If you have a single cell light with a non-boost driver, won’t the ~3V forward voltage of the emitters be enough to keep the battery from overdischarging even without any sort of LVP circuit?
Not reliably.
Forward voltage depends on the current, and at low currents the forward voltage can drop below the safe discharge voltage of 2.5V.
You might notice it, but not if you are running the light in moonlight or unattended.
Every re-chargeable Lithium cell in a pack usually has a BMS device that can control OV, UV, OC and OT. Even if the “pack” is a single cell, it would be wise to have such a feature within the device, e.g. rechargeable vape sticks or flashlights.
i doubt anyone would sell a Lithium single-cell flashlight that didn’t have some sort of internal protection device on the driver board, do you have or know of an example?
I can’t recall a specific model, but when I first cought the bug in 2012 it was still relatively common for budget lights and lights intended to run on multiple chemistries to not have LVP.
Malkoff and Fraz Labs are a couple examples that don’t seem to have LVP
Lumintop Tool AA 2.0 with lighted tailcaps, they will drain that beetch to 0 volts if you let them.
Lots of others that the parasitic drain will kill as well. Wuben E05, love the light but keep the tailcap locked out.
A lot of LEDs still draw significant current even below 3V.
It’s not like the LED turns off at below 3V and doesn’t use any power.
Even if the LED is off it can use power.
An EagleTac (SporTac) single-mode drop-in has NO low voltage protection, or warning.
Wanted to know that specifically. Was confirmed by their CS.
In general you notice a light won’t make it to turbo anymore. Time to recharge!
But when it is already on, or/and unattended, it can bleed your cell’s down till the very end.
Most of my lights don’t have any LVP, or warning, at all.
And even when they warn you, chances are you are just looking elsewhere when the blip occurs.
Sofirn SP32A has no LVP and afaik a buck driver, LED is a Cree XP-L2. The lack of LVP iirc is intentional because the LED has low vF, not a cost saving measure, a bad idea imho. It can easily drain a cell to 2.2V.
Lots of cheapo lights have no low voltage protection and are happy to discharge the cells. The only clue you have is how dim the light gets.
All the Best,
Jeff
You’d have to leave the light on for several hours after it starts to dim, to seriously risk putting the cell into a dangerous low-voltage state. When it gets down to around 2.7v, it can’t put many milliamps into the LED, and it will glow on low or a moonlight for a long time before the cell gets down below 2.5v or 2.0v. Personally, I’d be fine with recharging a cell at 2.0v (as long as I use a charger that does a slow charge until 3.0v). Even Samsung 30Q spec sheet states that 1.0v is okay to recharge (as long as it’s slow).
I’m not sure if it’s possible for a (non-boost) light to drain a cell to 1.0v, though I suppose the driver would keep sucking some juice after the LED is no longer on.
A lot of chargers allow you to recharge from 0v. So, there must be plenty of people that want to do that, and are probably okay 99.99% of the time. I wouldn’t risk it, though.
> Is Low Voltage Protection Necessary?
Yes! unless you monitor battery voltage manually, or the driver has LVP built in.
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Very few lights that are compatible with both Primary and LiIon batteries, have built in LVP… (I can only think of one)
Anduril lights dont need protected cells, they have LVP in the driver, but those lights are also not compatible with Primary cells. Generally it is not adviseable to use Protected Cells in Anduril lights, because the high drain will trip the protection prematurely.
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Pros and Cons of Unprotected and Protected Lithium Ion cells in Unprotected Flashlights
such as the Lumintop AA Tool and Jetbeam RRT-01
Most lights that are dual fuel, do not have built in protection, neither the AA/14500 Tool, nor the CR123/16340/18350 RRT-01, have Low Voltage Shutoff circuits built into the light.
Popular wisdom is that lights like those, should only be used with Protected LiIon, but there are a few of us that choose to live dangerously… here is why:
A protected cell will drop to 0 volts when protection is tripped. This produces Sudden Darkness, which is best avoided.
—
An UnProtected cell will continue to power a light, at a dim output level, even when it cannot support the maximum output. Just say NO! to Sudden Darkness.
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If I am in a cave (pure fiction), and my flashlight suddenly goes dark, I will be less happy, than if it gradually gets dimmer, and gives me time to change the battery. This dimming feature is inherent in UnProtected cells.
Therefore, after my initial fear of using UnProtected cells, I now use them. Besides the no sudden darkness advantage, UnProtected cells use a safer battery chemistry, INR and IMR, Plus they have much higher capacity. The older protected cells, use less safe chemistry, called ICR, that has much lower capacity.
The danger of using an unprotected cell, is that if it is allowed to overdischarge, such that the light drains the battery below 2 volts (for example, if the operator fell asleep with the light on, the switch got turned on in a backpack… etc), then there is a risk of the cell overheating during recharging.
It is often advised to dispose of an overdischarged cell. With ICR, I agree, but unprotected ICR are not current production. Only INR and IMR are in use for unprotected cells now.
imho, with unprotected INR and IMR, it can be safe to recharge promptly,
using safe practices; including not leaving the charger unattended, and observing that the battery does not overheat during recharge
safe use of LiIon by people who do not monitor battery voltage, calls for Protected Cells.
responsible use of UnProtected Cells in UnProtected lights, calls for an alert and trained operator, that recognizes when the light goes dim, and makes it a habit of measuring battery voltage periodically.
LiIon cells are best recharged when they fall below 3.6v, instead of waiting to trip protection circuits, either in the driver or the battery.
Can you provide a reference for this, i can’t find this on any of the spec sheets i have seen?
It’s on page 14.
Apparently mine has parasitic drain too. Just found it down to 1% sitting on the end table. Strange, first time I ever noticed this happening to it. It gets a protected cell now.
> ggf31416 wrote: Sofirn SP32A has no LVP
true,
instructions say:
“Tips: when the light is not in use, please unscrew the tail cap a little bit to prevent the flashlight from turn on by accident, it also prevent the battery from draining.”
it makes sense there is parasitic drain, as the light has an eSwitch, plus indicator lights
questions
how large is the parasitic drain?
are the indicator lights off when the light is off?
does the light come with a Protected Battery?
LVP cost nothing and takes zero space , why not to use it?
The only indicator light is for 5 seconds after first turning it on to show battery level. Does not come with a protected cell.
most unprotected lights use Protected Batteries instead
to me, the OP question was basically:,
Is it safe to use UnProtected batteries (flat tops with IMR chemistry, and high discharge rates) instead of Protected Batteries (Low Discharge rate ICR chemistry buttontops), in UnProtected lights, without risk of Parasitic drain causing UnProtected battery in UnProtected light, becoming overdischarged?
Part of the answer depends on the switch type. Only eSwitches have parasites. And usually the drain is negligible, like, takes years to kill a LiIon…
(notable exception, the stupid blue lights in the AA Tool tail, when using LiIon)
you sure?
that would make no sense to me. Best to use Lockout I suppose.
What Voltage did your battery go down to?