Best battery for high capacity / high discharge.

[Kurt_]

Hi! I'm looking for a battery that will drain safely at approximately 2.4V 8A or 3.7V 4A... without exploding. The high-current part of the circuit is regulated by a transistor, but can be adjusted anywhere from full power to no power, so the battery will essentially be a short circuit. Size is a large factor.

Due to size and capacity, Lithium Ion is the logical choice. But I worry that when shorted (Rather, dishcarging at 5-6A) they will catch on fire, especially when insulated by a case. (3.7V 2700mAh)

NiMH work, but don't have a large useful life for high discharge. (2x 1.2V 2700mAh)

Lithium Iron Phosphate has caught my attention, not requiring a protection circuit, able to store about the same energy as a NiMH AA, and storing about 3.2V 2700mAh in a single 18560 cell ('A' size).

My question is if there is a way to make lithium ion batteries work for this application or if I should just forget it. In addition, if there is any other type of battery I should consider.

[samuraiclinton]

I go with lead-acid batteries, since my application of use needs an inexpensive solution for mobile needs for accent lighting, audio system and bright headlights, since its a bicycle, it doesn't need ultra-lightweight materials, seeing that I have the muscle to handle moderately heavy weight.

I choose 12 volt systems since its the most universally understood voltage for DC powered mobile applications.

[Kurt_]

I'm talking about handheld-type devices with high discharge currents. That's where things get tricky: the smaller cell sizes can output less current.

[Triton]

what kind of handheld device are you making that has that high of a current draw?

[Kurt_]

I can't get in to specifics. But it is basically a small battery powered resistance heater. It heats a 1"x1" area to 200 C via conduction. The battery is connected through a power transistor to the heating element, so the flow isn't entirely unregulated, but it is still essentially a shorted battery.

[tom61]

For that application I'd recommend... fire. Something butane based should be able to do that well and be nice and compact, with just a simple valve to control the heat. If you need precision control, a microcontroller connected thermal sensor and an actuator could be programmed to handle it.

Either that, or get a hold of whatever materials those extremely quick warm-up/cool-down soldering irons use. I have one from Radio Shack that can get hot enough to melt solder in about a second, and it uses two AAs.

That kind of heat would be a serious issue for Li-Ion unless insulated extremely well, the cells that I checked all said to keep them below 150F maximum. The kind of drain you're talking worries me as well, I would definitely check out the datasheets for any battery you want to use before considering them.

[samuraiclinton]

If you're just gonna go for heated seat for winter weather comfort, then you don't need such extreme discharge. Besiides the lithium ion batteries you are looking for could easily power a car radio for 6 hours at FULL BLAST.

[Haunted360]

You could use a battery to charge up a capacitor and then discharge the capacitor as much as needed. Just, takes time is all to charge it up.

Of course, it will need all the correct circuitry

[bentendo64]

How long does it have to discharge these large currents for?

[Kurt_]

~30 seconds at a time.

[Triton]

for current capacity your best bet is lead acid, but if weight/size is a major concern i'm not sure what would be a good choice

[Haunted360]

for current capacity your best bet is lead acid

Yea, I guess this would be your only option

[gamemasterAS]

Enjoy your vape

[Kurt_]

I figure if I limit it to ~5 amps of current draw from the battery then I can use an 18650 Lithium Ion battery. So yeah, that.