I'm having a bit of trouble finding a really small (textile app kind) of battery that can deliver an amp on demand. It doesn't have to drain continuously but if it can reach 1A burst, that's good enough. I assume button cells are completely out of the question? Anything cylindrical would not be practical. I like the idea of a LiPo solution because their shape can be arbitrary and they tend to be pretty flat but the oncs sold in RC stores have these annoying plastic plugs on them that make them thick and the really flat ones look like they are meant to power a calculator or something weak.
Anyway, just wondering if anybody has a suggestion. It you have an idea but it doesn't make exactly 1A, that's fine too: 750, 600 mA... I can make that work if necessary. Just looking for ultra small/flat and relatively high pulse current without damage. Voltage isn't important. Thanks.
IF you would just say how long the cell needs to output that current, perhaps someone can help. Even the smallest cell can put out a lot of current for a millisecond.
Sorry, I should have specified what I meant by smallest. I'm looking for something probably 1/4 the size of that. Something the size of half a person's thumb for example but very flat. Kind of like the batteries you'd usually find in one of those tiny little quad copter things that can fit into your hand - although I don't know what kind of current they draw.
Fascinating. It claims 15C which would put it where I need it but I'm a natural skeptic. Can a little thing like that do 15C? I know big batteries can do 100C or more but I have found it doesn't scale very well on the small end. I guess it's worth trying anyway. Thanks.
Gahhhrrrlic:
Fascinating. It claims 15C which would put it where I need it but I'm a natural skeptic. Can a little thing like that do 15C? I know big batteries can do 100C or more but I have found it doesn't scale very well on the small end. I guess it's worth trying anyway. Thanks.
Of course it can, the C rating depends only on the detailed chemistry and electrode construction, nothing to
do with the size at all, although very large battery packs have to worry a lot more about cooling.
Gahhhrrrlic:
Fascinating. It claims 15C which would put it where I need it but I'm a natural skeptic. Can a little thing like that do 15C? I know big batteries can do 100C or more but I have found it doesn't scale very well on the small end. I guess it's worth trying anyway. Thanks.
It scales OK, a larger battery just have more active cell area, its what manufacturers choose to sell that affects what C ratings you typically see for typical sizes. 100C 50mAh cell is perfectly possible.
I have a museum's worth of Ni-Cd batteries ranging from soup can sized to something resembling a large pill. They are all Sanyo Branded and many of them belong to the general purpose series of product line. However the small 50mA batteries blister and die when you try to draw an amp from them (20C). However the 600mA variants can be loaded to 20 amps and survive (>30C). The 500mA cells, which admittedly are high drain variants, can be loaded to 20A as well (40C). I have found that the aspect ratio makes a difference and that batteries which are too wide or skinny will not perform well. Also very small batteries cannot dissipate heat as efficiently, leading to premature venting and thermal overload.
I suspect the other battery chemistries have the same challenges to face.
... just realized the above recommended LiPo is not available for purchase. Figures.
I have used 75mAh Fullriver lipos at over 1A (burst not continuous) and 120mAh lipos at 1.5A. I don't pretend to fully understand the chemistry so I settle for my own measurements and test results from trusted sources.
It's true that some C-ratings (which were never available for NiCds) may be inflated by marketing hype but they all have some basis in fact.