First time using 18650s (Please Scrutinize)

[forexer]

Guys,

I'm charging my new budget 18650 cells (WOW 2600mAh) now and its been around 2 hours in the charging.

Currently, one cell stands at 4.12v and the other 4.10V. Is this abnormal and should i be very weary? Does this mean the cells are off different qualities? Because i know this will lead to bad experiences if the 2 cells are used in series.

Cells came at 3.75v which means both are good right?

Also do good 18650 get warm during the cc stage? Do they get warm even in the cv stage? Mine is warm to the touch not hot, is this normal? The charger is quite warm but not hot. Seems less hot now than when the cells were at 3.9v.

I plan to see when the charging terminates. The charger is "digital li-ion charger" from DX. Open circuit was about 4.18V. Current for each channel is kinda balanced, around 0.25A per side during the so called cc stage (not sure if really cc) and is now around 0.12A per side at 4.12v and 4.10v per side. Ok for the charger?

The light is Thrunight Catapult that uses 2 18650s and drives a sst-50 at around 1.5-1.6A. Should not be a problem for the cells. My greatest concern is that the light is water proof and that means its battery tube is air tight sealed with o-rings. The tube is quite thick and the light is very sturdy. ALOT of pressure would have to be built up inside for the light to blow with super force. Any cautions for me? Should i remove the o-rings so that if the terrible vent does occur for whatever reason, gas can escape before the tube blows or the tail cap shoots off like a bullet? Please advise.

Also i know cells with different qualities like one having higher internal resistance than the other would cause cells to vent. Can you call explain this process and how to avoid it.

How do i check if my cells are close in quality and will not result in what i wrote in the previous paragraph?


Please answer all my questions. I'm paranoid but i guess thats a good thing when dealing with li ions, esp cheap ones.

 

[VidPro]

first cant believe you buy this hugely bright high power consumption light that costs big money, then go off and get "budget" batteries and a china site charger, so you desere all the parinoia you have :naughty: but that is ok because i am battery geek more than light geek, without good battery no Light

Currently, one cell stands at 4.12v and the other 4.10V. Is this abnormal
no finish the charge , then well talk about it :naughty:

Cells came at 3.75v which means both are good right?
it doesnt prove they are good, they take 2 dead batts off the shelf , set them to 3.80 right before sending them out :naughty:
Yes it shows they arent dead, and they might have been stored properly too.

Also do good 18650 get warm during the cc stage?
the charge acceptance for li-ion is really high, so most of the power you shove into them goes into charge , instead of comming out as heat.

so usually i would never call mine hot even when charging very fast, they might warm slightly. but the CHARGERS? well they can often add quite a bit of heat to the process and seal around the cell , and throw off any knowlege of the actual heat comming out of the battery being abnormal. so unless it is getting hot, i wouldnt worry about it. if the cell was out in the open and it was getting way warm, then that is abnormal.
Start with your Base temps, and knowing how your system is working, and THEN if things start to heat up beyond that, then investigate further.

My greatest concern is that the light is water proof
if pressure can build internally in the light , then the safety releace valves on a li-ion (or even an eneloop) will not open as easily if any gassing occurs. other than that, if a full thermal overload occured you would need a huge gaping hole to stop the end from blowing off, totally inpractical.

In the sitaution of something going horribly wrong inside, not being fully pressure sealed would be better, so the releace valves work as designed.


Also i know cells with different qualities like one having higher internal resistance than the other would cause cells to vent.
generally they would have to get off by quite a quantity, and still have the driver trying to push them both.
if one cell item is discharged completly, and the Path through the light continues the discharge, the one can reverse charge the other, when that happens it can all go horribly wrong.
a light that STILL operates with only 1 cell, has the capability of discharging one to low, and should use protected cell items in series (at least)

PROTECTED cell items prevent against too low of discharge, which can totally prevent any reverse charge. protected also protects against to high of voltage of charge, and to rapid of discharge AKA shorts.
if you dont have protected cell items, protected by the little added curcuits (not just the built into the cell protection), then you should use only 1 Cell in that light untill you do.

How do i check if my cells are close in quality
simplest cheapest way, charge them, then put a load on and test the voltage under the load.
other things you can do, read the voltage when you pull them out and see how they are doing, minor variations in voltage are not worth worrying about, huge differences might be.

Protected cells one could read 0V when it reaches the protection low end.

seems to me like your intelligent enough to have known most of the things that are possible issues, and in such that knowlege is the key , you pretty much have it covered.

