Charging 18650s - Big trouble...

[JimmerG]

I've had a load of difficulty here - I'm wondering if its something to do with the 220 - 240 volts we have here in England.

It may also be something to do with using cheap chargers, or indeed the dodgy slightly loose US/British plug adapter I got given. Or maybe trying to charge just one cell in a two slot charger

Two cheap chargers from DX have sparked and never worked again. Notably this one.... http://www.dealextreme.com/details.dx/sku.3499
So this time I've gone for the DSD 18650/CR123 charger as people claim to be able to use a Nokia phone charger - this should avoid the adapter problem. http://www.dealextreme.com/details.dx/sku.936

BUT if it takes a Nokia charger - does this mean I can also use a Nokia 12v charger and charge the batteries in the car?

And does anyone know if this charger will charge one cell at a time.

Thanks for you help.

J

 

[JimmerG]

Red hot 18650...!

I stuck an 18650 cell in a Cree flashlight - the light didn't come on - and the cell immediately heated up to the point where I burnt my fingers - getting it back out. Tried it with a different cell - and it works fine.

Seems the 'hot' cell is now utterly caput.

Any ideas what the hell happened there? I've ordered some protected cells now - hopefully it'll never happen again.

These lithiums really are quite tricky aren't they?

 

[1 what]

Re: Red hot 18650...!

I can tell you what happened:twothumbs You had a near miss!
Give thanks and dispose of the dud battery in a responsible way.
Use good quality protected cells (I like AW's) and hopefully it will never happen again.

 

[JimmerG]

Re: Red hot 18650...!

A near miss?!

So was this a simple dodgy battery?

 

[mdocod]

Re: Red hot 18650...!

You can use a 12V Nokia cell phone charging adapter for the DSD, (provided you get the right plug)...

You can charge 1 or 2 cells in the DSD, it doesn't matter: HOWEVER.... There are considerations that need to be taken into account for this.

The maximum charge rate for most li-ion cells, (LiCo cells), is 1C< that means essentially, that the charge rate in mA should not exceed the cell capacity in mAH.

The DSD is a single channel charger, but when you install 2 cells into it, it splits the charging load between the 2 slots.

If you use a Nokia cell phone charger with say, 800mA output, then the smallest single cell you can charge is going to be a ~800mAH cell, and it needs to be a TRUE 800mAH cell, not some bull crap bogus wannabee 800mAH cell that "claims" to be 800mAH on the label... For the record, RCR123s are all ~600mAH or less regardless of what the manufacture or reseller tries to tell you. Period.

Provided you charge 2 RCR123s simultaneously, or a single cell of larger size (17500 or bigger), then you should be fine...

Here's another important point that I must make about the DSD... The channels of the charger are wired in parallel. If you install a dead li-ion cell, with a nearly fully charged li-ion cell into the charger at the same time, the difference in electrical potential between the cells will cause a rush of current to flow from the charged one to the discharged one until they reach a balancing point. Small differences in the level of charge are fine, but large differences are not as it can result in unsafe discharge and charge rates occurring between the 2 cells.

--------------------------------------------------

If you had a cell suddenly and inexplicably heat up rapidly, then something went haywire...

I will say right now, that it seems that as time goes by, the majority of "incidences" of strange li-ion behavior or explosions can be traced back to user error. The user error is usually purely based in blissful ignorance of how to properly use the cells, but sometimes it's an accidental mistake made by an informed li-ion user.

If you even own unprotected cells, you should own a multi-meter. I have a hunch that we can trace that heating cell back to a combination of things, that combination of things is a bunch of things that you should know before owning unprotected li-ion cells that you do not know (this is not your fault, there is not reason that anyone should know any of this automatically). Unfortunately, DX and KD and so many other resellers could care less if you burn down your house with one of their dangerous products, they are in china, there is no liability, we have no jurisdiction.

I'd like to know more about what cell specifically it is we are talking about that heated up, and what the circumstances were leading up to the event. You may be able to learn from this and it may save you bigger headaches down the road.

Eric

 

[JimmerG]

Mdocod,

I thankyou wholeheartedly for your very helpful and detailed response - it must have taken a good chunk out of your day!

I've checked my Nokia charger - and it's output is 380mAH so I reckon that should be pretty safe with that.

I reckon I must have blown up cheap chargers in the past simply by mucking around with them too much, taking cells out, sticking them back in again to 'check' they're done. It seems there's a lot of power flying around and circuits are easily blown.

So with this DSD charger - If i need to charge 2x 18650s of wildly differening charge levels, I'd be better off charging them separately.


As for the fried 18650 - it really is a mystery, it stayed so hot for long once I took it out of the torch. The cell seems to be an unbranded 2400mAH from Iolanieh on ebay.

Guess I just need to be a lot more carefull and clued up...

 

[mudman cj]

There have been many reports of the power supplies for DSD chargers frying like yours on 220V, so it's not that you did anything wrong.

As for charging cells in parallel, a good rule of thumb is that the cell voltages should be within 0.5V before connecting them in parallel. More than that and there is enough potential to cause too much current flow.

 

[JimmerG]

Hmmmmm, so what's the best thing to do to avoid more charger frying?
Would it be safer to charge using a 12v battery - seeing as the DSD charger seems to accept a Nokia power supply?

 

[mdocod]

Just use the Nokia power supple on the DSD to solve your 240V problem, that's the easiest thing you can do IMO, and in my experience, the cell phone power adapters have tighter tolerances than the cheap adapters that come with the DSD, the result is more consistent and proper charging with the Nokia plugged in....

To really own and be using LiCo cells, protected or unprotected, but especially unprotected, you really need to own a multi-meter so you can test cell voltage to determine the state of charge.

