cutting-edge lithium battery techie stuff



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Guest

Guest
I use litium batteries in my R/C helicopter. You have to be VERY CAUTIOUS when charging as they can and have caused fires. When those things go, they go big time and if they are in your garage, they will burn it to the ground if they are not in a fireproof container.

NEVER LEAVE A CHARGING LITHIUM POLYMER BATTERY UNATTENDED WHILE CHARGING!!!!!!!
 
J

jerryt

Guest
Pretty dangerous Battery

Overcharged Lithium Battery
http://www.youtube.com/watch?v=dOMfdH76oi0

Mechanically Damaged Lithium Battery
http://www.youtube.com/watch?v=4OsBc8RqSKU

Lithium Battery and Water
http://www.youtube.com/watch?v=v7abq34mckg

EDIT: An Australian doing experiments with e-bikes and batteries has this to say about lithium batteries:

I'll refer to the batteries I've been testing as Non-Oxide type. The oxide type batteries (cobalt oxide and magnesium oxide) are potentially hazardous, they are used in cell phones and lap tops and almost all ebike lithium batteries as far as I know.. They are quite safe if used just one cell at a time (well not completely safe there have been cases of fires and recalls of some products due to the fires). When alot of cells are put together for a larger battery suitable for an ebike the cells can become quite hazardous if overcharged or overdischarged, or cells become unbalanced (in their voltages) or if a cell is short circuited somehow. There are only a handfull of manufacturers I'm aware of making the non-oxide type lithiums which according to the manufacturers wont catch fire.

Lithiums have a reputation for being dangerous!!! If they reach a certain temperature they can go into thermal runaway, which results in a large explosion and very hot fire. Seems from what I've heard most problems occur during charging (overcharging really) though a few years ago one large bike company jumped straight into lithiums and was having fires on bikes being sold (they were recalled of course!) I think at the moment it is just a fact that oxide type lithium batteries are inherently dangerous. Manufacturers are adding battery monitoring systems (bms circuits) which control the charging current going to the batteries to avoid overcharging incidences but fires are still occuring. Also lithium batteries have a maximum current which can be drawn from them which should not be exceeded or once again thermal runaway can occur and also the lifespan of the batteries can be shortened by going over there current rating.
But you really cant avoid the fact that the oxide type lithium cells themselves due to their chemistry are " potentially" explosive (thats the reason I've never sold lithiums, I've been hanging off waiting for safe varieties to come out).

THE BATTERIES

Chemistry:
Most lithium ion cells have cathodes using cobalt (also Nickel and Magnesium are used), under certain conditions (overcharging or short circuits) the cells release oxygen which can fuel an explosive chemical reaction (generally called thermal runaway)(these batteries are also referred to as oxide type lithium batteries). The lithiums I'm testing are chemically designed so that oxygen is not released from the cathode by using a novel cathode material making them very stable. There is some loss of energy density (about 10%) by using alternate chemistries but I think its a very small price to pay for safety. These safer type of lithium batteries are also referred to as non-oxide types.

This is his website
http://www.users.bigpond.com/solarbbq/lithiums.htm
 
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