 

[qwertyydude]

.25 amps should not get the cell hot during the cc stage. And current only goes down in the cv stage. The warmth you are feeling could only come from two places. The cell could have high internal resistance, though you'd know because the cells would get hot during flashlight use. The other possibility is that the charger is just getting warm because it is inefficient.

As for your low voltage. Somewhere here is a review of a charger and a modification to directly solder wires between the board to the back of the sliding mechanism to eliminate possible contact resistance which could result in low termination voltage at the battery.

As for water tight light I'm not sure how to deal with it unless you want to compromise the lights water tightness. But the only way to ensure your cells are good would be to discharge test them and make sure they have similar capacities and also measure voltage under load to ensure they have similar internal resistance. And also try not to drain them to cutoff.

 

[45/70]

OK forexer, I'll give this a shot.

Currently, one cell stands at 4.12v and the other 4.10V. Is this abnormal and should i be very weary? Does this mean the cells are off different qualities? Because i know this will lead to bad experiences if the 2 cells are used in series.

Cells came at 3.75v which means both are good right?

Your charger has independent channels, so it's not likely that the cells will always be at the same voltage, although this of course, would be ideal. 0.02 difference in voltage is probably not enough to worry about. 3.75 Volts is fine for recently received cells.

Also do good 18650 get warm during the cc stage? Do they get warm even in the cv stage? Mine is warm to the touch not hot, is this normal? The charger is quite warm but not hot. Seems less hot now than when the cells were at 3.9v.

Newer Li-Ion cells should not get warm at any point during the charging process. The problem is, when the electronic circuitry of the charger is included within the actual charging bay, the electronics get warm and this heat migrates to the cells. Suffice to say that your cells should never get "hot" during charging, as this would likely be an indication that you have a damaged cell, or cells. Also, as cells get older, or used quite a bit, they will warm slightly when being charged. Still, they should never actually get "hot".

With a charger that uses a proper algorithm (CC/CV, which yours doesn't) to charge the cells, the charger and the cells, will run cooler towards the end of the charge, as the current is steadily being reduced. Also chargers that reduce the amount of current applied to the charge near termination due to higher resistance of the cell being charged, may run a bit cooler towards the end.

I plan to see when the charging terminates. The charger is "digital li-ion charger" from DX. Open circuit was about 4.18V. Current for each channel is kinda balanced, around 0.25A per side during the so called cc stage (not sure if really cc) and is now around 0.12A per side at 4.12v and 4.10v per side. Ok for the charger?

As far as I know, this charger does not terminate charge. The voltage may stop rising, but the charger does not terminate. This is the reason that as soon as the indicators indicate that the charge is "finished", you should pull the cells out. Again, the Digital Li-Ion charger is not a CC/CV charger, but is a modified CC charger.

My greatest concern is that the light is water proof and that means its battery tube is air tight sealed with o-rings. The tube is quite thick and the light is very sturdy. ALOT of pressure would have to be built up inside for the light to blow with super force. Any cautions for me?

Regardless of what you've been led to believe, "loose" Li-Ion cells were never intended to be used in flashlights. That said, many of us do (obviously), but we understand the possible consequences, and take every measure possible to make sure our particular application is as safe as it can be made. IMO, taking the O-rings out, really isn't going to make much difference if an "incident" occurs.

The use of quality cells and a quality charger goes a long way towards insuring safety. This is why, while I personally have and use some cells and chargers similar to your setup, I am reluctant to recommend them to others.

Also i know cells with different qualities like one having higher internal resistance than the other would cause cells to vent. Can you call explain this process and how to avoid it.

How do i check if my cells are close in quality and will not result in what i wrote in the previous paragraph?

Cells that are used in series applications should be matched in performance as closely as possible. This applies to any cell chemistry, but is particularly important with Li-Ion cells. While it is possible to take measurements of the IR of cells etc, the best way to match cells is to discharge them, and note their behavior during discharge.

For example, charge up two cells for your Catapult. If the cells are not as close in voltage as you would like them to be, try placing each cell separately in the slot that charges cells to the higher voltage of the two slots in the charger, to "top them off". This may bring the voltages closer together.

Then go ahead and use your light. Every so often take the cells out and check their voltage (it's best if the cells are rested a few minutes first, before taking measurements). Watch for a growing difference in voltage between the cells. If the difference becomes greater than 0.05 Volt, or so, at voltages above ~3.80 Volts, I would consider trying to pair the cells differently (ie. with other cells), and see if you can get a better matched pair.

Just a note about the use of "protected" cells. Do not count on protected cells "protecting" you when using series applications. Protection PCB's are a plus, but have been known to fail/not work, particularly under low current loads. Ideally, you shouldn't be running cells down until the protection circuit trips anyway. It is not good for the cell(s) and potentially not good for you either.

