Charging Li-Ion battery

[Guest gts]

Hello!

The question is - "How to properly charge a Li-Ion battery in order to maximize its lifetime?"

One thing is clear about it - there's no need to do a deep discharge like for Ni-Mh or Ni-Cd batteries.

Some service people have told me that even though Li-Ion batteries are more resistant, they should not be charged for every 5 minutes because they have a limited number of charging cycles. It sounds logical to me because theoretically every device or thing has a limited count of times it can be used (not just usage duration).

Today some people pointed me to the opposite direction like - you should better charge the battery at every opportunity, no matter when or where. Does it mean that I can charge it for example thousand times per month? Would then it's lifetime be as long as it would be if I charged it once a day?

Another view. My previous laptop had a Li-Ion battery. I was keeping it connected and powered-on all the time 24/7 because I almost never had to move it away from the desk at my work. After some 6 months the battery was almost completely dead. It could power my laptop for some 5 to 10 minutes in opposite to my colleagues laptops which could run on batteries for hours. The other people don't mind carrying their laprops home and back every day, so they did dicharge on their batteries more often than I did.

Now about phones - WM5torage (click here to view the topic) users (at least those who have devices like Qtek 8310 with USB charging enabled by default) are charging their phones every time they connect them via USB. Is it healthy for the battery to use the smartphone just like a usual USB flash?

I want to know about all aspects, including all battery states and charging duratrions. Let's say - what if I take 7 brand new devices of the same manufacturer and model and do an experiment. Every one of them would be charged only one way all the time. Which one would be certainly dead in a short while (if any)?

1. deep discharge --> short charge
   
2. deep discharge --> full charge
   
3. half discharge --> short charge
   
4. half discharge --> full charge
   
5. little discharge --> very short charge
   
6. little discharge --> full charge
   
7. fully charged --> charge attempt
   

[Guest Ingvarr]

I beleive in any case it will age naturally a lot faster then any "optimization" will allow to tweak.

Li-Ion batteries age and lose capacity even when lying on the shelf.

But "usage-based" aging would depend almost solely on how much power you drew from battery in total since you started using it. So, think about it this way when battery is used & supplies power - it wears out. More power it supplies - more wear. Longer it supplies power - more wear.

So the only way to minimize wear is not to use the battery. Or try to lighten load on it - do not run heavely-CPU consuming apps, keep WiFi off, do not overclock, etc...

If you use the battery, 2 basic scenarios:

- ten cycles - discharge down to 90% and immediate charge to 100% - immediate discharge and so on

- one cycle - discharge down to 0% and charge to 100%

almost equal. Since they both placed about full capacity drawn on battery in total.

But there is that thing that when you put device on charge, usually this means that all electrical load is removed from battery (since device will draw power from charger directly).

So when device just lies on the table, battery is used by device electronics. And battery wears out (slightly) faster then it would age naturally.

When device sits in charger, battery is unused. And it will wear less (but still it will age naturally fast - this is LiIon for you...)

So if can plug device in charger - better plug it in.

If specific battery requires specific treatment, device is smart enough to manage it on its own without telling everything to you.

For example, in some cases when it shows "100% charged" and green led shines, it runs "micro-cycles" by discharging battery 1% and recharning it, or reduces current to trickle, etc.

Edited April 24, 2006 by Ingvarr

[Guest gts]

Thank you for the answer.

I have another question now. How did the laptop battery die so fast, if it was plugged in and powered on 24/7? It should be consuming the power from the adaptor thus keeping the battery unused. The laptop was IBM T23 and I am completely sure that it was full of different electronics that control the battery charging process. Is it possible that these little "invisible background maintenance processes" that the smart electronics were doing use so much wats from the battery that it just naturally wears out? If it is so, then it turns out that the electronical maintenance process 24 hours a day use much more battery power than my colleagues use (about 8 hours a day normal laptop usage with random charges).

Something seems to be wrong. Maybe my laptop was faulty? ;)

[Guest Ingvarr]

You could've got either faulty battery or an old one.

Since LiIon ages from the day of manufacture, there can be "invisible" aging even for "brand new" battery - if, say, it lied in the warehouse for a year before you bought it.

