Lumen per amp

ZoomieFan · January 29, 2019, 4:57pm

To be honest I have no clue how many amps a flashlight draws.
For that reason the cells I’m buying may not be capable supplying the full brightness of a flashlight.

I understand there are many factors (like efficiency) taken into account; but can someone give me some guidelines?
Like X lumen per Amp.

BTW I’m using single cell flashlights, so no cells in series.

Pete7874 · January 29, 2019, 5:33pm

I am afraid it’s not as simple as just lumens per amp due to the different LED efficiencies and different drivers used. You need to look at each flashlight individually.

But some examples from what I own:
convoy s2+ hp-l hi: under 1000 lumen, about 2.8A current.
BLF A6 - about 1400 lumen, about 6A current.
Emisar D4S xp-l hi - about 4000 lumen, about 15-20A current.

Serlite · January 29, 2019, 6:26pm

Without actually testing the light, I’ve found a quick way to ballpark the current drawn by a light is to take a look at the runtime figures given by a particular cell.
You can usually find this stuff written up on a sheet if you have the light, or included in some reviews. (This doesn’t help as much if a manufacturer falsifies their data, but it’s better than nothing.)
Then, you divide the capacity of the cell they tested with by the runtime to get some kind of current value.

For example, the Thorfire VG15S tested with Thorfire’s 3000mAh cell has stats of:
table(table#posts).
|Level|Runtime|Estimated Current (3000mAh/Runtime)|
|Firefly|360h|0.0083A|
|Low|50h|0.06A|
|Mid|2h45m|1.091A|
|High|1h25m|2.118A|
|Turbo|45m|4A|

Cheaper cells aren’t going to give quite as much capacity at higher current draw, which is probably why Turbo works out to 4A (I think I’ve heard more of a 3A value).
But it can be pretty on-target if the testing cell can handle the current, like the Sofirn SP33 stats: runtime of 52m on Turbo with their 5000mAh-5500mAh cell, working out to about 5.77A-6.35A. (Which is close enough to the 6A draw I’ve heard quoted for it before.)

ZoomieFan · January 29, 2019, 7:12pm

Looking go so far because my aim is around 1000lm (but high turbo is a nice bonus)

I’m wondering when those amps are measured. A full cell or an nearly empty cell?
I ask because if the cell gets depleted the voltage drops, so more amps are required to feed the LED with the same amount of watts.

Kame_Sennin · January 29, 2019, 7:49pm

That would be the case for a driver using a regulated switching converter (either buck or boost).

Lots of simple torches running from a single liion cell use a linear driver and/or some switching mode without regulation so the actual current usually decrease when the voltage decrease.

Pete7874 · January 29, 2019, 8:03pm

It’s measured with a fully charged cell for consistency and comparison reasons.

Brawler1588 · January 29, 2019, 9:28pm

Serlite:

Without actually testing the light, I’ve found a quick way to ballpark the current drawn by a light is to take a look at the runtime figures given by a particular cell.
You can usually find this stuff written up on a sheet if you have the light, or included in some reviews. (This doesn’t help as much if a manufacturer falsifies their data, but it’s better than nothing.)
Then, you divide the capacity of the cell they tested with by the runtime to get some kind of current value.

For example, the Thorfire VG15S tested with Thorfire’s 3000mAh cell has stats of:
table(table#posts).
|Level|Runtime|Estimated Current (3000mAh/Runtime)|
|Firefly|360h|0.0083A|
|Low|50h|0.06A|
|Mid|2h45m|1.091A|
|High|1h25m|2.118A|
|Turbo|45m|4A|

Cheaper cells aren’t going to give quite as much capacity at higher current draw, which is probably why Turbo works out to 4A (I think I’ve heard more of a 3A value).
But it can be pretty on-target if the testing cell can handle the current, like the Sofirn SP33 stats: runtime of 52m on Turbo with their 5000mAh-5500mAh cell, working out to about 5.77A-6.35A. (Which is close enough to the 6A draw I’ve heard quoted for it before.)

How would you get you estimate for let’s say a q8 that’s 5000 lumens turbo 40 min runtime 3000mah battery?

Cereal_killer · January 29, 2019, 10:04pm

The Q8 effectively has a 12,000mAh battery (four 3000mAh cells in parallel)

Serlite · January 29, 2019, 10:11pm

(Assuming you meant four 3000mAh cells in the Q8,) given those numbers, I would calculate it as 3Ah / 0.667h = 4.5A.
I think I’ve read somewhere that as long as your cells can sustain at least 4A each then they should be good enough for the Q8, so this seems pretty plausible.

komeko · January 29, 2019, 10:34pm

I can give some of my measurements from myself. All on fully charged batteries and measurement right after turning on in the turbo:

BLF Q8 65W, 16A (4A on one battery), 5301 Lumen, 82 Lm/1W
Emisar D4 60W, 14.7A (14.7A on one battery), 4143 Lumen, 69 Lm/1W
Emisar D4s 63W, 15.4A (15.4A on one battery), 4966 Lumen, 63 Lm/1W
Fireflies PL47 36W, 9A (9A on one battery), 2520 Lumen, 70 Lm/1W
Lumintop GTmini 24W, 5.8A (5.8A on one battery), 1441 Lumen, 60 Lm/1W
Lumintop SDmini 12W, 2.8A (2.8A on one battery), 946 Lumen, 79 Lm/1W
Meteor M43 82W, 20A (5A on one battery), 7291 Lumen, 89 Lm/1W
Olight H1 7W, 1.8A (1.8A on one battery), 524 Lumen, 75 Lm/1W
Skilhunt H03 10W, 2.4A (2.4A on one battery), 729 Lumen, 73 Lm/1W
Thrunite TN40S 72W, 8.8A (4.4A on one battery), 4624 Lumen, 64 Lm/1W
Thrunite TN42 36W, 4.4A (2.2A on one battery), 2164 Lumen, 60 Lm/1W
Thrunite V6 34W, 8.4A (8.4A on one battery), 1912 Lumen, 56 Lm/1W
Utorch UT01 7W, 1.8A (1.8A on one battery), 588 Lumen, 84 Lm/1W
Zebralight SC600W 15W, 3.6A (3.6A on one battery), 1110 Lumen, 74 Lm/1W
Haikelite MT07S 40W, 2.5A (2.5A on one battery), 2202 Lumen, 55 Lm/1W