Hope this helps. This is just my perspective on using Li-Ion cells in series applications. I've been doing so with both unprotected and protected cells in lights for about 6 years now, and I haven't blown myself up yet. I do know and understand that this could change however.

Dave

 

[forexer]

Thanks guys, that was really helpful :thumbsup:Will update on the discharge performances.

 

[forexer]

Well, i'm not sure why but charging terminated at 4.16V for both channels. Actually it was charging at 4.16V for both channels and i wanted to test the voltage of the cells. So i removed the cells from the charger (light was still red then) and both cells measured 4.16V. When i place the cells back on the terminals, the indicators were green. No matter what i did, i could not get it to start charging. That is way far off from completely charging the cells. I reckon however if i hadn't touch the cells wile charging, it would have charged up all the way to near 4.2V, any idea why i terminated charge this way. I tried to measure the current following thru the terminals when the indicators were green. At the smallest denomination (20m) on my DMM, it showed no current. Not sure if it's accurate but isn;t that strange since reading about other's posts about this charger reveals that it does charge cells even when green.


The cells seem to be good for now, i've run them down to about 4.13V each at around 2A on the catapult. Batteries didn't get hot. One cell gives a reading bouncing from 4.13V to 4.14V while the other a steady 4.14V. I plan to run them on max for about 20 minutes later and see how they cope. Hopefully then dont blow up:duh2:

 

[mvyrmnd]

old4570 has noted in some of his battery and charger tests that cells with higher internal resistance (old cell/poor quality, usually) tend to cause the charger to terminate prematurely. It's probably not an "end of the world" scenario, but something to keep an eye on.

If I were you, I'd be happy that the charger appears to terminate completely when the charge cycle is complete. Measure the termination current a few more times, and preferably with some different cells as well to confirm.

You may also find that after a few charge/discharge cycles your cells may stretch their legs a bit and take a fuller charge.

 

[how2]

Well, i'm not sure why but charging terminated at 4.16V for both channels.

when you charge other cells at what votage do they terminate?

 

[forexer]

I tried to charge again. Both went green @ 4.17V the cells, after 45 minutes both stand at 4.16V. The cells might have higher internal resistances and the charger is a weak one. Open circuit stands at 4.18V so that might explain why the max it went was 4.17V. Not sure whether charging voltage can go above the open circuit voltage of 4.18V. Is it theoretically possible? Also when you trickle charge the cell, voltage has to increase right? So if the charger can;t go above 4.18V then no trickle charging right?

I dont have other cells. Only those WOW cells. Next cells i plan to buy when i have more money will be either AW imrs or AW 2900mAh ones. Very expensive for the latter:ironic:

 

[45/70]

......That is way far off from completely charging the cells. I reckon however if i hadn't touch the cells wile charging, it would have charged up all the way to near 4.2V, any idea why i terminated charge this way......

A LiCo cell that reads 4.16 Volts is about 96% charged, so you're pretty close. While it seems to be everybody's goal to reach 4.20 Volts when charging LiCo cells, that really isn't true. Older cells, or cells that have been used a bit, shouldn't charge to 4.20 Volts, it's actually bad for these cells to charge to that high a voltage. The 4.20 Volt charge level is a convenient figure to work with, but not always the correct voltage for charge termination of a LiCo cell. All that said, if your charger reads 4.18 volts OC, then your cells will never charge higher than 4.18 Volts.

It's good that you're charger appears to actually stop charging. The easiest way to tell if a charger actually stops the current flow, and doesn't trickle, is to leave the cell(s) in the charger and see if the voltage drops after a while. For example, you said your charger indicated the cells were charged at 4.17 Volts, and after removing from the charger and sitting for 45 minutes the voltage dropped to 4.16 volts. If you leave the cells in the charger for 45 minutes after the charge is complete, and the voltage drop still occurs, this indicates that your charger doesn't trickle charge. On the other hand, if the voltage remains at 4.17 volts, this indicates that the charger is trickle charging.

The cells seem to be good for now, i've run them down to about 4.13V each at around 2A on the catapult. Batteries didn't get hot. One cell gives a reading bouncing from 4.13V to 4.14V while the other a steady 4.14V. I plan to run them on max for about 20 minutes later and see how they cope. Hopefully then dont blow up:duh2:

This sounds very good. I would still continue to run the cells down farther, and check voltages. Once the cell's voltages get below ~3.80 Volts, things begin to change a lot faster, and it is harder to say what is an acceptable voltage spread between cells. I would still say that if the cells are within 0.05 Volt of each other (preferably closer) down to ~3.80 Volts, your cells are matched well enough. Again, this is just my opinion.

