Is Low Voltage Protection Necessary?

LED Flashlights – General Info
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Why are Protection Circuits Needed?
“Figure 1 illustrates the top of an 18650 cell for Li-ion with built-in safety features.”

Learn what causes Li-ion to fail and what to do in case of fire.

“A mild short will only cause elevated self-discharge and the heat buildup is minimal because the discharging power is very low. If enough microscopic metallic particles converge on one spot, a sizable current begins to flow between the electrodes of the cell, and the spot heats up and weakens. As a small water leak in a faulty hydro dam can develop into a torrent and take a structure down, so too can heat buildup damage the insulation layer in a cell and cause an electrical short. The temperature can quickly reach 500C (932F), at which point the cell catches fire or it explodes. This thermal runaway that occurs is known as “venting with flame.” “Rapid disassembly” is the preferred term by the battery industry.”

https://batteryuniversity.com/learn/article/premature_voltage_cut_off
“Most mobile phones, laptops and other portable devices turn off when the lithium-ion battery reaches 3.00V/cell on discharge. At this point the battery has about 5 percent capacity left. Manufacturers choose this voltage threshold to preserve some energy for housekeeping, as well as to reduce battery stress and allow for some self-discharge if the battery is not immediately recharged. This grace period in empty state can last several months until self-discharge lowers the voltage of Li-ion to about 2.50V/cell, at which point the protection circuit opens and most packs become unserviceable with a regular charger. ( See BU-808a: How to awaken Sleeping Li-ion )”

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“Li-ion batteries contain a protection circuit that shields the battery against abuse. This important safeguard also turns the battery off and makes it unusable if over-discharged. Slipping into sleep mode can happen when storing a Li-ion pack in a discharged state for any length of time as self-discharge would gradually deplete the remaining charge. Depending on the manufacturer, the protection circuit of a Li-ion cuts off between 2.2 and 2.9V/cell. “

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You could have it both ways if the charger gives the tripped cell a quick pulse to untrip the protection and then checks the real Voltage to make sure it’s not too low……don’t know if there are chargers that do it this way or not.

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This is the way.

44

yes :+1:

45

If cells already have built in protection, why are add on protection circuits needed I’m wondering?

46

maybe I dont understand the question, but let me try and break it down for you

specific to LVP

1. Protected Cells have LVP

2. UnProtected Cells do not have LVP

3. Anduril lights have LVP in the driver, so they do not need to use Protected battery cells.

4. Most lights do not have LVP in the driver, and they should be used with battery cells that have LVP in the battery, since it is not in the driver.

make sense?

47

I guess I misunderstood the article to mean all LIs have protection circuits already built in.

48

they do, but they are overvoltage, overpressure, overheat protections in the cap

Low Voltage protection is a fourth type, that does not exist in all cells. They specify either Protected or UnProtected, depending on application.

High drain tends to be unprotected, and best used with drivers like Anduril that have LVP in the driver… and so on

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So reports range from 5 days to a couple of months. Lumintop themselves claim “One month, in theory”. Not good, but not terrible…
I would generally recharge a cell after using it anyway, so it’d not likely go more than 48hrs and not be stored in the light.

Do the 14500s from Fenix have sufficient LVP?

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I use the Fenix protected 14500s. They are a OK cell but I have not put the LVP to a test.