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Comment by ficklepickle | Hacker News Reader

This sounds like it could be rather dangerous, no? Connecting up a bunch of old lithium cells of unknown origin and using them hard.

I'd also worry about an insurance claim being denied if it burned my house down.

However, I very much approve of the DIY ingenuity and repurposing of old stuff.

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If they're from laptops the cells should be safe (as opposed to unknown new cells from AliExpress which may or may not be to spec); albeit not necessarily at maximum capacity. As long as appropriate protection circuitry is used, I don't see how using then hard would make any difference (laptops use batteries hard too).

opposed to unknown new cells from AliExpress which may or may not be to spec

Many of those are actually recycled old cells, likely from laptop batteries, and could still have a lot of capacity left --- often, what happens is that one of the cells in the pack fails/goes out of balance and the protection circuit disables the whole thing, meaning the rest of them are still very much usable.

Laptops catch fire sometimes.

Most of the videos on the subject I've seen have a simple idea: depending on the battery, one cell could turn a whole pack off for safety. Pulling them apart, and rewiring them to a new (and probably better) Battery Management Chip, could make the N-1 pack working. They also often charge them a few times individually to assess their stability.

[1] one bad cell could force too much current elsewhere or overheat IIUC

Kind of dangerous seems like quite the understatement, considering the nature of lithium batteries!

It'd be fun to play with something like this for the learning, but I wouldn't actually run one unless it was in its own shed, many dozens of yards from the nearest anything else. Lithium fires are no joke.

I've read claims (theoretical and practical) from both sides, so apparently the safety of lithium cells can vary widely based on manufacture quality and maintenance.

But also, on the video, they shows each pack of cells he uses has individual over and underchange and temperature sensors, so the system is able to tell if any individual section is going bad. It's a pretty neat, and external installation, so I don't think it is very harmful on a "massive heat incident".

A properly designed lithium ion pack with tested high-quality cells is a very safe thing in the environmental conditions it was designed for.

Notice how many qualifiers are used in that statement.

BTW I've seen lithium cell safety bags, that can hold the flame enough. I wonder how a case could be done in a similar way to at least contain the heat and gas.

Also, could there be a thermoelectric powered fan to slow down the heat rise when cell(s) starts to fail or burn ?

You absolutely can design a firewall system able to fully contain a runaway pack. They have small systems that look like briefcases to nab runaway laptops on planes, for example. But when a cells goes, it goes. No fan is going to remove anywhere near enough heat. And you wouldn't want it to spread the vapors, as HF is a genuinely dangerous byproduct. The only real solution is full containment. And being 100% confident in your containment solution would require a lot of destructive testing- it isn't a trivial problem.

Ok a fan was ridiculous, but I didn't mean to diffuse gaseous products; just tap into the heat to activate some endothermic reaction around the system to, well, delay or dampen the process.

Thanks nonetheless for the return

Very much so, a very good read:

http://www.candlepowerforums.com/vb/showthread.php?141137-In...

And also: http://budgetlightforum.com/node/45314

Can this thing be put in a fire-resistant compartment outside house? Even a couple layers of drywall would probably be enough to isolate the fire. A design with inner fireproof walls would prevent one cell from lighting up most of the pack. All this is neither hard nor expensive, and would limit the consequences of a fire severely.

No way I'd do this inside my house, either, but if you watch the video, the Australian fellow had his in two little aluminium sheds out back, set on concrete. Looks like, most likely, a catastrophic event would trip the wires and (at worst) burn down the sheds and couple computers/Arduino boards. Now, insurance folk will always fight a claim, but you might be able to get past... maybe =/

Cells are brought through charge and discharge cycles to test them individually before building a pack.

The hyperbolic response isn't warranted, as these are nearly identical lithium cells of known origin. Were they all different random cells, or if disassembly were required, then one might catch fire or explode like a small firecracker.

This isn't much more dangerous than putting batteries in a toy car, or putting gasoline into a hybrid.

