Toshiba satellite a120 battery hack

[Metiz]

Lithium is an alkali metal so no water

There is a thermal fuse in the battery pack, I should just re-wire it to the new pack then right?
Good advice on the soldering, I'll give that a go. I should probably practice on some sheet iron/ aluminium (what metal are the terminals?) to see if I can pull it off.

[UAirLtd]

Ok, I'm going to have to step in here and prevent misinformation, because battery safety is an important issue and I think everyone should be in full possession of the facts.

There is NO lithium metal in lithium-ion laptop batteries. In the case of laptop cells (such as the cylindrical 18650 cell you are probably using), and cell phone cells, the lithium chemistry used is lithium cobalt oxide, which does not react with water in the same way that lithium metal does.

In a similar way, the sodium ions in sodium chloride (i.e. table salt) do not explode when you mix salt and water.

Therefore, you CAN use water to help extinguish lithium-ion battery fires, but other types of extinguisher can be more effective, such as sand/salt bucket, ABC dry powder extinguishers, or some class D fire extinguishers. You'd want to avoid water extinguishers if there is a chance of it shorting out other non-burning cells which would exacerbate the problem, but in an emergency, a water hose will work.

We work with lipo batteries on our quadcopters, we have on hand buckets of sand and salt (the salt melts and creates a crust over the battery which helps prevent additional oxygen getting in, and the sand soaks up the heat), and we also have ABC dry powder extinguishers. We're soon investing in a class D extinguisher.

To give you some sources so that you can check this information for yourself (highly recommended), here are some links I quickly dug up via a google search.
http://ehs.whoi.edu/ehs/occsafety/Lithi ... deSG10.pdf (see pages 3 and 13)
http://highvoltagehotrods.com/arent-lit ... re-hazard/
http://www.apigroupinc.com/news/headlin ... klers.html

It's worth bearing in mind that non-rechargeable lithium cells do contain lithium metal, and you don't use water extinguishers on those types of cell. A lot of people often mistake the two.

In summary:
- lithium primary cell: contains lithium metal, adding water goes big boom
- lithium rechargeable cell: does not contain lithium metal, adding water is ok
- but still preferably use sand/salt bucket, class ABC dry powder extinguisher, or class D extinguisher

[st2000]

Thanks UAir. (You would have though after spending all that time with battery guys they would have explained things as well as you did to me.) I didn't realize secondary LION batteries were so stable. And that is interesting how different primary Li batteries are.

[UAirLtd]

Secondary lithium ion may be chemically more stable to water at room temperature than primary lithium cells; but if you're talking about fire risk, LiCoO2 lithium ion secondary cells have a little problem: they carry their own oxidizer (in the form of the lithium cobalt (di)oxide cathode); their own fuel (in the form of a hydrocarbon-based electrolyte); and being batteries, may heat up during use or spark during malfunctions. Basically you've got all three corners of the fire triangle packaged neatly into one.

The fact that they have their own oxidizer is why CO2 extinguishers don't work so well - they can still burn in the absence of atmospheric oxygen, perhaps less vigorously, but burn nevertheless. One thing I'm unsure about is whether a lithium battery can get hot enough to begin stripping oxygen from CO2, which is possible in some metal fires such as magnesium: http://www.youtube.com/results?search_q ... in+dry+ice

So you can't easily take away the oxygen source, and you can't take away the fuel source, since both are packed into the cell. Your only reliable recourse is to dissipate the heat. That's where the sand and/or salt comes into play, they soak up and/or spread the heat. Some Class D fire extinguishers contain either copper or graphite powder that conduct heat, and generally act like a big heat sink. And that's also why using a continuous stream of water such as from a hose will also work for small battery fires (perhaps the limited flow from a water extinguisher may not be enough)

Safer lithium ion cathode chemistries such as LiFePO4, and to some extent LiMn2O4 release less oxygen when decomposing, and so are safer chemistries in the case of a fire (see this presentation: http://www.college-de-france.fr/media/j ... _AMINE.pdf particularly page 5). Similarly new electrolyte chemistries are designed to be more chemically stable, and have higher flashpoints.

I'm going to clam up now. Have fun with batteries, but don't make them explode please. But if they do, you know what to do now.

[Metiz]

Ok, it took no less than 5 weeks for my batteries to arrive but I've gotten them and build a new battery pack. The tabs on the original battery were spot welded on so I couldn't use that (also accidentally shorted a copper pathway with my solder iron, vapourizing it, but I digress...) Next problem was that the lithium cells were 3mm longer that specified so I couldn't use 2 out of 3 of the old plastic casing.

I hotglued the cells together and solderd all the wires and fuses back to the pcb. Soldering to the cells was pretty easy: the endcaps were brass and using a bit of flux helped a lot as well. The pcb is not protected btw so that was a big help.

The battery is "secured" in place with some vilt and the top cover. All is looking good: the battery charges properly and the battery temperature never exceeds 31 degrees Centrigrade. The laptop is now recalibrating to the new charge. I'll make a pic later if anyone's interested. Fair warning: ductape (obviously )

[UAirLtd]

very nice and well done. Pics would be useful!

Yeah, I've had my own lithium-ion-related soldering mishap, I accidentally shorted the solder across some battery terminals while holding it (trying to solder one end, the other strayed onto another terminal). The solder exploded violently, showering molten solder everywhere.

[Metiz]

Here it is. I don't realy want to take it out. SHOULD be fine but you know, Murphy's law and all...

The cells are hot-glued together. The 2 other components, I think thermal resistors, are solderd on on the bottomside of the battery, embedded in the glue somewhat to reduce hight. I just used some wire I had lying around to solder together the batteries.


Pretty straight-forward PCB without "no charge" protection. There's a bit of hotglue on the right to prevent wires from touching.


snug fit

The ductape is there for protection and insulation. It's not pretty but I don't realy care - it works!

[UAirLtd]

I can't quite tell from that picture, but it seems very likely that you've purchased protected 18650 cells. These cells have a small built-in protection circuit attached to the negative end of the cell, which performs UVLO/over-discharge protection, this small circuit is built onto a disk-shaped board and mounted directly onto the negative end. It makes the cell about 3mm longer than a standard 18650 cell.

Let me show you. Here is a small collection of different 18650 cells that I have. The left four are taken out of laptop batteries, the right one, Ultrafire brand, is a protected type. It is 3mm longer.


Also look at the negative end of the cell, the protected cell's negative terminal is I think gold-flash on 1oz copper, on a dimpled PCB surface (which is why it's so shiny), while the others are standard battery end cap material (nickel-plated steel maybe?)


The main issue with using protected 18650 cells in a battery pack is resetting the protection. If you over-discharge any of these cells, they will just cut out completely (almost as if the cell is dead), and refuse to charge until the protection circuit is reset. I'm not sure if all protection circuits are the same, but the cells that I have can be reset by applying 5V to the cell (preferably through a resistor). Some 18650 cell chargers will reset the protection circuit, others will not.

So if you are indeed using protected 18650 cells (which would explain why you've found them to be 3mm longer), then you'll want to be careful not to trip the protection.

[Metiz]

The cells look exactly like yours, with the gold colored negatives. If I remember correctly it did say they were protected. The laptop turns off automatically when the charge drops below a certain point so I think I'm ok (for now).