Samsung 3000 mAh 18650 Testing

[jasonck08]

The problem with a bench power supply, is you will not be able to follow the recommend CC/CV Charging algorithm that most li-ion manufactures recommend.

For these cells specifically, I'd recommend first charging them via an RC (hobby charger) such as the Turnigy Accucel-6.

Then top them off with a bench / lab power supply at a regulated 4.35v @ <100mA.

 

[Whitedog1]

I purchased Samsung ICR18650 2800mAh cells six months ago and finally have a charger that can eventually "overcharge" up to 4.3V (soshine SC-S1 V2). I can confirm, that when charged to ~4.2V these cells have only around 2500mAh. But when charged up to 4.3V they are pretty good.

mWh are comparable to Panasonic NCR18650 2900mAh cells. The PTC kicks in at 10A discharge.

Panasonic 2900mAh: 4.2v charge termination
Samsung 2800mAh: 4.3v charge termination

So, actually the Panasonic 2900mAh cell is the best choice for end consumers because it can be charged in any lion charger with 4.2v shutoff and you will get the full capacity??:candle:

 

[Lion251]

The problem with a bench power supply, is you will not be able to follow the recommend CC/CV Charging algorithm that most li-ion manufactures recommend.

If you have a bench power supply where you can set both current and voltage, then it will follow the CC/CV algorithm perfectly.
Current will be limited until the set voltage is reached, then voltage will be kept constant.
The only thing you will be missing is the total switch-off of current when it has dropped to a few percent of maximum, so you cannot let the batteries be connected for extended periods of time.
And, with a bench power supply, you can charge only one cell at a time.
Otherwise, I don't see any problems.

 

[45/70]

The problem with a bench power supply, is you will not be able to follow the recommend CC/CV Charging algorithm that most li-ion manufactures recommend.

Sure you can!

......with a bench power supply, you can charge only one cell at a time......

Unless you charge cells in parallel.

Dave

 

[jirik_cz]

So, actually the Panasonic 2900mAh cell is the best choice for end consumers because it can be charged in any lion charger with 4.2v shutoff and you will get the full capacity??:candle:

Yes.

 

[Whitedog1]

Yes.

Thanks lovecpf

 

[jasonck08]

If you have a bench power supply where you can set both current and voltage, then it will follow the CC/CV algorithm perfectly.
Current will be limited until the set voltage is reached, then voltage will be kept constant.
The only thing you will be missing is the total switch-off of current when it has dropped to a few percent of maximum, so you cannot let the batteries be connected for extended periods of time.
And, with a bench power supply, you can charge only one cell at a time.
Otherwise, I don't see any problems.

How would you sent a bench power supply to behave like a hobby charger?

Most proper Li-ion chargers start off at a high current (say 1A for a 18650) then they slow down to <100mA once the voltage reaches about 4.1v and do the CC/CV stage.

I don't see how this is possible on a bench power supply?

Sure you could set the charger to 100mA @ 4.2v and let it charge for over a day, but that wouldn't be practical.

Sure you can!



Unless you charge cells in parallel.

Dave

How can you realistically charge a 18650 cell on a bench power supply in a reasonable amount of time?

 

[45/70]

How can you realistically charge a 18650 cell on a bench power supply in a reasonable amount of time?

It's pretty easy really. I used to do it quite a bit, especially for LiFe cells.

The PS in my old Metex MS-9140 is a "no frills" non-programmable PS, so everything has to be done manually. It simply has voltage and current control. So, say I want to charge a 1000mAh LiCo cell at a 0.5C rate, CC/CV. I set the PS up with the voltage set at 30 Volts and the current to zero. I hook up the cell and adjust the current up to 500mA. The cell begins to charge at a constant 500mA rate (CC). When the circuit (not the cell) voltage reaches 4.20 Volts, I then limit the voltage to 4.20 Volts (CV). When the current eventually drops down to 15mA (0.03C), I stop the charge.

Where I'm guessing a lot of people go wrong here using a simple type PS, is they initially set the voltage to 4.20, and the current to 500mA (in this example). This is really a "CV only" charge scenario, and not really CC/CV. Also, it will take about forever to do it this way.

And yes, if you don't watch the charge process very carefully, you can get into big trouble charging a LiCo cell at 30 Volts! The fact is though, that unless you are charging A123 cells at a 20C rate, or something, things happen pretty slowly, so provided you keep a close eye on things, it can be done safely. It's still a PITA compared to using a proper charger though. A programmable PS would be a big help in this regard.