I'm a EE, and a licensed PE. I wouldn't do this.

Please excuse my ignorance - what is a licensed PE?

Edit: Thanks for the answers. 2 questions:

1. Why would you not do this?

2. Were you to do this, what precautions would you take?

Professional Engineer

Professional engineer

Professional Engineer. There's an Engineer in Training certification first, typically gained by passing a Fundamentals of Engineering exam in college. Then you work for a few years under a PE and take an exam to become a PE yourself.

Someone licensed by their (US) state as an Engineer, and the only person (in most states) who can legally call himself an Engineer.

https://www.nspe.org/resources/licensure

>the only person (in most states) who can legally call himself an Engineer

Someone must have a PE to sign off on certain things when dealing with regulators and so forth. Which makes getting a PE in certain situations important. But not having a PE is hardly equivalent to calling yourself a lawyer if you haven't passed the bar in a state.

Whether or not it's equivalent is pretty irrelevant to the law

That’s not true for any of the United States. You can’t call yourself a Professional Engineer without being licensed, but anyone can call themselves an engineer. Train engineer, growth engineer, happiness engineer, and software engineer are all perfectly valid titles without a P.E. license.

Try calling yourself an engineer in Texas without proper licensure.

http://www.mystatesman.com/news/state--regional-govt--politi...

And the relevant court case:

http://www.soah.texas.gov/pfdsearch/pfds/460/16/460-16-0550-...

The funny thing about that is, at least when I worked in the oil business, I'm not sure I've seen another industry that threw around the "engineer" with more abandon for technicians of all stripes.

I'd note that's a case where a business is representing themselves as an engineering firm and, and in some situations, it would be reasonable to expect that meant they employed licensed engineers. (The specific case is pretty silly though so is calling themselves engineers.) But individuals certainly call themselves and are called engineers all the time who aren't licensed in Texas and everyplace else.

https://www.dice.com/jobs?q=software+engineer&l=Texas

-> 1 - 30 of 3,061 positions

doesn't seem to have scared too many away from the title..

To this day they still call themselves Tire Engineers, even through an acquisition last spring.

I'm not sure how relevant it is as an appeal to authority measure, but in the US there is a Professional Engineer license. It's mostly relevant when you have to sign off on designs for regulatory bodies.

Professional engineer

I'd rather use old cells than shady new cells. New cells are the dangerous ones- manufacturing defects can make it through QA, but everything gets found after a few years of use.

What area do you work in?

Luckily, home owners' insurance covers stupidity as well as acts of God. So as long as there is no evidence of intentional arson, then insurance would have to pay.

That sounds really unusual I feel, the insurance company should be within their right to deny a claim if the home was destroyed due to gross negligence, like someone deciding to make a pool on their roof without asking an architect, or throwing a raging party with 700 people and the floor collapsing.

If they can prove you knew it was an increased fire risk, they won’t cover it.

If it's not in the policy "we don't cover homemade lithium projects", your covered. Very few things a home policy won't cover like nuclear war, terrorist acts for example. If your operating as a home business building these then that could be an issue, otherwise you can be an idiot and build whatever you want and your covered.

We don't cover !@#$ing with the utilities in ways that are not standard is probably in there somewhere..

The tie-in to the utility can easily be professional or professionally verified. That's quite separate from the battery bank itself.

In the case of electrical improvements (like hooking your hacked battery up to mains power) your insurance company just needs to do a little digging. They just need to find out if there were improvements without permits or if those improvements weren't made to code.

Yes, this is extremely dangerous. I'm sure some of the people mentioned have the expertise to pull it off, but for most this is like building a massive bomb in your garage. There's a reason that 18650s aren't generally sold directly to consumers, in most applications they need dedicated circuitry to be used safely. And that's for brand new cells, it's another story entirely to be using random collections of "old" cells, at various points in their life cycles, different rated capacities, and subtly different chemistry. No thanks!

