Battery University

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Great site for battery info.

http://batteryuniversity.com/learn/

Sorry if it was posted before, no time to check right now.

cZ5WT :?

"I may make you feel but I can't make you think" - Jethro Tull - Thick As A Brick

"void transmigratus(void) {transmigratus();} // recursio infinitus" - larryvc

"It's much more practical to rely on the processing powers of the real debugger, i.e. the one between the keyboard and chair." - JW wek3

"When you arise in the morning think of what a privilege it is to be alive: to breathe, to think, to enjoy, to love." -  Marcus Aurelius

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Lots of battery stuff ! All in one place ! cool.

- Will find's a Way.

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larryvc wrote:
Great site for battery info.

http://batteryuniversity.com/learn/

Sorry if it was posted before, no time to check right now.

cZ5WT :?

I recently landed there a few times.
My NiCd cordless drill broke down last week. Should I buy new NiCd, change to NiMh or Li-Ion? The drill and batteries should last many years. I do not use it very often.

The NiCd still seems the best to me for raw use. NiMh (hope LowSelfDischarge is standard by now) do keep there charge longer. Good (better then NiCd)! But my charger cannot handle NiMh. How long will NiMh last compared to NiCd if used not frequently?

I have learned so far that Li-Ion is light weight but very computerised: both charger and batteries. That makes the system rather expensive. It also seems that Li-Ion is subject to ageing. I understand that even an unused battery is finished after a few years.

My impression is that Li-Ion is the new trend, but also that NiCd and NiMh are still innovated. Reading 10 year old articles may not lead to the right choice.

Please give your opinion about what battery technology is best for not so frequently used cordless drill.

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For home use I still have a bunch of AA NiCd that are rather useless because they are allways empty when you need them.

What I really use a lot is the AAA type NiMh (for my Microsoft Bluetooth Mouse). I wore out 1 set of 4 completely. Testing voltage drop over 47 ohms learned that there internal resistance had risen too much for practical use. No problem: they were some 10 years old.

Last year I bought new NiMh AAA en 9V blocks. I am most happy with the low self discharge. One is already for more then a year in a temperature meter. My NiCd's would be empty within a month...

(BTW: My new NiMh are these: http://www.vapex.nl/aaaaa-nimh-batterijen-c-48.html very affordable and send no extra cost, even if you buy only 1)

Last Edited: Tue. Sep 18, 2012 - 08:41 PM
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If you really want to know what battery technologies are "best" try flying electric model planes and helicopters. When I started out there simply was no choice it was always NiCd that was used. But they have a low energy density so to carry the kind of power needed for electric flight lead to heavy batteries and hence lethargic planes where the majority of the performance was used to simply carry the batteries aloft and there was nothing left for "performance flying". Then along came NiMh which had the advantages of less of a memory effect, higher energy density but not as high charge/discharge rates. Also new battery chargers were needed to cope with their charging which relied on "delta peak" to spot when the charge was close to completion. After that came Lithium Ion batteries in metal cans. They offered far higher energy density so a lightweight battery could replace the old heavy NiCd or NiMh batteries. But they again needed special chargers and if over charged or over/rapidly discharged they could ignite or even explode. For flight one typically wants to discharge a battery at 10 times (or more) it's capacity rate. So a 1Ah battery, instead of sourcing 1A for an hour would be made to provide 10A for 6 minutes. Batteries don't like this kind of discharge rate NiCd were best, then NiMh, then LiIon. Then (because of the development of laptops and mobile phones) battery technology really moved on with Lithium Polymer batteries which are a form of LiIon but with a different electrolyte and packaging method. These are the current state of the art for electric flight as almost all chargers now know how to do the Constant Current/Constant Voltage cycles that Li batteries required and these things can not only be driven to deliver 10C..30C (so 1Ah delivers 30A for 2 minutes!) but unlike Li batteries of old that had charge rates of just 1C or 2C (so a 1Ah battery could be charged at 1A for an hour or 2A for 30 minutes) they can now be fast charged at up to 10C or more. So you can charge your 1Ah battery in 6 minutes at 10A. While I have shelves full of NiCd and NiMh battery packs in my shed ("the skunk works") I haven't used them for years and years. For R/C flight which possibly pushes rechargeable batteries further than any other use they are ever put to (apart from full-size electric cars perhaps?) then it's been a few years since anyone would ever use anything but LiPo. I guess this is in part because electric flight needs the highest energy density possible so the batteries are light even for reasonable duration flights with high performance but it's no coincidence that you simply won't find a laptop or mobile phone these days that's using anything but Lithium batteries too in a more "sedate" use of the technology. Again I guess the drive here is for high density, light weight and maybe electric drills don't want to be light - in fact maybe there's an advantage to them feeling "solid" and that's why they still use NiMh or even NiCd?

