Lithium Ion battery question

How low of voltage do you let the Lithium Ion battery drain, before recharging ?

The battery I'm using is a 14500.

 

2.75V is what the datasheets seem to say.


EDIT: Nope nope. Too dead, don't discharge that far.

 

3.2V if you want to maximize cycle life.

 

Number of questions.

Lithium ion polymer or lithium iron phosphate?

How many cells?


I run both. Lithium poly for my RC toys, lithium iron phosphate on my camper. For both types of battery, it's really better to go by amps consumed rather than volts. That's because the lithium family doesn't have a linear volt drop like traditional transition metal batteries do. Get yourself a good battery monitor that can measure current, not just volts. Batteries are expensive, a good monitor protects your investment.

However, to answer your question:

Lithium iron phosphate: don't let it drop below 3.2V per cell, or 12.9V for a 4 cell unit. (that's 20% charge remaining. For the health of the battery, don't let it drop below that.)

Lithium ion polymer: don't let it drop below 3.7V, or 14.9V for a 4S battery. Risk of fire increases rapidly below that.

 

For a 14500 cell form it’s likely either a Li-ion nominal 3.7 V charged to 4.2V, or less likely could be a Lifepo4 (lithium ion phosphate) nominal voltage 3.2V, min 2V, charge at 3.5-3.65V.
Google the manufacturer/part number on the cell to see what you have.
I doubt it’s a polymer those are typically flat pack type batteries not the round cell 14500’s.

 

This is the headlamp I bought.

sofirn HS05 AA Flashlight Headlamp, Mini Headlamp 1000 Lumens with LH351D, Magnetic Tail Cap, Dual-Way Clip, for EDC Camping Running Hiking Outdoor (HS05-kit)

https://www.amazon.com/Flashlight-Headlamp-Magnetic-Dual-Way-HS05-kit/dp/B09V28Y3PN?th=1

This is my first rechargeable Lithium Ion item I own. I don't want to start any fire or cause damage to anything or someone.

I don't know to much about the supplied battery.

 

Aha. Those *should* have on board circuit protection that shuts down when the battery reaches a certain voltage. Most small electronics have a charge/discharge controller built into the unit. Nobody wants to start a fire on their forehead.

I wouldn't worry about that one. Run it until it gets low, charge whenever.

 

in automotive and motorcycle applications Lithium batteries are "cranking" batteries. they have higher cranking amps than lead batteries, but much less amp hours.

these are not deep cycle batteries and should not be discharged more than 20 or 30 percet.

not sure if that helps but it's my first hand experience

 

I don't think these 14500 has a protected circuit. At 48.8 MM in length. I don't know much anyway.

I found a review on these 14500, I don't understand the technical data.

https://budgetlightforum.com/node/60597

Sofirn 14500 is 48.8 MM, AA battery is around 50.5 MM, protected 14500 I was looking at was 52MM to 55MM.

Will I have fitment issues using a larger battery?

What do you think about the single bay charger that was supplied with the kit?

 

The flashlight itself will have the low volt protection. To be extra safe, charge it when the indicator first turns red, don't let it get to "critical" flashing red. The included charger should be fine.

 

The 14500 off the charger is 4.2 V using a Harbor Freight multimeter. The Uni-T meter is close to the same volt reading. I've been charging the battery when it reach about 3.5 V but don't know how much volts I should let the battery drain to.

When I get another 14500, Is there a way to see if the length is too long?

 

So I'll get a little nerdy. I personally wouldn't let it drop below 3.7-ish. For a small single cell battery, dropping it to 3.5 is probably ok. (measured at full rest, meaning the battery hasn't been powering anything for a few minutes.) Here is why.

For reference, this is the typical state of charge for lithium poly, at full rest:




If you want to get deep into battery geekery, the state of discharge depends on how fast you are draining it:


To read this chart, just in case you are interested, C-rate refers to how fast you are discharging the battery. For example, 1C beans it depletes the battery in one hour, 0.5C means you deplete in two hours. According to the advertisement of your flashlight, it claims that "medium mode" drains the battery in 3.5 hours (0.29C) and "low mode" lasts 30 hours (0.03C)

The short story is that the battery's happy place is living on the plateau of that graph. It doesn't really like to live on the slopes; that state of charge (or discharge) is unstable territory and will cause premature wear/tear on the battery.

Now on one hand, a 14500 size just a small single-cell unit, that is about the cheapest possible lithium battery you can buy, so its no huge loss if you trash one. On the other, hand, if you want to keep it living for a long time, keep it on the plateau. Which means your battery charger should stop charging at 4.2V (all chargers should do that anyway), and you should probably put it back on the charger at around 3.7-3.6V. But again, don't worry if you drop a little below that.


Also, disregard my earlier statement about fire - while it is still possible to have a meltdown at that size, smaller and fewer cells in a battery pack usually mean lower susceptibility to runaway thermal reactions. You have to be really trying to start a fire with a AA-sized single cell. Usually when people ask about lithium, I assume that they are talking about battery units that are at this size:






Or if dabbling in the world of LiPo, this size:

The only way to know that is to stick it in your appliance and see if it fits.

 

The chart are kind of confusing, Will the C rate be considered as Amp draw?

According to my multimeter the end of charge Volts reading is 4.2V. It's not over charging. While charging I'll put my hand on the charger. It doesn't get hot, just get slightly warmer than room temps.

Once I tried putting aluminum foil at the positive/negative of the battery while charging. Then use my multimeter to get a reading. The reading just fluctuate up/down.

From reading, the most common mistake people make is not checking Volts before pairing the battery together. One battery is working harder than other that causes fire, or other issues.

The graphs for the battery I have is in the link I posted above.

If the battery is to large will it leave some sort of marking from the spring on the negative side of the battery?

 

Correct. C rate is defined as the battery's capacity divided by one hour. For example, a typical battery has a rated capacity of 500 milliamp-hours (mAh). Therefore if your current is drawing 500 mA you follow the 1C curve; if your current is drawing 250mA you follow the 0.5C curve; etc. Notice the benefits of getting a higher capacity battery: Say if you switched to a 1Ah (or 1000mAh) battery, then suddenly your 500mA draw is following the 0.5C curve.

Normal.

If its too large you won't be able to close up the flashlight without breaking something. Small indents are normal, using muscle to screw the cap closed is not.

 

The Sofirn 14500 battery is 900 mAh. The other 14500 I may pick up is rated at 1000 mAh.

Does the protective circuit drain anything from the battery?

Is the only way to see if the 14500 will fit is to find one locally?

 

No or negligible parasitic drain.

You could always return it if it doesn't fit

 

Are lithium battery returnable? Due to safety issues I thought they were non returnable.

If the buyer has to pay return shipping then it may not be worth it.

 

For most modern batteries 2.5V is the discharge limit, and for an older one it were ususally rated at 2.75V or 3.0V.
Better take a look at the battery's manual things could varies wildly.