Lithium Iron Disulphide batteries.

Linear and non linear

Lithium Iron Disulphide batteries.

Postby chrismb » Fri Feb 01, 2013 1:39 pm

OK, so I have a remote control that likes to have a good 3.0V worth from two AAA batteries, else the signal isn't bright enough to switch the gadget it's pointed at.

I hate alkalines (should be ~1.55V open circuit). I have had too many leak in remote controls before to even contemplate ever using those filthy things, I'd only use them if I know I will use them up fairly quickly and chuck. Given they can last a while in a remote control and I have had them leak even before they stop working, it's why I always use NiMH in them. I have had hundreds of NiMH over 20 years, and I can recall only ever two having leaked, and that wasn't dribbly sticky stuff, it was just a bit of dry powder (not sure what that was exactly?).

The remote's ok with NiMH when fully charged (~1.40V open circuit ) but just a little use and once it drops to ~1.33V the remote gets unhappy.

It's not an uncommon thing in many circuits, where 1.5V batteries are 'recommended' and NiMH aren't, for this exact reason.

So I was just looking up getting some non-rechargeable lithium batteries, which are built with better non-leak construction and have a very long storage life. I've not really examined the chemistry before but did hesitate to wonder how lithium, with its 3V electropotential, works in a 1.5V cell. Well, a cathode of iron disulphide seems to fix that, which produces a combined open cell voltage of ~1.74V. This drops rapidly under load, so works very well in high current 1.5V applications especially as the construction is a spiral-wrapped type giving a very large surface area for the chemistry to do its stuff.

Well, that's just all background info. The thing I was wondering here is [as always!!!!] how best to use it despite the manufacturer's instructions. It's what we do here, isn't it!? ;)

So these things are not to be recharged. Yeah, sure!... :) All chemistry is reversible, but the question is whether these batteries can be reversed safely and if so how many times and under what circumstances.

First off, I would be dead certain that recharging these with low or high State-of-charge would be bad. If the construction is not meant for reformation of the ionic species then the electrodes will regrow in very peculiar ways and become damaged easily. So, first off, I guess the SOC strategy would be to ensure a 40%-60% operating range.

Secondly, they are high surface area devices which would mean they will draw a big current as the input voltage exceeds the cell voltage. So this would have to be a current-controlled recharge strategy rather than a voltage controlled one, else the heat build up will be dramatic and very quick! Also, I suspect that hot-spots would form rapidly where the electrodes regain mass at different points. I would hope/suspect, then, that short pulses would encourage reformation of the electrodes whilst the in-circuit internal resistance could help load the cell during switch-off periods so that the electrodes grow uniformly.

So I figure I might have a go at recharging these suckers once they are at no less than 40% SOC back up to 60% with a pulsed-cycle current-limited scheme. I was figuring y'all might have something to say about this, and if my understanding of attempting to recharge this cell-type is 'not even wrong', or worth a go!?

I suppose, thereagain, I should concern myself about the possibility of a recharged lithium battery going up in a puff of flames, though. It's what they are famed for!!

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Re: Lithium Iron Disulphide batteries.

Postby Starfire » Fri Feb 01, 2013 10:46 pm

Food for thought - metal fires are extremly dangerous - humble Aluminium is the basis of thermite which is used to weld railway lines and for firebombs.
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Re: Lithium Iron Disulphide batteries.

Postby Doug Coulter » Sat Feb 02, 2013 9:20 pm

I looked and found a 3v 1/2 aa at digikey, lithium, primary, 1 ah for about 5 bucks. You could use one of those and it should last nearly forever.
Of course, one full sized one and a short across the now-empty other one would do as well, and last years. If you look, they make these primary cells with 3, 3.3 and 3.6v outputs - different chemistries.

I don't have a bit of trouble with alkalines I buy that are fresh - I get them from McMaster, made like this month. I DO have troubles with dusty ones bought at the stores.

I wonder if there's a capacitor in your remote that lets even a very marginal battery work, even when it's on the threshold of leaking out? If so, I guess the cure is to check more often, even if the thing is working. Remotes don't draw much or for very long, so that could be why you get leaks before apparent failure - the batteries have had plenty time to charge up some capacitor that will run the remote for a bit, even near-dead ones might be able to.

Back when I was making prosthetics, and rechargable Li's were a new thing, they refused to sell them to us without a charger they wanted "way too much" money for because they were so dangerous then. You'll never hit that laptop fire crap though - that's from too-rapid drain (C/2 kinda junk).

I do know this, the more advanced the battery is, the harder to charge it right.
NiCd - just trickle at C/10 forever, no problem.
NiMH - nope, taking it past full on trickle kills it dead as a hammer - only takes once. They use much more sophisticated control, usually a uP, and a thermistor to determine charge endpoint.

And then we have GM's Volt battery - which contains 96 uP's, temp sensors for each cell in a 96 series string (three 96's in parallel) and active temperature management with it's own coolant loop with separate control for each cell - the up's can switch loads on each cell separately to make the others equalize, all kinds of crazy stuff is required to make those live.

I'd just get fresh alkies and check them now and again. Both EverReady and Duracell have worked fine for me when not already 2 years old on some store shelf. And they last longer when not having sat for a year already.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Re: Lithium Iron Disulphide batteries.

Postby Jerry » Sat Feb 02, 2013 11:05 pm

I use the 1.5v AA lithium cells in my weather station transmitters. They are the only batteries that have any output at low temps.

The lithium primary cells actually have strips of lithium metal in them. The metal is pretty much dissolved as it gets used. Recharging would mean you would have to reform that foil. That is just not going to happen.
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Re: Lithium Iron Disulphide batteries.

Postby Doug Coulter » Sun Feb 03, 2013 4:39 pm

I wasn't suggesting he try to recharge them, just use 'em. His main complaint seemed to be the leakage from the alkalines, a problem I rarely have, but then maybe he's buying the "bargain" ones, which are never truly a bargain.
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Re: Lithium Iron Disulphide batteries.

Postby chrismb » Sun Feb 03, 2013 5:20 pm

Doug Coulter wrote:I wasn't suggesting he try to recharge them, just use 'em. His main complaint seemed to be the leakage from the alkalines, a problem I rarely have, but then maybe he's buying the "bargain" ones, which are never truly a bargain.

For sure the cheaper ones leak more, but duracell, AA branded, and energiser types have all leaked in remote controls after a few-to-several months. In fact, there is probably nothing in it because the cheaper ones go flat quicker so get noticed and replaced sooner, whereas the more expensive ones keep going even when they start leaking.

Yeah, OK, I could check every once in a while, but there is a box of more than a dozen remote controls in the 'remote control' box and life's too short. Anyhow, remotes are actually less of a problem than other things I have had leaky batteries leak into - remotes generally are easily taken apart (snap fit, maybe a bit of broken plastic) and are water-washable because they have those carbon-pad type buttons which are no good in no-clean-flux type production lines, so the assemblies are usually water-compatible. Just time consuming and messy to clean up.

It's no big deal, I was just wondering about these 1.5V lithium cells as I've never considered using them before this problem.
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Re: Lithium Iron Disulphide batteries.

Postby Doug Coulter » Sun Feb 03, 2013 6:52 pm

We solved most of our remote problem here by buying a "universal remote". They come in various flavors, but one of those can replace many others, either by listening and learning, or in some cases by inputting a product code supplied by a factory.

It's weird you get leaks before the thing quits working. I can't recall that ever happening here - maybe you need to look in there and take out any supercap kind of thing, so they'll alert you by not working sooner?
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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