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Clawson: How old are your Lipo packs? In what extent are they subject to ageing?

I have a HP Pavilion laptop bought in 2008. I has allways has been connected to mains. This year I took it on a holiday trip. But at my first internet session 1 week after leaving home it stopped already after 10 minutes.
I was very disappointed with that.

I conclude that Li-Ion batteries are not so good in the long run. Probably because the laptop battery compartment is always warm. Most modern electronics are outdated within 2 years, so who cares for battery ageing there.

I think for (consumers) cordless tools it is important that the investment lasts for some 10 years. I do not really trust here the Li-Ion in the longer run.
The 3 year battery warranty from brands like Makita, Metabo do (only?) suggest that they have improved things.

I have tested this week the NiCd packs of a 2004 Hitachi drill. One had more(!) then full 100% of specified capacity. The other pack was reduced to 70%. Tested with lamp.

The reason for NiMh or NiCd in cordless drills may also be that the price per Wh capacity (and long term reliability) counts more then the weight.

Last Edited: Tue. Sep 18, 2012 - 12:40 PM
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Quote:

Clawson: How old are your Lipo packs? In what extent are they subject to ageing?

I've had packs with 400 or 500 cycles on them that are several years old. It's true that LiPo do have a finite life but AFAIK that's true of NiCd and NiMh and LiPo do not suffer from the "memory effect" that used to plague NiCd batteries.

LiPo are quite temperature sensitive but work better when it's warmer in fact. If you have cold batteries and try to fly on a cold winter's morning you get about half the flight time of a warm summer's days.

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If you leave your laptop connected to the mains while using it you will very quickly ruin the battery.
As I understand it, this is because Li batteries don't like to be fully charged for long periods and they don't like to be too warm. Leaving them connected to the mains permanently pretty much guarantees both these conditions.
Stupid as it might seem, you might want to remove the battery pack if you expect to be connected to the mains for extended periods, or, alternatively, if you replace the battery then keep the old one for permanent mains running.

Read the "Battery University" link that kicked off this thread for more details.

Lithium is fast gaining popularity in cordless tools, prtly because of the slow self-discharge, which means that you can pick up your cordless circular saw a couple of months after you last used it and the battery won't be flat. However, they do tend to be quite a bit more expensive.

Four legs good, two legs bad, three legs stable.

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It has been suggested that Li-Ion packs age so fast (just loose capacity by waiting to be sold, this is not the same as selfdischarge) that they should have a production date sticker.

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John_A_Brown wrote:

Stupid as it might seem, you might want to remove the battery pack if you expect to be connected to the mains for extended periods, or, alternatively, if you replace the battery then keep the old one for permanent mains running.

To what extent is it possible to run a laptop without the battery? I am "somewhat" reluctant to try it...

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Quote:

It has been suggested that Li-Ion packs age so fast

Is it the case that mobile phones and laptops are sold so quickly or go "out of date" so quickly that they never accumulate considerable "shelf life" then? I'm sure there must be ones that have been held in stock for a year or more and are still as fresh on day one as a week old model.

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clawson wrote:
I'm sure there must be ones that have been held in stock for a year or more and are still as fresh on day one as a week old model.

Are you really sure? Here
http://electronics.howstuffworks.com/everyday-tech/lithium-ion-battery2.htm
they say:

Lithium-ion batteries age. They only last two to three years, even if they are sitting on a shelf unused. So do not "avoid using" the battery with the thought that the battery pack will last five years. It won't. Also, if you are buying a new battery pack, you want to make sure it really is new. If it has been sitting on a shelf in the store for a year, it won't last very long. Manufacturing dates are important.