Or maybe particular brand of laptop had some mistake in the battery management, causing it to deteriorate.

Sadly, this all happens not so rarely, confusing things more for end users.

I know for sure, that in general, notebook battery will live longer if you prefer to run notebook from mains power. But "in general" not means "always", exceptions still happen, caused by quite different things. But you dont worry about what you cant predict.

Edited April 24, 2006 by Ingvarr

[Guest gts]

This post arrived in WM5torage topic (off-topic so I'm writing the reply here):

(Click here to view the original post)

That may not be the full truth... ;)

It's true that deep discharge may damage or even destroy a LiIon pack. But normally devices are switched off automatically at a specific current (cut-off current) that lies way above deep discharge (hopefully). So risk is low if you don't switch the device on afterwards without charging. (That may not be true for some Motorola devices since they use power even if current is very low).

What damages LiIon-packs is: Charging cycles - and time. You may count every reconnecting as full charging cycle if it even lasts for a short while and your battery ist on half charge.

But if that is relevant depends on general usage habits, since LiIon batteries degenerate even if they are not used at all. Normally capacity has somewhat halved after about two years in normal condition, not much difference between used or unused batteries.

So, if you charge your phone three times a week or connect it every second day it makes no big difference in life-cycle since thats about the same (with ~500 charging cycles) as normal half-life period...

And it's absolutely true that you don't have to care much for your LiIon Battery after it is correctly formatted during first charging cycles (and even that is no more than just one full charge and discharge til cut-off current - no big voodoo that you often read about).

Conclusion: No problem here with WM5torage if you don't connect it five times a day (who should???).

Yours,

DJ

Now i'm confused. Once again - somebody tells me something really reasonable and then... Somebody else tells the opposite. Which one is true? I'm talking about the very last sentence in the post:

No problem here with WM5torage if you don't connect it five times a day (who should???).

Well - I should! That's wat I meant with frequent usage of WM5torage.

When you have a USB flash drive (for example Kingston DataTraveler 128Mb) you never care how many times a day you connect it somewhere. And if this memory stick is too small to copy all the data from one PC to another - you can connect it as many times as you want and copy some part of data with every step. That's the same as if you had a single 1.44Mb floppy disk and you wanted to copy some 50 megs from one PC to another (and you have no other options like LAN or CD/RW or whatever else).

What is the problem with connecting it five times a day? Yes - five times every day, like nobody ever should! What happens? Any damage or premature wear-out?

Edited April 25, 2006 by gts

[Guest stu_ie_uk]

What about syncing your phone / pda? Most sync cables and pretty much all cradles will charge as well as sync, so every time you connect / disconnect you'll be giving your device a bit of charge? Is that going to hurt it?

**Just read all the other posts - think I've answered my own question**

Cheers all

Edited April 25, 2006 by stu_ie_uk

[Guest Leddy]

My 3.5 year old laptop's battery still gives me a good 2 hours out of it. (It's a P4-M one, btw, so 2 hours is like 0% wear.)

[Guest gts]

What about syncing your phone / pda? Most sync cables and pretty much all cradles will charge as well as sync, so every time you connect / disconnect you'll be giving your device a bit of charge? Is that going to hurt it?

**Just read all the other posts - think I've answered my own question**

(If I understand you correctly - you mean the manufaturers)

Maybe the manufaturers just thought the same way as deppjones - who should connect it five times a day?

For example, an average cordless phone (DECT) with Ni-Cd or Ni-Mh battery (which should be charged carefully) is sold together with a base-station which is designed like a stand for the handset. Many people actually think that it is a stand for it and place the handset in it after every phone-call. They damage their batteries VERY fast. I would not be so sure that manufacturers always do their best to save the batteries. They always say that they give no warranty to the battery and actually they earn a lot of mony by selling new batteries.

My 3.5 year old laptop's battery still gives me a good 2 hours out of it. (It's a P4-M one, btw, so 2 hours is like 0% wear.)

You should better tell us about your laptop charging and usage habits. How did you manage to save the battery from its natural death?

