Lithium-ion in your pocket?

Started Feb 7, 2013 | Discussions thread
mamallama
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Re: Lithium-ion in your pocket?
In reply to Roger99, Feb 11, 2013

Roger99 wrote:

mamallama wrote:

Roger99 wrote:

kcbeatty wrote:


Yes, one common application of the lithium ion is the CRC123 rechargeable batteries. The AA & AAA sizes are not referred to as AA & AAA batteries, I forget the name used. There are many uses for these batteries in things like laptop batteries. If you take apart a modern laptop battery you will find rows of these CRC123 batteries soldered together. In fact the very first hybrid car by Honda, the Insight, had 270 lithium ion batteries soldered together.

Lithium ion batteries have been around for several years in the smaller form factor. It's these new larger cell batteries that are new and apparently have protection circuits not too well designed. The lithium battery chargers are very simple, they just supply a specific voltage and current to the batteries and the protection circuit controls all the charging functions.

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Kevin

Yeah, for a few years now I've been making the most of the common cell design of these things by cutting open my laptop battery and replacing the cells within individually instead of doing the whole unit. It usually costs me around $8 to do this but I am aware I am playing Russian roulette for the savings. A plain green or yellow stick doesn't give you that much guarantee of the source of the unit but so far so good.

Anyway, while in these things I have noticed that the only real protection on offer is a simple thermistor arrangement. This isn't going to do much to read batteries that have gassed their contents and are preparing to blow. It is only going to stop the charge when the temp reaches a preset temperature. I think it wouldn't take that much to read pressure changes inside the outer casing of these units and render them dead rather than having them go off in your laptop.

I've seen versions of the car battery arrays that you mention. Great setup and a good solution to ongoing maintenance. I see it being a case that you would put the car in for a service and they could check the cells for failing units and then just swap them out rather than just dumping the whole block. It's about the only way they could make them financially viable for the user. Don't know why they don't make the cells hexagonal though for compactness. Time will tell on that one. Still, a fire in the center of that block of cells could make for an interesting afternoon as it spread to other cells.

Unless you know exactly how the protection circuits (hopefully both over-temperature and over-voltage sensors) operate with the charge monitoring device (in this case your laptop) I would not guess and hope. The problem is that the element lithium is very flammable and explosive and any mishap can be serious. Lithium is the metal used in the WWII flares so it burns with great ferocity.

The ones in the four laptops that I have worked on have had nothing in them but the thermistor going to the third contact in the casing. Beyond that all you can do is make sure that the cells you are using as swap outs have the same current ratings and capacities as the originals and aim for the same quality. Like I said, so far, so good.

Apparently for recent laptop batteries the safety circuits are external to the battery and in the laptop itself. The thermistor is to monitor the internal temperature of the battery and must be in the battery. I read that some safety circuits are small ICs and can be part of the charging circuit in the laptop.

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