Both the EC11 & DMM (& all voltmeters) measure voltage using a VERY Small current load (they have a very high resistance).
The voltage of your battery UNDER LOAD WAS LOWER than the 1.5 or 1.55V measured by both the EC11 & DMM afterwards (under NO load).
Whenever you put a load on a battery (draw current from it), its voltage drops (known as Voltage sag).
So when you used your EC11 as you mentioned, the voltage of the battery would have reached lower than the afterwards measured 1.5/1.55V (under NO load).
The readings are consistent with each other, thus the DMM's reading seems OK.
But you should regularly check the DMM's battery (say at least twice a year).
And as I said earlier:
Voltage of Lithium based rechargeable batteries rises when you rest them(ie: under no load) after use, due to their chemistry.
George - From what you are saying and I do not doubt you are correct, it would seem that the Nitecore EC11 is a very dangerous light to use!
The run times of the light are not that good and the first sign I had that the battery was running out of juice was when I switched to a higher mode and there was no change in brightness. If I remember correctly, after clicking the mode switch a few times the main light switched itself off and the red led started flashing - it was at that point I loosened & tightened the tail cap to measure the voltage = 1.5v
Removing the battery and testing it on my DDM confirmed a very low voltage = 1.55v
My worry with this light is that if it is allowing the battery to drop to such a low voltage under load - and with a Hi of 900+ lumens there would be a lot of load - but the battery recovers to an acceptable voltage after a short rest, then you could be duped into thinking all is well - especially if you only test a battery before use not immediately after.
The battery itself appears no worse for wear and accepted an indicated 904mAh of charge on my Opus charger.
EC11 like other many lights have not cut off , for example, the great Jetbeam RRT01… is your responsability; use battery with protection or if you use IMR check the voltage. EC11 is great, you can check the voltage with the flashlight, when is about 3.5V you must charge.
Trevi - just so you know, Nitecore recommends the use of IMR batteries in the EC11 and they don’t come with protection.
It is the rate at which the EC11 discharges the battery that makes it dangerous and it’s very impractical to switch off and test the voltage every minute or so.
So is the EC11 basicall a battery killer - at least as far as LiIon’s are concerned?
I’d love to see a review of this light by someone who can test the drain on the batteries properly to either put my mind at rest or confirm my fears.
In the meantime, I’m going to fully charge a battery then run the EC11 on high for one minute intervals and check the voltage immediately after each run.
I use my EA11 with IMR, and have not cut off, I know the risks and the use of Lithium. Not problem for me, perhaps some people don’t know about use of Lithium batterys, not a toy…
Start with a freshly charged battery. Use highest mode EC11 offers. Take out the battery after 5 min. and check voltage with your DMM. As voltage gets closer to 3.9 shorten the time between readings. Stop at 3.7. Now you know how long you can run your battery on Highest mode safely. Takes very little time and effort.
My guess is runtime on Highest setting is around 10-15 min.
When using such high powered light on a tiny little battery, you have to be actively involved. You are the protection circuit.
As for the cell that got run down to bellow 1.5V, you might consider recycling it. That poor little thing got the living daylights used out of it.
Ok - Freshly charged IMR - came off the charger @ 4.2v
Rested for about 1/2 hour before putting it into EC11
DDM = 4.18v | EC11 = 4 flashes indicating 4v
All further voltages taken from the EC11. Rest periods were 15 minutes
Start - time/mode - End
———————————————
4.0v - 1 minutes Hi - 3.9v
rest
4.0v - 1 minutes Hi - 3.8v
rest
3.9v - 2 minutes Hi - 3.8v
rest
3.9v - 3 minutes Hi - 3.7v
rest
3.7v - 2 minutes Hi - 3.5v << Battery should be removed and recharged at this point = 9 min on Hi
rest
3.6v - 2 minutes Hi - 3.5v
rest
3.5v - 2 minutes ?? - 3.5v << Now defintely dimmer than Hi
rest
3.5v - 3 minutes ?? - 3.4v << Only two modes available low and ?? (brighter than Lo)
rest
3.4v - 3 minutes ?? - 3.3v rested for 35 minutes
3.5v - 5 minutes ? - 1.2v <<? = Was getting progressively dimmer
Removed battery DDM = 1.4v but rising fast.
By the time I got my camera out the voltage had risen to over 2.0v
Currently it is at 3.1v
The main problem as I see it is that you could go out with the battery at 3.8v then use the light in one of the mid modes for not too long a period and suddenly find your battery has been knackered. This light drains the battery too quickly for my liking :Sp
I can see on specifications, that the battery has a short runtime ; MID 160 lumens 90 minutes, high 300 lumes 45 minutes.
Is not a surprise, is clearly indicate on the manual user and on the Nitecore web.
Your IMR, how many mA? perhaps 600-700mA, if you are at 3.8V, how many mA dou think rest on your battery?, i think very few mA.
If you have read the oficial Nitecore data, I do not understand why are you surprised?
For Turbo mode.
If someone make partial runtime test…the runtime will not be the same than in a continously runtime test.
There are a step down?… if someone make partial runtime, measure voltaje, new runtime start… with more powerful, consumption will be greater than on the continuosly test.
904mAh was the charge it accepted after the first time the EC11 blitzed it. It’s currently on charge again after its second mauling - I’ll check how much charge it takes this time
You can only measured the capacity of a battery in discharge. In charge is measured the mA that the charger send to the battery (there are losses on heat and more), not the mA that will be stored by the battery.
If the charger indicate 904 mA, perhaps the battery has a capacity of 750-800 mA. Is a good battery.