Also when you trickle charge the cell, voltage has to increase right? So if the charger can;t go above 4.18V then no trickle charging right?

No. This is incorrect. One of the basic definitions of a trickle, or "float charge", is supplying an amount of charge current that maintains a battery, or cell at a constant voltage. So yes, you can trickle charge a cell at 4.18 volts, or any voltage for that matter. As you know, lot of the inexpensive chargers are notorious for this and it is bad for cells, as well as being potentially dangerous. Both over oxidation of the cells internal components and the plating out of metallic lithium are possible when trickle charging a LiCo Li-Ion cell.

I dont have other cells. Only those WOW cells. Next cells i plan to buy when i have more money will be either AW imrs or AW 2900mAh ones. Very expensive for the latter:ironic:

Your brain's logic system should be sounding an alert here, when concerning Li-Ion cells, your cells are more expensive than the charger you are charging them with.

Dave

 

[pae77]

I would be pretty happy about the charger charging to 4.16 - 4.18 volts, rather than 4.20. To me, that's just about perfect as it's just very slightly less than charging to full capacity (4.20 V) and charging to slightly less than 4.20 V will allow your cells to last for many more cycles than they otherwise would if you always charged to 4.20 V.

 

[forexer]

Your brain's logic system should be sounding an alert here, when concerning Li-Ion cells, your cells are more expensive than the charger you are charging them with.

Haha true. I might get a hobby charger but then again i must learn how to use them and also find a power supply for the cheaper ones Thanks for the detailed explanation

 

[mfm]

I tried to charge again. Both went green @ 4.17V the cells, after 45 minutes both stand at 4.16V. The cells might have higher internal resistances and the charger is a weak one. Open circuit stands at 4.18V so that might explain why the max it went was 4.17V.

Yes, the open circuit voltage is limiting the charge. Also, there can not be any (trickle or otherwise) charge when the battery voltage is the same as or higher than the charger voltage.

Haha true. I might get a hobby charger but then again i must learn how to use them and also find a power supply for the cheaper ones Thanks for the detailed explanation

Don't bother if it's security you're after.

 

[Lion251]

The charger is "digital li-ion charger" from DX.

Can you tell us what SKU number?
I'd like to see a DX charger that terminates properly and doesn't charge too high.
The DX charger that I have holds a float voltage of 4.25 Volts.
I have a hobby charger as well, but sometimes a 2-cell charger comes in handy.

 

[45/70]

I might get a hobby charger but then again i must learn how to use them......

As mfm frequently points out, it is necessary to really understand what you're doing when using a hobby charger. Improper use can lead to big problems. If I had to do it all over again, I'd get a Pila IBC for cell sizes 16340 through 18650. I may still get one, as they are a lot easier to use than a hobby charger, when charging only one or two LiCo cells.

......Also, there can not be any (trickle or otherwise) charge when the battery voltage is the same as or higher than the charger voltage......

This isn't exactly true in the case of same voltages , although I know what you're getting at. A "float charge" which is a form of trickle charge, consists of a small amount of current applied to the cell which maintains voltage. This promotes more rapid oxidation of the internal components of Li-Ion cells, just as a regular trickle charge does. The point being, that a proper charge termination will completely stop the current flow through the cell. This necessitates that the charging circuit be open, or in effect, zero Volts, with some chargers only resuming a closed circuit to periodically check whether a cell is present, or not.

It is possible with cells that are in "like new" condition, that it may not be possible to detect a voltage drop after proper charge termination, unless you have a DMM with a 4.200 readout, or better. Most LiCo cells that I have, even when new, drop 0.003 Volt or more after termination. As I said, if you leave cells, particularly used/older ones, in a charger after termination and the voltage remains constant, this is an indication that the charger is trickle charging.

Dave

 

[forexer]

Can you tell us what SKU number?

Here

 

[forexer]

So i ran them down to 3.67V each and both were good on the recharge with no significant voltage differential. Cells did get a little warm being drained at 2A on high but was probably due to the heat from the emitter.

I like these cells and i feel i've made a good purchase. lovecpf

 

[45/70]

Sounds good, forexer. You might want to check them again after a few cycles. I check the cells I use in series every 5-10 cycles or so.

One of the biggest problems with inexpensive cells that I've seen, is inconsistency between cells. This doesn't always show up when the cells are fairly new. In fact most Li-Ion cells wherever they are from, perform well at first. It's after 10-20 cycles that problems start to show up. This is true with quality cells also, but the inconsistency between cells is far less.

In any event, if you keep an eye on them, you shouldn't run into any problems. Carry on!:thumbsup:

Dave