[DeTomaso] Minimum Battery Size?

[GW]

My Airplane began life with a Ni cad battery. Problem with Ni cad 
batteries is that when they weaken they get warm during the charge 
cycle. They get to a point where the system will continue to try to 
charge it until it self destructs. It can actually burn through the wing 
and drop out of the airplane. Most with these kinds of turboprops swap 
to lead acid. Problem with Lead acid is not only do they vent more acid 
but they do not do well at high altitudes with colder temps (-30, -40 c).

The problem I have with lead acid in cars is the acid. This has made 
glass mat batteries a really cool alternative. I put them in all my 
cars. One major problem is if you run them down, they are not 
recoverable. If you run down a lead acid battery you may get another 
6months out of it but with the glass mat battery the party is over. 
Glass mat batteries also don't like trickle charging. They need current 
otherwise will slowly damage the battery.

I have been messing with Lithium-ion and Li-poly batteries with R/C 
aircraft for some time. I have over charged and ignited a few. Lead acid 
batteries blow up due to the Hydrogen but generally don't cause fires; 
just a big mess. Lithium based batteries on the other hand don't blow 
up; they ignite like a fireworks. These are bad bad oozing fires!

 In general you are suppose to charge hobby based Lithium batteries in 
burn proof ceramic type containers (few do). I charge them on a metal 
plate and only when I am in the shop. If they ignite I run out the door 
and throw them in the yard. Some have not been so lucky.

The industry is using lithium type batteries more everyday but the 
scenario is different then a hobby situation in that they have 
integrated smart charging systems dedicated to the devices being 
charged. Batteries of all types last the longest if 1. Properly charged, 
2. Not charged to the point of generating heat as heat is the beginning 
of damage, and not to be run down too far. Lithium batteries can not be 
run down either or they will overheat and burst on the next charge cycle.

Lithium based batteries are getting better everyday but specific 
charging and discharging requirments are much much more critical.

One final note, if you throw water on a Lithium battery fire you will 
accelerate the fire. \

Gary....Let's see, male goes to female so put the red wire to the black 
wire right?


Sean Korb wrote:
> On 10/2/07, Chris Difani <cdifani at pacbell.net> wrote:
>
>   
>> One piece of information regarding the Li-Polymer batteries. They blow up.
>> They can blow up if they are over charged. Sometimes by over voltage
>> rather
>> than over amperage. But they can self destruct.... fire, lightning, and
>> other loud, expensive noises. All of which are something to be aware of...
>>
>>     
>
> No sense of adventure :)
>
> Newer cells developed by A123 are "blow up" resistant.  That's why Ford and
> GM are contracting with A123 for their hybrid lines coming out in 2010.  I'm
> not sure what the base technology is being used for the EV-Battery guys, but
> the KillaCycle guys are developing a small automotive battery based on A123
> cells: http://www.killacycle.com/photos/12-volt-racing-battery/
>
> Lead-acid has been known to blow up as well.  For heaven's sakes, be
> careful!
>
>