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Building a Lithium Ion Battery Pack. Need help.

J

James Arthur

Jan 1, 1970
0
Bighiller said:
Soiled dry suit! :)

There is a guy that builds these things and his says that it's not as
bad as was expected when lithium-ion batteries were first considered...

Hundreds of millions of cell phones and notebook computers say
LiIon is pretty darn good. Maybe even better now than initially.
But they can and do fail.

Notes:
o A hand grenade holds about 700kJ of energy; your pack will
hold about 220kJ electrical, plus thermal/chemical.
o Even flashlights that use alkalines and NiMH cells have
catalyst pellets (to recombine gases) and vents for safety.
o Don't use the pack electronics to limit charging, discharge,
etc. Your device & charger are responsible for that. The
pack electronics are a fall-back, not a primary control.
o You'll have zero low battery warning unless it's built into
the HID controller.

Have fun!

James Arthur
 
R

Raveninghorde

Jan 1, 1970
0
On Tue, 31 Mar 2009 17:04:17 GMT, James Arthur


SNIP
CONNECTION: several cells in series, or series-parallel, to
get the voltage the HID needs.

SAFETY: you need battery pack electronics, thermal switch, + a
one-way valve (vent) for the containing vessel.

The battery pack electronics protects each cell in the series
pack against reverse voltage, overdischarge, overcharging, and
the entire thing against short-circuit. The thermal switch
(PTC, positive temp. coefficient thermistor) is built-in to
many LiIon cells' anode contact. It's a back-up short-circuit
protector.

May not be an issue in this case but the PTC has a voltage limit of
typically 30V. This limits the number of cells in series without extra
protection.


SNIP
 
J

Jasen Betts

Jan 1, 1970
0
pressure relief valve.
That I understand. I think, so long as it doesn't pop off, I'd could
integrate a check valve. Just would suck if it popped off underwater
and then water seeped in an made a bigger mess. What I am building is
similar to one of these:

you're intending to carry round a sealed canister containing reactive
chemicals (formeed into a battery)

Should the battery fail spectacularly and produce large amounts of gas
and there not be a relief valve your canister has become a bomb.
 
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