I might add that this method is not for everybody. I don't suggest that folks go out and buy a bench PS to charge their Li-Ion cells. In addition to potential safety concerns with a PS like mine, it'd be a whole lot cheaper to just buy a hobby charger, or some other type charger that uses a proper CC/CV algorithm.

Dave

 

[jtsgalaxy]

Another thing to be aware of is most cheapo lab power supply will have voltage draft over time and tempurature also. Frequently check the voltage across the battery using DMM during charge is important too.

 

[shadowjk]

Um, if you don't limit the voltage to 4.2V wont it exceed 4.2 until you come and turn down the voltage limit?

I thought the whole idea of CC/CV was voltage limit @ 4.2V AND a current limiter, and then something to make it terminate when current has dropped to a certain threshold.. You're only missing the termination using a lab PS?

 

[45/70]

Another thing to be aware of is most cheapo lab power supply will have voltage draft over time and tempurature also. Frequently check the voltage across the battery using DMM during charge is important too.

Good point about drifting. In addition, most inexpensive PS's don't have all that accurate a display either. For that reason, I use the Metex's DMM for measuring voltage. Although precise accuracy of current measurement isn't really all that critical, I sometimes use a second DMM inline to measure current, as well.

As far as actual cell voltage during charging, this is pretty much irrelevant, as the circuit voltage is what is important, eg. if the circuit voltage is 4.20 Volts, there is no way the cell voltage can be any higher.

Um, if you don't limit the voltage to 4.2V wont it exceed 4.2 until you come and turn down the voltage limit?

Um, no. With a discharged cell in the circuit, the circuit voltage will remain below 4.20 Volts, regardless of the OC voltage of the PS during the CC stage. In the previously mentioned example of a 0.5C rate of charge, for example, the voltage will remain below 4.20 Volts for ~1 hour when charging a discharged LiCo cell. It is important to understand that the purpose of the CC stage, is to deliver a Constant Current through the cell. The only voltage requirement, is that the PS OC voltage be high enough to be capable of supplying the desired charging current.

I thought the whole idea of CC/CV was voltage limit @ 4.2V AND a current limiter, and then something to make it terminate when current has dropped to a certain threshold..

Yes, the circuit voltage is limited to 4.20 Volts. In order to maintain a Constant Current level during the CC stage however, necessitates that the voltage potential of the PS be higher than 4.20 Volts. Otherwise the current level would diminish throughout the CC stage. This is what occurs during the CV stage. The PS voltage is limited to 4.20 Volts, and as a result, the current gradually diminishes, as the cell approaches a fully charged state.

You're only missing the termination using a lab PS

More, or less, yes. And again, a programmable PS is much better suited (and safer) for the task.

OK. Waaay OT here. I'll stop.

Dave

 

[shadowjk]

Yes, the circuit voltage is limited to 4.20 Volts. In order to maintain a Constant Current level during the CC stage however, necessitates that the voltage potential of the PS be higher than 4.20 Volts. Otherwise the current level would diminish throughout the CC stage.

It would only diminish if there's extra resistance somewhere in the circuit, or, I dunno, if the power supply lacks proper regulation..

My phone for example has about 120 millOhms of resistance between its charger chip and the battery. At 1200mA charge rate, that's a voltage drop of about 0.144V, meaning the 4.2V output of the charger chip become 4.056V at the battery, making the charge current start tapering off at that battery voltage. But again, that's only because of the extra resistence present on the circuit board..

 

[45/70]

It would only diminish if there's extra resistance somewhere in the circuit......

The cell itself is the resistance variable. The more fully charged the cell becomes, the higher it's resistance to charge current.

......or, I dunno, if the power supply lacks proper regulation..

You can regulate the current, or you can regulate the voltage, but you can't regulate both. During the CC stage the current is regulated and the voltage increases. During the CV stage the voltage is regulated and the current decreases.

Dave

 

[shadowjk]

The cell's resistance causes the cell's voltage to rise when you charge, but it doesn't cause any taper-off before 4.2V..

OK, how about this:

Set powersupply to 4.2V / 1000mA. Attach some variable load. Observe voltage at different loads. If your voltage actually drops when you increase load, then I can understand you want to fudge it and set the voltage higher during earlier stages of charging...

