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Tuesday, 31 July 2007

Gentlemen Charge Your Batteries!

I've kept an eye on all the threads about battery usage and charging routines and I have some observations!
Some of you are cycling your batteries. Don't!
Some of you are conditioning your batteries. Don't!
Some of you are discharging your batteries. Don't!
Why? Well, contrary to one poster who said it makes no difference, it harms the Lithium Ion chemistry!
They don't like being discharged below a certain point. Do it too often and they won't recover!
They don't like a widely fluctuating charging band! This will hasten the reduction in capacity!
They don't like being overheated (although their operating temp range is quite broad!). And strangely they don't like it too cold.
They have a finite shelf life which starts from the day they are manufactured and their condition from then degrades to the point where they fail!
This is not to be confused with their charge holding abilities which are very good for their full life! When they go they just go!
Additional problems associated with low discharge is that they need the extra ooomph to get them charging again, but each discharge takes a little bit more out of them! That's why 500mA USB ports have trouble from "flat" and why the charger supplied is 800mA!
So what should you do?
Well, all the above is well documented as Lithium Ion battery characteristics, but, I haven't been able to find one example of an authoritative guide to charging! I heard ideas about doing it with the phone switched off or on standby or by so many hours, etc, but nothing was backed up by any reasoning.
Now, we all use our phones in different ways, but, the one thing we all need is max power so any method of gaining power should apply to us all.
I have run some tests on three N95s all purchased at the same time and all with batteries of approx the same age and they have had approx the same usage. I have charged each of three in different ways-
A. Was charged only every night (approx 6 hours) and nothing during the day, for a week.
B. Was charged when it went flat.
C. Was charged at every opportunity, day and night.
After the week, at the next opportunity when the phones all had an end of charge fall together, they were all unplugged and left without any use at all.
A, lasted for 50.5 hours.
B, lasted for 22 hours.
C, lasted for 58 hours.
That's a huge difference and could go part way to explaining why some people have different experiences with the battery.
All phones are approx 4 months old and all have the same batch no. on the battery.
Something I did notice was that phone B got hotter as it got closer to failing. This could be it's attempt to wring out the last drops, I don't honestly know!
The coolest in operation (subjectively) was phone C.
Also when the phones were next charged (to battery full) the quickest in order were C, A, B. None of the phones were switched off, when on charge, as, for this I would have to have a fourth phone so this was beyond the scope of this test, but, I intend to try a head to head with two phones over night for a week!
More experiments are needed so I would ask others to do similar tests!

20 comments:

Anonymous said...

here is another curly one ... I'm not sure if there is any science behind it ...

I go skiing a lot and i find, if i charge my phone to full at sea level and go up to the mountains approx 1700m high, the battery wastes quite quickly.

But if ia charge at altitude and go down to sea level, the battery lasts much longer without charge.

kooky I know ..

Groucho said...

Nice one!
At sea level the batteries molecules will be more densly packed and "work" more efficiently! This could be the reason as they will have less energy loss!
You would probably find that the charge times would differ as well. Longer at altitude?

Anonymous said...

Have you repeated these tests since the V12 Firmware was released?

I have noted my N95 battery life has doubled since V12, (3.5 days instead of 1.5 - 2 days between charges). This is confirmed by various other users on the A-A-S forums.

Any ideas?

Groucho said...

I get the same thing!
A it's all in the phone, more than likely better charge management software!

sjc said...

Thanks for the Info. on not draining down the N95 battery.

Interesting data on the three test batteries.

sjc

Groucho said...

Your welcome, sjc!

DKill_ said...

Thanks for doing these tests for the community.

Finally i have some clarity and 2nd person hands-on information for my N95 that i can actually use.

Again, thanks!

- DKill_

Groucho said...

Hi DKill_
Thanks for the response.
Feedback is great when it shows the blog is useful!

Anonymous said...

Great post, great detective work, congratulations! I've linked to it from several Windows Mobile forums; see their list at http://www.pocketpcmag.com/blogs/index.php?blog=3&p=2289&more=1&c=1&tb=1&pb=1

Tom said...

you may want to also compare the batteries' lifespan. for example, charging the battery as much as possible may make it last 10-20% longer on average, but it could also shorten the battery's lifespan by 10-20% compared to the battery that gets charged once a day. of course all this is hypothetical, so what we really need is a scientific method, or at least something cooked up in mythbusters' lab. ;)

Peter321 said...

Interesting results - I do however see one potential problem with the test.

You should have done the same durability test BEFORE the week of different charging, to ensure that all phones/batteries performed the same, BEFORE the test was made.

It could be that phone B simply had a bad battery to start with, but without an initial test we do not know.

Groucho said...

Hi peter321,
I did realise this after I had started the test. I rethought the whole thing and came to the conclusion that there are quite a few variables that really should be eliminated in order to give as perfect a picture as possible.
BUT, you have to draw the line somewhere.
I could have checked each charger for output with and without load. Checked for voltage operation level, circuit impedence, individual phone charging characteristics or even the ac input from mains at different wall sockets (were they on the same ring?) etc, etc.
In the end I left the variable unchallenged because I concluded that's how the phones will be used on a regular daily basis (different chargers (wall and car) different loads and operating conditions).
Suffice to say my subsequent observations have been in line with the 'test' findings and I have done some more tests with other brands and found the same thing.

Anonymous said...

Hello groucho, thanks for the article and tests, but could you please give a step by step guide of exactly what to do when you first get the phone out of the box?
Should you use it right away, then wait till its almost dead, and do a really long charge?

Thanks!

Groucho said...

That's straightforward!
Charge it until full and then at every opportunity.
Keep it topped up as much as possible as this works the battery and the charging circuits. Lithium ion like being used like this.
If you don't charge until full on first charge you will not harm the battery but getting it to full at some early stage maximises your capacity potential for when you need a long period of use.
If you do drain the battery (not recommended) just charge it to full again and keep topped up once more.

Daniel Smith said...

Nice post, thanks for all the info, before I was charging only when it was flat because I thought that was best for the battery, now I know i'm wrong and I should charge it at every opportunity I can!

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weikiat said...

this is shallow. the warmth/heat of keeping yr batt in the phone all the time will decrease battery life. If battery is kept is 100% charge at 20degrees for a year, u will be left with 80% of batt life. if kept at 100% charge and 40degrees, u left with 65% of batt life.

Meanwhile, if battery is kept at 40% charge at 20 degrees, it still has 96% of the original capacity after a year. Just use normally, don't deep discharge and avoid warmth/heat.

This warmth/heat issue is also why yr laptop batt dies faster if u keep it in yr laptop all the time.

Groucho said...

So what you're saying is if we use the batteries in the way that everybody does use the batteries, this will result in the effect we all know we get?
The 'warmth/heat issue' as you put it is simply a fact of physics that is a given to a greater or lesser degree when any equipment of any sort is in use.
But, I'm not quite sure, to what you refer, with your 'this is shallow' opener?

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