Does anyone know how many amps the basic Radioshack-type black plastic AA holders can take?
I'm looking to power an emergency light using 8 or 10 AA batteries for 9.6 to 12V. I plan to draw about an amp. Now, I can buy black plastic AA holders at radioshack, but I assume that the cheap metal springs would at best be adding unnecessary resistance, and at worst, would get hot and melt through the plastic. Using the Radioshack holders is the easiest thing to do. If I can't, I'm not sure where I can get higher-power AA holders.
The other thing about the radioshack holders, is they have terminals on them for 9V-style double-snap attachment. The 9V snap leads I've found all have like 28 guage wire. Even that may be OK at 1 amp; I will have to look up wire ampacity.
1A or so sounds about right. I've run 5A through them on occasion for some tests I was doing, and they get hot. Probably would have melted the insulation and burned up if I had left them for too long at that rate. If I remember correctly, the voltage sag was about 2.5V from a 4 cell AA Eneloop pack, and then reduced some as the cells warmed up a little. Of course some of that was due to the cells as well.
I think the real problem is the wire losses. I always change their wires to haevy guages...what i do is put the wire through the hole and solder it at the tip of the spring. Then I smooth the solder job
i'd say you got more loses on springs themselves than wires, at 2-3A springs heat up so much it hurts to touch them, but wires stay nice and cool, they are copper, springs however made of steel, and have higher resistance.
once i had to fix this resistance problem on RS holders, normaly i would throw them out and use better holder, (digikey sells steel holders with bigger contacts, capable of higher load) but in that particular case it was not possible, so i got thin copper braid, soldered to top of the spring, and over positive contact, so the cell touched the braid, and spring was only there to hold the cell, all power was going thru the braid, very similar to resistance mod in maglite. it fixed the problem, but you better off using better holders from the start, so you don't have problem to solve.
Years ago, I had tried using the RS style holders to pack charge a handful of AA NIMH cells in a similar state of charge. Anything over ~1.5A and the plastic would eventually melt. I would say for continuous use the limit is somewhere well below 1A if you don't want resistance to play a major unnecessary factor in your application.