Hi guys.
Decided to find out more about the cut-off voltage (low voltage protection) of various flashlights.
Benckie and I had a nice discussion about termination voltage of discharge tests with hobby chargers. It was mentioned that many guys like to terminate at 3.0V under load. Any lower and it's just only useful "in theory" and not useful in reality.
For me I think we can safely go lower than that and there is use in reality. Not that i'd recommend it, but sometimes you do run into such scenarios of long runtime. My experience is that as long as you recharge immediately and do not let the cells sit there, there is no issue. I have done so many times and the cells more or less can still discharge the same mAh as well and produce good high current.
My measurement is by using a key to complete the circuit of the light, while the + and - DMM probes are constantly touching the + and - as well. So when it cuts, i would take away the key immediately and do a reading. This is the best i can do and is the open circuit voltage figure of the cells (ie not under load). So the under load voltage is even lower.
In between the tests, i'd recharge the cells at 1.0A for 2 minutes.
To determine the extent of drop in output, i am using a lux meter.
1. Crelant 7G5. No low voltage cut-off by the driver. It just let the cells dive to about 4.2V before it starts to dim. Because this is a 2-cell light, there is enough juice supplied so that it does not dim as compared to what a single cell light would have.
2. Fandyfire STL-V6. About 4.7V. That's 2.35V per cell.
3. Balder BD-4. 3.9V! That's below 2.0V per cell. There is a low voltage warning in the form of the light ramping up and down smoothly and continuously <<-- Nice feature of Balder!
4. Sunwayman T40CS. Went to 4.4V and the light went into an erratic flickering randomly between like 15Hz-30Hz.. Sheesh, that's dangerous, thought i would spoil the driver so did not test further. The Sunwayman V10A does a 10Hz strobe when there is not enough juice. This is 2.2V per cell.
5. Shadow TC6+. At 4.6V, the light went into strobe, signalling low voltage. This is 2.3V per cell.
6. Solarforce Masterpiece Pro-1. No low voltage cut off. Still plenty of light at 4.0V and below. (that's expected)
7. Dereelight DBS aspheric. No low voltage cut off. Plenty of light.
8. Dereelight CL1H V4 with 3SM. No low voltage cut off. Plenty of light.