Warning: Do not put 21700 cells in chargers not made for that cell! (pics in post #4)

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raccoon city
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Warning: Do not put 21700 cells in chargers not made for that cell! (pics in post #4)

I feel really stupid.

 

I put this 21700 cell:

https://liionwholesale.com/collections/batteries/products/molicel-npe-inr-21700-p42a-45a-4200mah-flat-top-21700-battery-authorized-distributor?variant=15913210675294

 

in a Nitecore SC4.

 

The charger was not plugged in, and there appeared smoke!

I quickly took the cell out of the charger, and am airing out my room.

The cell and charger are both damaged.

...

I am now in the market for a charger that charges 21700 cells.

I don't need recommendations yet as I need to do some research first.

I thought any 18650 charger would charge an unprotected 21700 cell.

I was dead wrong.

(I hope my health isn't negatively affected.)

Edited by: raccoon city on 07/25/2020 - 04:02
lightdecay
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What do you think happened? Where did the smoke appear? Any pics?

The charger wasn’t even plugged in. Did it short the battery somehow?

raccoon city
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I don't know much about batteries or chargers, but I think the cell did short.

I'll some take photos later and post them up.

raccoon city
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The damage to the cell is obvious.

The damage to the charger is subtle.

I put a red circle around the damaged area of the charger.

The charger is a little dusty, and it shows.

damage_cell

damage_charger

lightdecay
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That does look bad. Was it difficult to put the cell in the charger, or did it appear to fit properly?

raccoon city
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The cell would not fit in the charger.

The cell was crooked, and was easy to remove when I saw the smoke.

Also, I was wrong about which Nitecore charger I have.

(I have a Nitecore SC4, and I have changed the OP.)

ChrisGarrett
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I have a ’14 I4 Nitecore charger, but I’ve never been a fan of the brand.

Xtar for me.

Chris

LoPan12
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my guess is that in putting the long cell in, you tore the wrap on the battery, and the positive contact terminal on your charger shorted the negative body to the positive terminal.

raccoon city
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I didn't tear the wrap on the battery.

I think the wrap caught on fire when the cell shorted.

...

I don't blame Nitecore.

I tried to put in a cell that is too long for the charger.

I take full blame for the problem.

raccoon city
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I think I'll get a Nitecore UM4.

They will accept really long cells (up to 79.8 mm) and they're pretty cheap.

Enderman
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You made it sound like an electrical problem.
“I thought any 18650 charger would charge an unprotected 21700 cell.”

They technically all can, since a 21700 is the same lithium technology and voltage as an 18650.
The only issue is physical compatibility, which is what went wrong here.
If a charger can fit the extra length of a 21700, or if you use wires and an external battery holder, there is no problem.
.
A wiser option would be not jamming cells into a charger so hard that you break through the wrap.
Also using higher quality batteries such as samsung or LG will also come with more durable insulation wraps.

raccoon city
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Enderman wrote:

A wiser option would be not jamming cells into a charger so hard that you break through the wrap.
Also using higher quality batteries such as samsung or LG will also come with more durable insulation wraps.

I didn't jam the cell into the charger hard.

I just tried to put the cell in the charger, quite carefully might I add.

I didn't break the wrap, either.

I think when the battery shorted, the wrap caught on fire.

Also, this is a very high quality cell.

I don't know how good the insulation wrap is, but it's a great 21700 cell.

raccoon city
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Enderman wrote:

You made it sound like an electrical problem.
“I thought any 18650 charger would charge an unprotected 21700 cell.”

They technically all can, since a 21700 is the same lithium technology and voltage as an 18650.
The only issue is physical compatibility, which is what went wrong here.
If a charger can fit the extra length of a 21700, or if you use wires and an external battery holder, there is no problem.

I never made it sound like it was an electrical problem, and I never believed that.

I just figured since a protected 18650 is about 70mm long and an unprotected 21700 cell is about 70mm long that it would work.

(Obviously it didn't because my 21700 cell is too long, hence the title of this thread.)

Light Veteran
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I think 21700 it’s defective in wrap and the negative side of battery touch the positive side (nitecore) when you plugged in

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raccoon city
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I've been thinking...

How easy is it to tear an insulation wrap?

If it doesn't take much pressure, I might have torn the wrap without even knowing it.

Light Veteran
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Or the wrap is faulty from shopping and you don’t see.. it happen
Before put battery check always technical spec on original site.
For example, I don’t know why but Xtar Vp4 Drugon Plus don’t charge 21700 protected
but charge 21700 unprotected.

