What are my 18650 laptop pull cells useful for?

phouton · 2019-10-30T05:37:48.000Z

I recovered 8 18650 cells which are labelled Samsung SDI ICR18650-24E 6B3. I found a datasheet for them: ICR18650-24E Datasheet PDF - Datasheet4U.com

They measured at 3.1V to 2.89V, which I’m guessing isn’t too bad considering the battery pack had not been plugged in or charged for nearly 2 years. Before that, it was in a laptop used for over a decade, but not often on battery. At last check, the laptop reported around 60% capacity left on a full charge.

I don’t have a charger or LiIon flashlight yet so I haven’t tested charging or voltage retention.

Are they likely safe to use? Even if they are at half of the original 2400mAh capacity, given that I have 8 of them, it will be plenty for my needs with some swapping. I like to use what I have as long as possible, plus I have the reassurance of knowing their history and the fact that I take care of my stuff. This is especially true given the high cost and counterfeit problems with new batteries.

Also, how safe is it to use under-rated batteries on higher-drain flashlights? Do the drivers take care of that and simply operate at lower brightness (or not at all) or could the cell overheat or worse? I’m considering only single cell flashlights, particularly the Sofirn SP40 or SC31[B], and maybe some higher current drawing ones like the SP33 and/or the Astrolux EC01.

Yokiamy · 2019-10-30T07:39:47.000Z

Yes, they are safe to use in any (not too much current consuming ~3A) lights. But you will need a decent charger, for example the Litokala Li-500, which is not too expensive

YuvalS · 2019-10-30T09:38:41.000Z

I am almost exclusively use cells from old laptops. I use it for lights, power banks, power tools etc.
Assuming your flashlight has over discharge protection it is not risky to use old cells.
It is advised to measure some parameters as capacity, internal resistance and self discharge but it requires special charger and after some use you will figure which cells are better (you can mark them by number with permanent marker)

A light will not draw more current than the cell can provide so don't expect to more than 1000Lm from a single cell.

phouton · 2019-10-30T16:23:48.000Z

@Yokiami What about the safety if used in higher current drawing lights such as the SP33 or EC01? I’m not worried about getting 1000+ lm right now, even 300-500 lm is probably plenty for most uses for me.

@YuvalS Not sure but I think the SP40, SP33, and EC01 might have low voltage protection, while the SC31[B] has only a warning. Is that what is meant by over discharge protection? The datasheet for the ICR18650-24E mentions 2.75V as the discharge cut-off voltage.

I already marked the pairs of cells that were in parallel and their voltages matched exactly. Only one pair had the lowest voltage at 2.89V.

The latest versions of all above lights also have USB charging so I could maybe even skip getting a charger for now.

I was going to make a post asking for recommendations for a charger based on my factors. In summary I want one good charger that:

quality: will last a long time
analysis: can report capacity and maybe internal resistance and maybe refresh cells
long-term compatibility: supports current and likely future popular formats
reviewed by experts: gets good recommendations (eg. by HKJ)

The Liitokala Li-500 was my first consideration but it doesn’t seem to support 20700/21700 (the updated 500S does), plus I’m not sure I want to buy from Liitokala given their shenanigans with fake/mislabelled batteries.

Lightbringer · 2019-10-30T16:38:33.000Z

I’ve been using laptop pulls in low-stress lights for ages. Headlamps, drop-ins, anything that doesn’t draw more’n 2A-3A or so, preferably lots less.

phouton · 2019-10-30T19:38:02.000Z

What about the safety if used in higher current drawing lights such as the SP33 or EC01? I believe they draw more than 2A-3A.

From reviews it seems the SP40 can draw a touch over 3A. The SP33 draws over 6A and I guess the EC01 might be similar or more since its product listing recommends a 40A unprotected 21700 cell and suggests 18650 >20A for “emergency”.

So what happens if using a lower rated cell?

Lightbringer · 2019-10-30T19:46:39.000Z

Higher internal resistance × higher current = more heat.

So the battery will heat up faster, and terminal voltage will sag.

In short, I wouldn’t, and I’m not quite Mr Safety, either.

phouton · 2019-10-30T20:03:15.000Z

Will the flashlights avoid drawing more current than is safe, i.e. will they simply operate safely at a lower light output? Or can a user get in trouble by using an insufficiently performing battery?

Sirstinky · 2019-10-31T00:07:41.000Z

Drivers have either temperature protection or low voltage protection. If too hot or low voltage, the UI will decrease the power to a preset level and shut the light off if voltage goes under 2.8v or so. ICR type li-ion like laptop pulls can’t really take more than 4A continuous or they voltage sag real bad and trigger low voltage protection really fast in higher drain lights so you can pretty much use them on med to high at the most for an extended period. They will heat up excessively too and that can damage them. If you want to use the ICR cells in your higher power lights, keep the output low and you’ll be fine.

Cereal_killer · 2019-10-31T00:41:51.000Z

I wouldn’t try them in an SP33, it’s a boost driver and, depending on the specific boost converter they’ve used in their driver and just how well the driver is designed it could potentially draw to much current from the low power cells. The EC01 is just a linear driver and will only draw what the battery allows so you’re 100% safe there.

jf_smm · 2019-10-31T01:48:36.000Z

Used laptop pull batteries exclusively during the blackouts this weekend. Had a bunch of flashlights on low power that ran an evening or so before they started failing. Swapped them out for more of the same and recharged them as necessary.

phouton · 2019-10-31T05:57:46.000Z

@Sirstinky Where are the temperature sensors for temperature protection? If they don’t also measure at the battery I suppose that leaves a safety risk. In general, medium or high would be plenty, but I’m trying to get a broad sense of the safety risks.

@Cereal_killer According to New Sofirn SP33 V3 !! - #3 by Lux-Perpetua the SP33 v3 is now using a FET driver instead of a boost driver, and seems basically identical to the EC01.

It would be great to have clarity on when it’s 100% safe or not. Sounds like the drivers and other electronic protections are the determining factors, and I’m not too knowledgeable on that topic yet.