Best battery for high capacity / high discharge.

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Kurt_
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Best battery for high capacity / high discharge.

Post by Kurt_ » Wed Aug 24, 2011 11:20 am

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.
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Re: Best battery for high capacity / high discharge.

Post by samuraiclinton » Wed Aug 24, 2011 9:24 pm

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.

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Re: Best battery for high capacity / high discharge.

Post by Kurt_ » Thu Aug 25, 2011 12:16 am

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.
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Re: Best battery for high capacity / high discharge.

Post by Triton » Fri Aug 26, 2011 1:21 pm

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

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Re: Best battery for high capacity / high discharge.

Post by Kurt_ » Fri Aug 26, 2011 3:28 pm

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.
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Re: Best battery for high capacity / high discharge.

Post by tom61 » Fri Aug 26, 2011 10:46 pm

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.

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Re: Best battery for high capacity / high discharge.

Post by samuraiclinton » Fri Aug 26, 2011 11:21 pm

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.

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Re: Best battery for high capacity / high discharge.

Post by Haunted360 » Sat Aug 27, 2011 1:50 am

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 :roll:

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Re: Best battery for high capacity / high discharge.

Post by bentendo64 » Sat Aug 27, 2011 7:36 am

How long does it have to discharge these large currents for?
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Re: Best battery for high capacity / high discharge.

Post by Kurt_ » Sat Aug 27, 2011 12:31 pm

~30 seconds at a time.
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Re: Best battery for high capacity / high discharge.

Post by Triton » Sat Aug 27, 2011 8:06 pm

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

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Re: Best battery for high capacity / high discharge.

Post by Haunted360 » Sun Aug 28, 2011 3:01 am

Triton wrote:for current capacity your best bet is lead acid
Yea, I guess this would be your only option :arrow:

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Re: Best battery for high capacity / high discharge.

Post by gamemasterAS » Tue Aug 30, 2011 5:57 pm

Enjoy your vape :lol:
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Re: Best battery for high capacity / high discharge.

Post by Kurt_ » Wed Aug 31, 2011 11:18 pm

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.
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