Li-ion charger

Texas Instruments has Benchmarks line of gas guage and charger I.C.'s for Li+ batteries. They are fairly simple to use and should save you the trouble of blowing things up.

Not having accounts with any trade suppliers unfortunately limits me to the rather meagre range of semiconductors stocked by Maplin - and whatever I can skip raid!

A plethory of stuff at Linear

BTW dont put a Sony label on it

martin

I wasn't going to put any label on it - why particularly not Sony?!

Besides - I thought it was Dell laptops leading the way in using Li-ion batteries as incendiary devices!!!

Sony make the batteries for Dell and Apple laptops which have recently been in the media recently for removing eyebrows.

Get a RS or farnell account, fake some letter heads, as long as you pay by credit/debit card no probs.

BTW where are you based?

martin

They were made by Sony, for Dell, but they have no indication that they are made by Sony, unless you enter the code numbers on Dell's non working battery recall website and it spits out a recall notice. All I ever get is "Server not found", but I have at least one battery involved in the recall. Sony also made the battery packs for Apple that are being recalled. I've pulled the batteries out of all my newer laptops, just in case.

BTW, on the TV news out of Orlando a couple days ago they reported on a Dell laptop that caught on fire in the cab of a big pickup truck. The moron threw it into the back of the cab where it set the truck on fire. His excuse was that he just wanted to get it away from his daughter. I would have either thrown it out the window, or pulled off to the side of the road and set it off in the dirt to burn. Tourists!

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Go to the website of the battery cell manufacturer and get the datasheet. If you don't put several cells in series but rather just use one cell, then you should be able to get away with just a current-limited constant voltage power supply, but some kind of redundant circuitry to disconnect the battery if the charger develops a fault might be needed depending on where the thing is being used. You must make sure that you don't charge the battery above a certain voltage (about 4.2V but read the datasheet) nor discharge it below another certain voltage (again see datasheet). If you want to float-charge a lithium cell then the voltage is supposed to be a bit lower than the value used for cyclic charging and discharging. You should consider the likelihood and consequences of any component failing, and I would choose to put the battery in a substantial diecast metal box in case it catches fire anyway.

Chris

In message , dated Fri, 8 Sep

2006, ian field writes

RS (in UK, not Radio Shack) will take credit card orders on the Web. So will Rapid. Farnell will, but only for orders over a value which I've temporarily forgotten. There are other suppliers, too. Get a copy of 'Television' magazine.

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Either £20 or £30 for mail order, or £5 if you're going down to the trade counter to pick it up. That £5 limit applies to cash-at-the-trade-counter orders too, IIRC.

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The Maxim MAX1811 - it's a single-chip 500mA lithium-ion battery charger. Feed it +5V, add some decoupling capacitors and wire it up to a lithium battery. Simple.

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If you don't want to use a pre-made charge controller, then here's the standard charge method for _standard_ Li+ (but check the battery datasheet from the mfr carefully)

Constant current (at up to the 1C rate) until the battery terminal potential reaches 4.2V per cell. It's usually ok to charge Li+ in series, but due to imbalance (especially in older batteries), it's best to measure each individual cell for the 4.2V (The line of T.I. gas gauges and chargers mentioned earlier do, in fact, do this).

Switch to constant voltage mode until the charge current drops below some threshold (usually CCrate/10) Stop charging.

Do not trickle charge Li+ (this can have spectacular side effects).

Cheers

PeteS

UK!

Recently I heard RS had waived the requirement to be an account holder, so I emailed them and they sent me the CD cat. As I wanted some LEDs I logged on to view the data sheets before deciding which ones to buy and their system refused me access! They ignored my email asking about this so I didn't bother with them anymore!!!

Allegedly someone in Aus' described it as a "flamethrower"! - and going by the photo of an unusually well illuminated conference room shown on the news that's a fair comment!!!

The Sony connection is something I should have guessed! From my monitor repair days quite a lot of Dell monitors were Sony's in disguise. Quality was either very good or very bad _ one model in particular had a tall steel heatsink in the middle of the board which hit the CRT bowl if the base flexed, Sony decided that the best cure was to glue a rubber block to the CRT, this trapped the heatsink between the PCB and block so the PCB warped and cracked!!!

Thanks - all good advice, the question was more general as pertaining to whatever cells I might happen to come by, but one Toshiba pack contained an array of Panasonic cells which have what might be part numbers stamped on them, this might be a good starting point.

By 'refused me access' do you mean it wouldn't let you have the datasheets without logging in? That always was annoying, but I noticed recently that you don't need to be logged in to see datashets any more. Even before that, creating the required account was pretty straightforward, even if it was a pointless inconvenience.

Tim