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Quote:

They only last two to three years, even if they are sitting on a shelf unused.

This is not my experience of LiPo batteries. I've used them after sitting idle for a year or more and not noticed degradation. With the site you quoted were they making that comment based on modern LiPo's or the very first ones that appeared? (I notice they use the term LiIon not LiPo in fact).

EDIT actually reading the HTML source of that page says:

Brain, Marshall.  "How Lithium-ion Batteries Work"  14 November 2006.  HowStuffWorks.com. <http://electronics.howstuffworks...  18 September 2012.

So the article appears to date from 2006. That's a long time in battery chemistry development!

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No mention of LiFePo yet? They seem to be all the rage these days...

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gdhospers wrote:
John_A_Brown wrote:

Stupid as it might seem, you might want to remove the battery pack if you expect to be connected to the mains for extended periods, or, alternatively, if you replace the battery then keep the old one for permanent mains running.

To what extent is it possible to run a laptop without the battery? I am "somewhat" reluctant to try it...

I do it with my Dell all the time, after trashing the first battery by using it connected to the mains all the time.

Four legs good, two legs bad, three legs stable.

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Dell batteries keep a 'number of recharges' counter, when it reaches a certain number it stops working.

So the conspirators say.

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It is somewhat confusing to distinguish between all the Lithium types.
The cordless drills I looked at have 3.7V cells, and according to this (nice!) site: http://www.batteryspace.com/li-ionsinglecell.aspx they live for about 500 cycles, not better then NiMh. NiCd lives longer. And LiMnxNiyCozO2 Li-Ion type has the lowest working temperature: only up to 40°C.

But LiFePO4 outperforms everything. Their cells are 3.2V.
I think Clawson must be talking about these cells.

And I also think that my laptop has the not so good 3.7V type.

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Quote:

I think Clawson must be talking about these cells.

Nope I was talking about the 3,7V (nominal, 4.2V max) LiPo cells that do have about a 500 cycle life though I've had some with more than 1,000 cycles on them and only starting to show charge degradation. As I say laptops and mobile phones are driving battery chemistry hard, LiFePO4 is just the next step. No doubt there will be even greater things to come:

http://en.wikipedia.org/wiki/Rec...

(that confirms 500-1000 for LiPo, 500 for NiMh, 1500 for NiCd (but with memory effect))

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The usual 3.7V (4.2V charge) cells are Lithium Cobalt Oxide chemistry.

You can get them with two different separators, either one that behaves basically as (wet) paper, or a porous polymer. The polymer can be bonded to the electrodes, allowing you to make strange shapes, and has better cross section giving less ESR. The papery one requires compression, and thus an outer metal casing, but the battery is 30% cheaper to manufacture.

You can also get them with different electrolytes. Depending on the composition of the electrolyte, they have different storage life, and different self discharge. I have stripped ~50 Dell battery packs over the years, and they have used a plethora of variations. Some of the slightly older ones have very low self-discharge, comparatively low capacity, but last forever. Some newer very-high-capacity cells (in a given volume) show large self discharge, and leaving these for 6 months may discharge them below the safe level.

LiPo is a slang term invented by the RC community. It is not a chemistry.

/Kasper

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About cell life/ageing of Li-Ion from wikipedia http://en.wikipedia.org/wiki/Lithium-ion_battery says:

A Standard (Cobalt) Li-ion cell that is full most of the time at 25 °C (77 °F) irreversibly loses approximately 20% capacity per year.
Poor ventilation may increase temperatures, further shortening battery life.
Loss rates vary by temperature: 6% loss at 0 °C (32 °F), 20% at 25 °C (77 °F), and 35% at 40 °C (104 °F).
When stored at 40%–60% charge level, the capacity loss is reduced to 2%, 4%, and 15%, respectively.
In contrast, the calendar life of LiFePO4 cells is not affected by being kept at a high state of charge.

(My laptop battery has allways been charged 100% and probably was warmer than 40°C during 4 years, so yes it may be EOL)

(I can not find a battery/energy saving option that keeps the battery charged at 40%-60%.
That should be implemented in my next laptop!)

