge batteries as often as possible, or to let them fully discharge between charges. With both methods claiming longer life over time.
The answer would depend on the type of battery. What kind of battery is it?
Different types of batteries prefer different charge setups. If you’re like me, you charge whatever device you have when it gets low, and sometimes when it’s not really low, just because it’s convenient.
More important is to know how many and where these batteries are in your house. Batteries can fail, catastrophically, and injure or kill you or burn your house down. They can store a lot of energy and when they fail it can be ugly.
My friend just got burned by a lithium battery. At least it didn’t burn his house down.
All kinds, mostly thinking of tabets and cell phones which I believe are all lithium ion. And rechargeable batteries for cameras etc which are nickle cadmium?
On all types I have seen it said discharge fully first before chaetrging, or charge as often as possible, then I have seen both of these strategies called myths, or that the discharge first before charging only applied to early LI batteries and is no longer needed(much like they say the advice to overwrite data X amount of tiimes no longer applies to modern hard drives and one or two overwrites is sufficient).
Basically everyone seems to say something different.
On the topic of batteries exploding, I noticed a broken OQO handheld PC I had in a closet the LI battery which had not been charged in years had swollen to nearly four times its original size recently:eek: Not sure what to do with it, I put it in a bag at least in case it leaks.
With modern Li-ion batteries, best practice is to recharge them whenever possible. Actually, very best practice would be to charge to about 80%, deplete to about 50%, then recharge back to 80% and to repeat this cycle. However, this kind of usage is impractical for most users.
The worst thing you could do is to expose them to high heat as this degrades battery capacity and number of recharging cycles. Try to avoid deep discharges/recharges (100%⇔0%) and using the battery at a constant 100% as smaller discharge/recharge depth is less stressful to the battery.
With all that being said, all batteries will eventually die. With modern Li-ion batteries, the life of the device is often shorter than the batteries themselves.
Do not routinely completely discharge Lithium Ion batteries before charging. If anyone is saying this, they are confused and not right. It may be useful to give a Li-Ion battery a full discharge every once in a while for other purposes though. Please read below.
From batteryuniversity.com:
Similar to a mechanical device that wears out faster with heavy use, so also does the depth of discharge (DoD) determine the cycle count. The shorter 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. The exception may be a periodic calibration of the fuel gauge on a smart battery or intelligent device.
From Ars Technica(very reputable tech site):
One of the worst things you can do to a Li-ion battery is to run it out completely all the time. Full discharges put a lot of strain on the battery, and it’s much better practice to do shallow discharges to no lower than 20 percent. In a way, this is like people running for exercise—running a few miles a day is fine, but running a marathon every day is generally not sustainable. If your Li-ion-powered device is running out of juice on a daily basis, you’re decreasing its overall useful lifespan, and should probably work some charging stations into your day or change your devices’ settings so that it’s not churning through its battery so quickly.
There used to be certain types of batteries whose “memory” of their total charge capacity seemed to get confused by shallow discharges. This is not, and never was, the case with Li-ion batteries. However, if you are using something like a notebook computer that gives you time estimates of how much longer the battery will last, this clock can be confused by shallow charging intervals. Most manufacturers recommend that you do a full discharge of the battery about once a month to help your device calibrate the time gauge.
…On the other end of the spectrum, keeping a Li-ion battery fully charged is not good for it either. This isn’t because Li-ion batteries can get “overcharged” (something that people used to worry about in The Olden Days of portable computers), but a Li-ion battery that doesn’t get used will suffer from capacity loss, meaning that it won’t be able to hold as much charge and power your gadgets for as long. Extremely shallow discharges of only a couple percent are also not enough to keep a Li-ion battery in practice, so if you’re going to pull the plug, let the battery run down for a little bit.
Wife has a bazillion apps running on her smart phone all the time. Charges a lot, has a charger that stops when battery is 100%.
My smart phone is lean & mean. In 36 hours I have gone from 100% to 96%. Recharge when at 50% or lower. ( Yeah, I don’t get or make many calls. I know where I am at and I don’t play games.
Which battery is going to last better or preform better is there can be two answers depending…???
Both phones will be obsolete in 3-4 years. 
Don’t worry about it too much. No battery is going to last forever anyway.
If you want to worry about something, worry about keeping the batteries from getting too hot or too cold.
You absolutely don’t want to drain your batteries all the way all the time, mostly because if you need your device and the battery is at 2% you’re not going to be happy. But also because lithium batteries really don’t want to be drained all the way. They have protections against this, but if you leave them in a device at “0%” too long they may be damaged.
However, you do want to run them down as far as they will go once in a while to calibrate the controller’s idea of how much charge the battery can hold.
I’ve heard that the last 20% of the charging cycle adds more stress to the battery. So when I’m charging my phone during the day I usually disconnect once it hits 80%. (It helps that charging to 80% takes about the same time as charging the remaining 20%.)
Never read anything saying this, but I’ve always suspected that switching between charging and discharging too quickly also isn’t ideal, so I try to avoid that. So that advice to keep the battery between 50 and 80 % (= charge when you get < 50 and disconnect from power when you get to > 80) seems like good advice.
But again, don’t worry about it too much, the battery is there to serve you, not the other way around.
This is spot on very good advice, but the one thing missing is that these batteries are usually monitored by computer circuits and the occasional 0>100% charge>discharge cycle helps the computer know where the battery is at.
Depends. Li-Ion batteries in general do best at 40% remaining. Cycle life is not really much of a factor here, but an industry artifact of previous battery technology. What seems to matter most is ‘depth of discharge’ and temperature and time spend at both for Li-ion.
If you extend your recharge to 25%-30% left you might have a edge.
Complete discharge/recharge is only recommended to recalibrate the battery meter so you get a more accurate reading of how much juice you have left, and can be done once every 2-3 months. However, it is very stressful on the battery and does nothing to improve its life.