Hi,
Summary question: Why aren't short, fat Li-ion cells, like "25180"s made?
This is really more a question for manufacturers than users, but as a lot of the users on this forum seem to have intimate knowledge I thought I would post it for discussion as well;
High flux LEDs take from 3V (low driven Cree/SSC) to anywhere around 21V, or something insane for 20W Ostars.
Hotwires also take high voltage.
Li-Ion chemistries range from nominal 3.0V (stepped down for consumer use), ~3.2V (?) LiFePO4, to 3.6V conventional Li-Ion. (More when fully charged)
When running single high V, or multiple low V LEDs*, even incorporating a boost driver, a single Li-ion doesn't make the voltage grade.
This is the point at which multiple 14500/18500, so on are used in series to boost the voltage to a level where it meets the LED string's V requirements.
(*I gather multiple Cree or SSC are best run in Series to avoid unbalanced output from bin-variance)
This is very space-inefficient with long cells, due to all of the space around the cells that is dead-air. The only candidates for short-cells in series seem to be RCR123s.
When comparing fatter cells, the energy capacity seems to be dramatically increased over skinny cells. AW's new C cell is roughly 80% of 17670 length, 150% its diameter, (120% the volume) and just over 200% its capacity. Bottom line ~66% greater energy-by-volume.
This leads me to the conclusion:
People are willing to bore C and D-cell lights to insert 3 or 4 long cells.
If high voltage is wanted, and this is achieved by putting li-ion in series, why does no battery manufacturer (to my knowledge) produce protected, short, large diameter cells, that will go in series in an unmodified C or D sized light?
It would;
Simply; why are there no 25180 (1000Mah) Li-ion cells?
Summary question: Why aren't short, fat Li-ion cells, like "25180"s made?
This is really more a question for manufacturers than users, but as a lot of the users on this forum seem to have intimate knowledge I thought I would post it for discussion as well;
High flux LEDs take from 3V (low driven Cree/SSC) to anywhere around 21V, or something insane for 20W Ostars.
Hotwires also take high voltage.
Li-Ion chemistries range from nominal 3.0V (stepped down for consumer use), ~3.2V (?) LiFePO4, to 3.6V conventional Li-Ion. (More when fully charged)
When running single high V, or multiple low V LEDs*, even incorporating a boost driver, a single Li-ion doesn't make the voltage grade.
This is the point at which multiple 14500/18500, so on are used in series to boost the voltage to a level where it meets the LED string's V requirements.
(*I gather multiple Cree or SSC are best run in Series to avoid unbalanced output from bin-variance)
This is very space-inefficient with long cells, due to all of the space around the cells that is dead-air. The only candidates for short-cells in series seem to be RCR123s.
When comparing fatter cells, the energy capacity seems to be dramatically increased over skinny cells. AW's new C cell is roughly 80% of 17670 length, 150% its diameter, (120% the volume) and just over 200% its capacity. Bottom line ~66% greater energy-by-volume.
This leads me to the conclusion:
People are willing to bore C and D-cell lights to insert 3 or 4 long cells.
If high voltage is wanted, and this is achieved by putting li-ion in series, why does no battery manufacturer (to my knowledge) produce protected, short, large diameter cells, that will go in series in an unmodified C or D sized light?
It would;
- save work
- require no battery holder
- decrease wasted space
- increase real capacity
Simply; why are there no 25180 (1000Mah) Li-ion cells?
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