Theres no way to detonate a pack like this. 18650s have a pressure release, so the cstch fire but dont explode. In the very unlikely event that fails, a cell could burst, but it cant cause other cells to burst unless the entire pack failed to vent under extreme pressure.

Yeah. It's a total misconception that Lithium batteries can "explode". Sure, there's a fire risk if you have faulty or unprotected cells.

But there's no explosion risk unless there's something very wrong with the way they're packaged.

Semantics. Is a battery undergoing thermal runaway/venting "exploding"? Or merely "ejecting scorching hot gas and catching fire?" Maybe it's not blowing up like an IED, but either way I don't want it happening in my garage.

The difference between "can be ignited" and "massive bomb" is not semantics. Even new pouch cells are way safer than they used to be. Unregulated 18650 cells are quite safe if the correct circuitry is used. The only dependable way to ignite them is to smash completely open them at full charge.

Cool, you caught me being hyperbolic. They are not literally a massive bomb.

> Even new pouch cells are way safer than they used to be.

Right, because these packs filled with recycled cells are going to have the latest protections.

> Unregulated 18650 cells are quite safe if the correct circuitry is used.

Which is my whole point, I'm not sure I trust the guy down the street to correctly wire and have adequate circuit protection for his DIY battery pack in his garage.

> The only dependable way to ignite them is to smash completely open them at full charge.

https://www.youtube.com/watch?v=24fYrV2vCPk

Lithium ion batteries are able to experience thermal runaway caused by internal shorts. This can be mitigated by quality control and proper handling (a lesson Samsung recently learned), and also other chemistries (like LiFePo, which is much more stable).

https://www.youtube.com/watch?v=Md4l9bFDOtc

That, to my untrained eye, looks like enough batteries to take down nearby structures if they went up, and packaged in such a way that a runaway in one cell that caused it to vent would propagate to other cells nearby.

Granted they're pretty reasonably protected by 2-3 layers of electronic monitoring and on-cell fuses, but lord, a small fire would burn the neighborhood.

I think all that it would take to render them marginally safer is a firewall between the different packs made of some good steel or refractory material.

> Sure, there's a fire risk if you have faulty or unprotected cells.

Or if an unrelated fire occurs in the garage/basement where it's located...

This is certainly enough stored energy to seriously ruin a firefighter's day if they didn't know it was there and how to properly deal with (or, more properly, to not bother dealing with it until it burns out).

>There's a reason that 18650s aren't generally sold directly to consumers https://www.amazon.com/gp/aw/s/ref=is_s?k=18650 has pages of them.

The last flashlight I bought requires them too.

Yeah, I'm aware you can buy them. I have 4 cells sitting in front of me right now. But there is a big difference between someone specifically buying them for use in a high-discharge device like a flashlight or vaporizer versus picking up a pack at Walmart next to the AA/AAA. Because of the high discharge you can hurt yourself or start a fire much more easily. Just look at the stories of people with burns on their thighs from throwing them into a pocket with keys/change.

But there is a big difference between someone specifically buying them for use in a high-discharge device like a flashlight or vaporizer versus picking up a pack at Walmart next to the AA/AAA

You can find 18650s for sale on walmart.com . I'm not sure if the physical stores carry them, because there aren't any where I live, but I know that in Shenzhen/HK and other parts of Asia you can easily find 18650s for sale amongst other batteries in physical stores.

Because of the high discharge you can hurt yourself or start a fire much more easily. Just look at the stories of people with burns on their thighs from throwing them into a pocket with keys/change.

NiCd/NiMH can also source huge currents if shorted.

> I'm not sure if the physical stores carry them

Flashlight geek here. Several people on flashlight forums have reported finding the Westinghouse branded 18650s in physical Walmart stores. They have a low capacity - 2000 mAh, compared to 3000-3500 for the latest cells from Sony/LG/Samsung/Sanyo/Panasonic. They also use a cell of unknown manufacture, so I can't be sure of the quality.

