How safe is to use AAA draining 1Amp or even more?

[voiceiptester]

I was just wondering, How safe is to discharge NiMH AAA batteries rated 800mAh or 1000mAh at high amps like 1A or 1.5A?

Would there be a major difference between Sanyo and other good brands and Tenergy and other (I guess) lower quality ones?

 

[jasonsmaglites]

is there a aaa flashlight pullin a full amp cause i want that one!

 

[AzN1337c0d3r]

It'll be ok as long as you don't discharge the cell below 1.0 V.

1A for an 850 mAH cell would represent a discharge rate of 1.18C and if you go look up Energizer datasheets, they test their cells up to 2C

The runtime won't be very long though, around 35 minutes.

http://data.energizer.com/PDFs/nh12-850.pdf

 

[Handlobraesing]

It's not so much the nC. I would think a 700mAh cell would handle 1A better than a 1,000mAh cell. The highest capacity cells aren't the best at high rate of discharge.

 

[LEDninja]

NiMh Battery Shoot Out
Mostly AA but there is a test of Titanium 1000mAH AAA up to 3A.

Most AAA 1 watt flashlights pull 1 to 1.2A from the battery. Fenix L0P through L0D-CE/high, Ultrafire 602c etc.
Electrolumens My Little Friend 3x3W luxeon pulls 2A.
Electrolumens My Little Friend 3xSSC-P4 pulls 3A.

 

[voiceiptester]

is there a aaa flashlight pullin a full amp cause i want that one!

Yes, This one

 

[LukeA]

Yes, This one

Also the AAA Ultrafires.

 

[CM]

High capacity translates to higher internal resistance. YOu can discharge it at 1.5C to 2C but it's going to get hot and you'll probably shorten the life. If you want to pull that much current from a cell, you're better off with AA's.

 

[AzN1337c0d3r]

I do not see a reason why higher capacities should lead to higher internal resistance, but im no electrochemistry major either. Please provide evidence to support that claim.

Regardless, just for comparison, the Fenix L2D pulls 1400 mA from my 2000 mAH AA, which is a 1.4C discharge rate and the batteries don't really even get warm.

 

[StandardBattery]

... just for comparison, the Fenix L2D pulls 1400 mA from my 2000 mAH AA, which is a 1.4C discharge rate and the batteries don't really even get warm.

Ummm that would be a .7C discharge rate...

 

[rwolff]

I do not see a reason why higher capacities should lead to higher internal resistance, but im no electrochemistry major either. Please provide evidence to support that claim.

I'm no chemist either, but here's my interpretation:
NiMH and NiCd cells are made up of a "sandwich" (cathode foil/electrolyte layer/anode foil/insulating layer)that's rolled up and stuffed into the can. To get the current out, electricity has to flow along the foil to the appropriate end of the "sandwich", where it gets gathered at the terminal. The thinner the foil, the more resistance.

The thickness of the electrolyte layer (I beileve it's absorbed into a mat) and the insulating layer (I believe it's a mylar film) are pretty much constant. Cells optimized for capacity will have as thin a foil as possible (ultimate is just a thin plating on the insulating film) to get as large as possible a (pre-rolling) area in the "sandwich" (the electrolyte layer, which is where the action takes place, occupies as high a proportion of the cell volume as possible). Cells optimized for high drain will use thicker foils (for lower resistance), with the metal occupying a higher proportion of the cell volume.

 

[voiceiptester]

Is there any risk of explotion at high discharge rates?

 

[Luminescent]

Is there any risk of explotion at high discharge rates?

With lithium cells like CR123's there have been reports of some fairly serious explosions, but I haven't heard of a single case of a serious explosion with a NiMH battery.

The main hazard would seem to be cell venting, but NiMH cells don't seem to go 'high order' and let go with the kind of violence that a lithium cell can generate when it decides to let go.

A discharge rate of 1C isn't too bad, but discharge rates of 2C or greater will generate a LOT of heat, and even if you avoid venting and don't destroy the cell, it's cycle life will be greatly reduced.