The 5C discharge rate with very little loss in capacity and life doesn't hurt either.
On Mon, Jul 14, 2014 at 11:18 AM, <[email protected]> wrote: > This quality issue comes from the poor quality batteries that have flooded > the market. There is a reason why Tesla uses the Panasonic NCR18650 > batteries because they seem to have the best manufacturing reliability. > I've seen USB batteries from China that have no markings and covered with > masking tape. That's why I use the same batteries Tesla uses. Using any > other brand seems to have very little documentation, false claims, or just > bad quality. I've been using the NCR18650A and B batteries for years and > they have not died or caught fire despite camping and biking with them > exposed to heat, rain, vibration, and even undercharged. > > If the wrong charge controller is matched with a battery that claims to be > high performance and isn't, then a fire will occur. > > Isaac > > -------- Original Message -------- > Subject: Re: [dorkbotpdx-blabber] Lithium-Ion USB Charger Workshop Idea > From: Doug Ausmus <[email protected]> > Date: Mon, July 14, 2014 11:09 am > To: "A discussion list for dorkbot-pdx (portland, or)" > <[email protected]> > > Just a note to add a bit of quite recent detail to Lithium charging.. > > A symposium for reliability engineers and product safety engineers earlier > this year discussed some recent findings that trickle-charging lithium > chemistries can cause cobalt (and other things depending on exact design) > to migrate and form nodules on the surface and and then potentially > mechanically puncturing their dielectric and after which some nice > exothermic reactions can/may/might/will occur. > > This failure mode has been found (and others), but they are still trying > to figure out why some will exhibit this behavior easily and some (from the > same batch) may do not do so as readily. Many other charge/discharge things > which make fire were discussed for which there are (AFAIK) no "controller > solutions" for... yet. Lots of variables in manufacturing, materials, > designs and chemistry and a number of metallurgical variations. > > This symposium was attended by one of my engineers (who also presented), > and he came back with lots of interesting and depressing issues WRT Lithium > batteries... depressing since we are in the middle of a project involving > this stuff and have had to tell the principles the bad news about the > direction safety certifications are going with Lithiums. We are still > trying to work out a safe path for getting our project done and out the > door (Certified packs and chargers? Deep due diligence in design,? Buy more > insurance?). Not quite sure what the legal ramifications are since we are > now aware of these issues, but the issues have no engineering direction for > solution yet, and meanwhile Lithium continues to march along without > slowdown nor action... > > Just thought I would pass-on this very recent development, especially > since hobby electronics design issues have been mentioned by several > engineers in this arena as being an additional safety concern... not sure > what direction this will eventually go. > > FWIW, > Doug > > > On Mon, Jul 14, 2014 at 10:10 AM, <[email protected]> wrote: > >> Yeah, I use a MAX8903G myself. It has all those features and also has >> "smart selector technology", which gives the charger intellegence on when >> to store and release energy. I would like to cover that in the workshop too. >> >> Isaac >> >> -------- Original Message -------- >> Subject: Re: [dorkbotpdx-blabber] Lithium-Ion USB Charger Workshop Idea >> From: [email protected] >> Date: Mon, July 14, 2014 9:34 am >> To: [email protected] >> >> I would strongly recommend you make sure you understand the relationship >> between voltage-mode and constant current mode when working with Li+ >> chargers. A common booboo happens when the current flow into a Li+ cell >> decreases as the charging cycle is nearing completion, and is not detected >> within some reasonable amount of time, which causes over-charging. That >> would be an (ahem) exothermic reaction phase. Think of the news stories >> about early Apple lapbooks catching fire, which was largely caused by a >> slow current sense switch in the charger. When you feel you switch has >> reached the inflection point of current load vs cell potential, then a >> current limiter needs to be switched-in to keep the cell in low-current >> trickle charge. If you want to roll your own controller for that would be >> fine, but it is important to realize that the charging curve would have to >> be recharacterized each time you change from one Li+ cell manufacturer to >> another. Or try to have some kind of self-servoing current sense amplifier >> somewhere on the load. Another thing that is fun to do (I mean that) is >> figuring out how to switch MOSFET's so that a load can remain connected to >> the cell even when the charging source (USB) is disconnected (or >> reconnected to charge up the cell). Make sure, in that case, that you have >> an output L-C filter on the load-side to squelch the switching transients >> from the charger. I had to design in all these things in my Blivit charger >> system, but did not have the real-estate to do it all in discrete >> elements. I opted for the simple way to do it with a Maxim part as the >> control element for the charger (MAX1874). >> >> ------------------------------ >> _______________________________________________ >> dorkbotpdx-blabber mailing list >> [email protected] >> http://music.columbia.edu/mailman/listinfo/dorkbotpdx-blabber >> >> >> _______________________________________________ >> dorkbotpdx-blabber mailing list >> [email protected] >> http://music.columbia.edu/mailman/listinfo/dorkbotpdx-blabber >> > > ------------------------------ > _______________________________________________ > dorkbotpdx-blabber mailing list > [email protected] > http://music.columbia.edu/mailman/listinfo/dorkbotpdx-blabber > > > _______________________________________________ > dorkbotpdx-blabber mailing list > [email protected] > http://music.columbia.edu/mailman/listinfo/dorkbotpdx-blabber >
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