[Harrson] was really excited to get a deal on this Goal Zero Bolt flashlight. It’s and LED flashlight that uses Lithium batteries that are recharged via USB. That’s really handy. But when he cracked it open, like any good hacker does with new toys, he found that it won’t charge standard 18650 Lithium cells. That’s the form factor it’s using, but the proprietary cell that comes with it has both conductors at the top.
So where did [Harrson] start with the project? He called the company to ask about the setup. They were able to confirm that the proprietary cells just have a conductor which brings the bottom contact of the cell up to the top. We’d bet this is to make the flashlight itself easier to manufacture.
He got to work by scavenging a flat Kapton covered conductor from an old laptop battery. This thin strip is manufactured for connecting the cells of a battery, and it’s quite flat so it will be able to bypass the 18650 cell housing inside of the battery compartment. He made a solder connection for the strip inside the recharging compartment, leaving a tail which makes contact with the base of a standard cell.
If you’ve ever cracked open a dead laptop battery you probably found round Lithium cells. These are most commonly the 18650 variant we’ve been talking about. The battery dies when just one cell goes bad, so [Harrson] has a supplies of the good cells which he’ll be able to substitute into his flashlight as needed.
that design is ver dangerous because if something came across the contacts on the top of the battery then it could cause the battery to overheat and start a fire or even blow up.
Yes but the batteries stay inside the flashlight at all (most) times…. So that’s not really an issue.
And that’s what the protection circuitry in the battery is there for. In addition to cut off the battery in case of overcharging/overdischarging.
18650s aren’t protected…
Some of them are really well protected, you’d be surprised. Termal shutdown (mechanical), safety vent, overcharge, overdischarge. But yes they are not short-circuit protected per se.
Here we go again with the “swapping batteries” comments…
Is there anything wrong with doing that?
Oh zomg you touched a battery it might asplode in your house and u might die!!!!!
Seriously people, we know that batteries are a little risky to play with. We know this. We know to be careful when modifying batteries, so relax, we got this. Please keep your comments about the dangers of batteries to yourself.
I have done extensive testing with rechargeable lithium batteries including some attempts to get them to explode as well as extensive reading on the subject.
Except for extremely rare occasions, li* batteries will only catch fire or explode when:
-Charged over maximum voltage.
-Discharged under 2.5V and then recharged.
-Shorted out (only applies to high current cells such as you will find in power tools, RC toys and such).
This means regular consumer cells that you find in laptops and cellphones are very unlikely to do more than go hot, swell up and/or vent gas unless you use a faulty charger. LiPo cells may swell up slowly until they go pop, without fire or shrapnel, which i wouldn’t quite call an explosion in this context.
Thank you for validating my claims Sven!
NP.
I just pre-empted the otherwise unavoidable video reply with someone blowing up a large RC powerpack using a car battery charger, thus proving that all cell phone batteries can explode at any time…
I’m getting quite tired of all the “Li*batteries are dangerous” comments from people using sensationalist media and youtube videos as their source.
And to reinforce your point, many batteries are now “UN Approved” to pass the UN Manual of Tests and Criteria, Part III, section 38.3 tests T1-T8, which define rather serious failure-inducing punishment such as shorting it or applying double the nominal cell voltage across it. If they don’t explode from that (and such carry the “Approved” tag), you can bet they’re pretty safe.
http://www.unece.org/trans/danger/publi/manual/rev5/manrev5-files_e.html has the UN test battery (battery, get it? ha!)
Man that is a sexy flashlight
Yeah, it’s starting to grow on me.
My question is how the hell did he get to talk to some one with detailed knowledge of the product through a phone call. My attempts usually end with talking to “telemarketer” that has a procedure to follow . Usually starting with “have you tried turning it off and on again.” I had one problem with the mains voltage and was assured that 255 volts are perfectly fine for 240V appliances (in Australia). I asked for the persons credentials and was informed they had no electrical engineering experience. A call to the ombudsman latter and they taped down the transformer.
Well, I called the company to complain, since the product advertisement didn’t mention proprietary batteries anywhere (didn’t find them on the website, either, though I didn’t look all that hard), and was considering returning it. Still, returning things is boring and too much work, so while I was talking to the CS guy, I mentioned that I had questions about the design, and he gave me the engineering email address. Like, _volunteered_ it.
Awesome.
So, I sent an email to the address with some questions and one of the engineers answered, which was great, but like many engineers I’ve met, emails were terse and not as helpful as I’d hoped. Thankfully, his phone number was in the email sig, so I called the guy and we chatted a bit about it..
That reminds me – I told him I’d let him know if it worked. I’ll have to email him and tell him.
I wouldn’t put names or other identifiers online anywhere, without explicit consent.
But when you talk/mail to the Engineers again
please let them know you gave them
some positive comments here.
if done with appropriate discretions….
Who knows, could encourage a little more
helpfulness in other places.
and from your results:
I’m guessing that you approached them
in a polite, but to the point fashion.
If so, thanks for helping the image of all
of us who take things apart to fix them.
I sent the guy an email just yesterday, actually.
As to my phone conversation with the engineer, it became much smoother once he realized that I wasn’t starting from the ground up. Have specific questions when you talk to people at their jobs – they’re on the clock, and their job isn’t to teach you everything they know. It’s one thing to talk shop with a customer, but something else entirely to be answering questions like a lecturer. That said, the guy I talked to was very friendly, and (clearly) willing to help a customer, which is _exactly_ what I want in a company.
I would just hack it into a wired light for outdoor mounted use or handheld for bench use. Screw such proprietary design!
A similar flat conductor can be made from layering adhesive copper tape (e.g. the Tiffany glass art kind) and kapton (or other dielectric) tape. Does wonders!
I agree with echodelta. Just hack it into a wired light. LED flashlights are really useful, but the proprietary designs are so complex!