I'm not talking about cells of different sizes here. What I mean is: if you compare the best available NiMh cell of one size to the best available NiCd cell of the same size. (when I say best, I mean high current capability in this case.)
Surely comparing the best available cells is what's important here and not equal capacities?
EDIT: By "size" I mean dimensions.
I don't think NiCd has a high current advantage though.
Eneloop 2000mAh AA can handle 10A easily
in response to the query posed in the first quote, i would answer "yes".
the context of the second quote is a comparison w/NiMH chemistry. therefore, this second quote is incorrect. combining the second quote with the third quote reveals an easily handled 10A discharge rate. i don't know the max discharge rate of a AA Eneloop, but somewhere around twice that 10A is doable for a AA NiCd cell. it would be interesting to examine voltage sag for these two chemistries at such high discharge rates. this is a benefit of NiCd over NiMH chemistry.
referring back to the first quote, by the words "high current capability" and "high current advantage", quoted both here and above, i'm assuming that what is meant is the ability to deliver large amounts of instantaneous current and NOT the energy storage capability (i.e., capacity) of a particular cell, meaning its ability to deliver a certain level of current for a certain extended period of time. if so, then NiCd's are inherently superior to NiMH's due to the NiCd chemistry's lower internal resistance. and NiCd's would perform better in some high current drain/draw applications, viz. those that require more current than a NiMH chemistry could supply w/o excessive voltage sag. now, if one were to only draw current at a rate, even though a relatively high rate, that could be supplied by either chemistry (i.e., NiCd or NiMH) w/minimal or no voltage sag fr/the NiMH cell/battery, then the NiMH cell/battery would run/burn longer due to its greater ENERGY STORAGE capacity, not b/c it has a higher current supply capability/ability than NiCd , which it does not.
again, using somewhat different wording, all other things being equal, NiMH cells do *NOT* have a greater ability to deliver higher current levels than comparable, but lower energy storage capacity, NiCd cells.
it's just the opposite. NiCd chemistry has a greater ability to deliver higher current levels than NiMH.
this is one of the primary reasons that NiCd's are still used in cordless power tools.
if by, "high current capability", what is meant is energy storage capacity (and, i don't think that is what is meant) , then, assuming equal size, NiMH would have 40%-50% (and perhaps even a larger pct nowadays, some of my info is quite old and may have been improved upon) greater energy storage capacity as stated immediately above at the end of the prev. paragraph.
so, for a given physical battery size (i.e., three dimensional space), if maximizing current draw/delivery is critical/paramount in a design, then NiCd chemistry would still be superior to NiMH chemistry. if however, for a given physical battery size, maximizing burn/run time is more critical, then NiMH chemistry would be the way to go (versus NiCd). this is not to say that NiMH cells can't provide large amounts of instantaneous current. they can, certainly far more than alkaline chemistry, but not as much as NiCd chemistry.
NiCd's have other benefits over NiMH cells as well (e.g. it's a more robust chemistry and tolerates some types of abuse better than NiMH cells). NiMH has other advantages over NiCd as well, in addition to being less toxic to the environment (Cd does not "play nice" with the environment).
as i think about our exchange of Posts in this Thread, i think the confusion has arisen in this regard. we need to clearly define, and now, i believe we have, if we are speaking of the cell's/battery's energy storage capacity (for our purposes on CPF, generally measured in mAh), or it's maximum current delivery capacity/capability with current being typically measured in A or mA. it seems to me now that we were each thinking of a different aspect when we write "capacity" or "capability" in our Posts and we read the word "capacity"/"capability" in the others' Posts.
all this said, please know that i make no claim to being an expert on batteries in any way, shape, or form. if anything i've written here seems incorrect, then i would encourage a web search to see if, in fact, i am in error. i think that i ought to now take the time to do likewise and make sure that my memory of these things, from my school days long ago, are still clear. i believe they are, otherwise i would have already done a search myself.
perhaps an illustration is in order:
take, for example, two identical in dimensions (as well as the orientation of those three dimensions) and therefore volume, fish tanks.
[energy storage] capacity is analogous to the volume of a fish tank. it is the therefore the same in both fish tanks in this illustration.
taking the words fr/a prev. Post in this Thread, viz. "Since voltage is roughly the same for NiCd and NiMh", the voltage would be analogous to gravity and the atmospheric pressure (determined by gravity and the height of an identical column of air above the identical open top area of each tank, and the identical column starting height of water in each tank before the full tanks start to empty) which exerts its force simultaneously in the exact SAME amount upon BOTH identical fish tanks in this illustration.
lastly, the rate at which current can be supplied by the cell is analogous to a hole in the bottom of the fish tank. since NiCd chemistry has lower internal resistance than NiMH chemistry, the hole in the fish tank representing NiCd chemistry is LARGER than the hole in the bottom of the fish tank representing NiMH chemistry, thus, providing lower resistance to the flow of water out of the tank, and so, providing faster emptying of the water in the fish tank representing NiCd chemistry as compared to the smaller hole in the fish tank representing NiMH chemistry. this is analogous to the greater ability, all other things being equal, to flow current that NiCd chemistry has versus NiMH chemistry.
so, keeping the fish tank illustration in mind, and recalling the words fr/a prev. Post "No, by power I mean power in watts = voltage x current.", and combining them with these words "Since voltage is roughly the same for NiCd and NiMh", what would this tell us about each chemistry's the ability to supply current and power? the answer is obvious isn't it?
i hope that i have now finally made myself clear. if not, then i would really welcome another's assistance in communicating the differences b/t cells/batteries having these two chemistries as far as the scope of this discussion is concerned.
--------
Note: please keep in mind that when i mention internal resistance in my Posts in this Thread, that i am not speaking of that portion of a cell's internal resistance which is contributed by the quality of a cell's mechanical design or manufacture. i am speaking of that portion of a cell's total internal resistance contributed by just its chemistry and the thermal effects upon that chemistry.
since we normally discuss a cell/battery as a whole entity, it is common to just speak of "internal resistance", meaning the SUM of all the various factors that contribute to a cell's overall or total internal resistance at any point in time without breaking it down into its various parts based upon what aspect of the cell is contribution what portion to the cell's total internal resistance.
