Bike lights...

Sorry, thought of one other thing:

I don't care how many videos you've seen or RC hobby friends, NEVER EVER SOLDER TO THE CELLS.

Any cell manufacturer will tell you this is insanely dangerous. The internal structures aren't capable of taking the heat, and you will damage them. The damage may or may not result in an immediate explosion, or loss of capacity, but it is there.
Battery cells can be safely welded, because although the welding temperatures are higher, the total heat delivered to the cell is much lower and the temperature rise inside the cell during a weld is tiny. Most shops like batteries plus will weld cells for you for a small fee. They weld on tabs that you can safely solder to.

 

As a safety mechanism some types of batteries will shut down if the heat gets too high. This helps prevent runaway discharge events. The pores on the separators shrink severely diminishing the capability to deliver current. The damage is permanent.

So, yes, avoid soldering.

 

So in an example:

A light that works on 3AAA batteries, is designed for a current of 3 x 1.5v = 4.5 (Not sure how the arrangment of the circuit is).

Would it be possible to put 2 AAA sized Li-ion 3.6v, totalling a 7.2v and one "Dummy" AAA cell to just close the circuit and operate the light at an even higher voltage?

Btw I was googling some of these Li - On and Li - Po cells yesterday and some say that have a "vented" designed in order to prevent pressure from building inside the cell. So basically any internal pressure is vented in a controlled way and they wont explode, but they would probably still burn...

...and also a secondary circuit that shuts off the battery when the temperature goes beyond a point, but it doest seem that this would be an actuall circuit, it would probably depend on a part of the normal battery circuit to get destroyed from the heat first, so the current is routed in the secondary circuit?

 

The more powerful flashlights are designed to take Li-ion batteries.

I heard that the UltraFire Li-ions are dangerous. Go figure.

How about the UltraLeak raft, or the UltraToxic supplement?

 

Lolololol

 

You have to work with what's available, if you can find small cells like that, then I would be nervous going to 7.2V because common component ratings for the parts that might be exposed to the battery are 5V and 6.3V. There are ways to efficiently reduce the voltage (google AnyVolt regulators) but that's not something the average cyclist will want to take on. I'm more than willing to assist anyone who is though. A series diode or two would do the job, but you're then wasting a significant amount of power.

Venting and thermal protection is real, but it's only as real as the manufacturer makes it. With quality cells there is a venting mechanism (one of the things that gets damaged when soldered to!), and if the cell spec indicates so, a PTC (Positive Temperature Coefficient) component in series with the cell. These are normally very close to zero ohms, but if the cell gets hot they increase resistance rapidly, which effectively shuts off the cell.

All that being said, an internal short in the cell won't be stopped by a PTC, and the vent may not be able to cope. The scariest battery I've built so far was for a sensor platform, I needed 14V at 50AH. Four huge cells about 10 x 12 x 3/4 inch, with fuses and charge balancing built into a pelican case. I told the sales guys taking it to a show, if it starts acting wierd, just run. If one of those cells develops an internal short, the energy released would be huge, and that would cause the others to fail as well, so there's nothing you can do other than get away from them.

Yes, apparently "Trustfire" is a cell brand to stay away from, in addition to "No-Name" cells from China. Counterfeiting is rampant, some are so good that it takes a factory engineer to spot them, and some are so laughably bad, like "Dunacell" brand.. Buy your batteries from reputable vendors, and hope for the best.

I've seen Nimh cells that had no functional venting, and apparently were a little short on the catalyst that recombines the hydrogen and oxygen produced in the cell. About 1% of them would eventually have an explosive venting event, spewing boiling electrolyte out the end under high pressure. But at least the electrolyte in those isn't flammable.


FWIW: I had occasion to test 123A cells for a military application that I was designing, and under heavy loads (1.5 - 2.2A) the Titanium Innovations cells performed about 10% better than any others including Duracell and Energizer. Sanyo cells ran about 50% below Duracell and Energizer. I buy the titanium innovations cells in 50 count packages at <$1 each, which is WAY better than wal-mart pricing.

 

How intense is the venting? This video refers to the smoke discharges as "venting". It still looks dangerous to me.

 

That video is fairly typical from what I've seen. That smoke is flammable and toxic. There's a fair amount of pressure involved with metal cased cells.
Even NIMH cells have similar pressure, and the electrolyte is basically boiling lye.

You can't trust all the Youtube videos either though, some are rigged, and some of the cell failures are induced by doing things to the cells that would never happen in real life.


Should you have an event like this while riding, immediately get off, if possible lay the bike down where it won't cause a brushfire, and stay clear.

 

Maybe that's a bit more "combustion" then "venting", but there was no "explosion". (Where did they get the pyromaniac audience on the background? )

Yes that could be pretty dangerous in a small room with no windows and a few boxes of printer paper next to the laptop...

The "venting" system is basically some "soft spots" or "venting holes" on the cell so the pressure will be "vented" from those and not create pressure build up in the cell, which would cause it to explode.

