I have spent a few years reading about flashlights and batteries. However I still don’t understand the relationship between the flashlight and the amp rating on the battery.
I’m replacing some cheap batteries that are no longer working. Most of my batteries are around 10A with a couple of 21700’s that are a little higher. I don’t want to waste money by getting a battery that doesn’t give me anything more. For example I don’t want to buy a 4100mAh 20A battery when the 3000mAh10A battery will do the job.
I will be buying 15-20 batteries and that adds up quickly. I have read plenty on here about it and I still don’t quite understand. If you can answer or direct me to a thread that would be great. Once I find a answer that I can understand, I’m going to make a copy so that I have it for reference. Thank you
Well it’s been 5 hours and no one has tried to help you out. If I may, I will try, but don’t take this as 100% correct, please. As I understand it, the MAh rating is the capacity of the battery. The other amp rating is the maximum current the battery can give without any nasty things happening, like fires. So if you have a 4100mAh 20A battery, that battery will give 20Amps for like .2 hours…that is 4.1Ah/ 20A = .2 hours or around 12 minutes. If your flashlights have a driver that can drive the led(s) at 20 amp, then for the brightest light you need a battery that will deliver 20 amps minimum…if your flashlight only needs 10 amp to drive the led to it’s brightest level, then you need a battery that can source 10 amps…there are other things happening in the flashlight here…like if your really drawing 10 amps current the driver and/or LED may start to overheat and therefore, throttle down the current draw after a time to save the driver/led from overheating and failing. Hopefully this is all correct…maybe someone else can help out more than me and correct any of my assumptions.
That gives me what I needed to know. I’m pretty sure that I don’t have anything over a10A draw on any of my flashlights except for my Convoy L6 but I will have to double check it.
It seems to me that if I get a 15A to 10A 18650 and maybe 15A to 20A 21700 I should be ok. I read somewhere that I need at least a 15A 26650 for the Convoy L6 which I already have.
Thanks for the reply.
I agree w Macgravy… the CDR rating should meet or exceed the maximum power draw of the driver
there is another factor, Cold Weather Tolerance. If that is important, batteries such as Molicel P30B, which has a 30A CDR (max constant drain rate), tolerate lower temperatures than most batteries w 10A CDR
there is a tradeoff that higher CDR usually comes with lower total capacity, such as 3000mAh instead of 3500mAh (for 18650 size)
The higher CDR wont hurt a light that does not ask for it… otoh, too low a CDR does hurt the battery if the light asks for more
And if cold weather is a factor, a 10A CDR battery will suffer more capacity limitation in below 0C weather, than a 30A CDR battery
but if the light is not operated at maximum output, nor in subzero weather, then there is no need for a High CDR battery
Im recently on a deep dive into 18650 battery options
Im learning that an UnProtected Flat Top is 65mm Long, while a Protected Button top is closer to 70mm long.
lights whose drivers have built in LVP, dont need protected batteries, but lights that dont have LVP in the driver, need it to be in the Battery
so, consider which lights of yours require a Protected Button Top Battery, but know protected batteries wont fit some lights that require Flat Top batteries
for example, my 18650 Zebra only fits flat tops. But if I put a flat top in my Skilhunt H300, the light shuts off if I bump the tail, because the battery is too short… otoh, the protected button top from my H300 is too long to allow the Zebra to close all the way, so it wont turn on.
Fortunately I don’t have any lights that need a protected battery. Although my L6 needs a button top but I have an adapter from Convoy that fixed that problem.
Regulated drivers.
These drivers will try to output constant amount of amperes and won’t exceed the programmed maximum. If you know that maximum then pick the battery correspondingly - CDR should be bigger or equal to [driver maximum]. In case of 3V class emitter the battery should be rated for at least exactly that maximum output current, in case of 6V class emitter the battery’s rating shoud be double the output current (e.g. for 6V 4A driver the battery should have 8A CDR or higher) and so on.
Actually if you are not a turbo user even batteries with lower CDR than needed will be OK. But I don’t think sourcing right batteries is a problem nowadays, at least for EDC flashlights.
Direct drive (FET drivers)
There’s no specific output current. Amount of amperes flowing will be defined by the configuration of whole circuit. And the battery is a part of the circuit. If the battery has very low internal resistance and can sustain higher voltage under high load (high CDR battery) then such battery will result in a higher current. If that current is too high it could damage the emitter or components of the driver. Otoh, low CDR battery will result in lower current than designed by flashlight’s manufacturer thus will pose no risk to flashlight. But that current might be still higher than that poor battery’s CDR rating and thus will be killing it.
So it’s better to stick to the params of the stock battery or manufacturer’s recommendations. I’m not saying you should pick the battery’s CDR with 5% precision, just stay away from extreems.
Yes you are right but I don’t have any protected 26650 batteries but I thought I read that the new L6’s don’t need a protected battery. I could be wrong because I can’t remember where I read that.
That’s not how it usually works. We all want the high capacity 4100mAh battery with 20A CDR but it doesn’t exist. The higher capacity battery usually has the lower continuous discharge rating (CDR) amperage. So your real choice for 18650 might be the high capacity Vapcel N41 4050mAh 10A or the excellent Molicell P30b 3000mAh 36A. For a light that has a less than 5amp driver the N41 might be the cell of choice with a runtime that could be 25% longer. At 10A the N41 might struggle to deliver and be outpaced by the P30b.
The CDR is a rating its capable of delivering, but its not the capacity at that CDR. It also doesn’t mean the cell performs well at that amperage. At a 10amp rating for example the lower capacity Molicell may actually have more useable capacity than the higher capacity N41 cell that is struggling to deliver 10A. It’s a good idea to cut the battery rating in half when comparing to the max draw of your light. So for a light that can draw 10amps you would want a battery rated at >20A.
If you want to compare batteries the best thing to do is google Mooch and the battery name. Like “Mooch 18650” or “Mooch Vapcell N41”. Mooch is a battery expert on the vaping forums and a real treasure to the flashlight community as well.
PS: I wouldn’t buy 15-20 batteries right now especially 21700. Sometime, hopefully this year, Molicell is going to release a gamechanger, the Molicel INR-21700-M65A. That cell will be the highest capacity 21700 on the market at 6500mAh with a very usable 26CDR, which will be plenty for most EDC type lights. And if you need more amps than that the 90Amp P60b is in the works.
