As has been stated, it's all about the total energy capacity. They are modeled as a non ideal Thevenin voltage source. This means it will try and keep the voltage across its terminals constant, but the current can vary widely, it can be almost anything. The problems you run into are the internal resistance of the battery, the rate at which the chemical reaction can take place, and heat that can cause problems with the battery. Just as an example, Google tuned up this link that gives some AA battery discharge curves.
You've seen Star Trek where they rig a phaser to explode? That happens with a shorted-out NiCd, I've burnt my fingers on one.
Awesome necro cheesecake. If only batteries were 'perfect' though... 20Amps for a second or two could be spectacular.
Last time I checked the uk regs - the Ah rating of a battery is the avarage current rating over a 5 hr test periode!
Most batteries that I deal with are rated at a 20h rate though that's mostly lead acid batteries. What limits the short period maximum output current is the internal resistance of the battery, this is the batteries own resistance and is functionally identical to a resistor placed in series with the battery, V=IR will then give you the batteries maximum output current. I say it's the short period maximum because if you draw very large currents from a battery it will heat up, the energy lost through the internal resistance is converted to heat in the battery, this has two effects; 1, it increases the internal resistance of the battery meaning the current will drop and 2, it makes the battery go bang, most modern batteries have an relief valve to dissipate internal pressure but it can be overcome and anyway you'd get nice caustic chemicals squirting out. A 1200mAh NiMH battery that I found had an internal resistance of 22mOhms which at 1.2 volts would give a maximum output of ~54 amps in a short circuit. Moriquendi
Pardon me for jumping into this discussion with a slightly different (but related) question. I want to buy an external battery charger for my Samsung galaxy tab and i have found one that promises to deliver the 2A it needs into the Tabs charging connector. The thing is this charger uses 4 AA rechargeable batteries (It recommends using 2700mah Mignon). My question is how long will 4 of these batteries be able to push out 2A safely?
in a perfect world the four batteries would be able to put out 2A for about 5.4 hours, since; 2,7Ah * 4 = 10.8Ah 10.8Ah / 2A = 5.4h. or: each battery puts out 0.5Ah (2/4) and 2,7/0,5 = 5.4 (5 hours 24 minutes) using regular 2400mAh it would give you 4,8 hours. (4 hours 48 minutes) but in real life i'd expect something like 4 hours for the 2700mAh and 3,5 for the "regulars".
Not if you put them in series, since only the voltage will add, not the total mah capacity. If you put them in parrallel, then theoretically your calculations will apply, but practically you would have problems due to any slight variance between the specific voltages of each cell. I'd expect up to about 1 hour and 20 minutes charging time from the battery powered charger, since only the 2700mah applies - but that's from brand new fully charged batteries, and if the 2700 rating is accurate. The performance will slowly degrade as the batteries age btw. Can you just get a higher capacity battery for the tablet?
They can easily put out 20 + amps there are very popular nimh batteries ( KAN ) that are able to put out even more.
Yeah, back in 2008 I would have been amazed if a single AA could do it, but yeah, most decent rechargeables can do ~20a for a few minutes... they'll be working very hard and run hot, but they'll do it.
Sometimes theyre called "high discharge" or similar, used mainly for rc models i think, and they do get really hot but if ure rc flying in winter the battery packs always make a nice pocket heater