But the energy release is quite substantial for a small cell... It's probably on a similar scale with gunpowder for a given volume of material.

 

Because of the law of conservation of mass, an increase of pressure within a battery can only mean that the temperature is increasing.
That's going to be one hot discharge from your battery.

 

There are a lot of headlights on the market that don't require wires, and you can get ones that are far brighter than the AAA and the AA variety. There are several really top brands in this catagory. This site shows some of the AAA and AA powered and self contained battery powered lights as well as some batter pack lights which you don't want, but the site shows beam comparisons; see: http://www.modernbike.com/guide.asp?ListID=61 As you'll see when you look at the beam outputs the AAA and AA battery lights are very anemic. Just my opinion but I would not ride around on a light like those AAA and AA lights put out. You probably don't want to spend a lot of money, and that's ok because you can get a Cygolite Expilion 350 on Amazon for just $56 which would be just a bit brighter than the Streak 280 in the review site. The Streak and the Metro series of lights do not have replaceable batteries, I cannot recommend spending money on a light then when the light battery goes dead you have to throw it away and get new one, the Expilion series of lights on the other hand Cygolite sells replacement battery packs for these that simply slide into the light housing. See this: http://www.amazon.com/Cygolite-350-Lumen-USB-Rechargeable-Headlight/dp/B005DVA37Q/ref=sr_1_3?ie=UTF8&qid=1395764341&sr=8-3&keywords=cygolite+expilion

You should seriously consider for your safety to get the brightest light you can afford, but those little AAA and AA lights are more for being seen rather than to see the road with, and if all you want is to be seen you would be better off with a bright front flasher than a dim headlight. Flashers like the Blackburn Voyager run about $15 each; or the Cateye Rapid 3 for about $25, another really bright flasher is the Serfas Thunderbolt but those run around $35 and seems expensive to me especially considering for just another $20 you can get the Expilion 350 I mentioned earlier. I'm not sure but I think you live in Europe and flashers are illegal there, so if you live there double check the laws before getting a flasher.

Again all the above is just an opinion.

Also rechargeable batteries are odd, except those posted earlier that come pre-charged, but the self contained ones like the Cygolite you have to charge up for at least 24 hours REGARDLESS that the charge indicator showed it fully charged in 5 hours; then you have to use the light till it's dead, and recharge but this time you can stop when the charge completed indicator is lit, then discharge to dead and recharge 2 more times, after that you can charge and discharge anyway you want. Even with those batteries the other poster mentioned you still have to do the 3 cycles of full discharge and full recharge, if you don't do that the battery life will be shortened which is why some people complain they only get 6 months to a year on set a batteries. They do recommend about once every 6 months to discharge completely and recharge fully.

 

Torch-hot by the look of it... Probably wont happen with an integrated unit like a laptop with battery and charger. Might happen when using Li cells with non compatible circuits and chargers though.

Do they have any clearly visible warnings on them?


Btw that's what? 2 grams of battery?:

 

I'm in South Europe (not in the UK) and flashing lights are legal. Actually the law doesnt care much about cyclists around here, allthough there are a few occasions where somebody is pulled for not having reflectors or something, which are a legal requirement.

At the moment I am using a Giant Numen 1.0 or something, which has a 1watt Cree led at the front, with three AAA 1.2v GP Recyko's. It works just fine, enough light for up to 20+km/h. When the "battery low" light goes on, the light is practically off withing 20min. But its constantly bright until then.

It''s a bit like this one:








On the back I am using a 0.5watt Giant light which also has and additional 6 "bright" leds. It's pretty visible (I guess). I am using it with a pair of energizer rechargables but doesnt get dim for long, but it does go dim gradually though.

Problem is, that on my last "accident", which was at night, both of the lights mounting brackets broke. So now I am suspending the front with a piece of elastic band, which doesnt really provide a steady beam of light to the road and the back with a clamp that was in the box, from the rear brake cable.

I dont ride much in the dark, except for commuting so it's Ok I guess...

 

It's all about energy density.

That's slow!

 

Apparently Lithium is also popular in Tritium production for Fission bombs! Wonder what they do with the recyced cells...

 

It looks like it's just the cathode or anode from a battery. Does the entire battery explode, or just part of it?


https://commons.wikimedia.org/wiki/File:Lithium-Ion_Cell_cylindric.JPG
Photo owned by RudolfSimon of Wikimedia

 

No idea... Might check with the electronics store:

 

Damn thats nuts, they also do a lot of damage to small childrens throats when they swallow them. They've quite dangerous to have laying around the house when you have kids.

 

This bike light is probably the easiest light for attaching to your bike. It's very bright and waterproof as well.

Check it out.

http://www.amazon.com/Brightest-Flashlight-Waterproof-Xtreme-Bright/dp/B00CULFR4Q/ref=as_li_tf_cw?&linkCode=waf&tag=urbicyclecomu-20