FW: Battery

[John Teller]

Lithium ion cells are extraordinarily sensitive.  If you overcharge 
them, they will overheat, catch fire or explode.  If you discharge them 
past that magic number, they will undergo an irreversible chemical 
reaction such that if you try to recharge them they will overheat, catch 
fire or explode. If you discharge them too quickly, as in short them out 
when fully charged, they will overheat, catch fire or explode.  If you 
puncture a cell it is very likely to overheat, catch fire or explode.  
Monotonous, isn't it?

Every cell that ends up in consumer service includes a fuse and a small 
IC whose only function is to permanently short out the cell once it 
falls below the minimum charge level. This isn't just lawyer stuff - see 
Boeing's recent experience with the 787 for an example of how hard it is 
to get this right, especially when the cells get really big.  Tesla, 
Nissan, GM et. al. have done an amazing job protecting their massive 
automotive lithium battery packs.  Each cell is equipped with its own 
cell minder which can communicate with the charger to provide all kinds 
of telemetry about the cell condition.  These packs are also centrally 
located not only for CG purposes, but also to shield them from collision 
damage.

---JST



On 01/27/2014 05:29 PM, Alex Fraser wrote:
> I agree, I wasn't hooking up the battery,  I was hooking up the 
> camera.  I have read that when Lithium ion go below 2.x volts, they 
> can't be recovered.
>
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