18650 powered gadgets - Page 1
Forum section: electronics / projects

author: ice595
author_rank: Regular Contributor
timestamp: July 27, 2016, 02:18:16 pm
content: Just a random question popped up in my head this morning: why don't we have more gadgets that are powered by removable 18650 batteries?Sure, there are flashlights and e-cigarettes that uses removable 18650s, but I'd love to see other gadgets that would use them.Maybe perhaps a laptop, portable battery bank, professional camera flash units or wireless microphones?

author: cowana
author_rank: Frequent Contributor
timestamp: July 27, 2016, 02:26:16 pm
content: Quote from: ice595 on July 27, 2016, 02:18:16 pmThe vast majority of laptops and portable power banks do run on 18650 cells. For the general user, rather than have to own a dedicated external battery charger, it's all built in to the device - which is very handy.if you want to carry additional cells, most laptops have detachable batteries and thus spares can be carried.

author: Fungus
author_rank: Super Contributor
timestamp: July 27, 2016, 02:27:10 pm
content: Quote from: ice595 on July 27, 2016, 02:18:16 pmThey're expensive. And quite big .Quote from: ice595 on July 27, 2016, 02:18:16 pmEver open up a laptop battery? Guess what's inside them...

author: tszaboo
author_rank: Super Contributor
timestamp: July 27, 2016, 02:29:10 pm
content: Because you cannot buy 18650 cell in the local store, because they dont want to sell products which might blow up if you look at them funny.

author: Kilrah
author_rank: Unknown
timestamp: July 27, 2016, 02:50:19 pm
content: Quote from: ice595 on July 27, 2016, 02:18:16 pmhttps://www.google.ch/search?q=power+bank+18650&safe=off&espv=2&biw=1769&bih=1085&tbm=isch&imgil=ZUdarsHy5hUZDM%253A%253BjmWL2Ja7HIiOjM%253Bhttp%25253A%25252F%25252Fwww.aliexpress.com%25252Fw%25252Fwholesale-power-bank-18650.html&source=iu&pf=m&fir=ZUdarsHy5hUZDM%253A%252CjmWL2Ja7HIiOjM%252C_&usg=__4tD1zXUl9oeVoh-wHvqh8twB0JM%3D#imgrc=ZUdarsHy5hUZDM%3A

author: ice595
author_rank: Regular Contributor
timestamp: July 27, 2016, 03:33:02 pm
content: yeah I've taken apart laptop battery packs and salvage 18650s inside, but all those laptop batteries need a destructive teardown to get to the goodies. It would be nice if I can just swap them like AA and AAA cellsQuote from: Kilrah on July 27, 2016, 02:50:19 pmOH NICE, I DIDN'T EVEN KNOW THEY EXISTED, I'll be definitely getting one of those.pretty much all the removable 18650 gadgets I see are either single cell or multi-cell in parallel, and all the series 18650s are sealed, thats dues to balancing issues similar to li-po cells right?

author: CJay
author_rank: Super Contributor
timestamp: July 27, 2016, 03:39:49 pm
content: Quote from: NANDBlog on July 27, 2016, 02:29:10 pmWell, possibly but the vast majority of cell phone 'emergency' chargers have an 18650 in and they're becoming almost throwaway items, I've recently bought a load of them for £1 each and they have a removable 18650.The only difference between those and a bare cell is that you could possibly short the contacts on the bare cell.

author: Kilrah
author_rank: Unknown
timestamp: July 27, 2016, 04:17:47 pm
content: Quote from: CJay on July 27, 2016, 03:39:49 pmAnd that's all the difference that's needed - the sealed device has protection circuitry that prevents a user from abusing it. Once you take the cell out you need to start thinking about what you do to have the same safety level, and that's too much for the average customer.Quote from: ice595 on July 27, 2016, 03:33:02 pmYup. A series device would need to measure each cell and cut off supply if any is off limits, especially given that a bunch of individual 18650s can have random characteristics, while a proper battery pack e.g. for a laptop has factory-matched cells in addition to the protection and balancing circuitry.Note that you can make mistakes and fire with parallel devices too, e.g. short the bare contacts for one cell when you've already got others in, shorting the terminals of a cell when inserting it if not well insulated, screwing up and mixing an empty cell in a pack of full ones etc.

author: Fungus
author_rank: Super Contributor
timestamp: July 27, 2016, 04:55:26 pm
content: Quote from: ice595 on July 27, 2016, 03:33:02 pmCharging in series is very dangerous. If you build a series charger designed for protected cells then Joe Public would go out and buy the cheapest unprotected batteries possible to use with it. Result: Fire.Youcanget multi cell charge controllers that charge in parallel and discharge in series:eg.http://www.ebay.com/itm/262533839243

author: ice595
author_rank: Regular Contributor
timestamp: July 27, 2016, 05:40:35 pm
content: Quote from: Fungus on July 27, 2016, 04:55:26 pmwith great "power" come with great responsibilitiesIs there something inherently "funky" with lithium secondary batteries in general? Charging a series ni-mh pack or lead-acid pack doesn't require such delicate balancing.