[Guest gts]

Besides - I prefer synching via BlueTooth for 2 reasons:

1. I don't have to plug anything. No cables, no craddles, just the air.
   
2. I don't charge the battery without a reason. For me, USB cable is almost the same as the charger.
   

[Guest Ingvarr]

What is the problem with connecting it five times a day? Yes - five times every day, like nobody ever should! What happens? Any damage or premature wear-out?

You dont really have much choice here. Say, you are going around lot of PCs installing something from Mass Storage drive.

So, variant A:

- You will little recharge it a little all these times. It will discharge a little (since when you just carry phone around, it uses lesser amount of power). And it will recharge just a little. But when you actually use mass storage and electronics draw significant current by writing/reading flash, transmitting data, etc - it will not place load on battery - it will draw load from charger and mains power.

Variant B.

- You "try to save cycles" and disable charging. So all these times when you plug device and work with mass storage, device place heavy load on battery. Summary load (comparing to variant A) will be a lot more, and strain on battery a lot more. Yes, formally you have "less cycles", but in practice you've discharged battery a lot deeper and placed a lot more work on it in total.

So I think its pretty obvious that (A) is better.

"Trying to minimize cycles' is oversimplification.

[Guest deppjones]

"Trying to minimize cycles' is oversimplification.

With that I fully agree even if I don't think Variant B is right. LiIon-batteries usually don't wear much more on full load than normal aging does (apart from temperature effects). Main problem is deep discharge since it bears chance to irreparably damage the cell(s).

Variant A is only true for the time where the device is fully loaded, since normally the phone not just takes power from the charger but also charges the battery. Even after a short while without load (phone switched off) self-discharge may be enough to make the device put the batteriy on charging for long enough to have the same effect as normal charge-cycle.

It all depends on the way the battery is charged by the phone.

But I would not waste to much thought on tat problem since normally the battery lasts about 2 years even with heavy stress (cycles or load). btw. a small usb-stick maybe much more practicable as allways fiddling with a cable an a phone. ;) Its just very cool to be able to access the phones sd-card on computers without ActiveSync.

Yours,

DJ

PS: The early death of your notebook battery may be the result of a faulty battery or, more obvious, heat from processor or grafik-chip or hd. Heat makes LiIon-batteries age way faster...

[Guest Ingvarr]

Battery ages faster when higher current drawn from it. When it approaches "maximum nominal" current the battery can draw, it can age very fast. Actually there is no such thing as "maximal nominal current", every manufacturer just chooses some value when aging (in their opinion) becomes "too" fast.

Maybe it not *that* faster, but it still can be noticeable, if you, say, compare two same devices, one of which used battery often, and other almost never used the battery, after a year passed.

I know that device will charge battery when it was little discharged.

Iam omitting charging on purpose - since every charge is perfect mirror of discharge (on long term), you can safely take only discharge half into account of battery usage.

Edited April 25, 2006 by Ingvarr

[Guest gts]

Wow... Looks like there is no such thing as one real truth about it.

Anyway, thank you for your notions.

PS: The early death of your notebook battery may be the result of a faulty battery or, more obvious, heat from processor or grafik-chip or hd. Heat makes LiIon-batteries age way faster...

Besides - this is something really new that I never thought about. The heat must be the problem because the laptop was powered on all the time. Sometimes when I had to take it away I noticed that the table stays noticeably warm even if the laptop has already been taken ayay. The heat could be sensed even by touching the bottom of the desk. ;)

That should probably be one of the reasons why AC adaptors are almost never integrated in laptops.

[Guest danolaru]

I think that you should take the ac adaptor once every 4, 5 days and let it discharge the battery without any power consumption applications or heavy processor using and this refresh will extend the battery of a laptop.

The next thing is the quality of the battery, that is by luck(all made in china) you can imagine

You can buy an invertor for car that converts 12v in to 220v and gives a max of 150w nominal and 300 w max(never tried) for your car- this is good also for mobile chargers

I see that on the market there is no laptop li-polymer based battery, just li-ion

[Guest kam_]

Lithium-Ion batteries don't like overcharge, high current draw, and over-discharge. The battery itself has to contain a protection circuit to protect against these conditions.

Lithium Ion batteries are considered fully charges at 4.2v +/- 0.05v, and protection circuits have to protect charging over this point. As you can imagine 0.05v isn't much leeway for overcharging!