Last Edited: Tue. Sep 18, 2012 - 09:01 PM
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Interesting.

I've been using NIMH to run trains for years. Just got a set of Lithium Ion, but haven't successfully used them as one cell is dead. Waiting for a replacement from cheap far-east source.

The largest known prime number: 282589933-1

It's easy to stop breaking the 10th commandment! Break the 8th instead. 

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The short lifetime of rechargeable batteries has bugged me for quite a while. I want a laptop powered by a fuel cell + methanol reformer. If we're allowed to bring lithium onto airplanes, methanol should be fine too :)

And why can't a laptop's charger maintain the capacity at a level that prolongs the life of the battery? I'm pretty sure electric cars do this. I suppose it would reduce the time you can use the device after it's disconnected from the mains, but it ought to be optional, at least.

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Quote:
And why can't a laptop's charger maintain the capacity at a level that prolongs the life of the battery?

So they can sell you more new batteries ;) It's planned obsolescence.

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Today I have opened my Philishave. I has been on its charger (for 1 dayly shave) for about 10 years.
Its condition is weakening now, but I still can (and have to) use it. At least until christmas :)
It has only one 1.35V(at full charge) NiMh cell inside.
I have measured open voltage and over a 33ohm resistor and from that I found that internal resistance is now 0.5 ohms. Recent cells have internal resistance of about 0.025 ohms. This shaver motor http://www.mabuchi-motor.co.jp/cgi-bin/catalog/e_catalog.cgi?CAT_ID=ff_260pa may need between 1 and 2 amps. So now I am shaving at half power, while the other half heats up the battery. (Why is all my stuff EOL?) :(
Anyway, for the statistics: this NiMh had a practical life time of about 10 years.

Edit:
I stated that recent cells have internal resistance of about 0.025 ohms. What I did not mention is that this is impedance at 1000Hz, not DC.
Battery university says: "For example, Li-ion in an 18650 cell produces about 36mOhm with a 1000Hz AC signal and roughly 110mOhm with a DC load".
http://batteryuniversity.com/lea...
I did not expect that the difference between AC and DC resistance would be so big! I guess that the same behaviour applies to NiMH, but I cannot find data now. The 1000Hz spec is a pitfall for the less educated (like me).

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krazatchu wrote:
No mention of LiFePo yet? They seem to be all the rage these days...

Here they are:
http://www.a123systems.com/lithi...

And off they go:
http://www.technologyreview.com/...

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I now have 4 dead cells and 2 live ones from that far east source. Perhaps I'll look elsewhere.

The largest known prime number: 282589933-1

It's easy to stop breaking the 10th commandment! Break the 8th instead. 

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Torby:

I use these guys.

http://www.batteryspace.com/

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Stumbled over this promising new battery technology (new effort on an older idea): the fluoride battery.

"Fluoride battery has potential to hold ten times more energy than lithium battery"
http://www.dailytech.com/Researchers+Create+Fluoride+Battery+Look+to+Replace+Lithiumion+Technology/article23093.htm

http://www.youtube.com/watch?v=3O-WG74_xnw

Eglish version:
http://www.youtube.com/watch?v=Itd4V72VvTg

More to read: http://www.int.kit.edu/665.php

Last Edited: Tue. Jun 11, 2013 - 09:01 PM
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I think i am safe in saying, buy some popcorn, sit back and watch the world explode.

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My 2 cents:

Quote:
When stored at 40%–60% charge level, the capacity loss is reduced to 2%, 4%, and 15%, respectively.

combined with cold store this is NASA recommendation for emergency/spare laptop batteries.
Regular laptop operation on mains does not damage battery; heat, generated from other elements and full charge all the time do, indeed.
Dell laptops have smart battery controller with hard coded life limit: cycle count and loss of capacity for correct fuel gauge operation.

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A Li-ion battery immediately starts to degrade when its temperature rises above 86 °F = 30 °C.

http://phys.org/news/2013-04-life-lithium-ion-batteries-electric.html#inlRlv

Most laptop batteries are hotter than the threshold temperature. Even a phone's battery close to the human body will degrade.