author: Siwastaja
author_rank: Super Contributor
timestamp: July 27, 2016, 07:25:05 pm
content: Quote from: ice595 on July 27, 2016, 05:40:35 pmIt definitely does, for the exact same reasons. This is also why there are no nicd/nimh charges that charge user-supplied single cells in series - theyalwayscharge each cell separately. Cells charged in series are always inside a factory-built pack, meant to be charged using the factory-supplied charger only."Normal users" also never charge separate lead acid cells in series - they practically always charge a factory-built 3s or 6s pack, which cannot be taken apart.Li-ion packs do notalwaysuse "delicate" balancing, but sometimes the exact same measures are enough - for example, BOSCH power tools use 4s and 6s li-ion packs identical to the style used in NiCd/NiMh packs - all cells are in series, with no center taps nor any management nor protection circuitry present. The cells stay in balance well enough.---The most important reason IMO why 18650 is not and should not be used as a changeable cell by general public is that they can provide very high short circuit currents and can short accidentally easily due to the construction - the negative terminal is the case, which is also present around the positive tab; and the positive tab is actuallyfurther inside. A simple scratch can damage the plastic sleeve so that the cell is accidentally shorted.

author: Fungus
author_rank: Super Contributor
timestamp: July 27, 2016, 08:19:28 pm
content: Quote from: Siwastaja on July 27, 2016, 07:25:05 pmYou wouldn't want to carry one in your pocket.

author: Kilrah
author_rank: Unknown
timestamp: July 27, 2016, 09:12:22 pm
content: Quote from: ice595 on July 27, 2016, 05:40:35 pmYep. An NiMH will just dissipate excess energy as heat, as long as charge current is reasonable a cell that's full before the others will just heat up a bit until the others catch up in a pretty safe manner, i.e. when you stop the current they stop heating.Lithium ion/poly batteries will break down catastophically, they'll also heat up initially but there's a critical point that when exceeded they'll start dumping their own energy heating themselves further and releasing yet more energy, and the next second you've got a fireball.That's the price to pay for the much higher energy density, the chemistry is stable when maintained within precisely given parameters but if you wander away all bets are off.Quote from: Fungus on July 27, 2016, 04:55:26 pmThat's why common "user-replaceable 18650-powered devices that uses cells in series" either don't recharge them (you have to take them out and put them in a charger with individually-controlled slots e.g.thisand be careful about managing them / recognise charged and empty ones), or have center taps and safety cutoffs.

author: KE5FX
author_rank: Super Contributor
timestamp: July 28, 2016, 02:10:54 am
content: Quote from: Siwastaja on July 27, 2016, 07:25:05 pmThat's certainly not the case for NiMH and NiCd. Nor does it need to be. They don't have a thermal runaway characteristic like lithium cells do.

author: ice595
author_rank: Regular Contributor
timestamp: July 28, 2016, 03:47:11 am
content: Quote from: Siwastaja on July 27, 2016, 07:25:05 pmnot the case in my Sanyo eneloop charger, it only charge 2 or 4 ni-mh series cells at once. which is quite annoying because my gadgets use 3 cells but I can only charge them in multiples of 2

author: Kilrah
author_rank: Unknown
timestamp: July 28, 2016, 08:17:08 am
content: Yep, it's actually hard to find an NiMH charger that doesn't do groups of 2.

author: Siwastaja
author_rank: Super Contributor
timestamp: July 28, 2016, 08:26:15 am
content: Quote from: Kilrah on July 28, 2016, 08:17:08 amAll I have ever seen (and owned) have charged each one separately - maybe I have been lucky. This applies to a 5-hour "semiquick" and several 1-hour quick chargers with microcontrollers performing dV/dt and dT/dt stopping. (Which is also why NiMH is complex to charge, and having cells in series makes it even more difficult).It's pain in the ass to charge NiMH in series, so those series chargers are very poor design. It's also a serious usability issue, indeed, as there are devices requiring odd number of cells!It's true that overcharging NiCd, NiMH or lead acid does not pose such a safety issue as overcharging li-ion. (Overcharging lead acid in a closed space is a safety risk, however.)OTOH, I have the gut feeling that the magical "self-balancing" of NiXX is often exaggerated (I'm no expert in NiXX chemistries however.). It only works at very low currents (typically specified at C/10 and 14 hour charge, which is more than overnight) and I have serious doubts it's good for battery life, especially if the series cells are in a very different state of charge, so that one of cells (initially almost full) must undergo "shunting" the full charge going in the other cells.

author: Kilrah
author_rank: Unknown
timestamp: July 28, 2016, 08:41:28 am
content: OK, should have detailed "cheap standard C/5 chargers". Sure the high end or fast ones have individual control.

author: Siwastaja
author_rank: Super Contributor
timestamp: July 28, 2016, 09:01:24 am
content: Quote from: Kilrah on July 28, 2016, 08:41:28 amI have been lucky even with the cheap standard C/5 and C/10 chargers, which all have had individual 1.2V outputs! But these standard chargers seemed to start disappearing from the market somewhere around 2002-2003, when the "high end" became the cheap.

author: KE5FX
author_rank: Super Contributor
timestamp: July 28, 2016, 09:32:32 am
content: I like to slow-charge AA NiMH cells at C/10 and leave them on a C/40 maintenance charge. Of course few if any commercial chargers would do that, because reviewers would slam them for taking too long.In a couple of homebrew projects, I charge a string of 8 Energizer NiMHs in series. They just worktm.