My new “battery charger” :-)

[Barkuti]

… stopping the charge at the 450 minute mark when then current the battery is pulling from the (then constant voltage) drops below the charger's threshold. It looks to be doing exactly what a charger is supposed to do, but @Barkuti 's power supply won't do that. It will sit there supplying 4.2V (or whatever he's got it set to) until he manually intervenes.

There's really no need to stop or cut-off, besides the fact it triggers an event which can be used to light up an end of charge led light, for example.
I have some DC/DC buck modules which also never stop, yet still they light up an end of charge led (XL4015 based). However, maximum cell voltage can never go above supply's output voltage. I can set supply's voltage to 4.1V with ease and end up seeing average ≈4.09V tapered cell voltage, ≈4.07V with a quick tapering. That still is close to 95% maximum capacity, and a better cycle life.

Cheers

 

[Mooch]

There's really no need to stop or cut-off, besides the fact it triggers an event which can be used to light up an end of charge led light, for example.
I have some DC/DC buck modules which also never stop, yet still they light up an end of charge led (XL4015 based). However, maximum cell voltage can never go above supply's output voltage. I can set supply's voltage to 4.1V with ease and end up seeing average ≈4.09V tapered cell voltage, ≈4.07V with a quick tapering. That still is close to 95% maximum capacity, and a better cycle life.

Cheers

Those modules are designed as battery chargers with a termination current setup of 10% of the bulk charging rate you use. They’re set up as battery chargers, not simple buck converters.

Continuous charging of a li-ion cell accelerates aging and cannot be considered as a non event. Stopping at a reasonable termination current level not only significantly speeds up charging and helps to reduce cell damage but it also provides for a consistent charge. This is critical if you are doing any testing of the cell.

 

[Barkuti]

…
Continuous charging of a li-ion cell accelerates aging and cannot be considered as a non event. …

0K, let's bust this myth.
Continuous charging… once current flow has tapered below a certain value, intrinsic current flow cell stress is absolutely insignificant. Cell dissipated power equals I²R, already at or below 4mW for a 100mΩ cell at 0.2A (which is a high cutoff) because P = (0.2)² × (0.1). If allowing the cell to reach a little bit higher voltage is a concern, just slightly reduce output voltage. Just selecting 4.12V, for example, will get us 4.09 - 4.11V charged cell voltage most of the time, 4.12V worst case scenario. Seriously, cell voltage cannot go above output voltage, this is laws of physics.

Charger cut-off and its corresponding indication is something you may be accostumed to. But I am an old school technician, I do not need something to tell me what to do. I prefer taking my own decisions reading a nice instrumentation, manually pushing buttons and levers… it has something to do with dad & mom gifting me with a game of electronics at the age of ≈8 or earlier.

Cheers

 

[Rossum]

0K, let's bust this myth.
Continuous charging… once current flow has tapered below a certain value, intrinsic current flow cell stress is absolutely insignificant.

Then why do all the cell manufacturers' specifications prohibit continuous charging?

Seriously, cell voltage cannot go above output voltage, this is laws of physics.

Agreed, it cannot, but that doesn't mean some amount won't continue to flow.

 

[Barkuti]

Then why do all the cell manufacturers' specifications prohibit continuous charging?


Agreed, it cannot, but that doesn't mean some amount won't continue to flow.

Sources? Pretty sure one of those li-ion cell engineers would tell you what I do can't be considered continuous charging. Cell cannot go above maximum voltage, this means current flow eventually stops.

There's nothing wrong with no cut-off. Once current flow is insignificant it just is about the same as no current flow. Think outside the box please.
Upon supply's entering CV phase (current tapering), if we were to measure the time it takes for the current flow to first halve I believe we can expect to wait twice the previous time frame for each subsequent current halving, with each subsequent current halving being half as significant as the previous one with regards to flow of charge.
A perfect constant current li-ion charger can be built, but needs to peek cell voltage right at its terminals and adjust output voltage accordingly to maintain current flow. In this case cut-off is required and end of charge condition is the cell reaching desired voltage Vc = 4.2V (for example).

Cheers

 

[Vinnybagodoughnuts]

 

[Mooch]

0K, let's bust this myth.
Continuous charging… once current flow has tapered below a certain value, intrinsic current flow cell stress is absolutely insignificant. Cell dissipated power equals I²R, already at or below 4mW for a 100mΩ cell at 0.2A (which is a high cutoff) because P = (0.2)² × (0.1). If allowing the cell to reach a little bit higher voltage is a concern, just slightly reduce output voltage. Just selecting 4.12V, for example, will get us 4.09 - 4.11V charged cell voltage most of the time, 4.12V worst case scenario. Seriously, cell voltage cannot go above output voltage, this is laws of physics.

