If I run a common light, that may be designed for a 2 amp li-ion, what happens if I run it with, for example, a 15amp cell?
Is amperage wasted? Is more heat generated than normal?
Or does the light just draw the 2 amps it was designed for and the extra amperage of the cell is not wasted?
And, on the other hand, what happens if I power a light that was designed to drawn very high amps, with a common, low-amperage li-ion cell? Is the cell depleted super quickly, does the cell get overly hot trying to feed an amp-hungry light?
And a related question… is the driver essentially a “valve” controlling how much amperage is passed from the cell to the emitter? And do some drivers act to not restrict any amperage - allowing the full amps of the cell to reach the emitter?
Is it the level of amps that determines the flashlight’s brightness? How does the voltage play into that?
These are certainly elements of “basic knowledge” to flashlight modders, but a mystery to me.
If anyone can explain how this works, I would greatly appreciate the knowledge. Thank you.
“Amps” of the light is like the top speed of a car. Just because it can go 142mph doesn’t mean you can’t just tootle along at 55.
If you use a “15A” cell in a putzy little light, no harm. If you try using a putzy “2A” cell in a hotrod light that tries to draw 10A or more, the light won’t be as bright (voltage sag), and the cell will heat up because of too much internal resistance (the way the power cord to your toaster gets warm after using it).
Most high-amp cells have lower capacity, and v/v. So you can get a 2600mAH cell that can spit out 15A, but the only cells that can deliver 3400mAH will likely be lower-amp cells, like 5A or so.
Also, the Amp rating on the battery is the ceiling for how much power it can actually push safely.
Fairly common misconception between that and Voltage. For example, if your light can handle a single fully charged cell at 4.2 volts, no problem. If ya try to wire 2 cells in, say goodbye to the LED and electronics!
To answer your other question, if the driver has a Current Limit function, that means it will limit, say 2 amps, to the LED itself. So the Amperage Rating of the battery doesn’t matter if it is over that limit. Under that, you’ll have bigger problems like Lightbringer mentioned.
And yes, FET Drivers for example do not limit anything, voltage or amperage, going to the LED, except for any kind of built in Resistance in the light itself, like the wires, switch and even the tube itself.
I have some older black AW 18650 and 16340 cells, and a few red AW IMR18650, 18340, and 16340 cells. I’m sure the black ones have lower available current than the red ones do. Is there any way of knowing how much current a Li-Ion has available? Can this be measured with a basic VOM?
Also, is an FET driver the same thing as “Direct Drive”?
Lastly, is there a good site or thread where I can learn the technical essentials of flashlight drivers and how different batteries work with them?
No problem using a high drain cell in a low amperage light, it will just draw what it needs. The opposite does not work well though. If a light can pull 15A and you provide a 5A cell, it will not shine as well and will stress the cell to it’s limit which is not recommended.
A driver can indeed be compared to a valve or a carburetor. It handles how much power is sent to the led(s).
A FET driver works essentially like a switch that turns on and off the led(s) at full power - direct drive. However it can do that very quickly and will be able to simulate lower levels by switching on and off very fast. That’s called PWM - Pulse Width Modulation.
Note that Li-ion cells do age even if not used. They slowly lose capacity. You can check them with an appropriate charger like Liitokala 500 or Opus BT-C3100 for instance. However testing how much current a cell can provide is a bit more complicated since it will mainly show over time - after 10sec, 30sec, one minute and so on.
You can nonetheless compare different cells by measuring how bright a DD light is shining with each. You need a lux-meter or a phone app. Some apps will even be able to monitor the brightness over time and produce a graph so you can compare the effect of each cell.
it’;s fine, though you are probably paying for more battery than you need
high current is expensive
it also conflicts with ‘high energy content’ to some extent
so if you do not need that, get a 3500 mah or other high capacity battery, usually they do not also have over 5A or so max drain