Specialty battery stores, higher-end outdoor gear stores and vape shops have 18650s, but it's best to get them online from dealers that know what they're doing. In the US, good options include Illumn, MTNelectronics and Li-ion Wholesale. These places have the gear to test batteries to make sure their suppliers didn't send them fakes, and usually have very competitive prices.

> Flashlight geek here.

Can I ask a flashlight question? :) How do I tell how many lumens a flashlight really is? I go on Amazon and I see XyzFire flashlights that claim to give out many more lumens than would make sense, and many times they're inconsistent on the page itself. I don't know how to really tell. (If it matters, I'm trying to find a flashlight that fits in my pocket, is < $20, is ideally zoomable, and is as bright as possible. Best one I've found so far is this: https://www.amazon.com/gp/product/B011B1U2QS)

You need to find a review written by an enthusiast with measuring, or at least estimating equipment. Assume all the *fire brands are outright lying. Cheap stuff claiming more than about 1500 lumens per 18650 is usually lying. There is, however a pocketable, $40 flashlight that makes an honest 4000+ lumens on a single 18650: the Emisar D4. There's a catch though: it's dissipating about 80 watts of power to do that and thermal throttling kicks in after a few seconds. To give it more HN cred, it has an open source firmware.

As to your request, a couple general recommendations first: skip the zoom, and don't chase output numbers. Zoom is pretty optically inefficient, and small zoomable flashlights don't end up with much more throw distance than similar size fixed reflector flashlights. They don't do wide-angle illumination as well either. A good reflector with sufficient output provides both at once. As for brightness, human perception of brightness is roughly logarithmic (with a base between 2 and 3), so it takes four times the output to look twice as bright. Anything over about 500 in a pocketable flashlight is pretty decent, and most 18650 lights have more.

Specific recommendation: the Wowtac/Atactical (both names show up on Amazon sometimes) A2. This is one of the smallest 18650 lights, has shortcuts to low, high and last-used modes from off and has a right-angle configuration that works equally well handheld of as a headlamp. A pocket clip, headband and 18650 battery with built-in USB charging port are included. It costs $20, and I have no idea how they make a profit given all the stuff it comes with. Go with the neutral white tint if you can find it; this looks more like sunlight and won't wash out colors as much as the cool white.

Any way to buy off Aliexpress without getting fakes?

A few of the budget brands like Convoy, Eagle Eye, and Maxtoch have official Aliexpress stores. I'm not sure about linking Aliexpress here, as the filter might think I sold my account to a spambot, but their store IDs are:

* Convoy: 330416

* Eagle Eye: 1735126

* Maxtoch: 314381

All three make good stuff that has been popular with flashlight geeks. Convoys with "new firmware" or "Biscotti" have an open source firmware: http://bazaar.launchpad.net/~toykeeper/flashlight-firmware/t...

Forgive me for my ignorance, but why do I need my flashlight to have open firmware?

This is Hacker News. Open source is generally appreciated here even when there isn't a direct, concrete benefit to most end users.

But if you're here, there's a good chance you're the sort of person who could get an AVR programmer and tweak something if you don't like it. Different modes? Timed stepdowns to prevent overheating or not, or more sophisticated thermal regulation for the attiny25 based drivers that have a temperature sensor? A firmware with completely different behavior like near-continuous ramping instead of fixed modes?

It's hackable, and hackable is good.

Any thoughts on the Wowtac A2 vs Wowtac A2S?

The A2S is not worth a 50% price increase for most users, but if you really want more output (in the form of a bigger hotspot, probably not more intensity or throw distance), it's only $10 extra.

> There's a reason that 18650s aren't generally sold directly to consumers

They are, but IME the sourcing on some of those (especially through Amazon.com, which comingles items from different sources) is hinky. That 18650s can be dangerous if misused or if counterfeit isn't an argument for restricting availability, it's an argument for making them available directly to consumers from legitimate authentic sources.

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