Light addicted

LoPan12
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The wraps can be pretty durable, but catching it just right can tear it. All its takes is a tiny little hole…

thijsco19
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raccoon city wrote:

I've been thinking...

How easy is it to tear an insulation wrap?

If it doesn't take much pressure, I might have torn the wrap without even knowing it.

 

Probably what happened. Either the insulation was already damage or it got damaged by inserting it in the charger. (not saying that you were careless or something like that!)

 

Either way, this is a great lesson to all of us to really be careful when handling a cell. And to not put any other cells in a charger that's not designed for them.

 

Thank god it didn't get out of hand and that you are fine!

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Well, it does not suddenly make a short.
Are you 100% sure your charger is ok?
Are you 100% sure your cell was ok?

If so, it must be a human error as described above.
Probably by damaging the wrapping by trying to fit it in a charger which is not suited for that size cell.

Quillz
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Someone correct me if I’m wrong but aren’t you supposed to have a charger powered up before putting in batteries to charge?

Quillz

raccoon city
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thijsco19 wrote:

this is a great lesson to all of us to really be careful when handling a cell. And to not put any other cells in a charger that's not designed for them.

Thank god it didn't get out of hand and that you are fine!

Yes, I'm always very careful when handling cells, and this is the first time I have tried to put a cell in a charger that doesn't fit.

I think I ruined that one cell, and I won't be using that slot in that charger any more, so I did get lucky.

raccoon city
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Quillz wrote:

Someone correct me if I’m wrong but aren’t you supposed to have a charger powered up before putting in batteries to charge?

Good question.

I always put the cells in first, then plug in the charger.

In today's incident, I didn't even plug in the charger.

2A
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The ring on top of the cell is were most wraps tear up first, IMO. those tears can be really thin and invisible; when the cell was inserted the charging contact accidentally connected BAT+ and the cell body.

Quillz
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I’m not an expert on battery chargers nor an electrical engineer but how is the charger and all its built in protections supposed to work if it’s not plugged in?

Quillz

2A
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Some people put the cells in first and would then connect the charger. In fact, in the RC hobby many people do it this way. hobby chargers can be finicky at times…

I would rather be elsewhere when switching on the charger rather than put the cell in when already powered on… I mean… normally nothing happens.. but what if?! I like my face the way it is.

Quillz
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Like I said I’m no expert but I’m pretty sure the chip in your charger is not powered by putting your batteries in to charge so how can it work? It’s not like a flashlight where the chip is powered by the battery. So I’m assuming here but you basically put in a very powerful battery in and completed the circuit with no control and it dumped all that power with no regulation and nowhere to go, unlike when it’s plugged in.

Quillz

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With sprung bay chargers like the one used, if there is no clearance of the cell positive and the charger positive when inserting the cell then there is a risk of damaging the wrap when inserting.

You should use the cell to push the sprung charger contact down, lay the cell flat in it’s bay then it should slide up to make contact.
Don’t push them directly in flat as you will catch the cell wrapper on the charger contact and wear or a direct rip may occur in time.

Cell wrappers are very thin plastic and easily damaged especially on corners when pressing over other hard objects like metal with protrusions.

If you do need to cram one of the larger cells into a charger then use a thin sheet of tough plastic etc to hold in the bay over the charger positive contact while inserting the cell to prevent wrapper damage. Once the cell is flat in the bay pull the plastic sheet out while holding the cell flat.

Also check your cells wrap from time to time to make sure it is intact, chargers with dimple protrusions on the contacts like the one pictured are better at poking through any holes and welding, I prefer contacts that are flat.

texas shooter
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I use several Molicel INR-21700-P42A. I have found their wrappers to be brittle and easier to damage than the others. Great cell, weak wrapper.

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rewrap the cell and move on.
that charger is too tight for a 21700.
it tore the wrapper with the 2 contacts due to the pressure of forcing it in.
at least you got it out.
super high drain cells like the p42 get pissed off very quickly when shorted.

Oli
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raccoon city wrote:

The cell would not fit in the charger.


The cell was crooked, and was easy to remove when I saw the smoke

Some wraps are tougher than others. Clearly it tore. Check battery voltage. Likely still good, just need to rewrap it. Edit, as others have said.
hank
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Yep. I’ve had several cells where the wrap cracked and peeled back near the positive end.

Remember plastic is made with plasticizers — chemicals used to keep it soft and flexible.

Cheap plastic uses less of the material or cheaper material.

Those evaporate eventually (they’re what makes that “new car smell” and oily film on the inside of new car windows)
Once they’re gone the plastic isn’t plastic any longer — leaving a brittle fragile material behind

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