If the battery is contantly overcharged metalic lithium can plate the cell. This reduces the effective surface area and restricts ion flow thus reducing the capacity of the battery AND the top current draw.

If mositure has entered the cell (after production, or during production using a low quality process) this can actually be quite hazardous. This is the main reason protection circuits are required in LiIon cells and not just optional.

The protection circuit uses an algorithm based on the current being drawn, and the voltage across the battery to determine how charged it is. It gets it right most of the time, but if you keep plugging and unplugging the charger when the battery is at 100% it will eventually overcharge it and cause plating.

Over discharging can cause copper plating which can cause the cell to short internally. Again this is hazardous as it can cause alot of heat. The protection circuits should stop discharge well before the battery gets below 2.5V per cell, and physically disconnect the battery at around below 1.7v.

If the battery is discharged at a fast rate, the excessive transition of Ions can cause the crystalline-layered structure of the plates to breakdown. This happens in LiIon cells using cobalt oxide plates, and not in Lithium Polymer batteries (which are the new higher capacity cells - not used in phones yet!).

If this happens there will be a quick rize in temperature which can cause the solvent of the electrolyte to catch fire. This could cause toxic fumes in some special circumstances, and the fire itself would continue to burn at a high temperature until all the solvent was burnt i.e. you wouldn't be able to put it out very easily.

Again the protection circuit would regulate current draw and cut off the battery before this happened. This is another reason why LiIon batteries have thermistors in them to check battery temperature. The cheap knock offs that don't have them are potentially dangeours - at worst, or have to cut off much earlier meaning less capacity - at best.

Even if you don't use the cell it will deteriorate and plating will occur naturally. The elecrolyte may also begin to seperate and cause some shorting. Both processes will happen so slowly that it should not be dangerous, but capacity will suffer.

When LiIon batteries are stored (shipped in the phone box) they are typically charged to 70% for these reasons. This is the optimum capacity that decreases the rate of all the negative processes going on. Signifcantly too, it offers a long time before the battery voltage gets to a dangerously low level - causing battery failure.

The bottom line is:

- Never plug/unplug the phone repeatedly in a short period of time - especially if the battery is near 100%. This can cause overcharging.

- Never leave a fully discharged battery to rest or in the phone for a long period before recharging it. The battery may discharge to a over-discharge level.

- To maximise battery life, don't use super intensive programs for very long periods. Like games which require overclocking. You'll know when its not a good idea when your phone gets really hot!

You can do all of these things if you want, the protection circuit will take care of it, but capacity will suffer.

As for general charging, the best point to charge the battery is when its at around 50%, and stop charging at 80%. This of course isn't practical, and anyway won't make that much difference. So my advice is to charge the battery before it gets below 20%, and only charge it if its below 70% - ONLY if its convenient. Don't be too pedantic about these rules as it makes less difference that u might think!

[Guest Saeed77]

I know the replies to the topic date back to last year so not sure if my reply will be relevant.

I have an Orange SPV C500 (HTC Typhoon) since May 2005. I was aware about the issues with continuously charging and overcharging devices on a regular basis so what I use is a timer plug (these things are used with lamps to switch them off and on at certain times set on the device itself - home security reasons).

I set it about two and a half hours for full charge and plug the adaptor in. Typical setting on there would be 12am to 2:30am. Once the time has been reached, the mains supply is swtiched off. I only do this when I get a message that the battery power is low or if it's on one bar and I know that I'll need the phone fully charged for the next couple of days. The charge lasts me for a good 4 days. Apart from that, sync wise I tend to use Bluetooth. No wires needed and doesn't charge. The only time I use a cable is if I want to transfer podcasts.

The advantage with the time plug is that say you have two bars showing on your phone but you want to charge it since you may be away from a power source for the next few days, you can set it for a one hour charge only.

The "timer plug" charge may sound a bit silly but before discovering Windows Mobile and purchasing the SPV C500, I had a Nokia 3310 and I used the same method. I had the Nokia for about 4 years and the battery worked just fine. I'm not technical minded on these things so I'm not sure if it was the timer plug method that may have helped but it certainly stops the "over charge" issue!

Hope the idea helps.