Here are some rules of thumb:

4.20V 100% charge
4.10V or higher, close enough to full, don't "top off" just to "make sure" as it's not worth it.
3.60V basically dead, very little stored energy remaining
3.50V or less: dead

state-of-charge is fairly linear from ~3.6-4.2V as far as state of charge is concerned.

Over 4.2V is over-charged, not good for the cell, a few hundredths of a volt over 4.20V sometimes occurs in the last few minutes of a charge on the DSD but this is not a major problem. It settles to under 4.20V in my experience most of the time.

Under 3.5V is dis-charged more than ideal, try to avoid this.

Under 3V open circuit is generally considered over-discharged, but most cells will recover without major problems even with over-discharging down to ~2.5V, but this will wear them out faster, especially if they sit in a state of over-discharge like that for long periods of time.

Recharging cells that have been severely over-discharged (under 2.5V) and and especially those that have remained in a state of over-discharge for long periods of time, are more dangerous to charge back up. I have a hunch that your heating 18650 incident is directly related to the cell being over-discharged in use with no protection circuit to prevent it. Or possibly severely over-charged in a malfunctioning charger, again, with no protection circuit to prevent it. Probably developed an internal short via oxidation, you were probably lucky it didn't explode.

I'd be curious to know what the voltage is of the questionable cell... It's possible that you just had an external short caused by strange contact issues, or maybe missing shrink-wrap on the cell. (another condition that a protected cell would be safer for as the PCB will severe the circuit when confronted with a short circuit)

Eric

 

[Savvysteve]

DSD Charger which Nokia Charger will work?

Sorry for digging up an older post... This is my exact question, been searching google.

Hello all, first post on this forum. I need some answers please. Thanks for your time in advance.

I just recently bought a Surefire 6P LED from ebay and the seller sold me two sets of Trustfire 16340 880mah 3.6v Li-on batteries. He also sold me a DSD charger.

Well like many others, the AC adapter did not work. The charger itself works fine. I have tested this theory and know for certain.

I have found all over get a Nokia charger... but which one? There are different output voltages and amps that I found out. Also references to phone models and the charger model.

So I acquired (after searching my sister's house late last night :laughing: ) an OEM Nokia charger with the following specs:

Nokia ACP-7U
Output DC 3.7v, 350 mA

I keep seeing to get the ACP-12U charger. Is this only for the reason you will charge the batteries faster? Am I going to damage the cells? I went ahead today and ordered one from ebay for $4 shipped. Supposedly OEM Nokia.

I have been baby sitting this charger and this is what I have found.

This morning the cells were at 3.55v. I charged them for about 30 minutes last night. I have charged them for about 3 hours or so today and now they are sitting at 4.10v. The AC adapter is getting warm. So I suspect it is due to the resistance the batteries are putting on it. I will note that when checking the charger output (placing my voltmeter on the connectors with the batteries still in) when the batteries got near 4.10v hit 7.62v instead of 4.20 or 4.25v that I noticed before. Sounds like the PCB kicked in and stopped charging the batteries. After letting the batteries rest again for a few minutes I put them back in the charger. Enjoyed messing with it. Now the batteries are holding at 4.17v and 4.18v. I am stopping now. It was odd I had to put the batteries back in the charger to get it to this point.

So with a DSD charger for CR123 or 16340 batteries, what is the proper/best solution to replace the dead AC adapter shipped with it?

 

[Savvysteve]

Re: DSD Charger which Nokia Charger will work?

Bump.

 

[mdocod]

Re: DSD Charger which Nokia Charger will work?

Any cell phone charger would technically work, it just needs the right plug, it just so happens that nokia shares the same plug as the DSD so it's a nice convenient simple solution. You could use a cell phone charger from any brand, and just splice the wire and install the correct plug, and it would be fine.

A cell phone charger is nothing more than a AC to DC transformer with ~5.5V output. In the case of cell phones, the charging is handled internally, using power from the power supply. The DSD works the same way, using the external power supply as nothing more, just a power supply, and terminating the charge at an appropriate time.

If you are always planning on charging your RCR123s together, at the same time, then I would suggest getting the highest current nokia charger you can, which should be the 800mA one. This will charge your cells in ~2 hours, which aint bad. If you are thinking you might be charging cells individually at any point in the future for some reason (can't imagine why), you should get one with a slower charge rate (~300-450mA would be good).

When you tested voltage on the charger and got the "7.xxV" reading, was the light green or red? Are you absolutely certain you have good contact on the cells. The cheesy little contacts on the DSD need to be "bent" out once and awhile to make solid contact with cells.

I noticed you said that the cells were at 3.55V there, and I'm having a hard time putting all of the pieces together as far as time frames go... was 3.55V the voltage achieved AFTER 30 minutes on the charger? Was this the voltage you received the cells at, or did you drain them down when you first received them? If the cells were sent to you in a heavily discharged state they may not be in the best shape...

Eric

 

[Savvysteve]

The 3.55v reading was taken after I had run them down some in my light. I was thinking for some reason the charger wasn't charging because they already had a good enough charge. Plus it was a new toy so I was curious about how long/good the light was.


Another set of batteries were at 3.73v each. I ran them for about 20 minutes and the dropped to 3.58v each. I checked them for heat and turned them off for about 2 minutes. I then ran them for another 17 minutes and the light turned off. The PCD kicked in. I understand this isn't a great idea but honestly I am just trying to get a feel for these batteries. New light, new toy, testing etc...

The cells were at 3.29v and 3.39v at this point. I am going to let them sit for about 30 minutes and start charging them again until I head to bed and check them.

I am hoping this will help someone while it helps me learn about these.