18650 powered gadgets

[ice595]

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?

[cowana]

Maybe perhaps a laptop, portable battery bank

The 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.

[Fungus]

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?

They're expensive. And quite big .

Maybe perhaps a laptop, portable battery bank, professional camera flash units or wireless microphones?

Ever open up a laptop battery? Guess what's inside them... 

[tszaboo]

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.

[Kilrah]

portable battery bank

https://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

[ice595]

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 cells 

portable battery bank

https://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

OH 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?

[CJay]

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.

Well, 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.

[Kilrah]

The only difference between those and a bare cell is that you could possibly short the contacts on the bare cell.

And 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.

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?

Yup. 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.

[Fungus]

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?

Charging 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.

You can get multi cell charge controllers that charge in parallel and discharge in series:

eg. http://www.ebay.com/itm/262533839243

[ice595]

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?

Charging 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.

You can get multi cell charge controllers that charge in parallel and discharge in series:

eg. http://www.ebay.com/itm/262533839243

with great "power" come with great responsibilities 
Is 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.

[Siwastaja]

Charging a series ni-mh pack or lead-acid pack doesn't require such delicate balancing.

It 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 - they always charge 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 not always use "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 actually further inside. A simple scratch can damage the plastic sleeve so that the cell is accidentally shorted.

[Fungus]

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 actually further inside. A simple scratch can damage the plastic sleeve so that the cell is accidentally shorted.

You wouldn't want to carry one in your pocket. 

[Kilrah]

Is 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.

Yep. 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.

Charging 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.

That'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. this and be careful about managing them / recognise charged and empty ones), or have center taps and safety cutoffs.

[KE5FX]

It 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 - they always charge each cell separately. Cells charged in series are always inside a factory-built pack, meant to be charged using the factory-supplied charger only.

That'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.

[ice595]

Charging a series ni-mh pack or lead-acid pack doesn't require such delicate balancing.

It 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 - they always charge 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 not always use "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 actually further inside. A simple scratch can damage the plastic sleeve so that the cell is accidentally shorted.

not 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

[Kilrah]

Yep, it's actually hard to find an NiMH charger that doesn't do groups of 2.

[Siwastaja]

Yep, it's actually hard to find an NiMH charger that doesn't do groups of 2.

All 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.

[Kilrah]

OK, should have detailed "cheap standard C/5 chargers". Sure the high end or fast ones have individual control.

[Siwastaja]

OK, should have detailed "cheap standard C/5 chargers". Sure the high end or fast ones have individual control.

I 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.

[KE5FX]

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 work^tm.