 

[45/70]

OK, it's been so long since I've done it any other way, that I don't actually remember precisely what happens. Mind you, that using a bench PS has never been my primary means of charging any kind of cells, with the exception of NiCd/NiMH battery packs, at a 0.1C rate. Also, I used the PS to charge LiFePO4 cells in parallel for a couple months, as I didn't have a proper LiFe charger for cells larger than 16340's. Presently, I only use the PS for parallel charging NiZn cells. For Li-Ion cells and NiCd/NiMH packs, I use a hobby charger.

That said, from what I can remember, with my PS you cannot preset or adjust the voltage or current with an open circuit. With a cell in the circuit, the voltage can be limited (but of course cannot be set below the present circuit voltage), and current can be adjusted from 0-2A.

With the cell in place, you cannot push current through the cell until the voltage knob is turned up to some point higher than the circuit voltage. This is a "blind" operation, as the voltage reading will still read the circuit voltage. As the voltage knob is turned up, at some point, you will be able to start pushing current through the cell. If you turn the voltage up just enough to allow, say 500mA current flow, as the cell's voltage increases, the current will decrease, and you're basically running CV. Therefore, with this type setup, it's a whole lot easier to just turn the voltage knob up all the way, rather than trying to guess where the "sweet spot" is that would allow 500mA of current to flow until the 4.20 Volt point is reached.

Again, a programmable PS would make this part a whole lot easier to accomplish. And, for me anyway, a hobby charger actually works out better.

My apologies to SilverFox, for taking this thread way off topic.:candle:

Dave

 

[Aquanaut]

Welcome me! This is my first post on Candle Power! I have been lurking here for many days and learned a lot. I am a battery nut so this forum has attracted my attention. Due to posts on this site, I have ordered a Fenix TK11 R5 and a few different chemistry batteries. My background is in chemistry with a minor in electrical engineering.

My bench power supply operates as follows: first, I short the outputs and set the constant current. Then, without a load I set the desired constant voltage.

When the supply is hooked up to the battery, it supplies a rising current until the set voltage is reached. Then the supply switches over to constant voltage mode and the current reduces at the set voltage.

 

[45/70]

Welcome to CPF Aquanaut! :thumbsup:

My bench power supply operates as follows: first, I short the outputs and set the constant current. Then, without a load I set the desired constant voltage.

Hummm. I had never thought about setting the PS up in this manner. Mind you, I don't have any formal education, or professional background in electronics, it's just a hobby. I did get to try this out however, and it works!

I set up an AW protected 14500 LiCo cell that read 3.80 Volts OC. I set the current at 500mA and the Voltage to 4.20 Volts, in the manner you suggested. I monitored the voltage with the DMM in the Metex (I didn't refer to the PS readout, as it's not very accurate for Volts, or Amps) and ran a Fluke 27/FM inline, to monitor current. Everything progressed just as it should. At ~4.18 Volts the current began to drop. While I stopped the charge early, as this cell is headed back to storage, I can see this is a much better (and safer!) way to use a simple PS to charge Li-Ion cells.

When the supply is hooked up to the battery, it supplies a rising current until the set voltage is reached......

One thing, don't you mean constant current here?

At any rate, Thanks for the information, Aquanaut. I learned something today! Old dogs, new tricks, and so on.

Dave

 

[Aquanaut]

One thing, don't you mean constant current here?

Oops, my bad. I meant: "When the supply is hooked up to the battery, it supplies a rising voltage at the set constant current until the set voltage is reached."

 

[45/70]

Yeah, I figured.

I haven't attempted to charge anymore Li-Ion cells, as I really have no need to use a PS for this purpose, but did charge a couple NiZn cells using the "new" method. One thing I noticed, is that it would appear that cells take considerably longer to charge now. I wouldn't think that it would make that much difference, but apparently it does. In the case of LiCo cells though, it makes things a lot safer, anyway.

Dave

 

[CKOD]

If it makes anyone feel any better, we charge li-po cells at work with an xantrex dc power supply, when the output is off, it lets you set the current and voltage, and when you turn it on, it displays actual values.

4.2V/cell and usualy a 1C for current, + to +, - to - and let it sit for ~2-3 hours. Its perfectly fine, no one has died yet, and no puffed up batteries, perfectly fine to do if its being monitored, due to the lack of charge termination, as mentioned.


Oh, and if anyone wants to make your own 500mA or 100mA charger, the maxim max1811 and a 500mA+ phone/ipod AC-usb adaptor would make a fine combination. The little chip could probably use some heatsinking though if youre running 500mA though. But it has built in thermal limiting, so it wont roast itself, just limit current to < 500mA.