Charger cut-off and its corresponding indication is something you may be accostumed to. But I am an old school technician, I do not need something to tell me what to do. I prefer taking my own decisions reading a nice instrumentation, manually pushing buttons and levers… it has something to do with dad & mom gifting me with a game of electronics at the age of ≈8 or earlier.

Cheers

Being a lot older than you I can pull that “old school” stuff at any time. It means nothing though. You can use any tech you want but I don’t “need” anything to tell me a damn thing.

Let’s bust your attempt to create a myth you felt needed busting.
The stress from charging is NOT current induced, it has nothing to do with power dissipation.

I never even hinted that charging goes to a point above the supply’s voltage. Why do you keep going back to that?

Accelerated aging is caused by the electrochemical reactions that are forced to occur continuously at the max rated voltage of the battery versus the slightly lower resting voltage. Higher potential = faster oxidation and other compound breakdown.

If you want to charge manually, that’s fine. Do it. Just don’t make up things to justify continuous charging. Any quick search will turn up huge numbers of things showing you that non stop charging and/or float or trickle charging is not something to do with li-ion cells.

You can charge manually charge for informal vaping use but you cannot do that for any cells you want to test due to the inconsistent amount of charge transferred to the cell. Good testing methodology doesn’t care about old school or new tech. It demands doing things properly though and I hope you don’t feel manual charging is any way to prepare cells for testing.

Lastly, don’t ever assume you know how I do things here. I use five CC/CV supplies for all my personal charging and most of my other charging except when testing cells that need consistent charging with a fixed termination current level.

 

[Mooch]

Sources? Pretty sure one of those li-ion cell engineers would tell you what I do can't be considered continuous charging. Cell cannot go above maximum voltage, this means current flow eventually stops.

There's nothing wrong with no cut-off. Once current flow is insignificant it just is about the same as no current flow. Think outside the box please.
Upon supply's entering CV phase (current tapering), if we were to measure the time it takes for the current flow to first halve I believe we can expect to wait twice the previous time frame for each subsequent current halving, with each subsequent current halving being half as significant as the previous one with regards to flow of charge.
A perfect constant current li-ion charger can be built, but needs to peek cell voltage right at its terminals and adjust output voltage accordingly to maintain current flow. In this case cut-off is required and end of charge condition is the cell reaching desired voltage Vc = 4.2V (for example).

Cheers

Current flow does NOT stop! Please, I beg you, research these cells a LOT more!

The current flow eventually drops down to the leakage current rate of the cell, taking up to three days for this to happen. It then never drops below this rate. It is low but it means the cell is active 24 hours a day when being charge continuously with the electrolyte oxidizing, the SEI layer getting thicker, etc., all that time due to the continuous electrochemical activity.

“Insignificant current flow” is never the same as no current flow for li-ion cells when forced to continuously shuttle ions.

Please do some research regarding float and trickle charging of li-ion cells.

 

[DaveP]

You can't really see what's going on with a modern phone's battery because the dang thing isn't accessible to an external meter, and using an app that shows voltage while the phone is running isn't very telling either because the phone itself is presenting a constantly varying load.

You can with an inline USB voltage/current monitor. I use a Drok monitor. My Galaxy S7 Edge shows 980ma charge rate on a drained battery. About $11 at Amazon.

Agreed, this would happen if you allowed it. Yet no spec sheet I've seen for the cylindrical cells we use allows that. They all demand that charging stop when the current the battery is accepting at final voltage drops below some specified value, generally 50-100 mA.

Agree. I was just talking about theoretical current draw with a constant voltage charger.

Huh? That graph clearly shows the charger stopping the charge at the 450 minute mark when then current the battery is pulling from the (then constant voltage) drops below the charger's threshold. It looks to be doing exactly what a charger is supposed to do, but @Barkuti 's power supply won't do that. It will sit there supplying 4.2V (or whatever he's got it set to) until he manually intervenes.

The LUC 4 is a constant current charger, so it would be dangerous if it didn't have a voltage cutoff. It does stop and cut off when the voltage reaches 4.2v. Current is the same value until the charger senses 4.2v. The wiggle in the curve at the end looks to me like capacitor discharge occurring as the voltage falls to zero after the charger cuts off. I wouldn't want a charger that didn't cut off at end of charge. It's the reason I use Efest and Xtar and other chargers that have cutoff features. I like fail-safe devices.

Uptopic I was just musing over the idea that a Constant Voltage charger will allow the battery to reduce it's charge current as charge reaches maximum because the voltages equal out and current flow drops to a minimum level (millamps) as internal resistance rises due to increased charge saturation.

A Constant Current charger doesn't do that and must shut down when voltage reaches coincidence with a set parameter.

Barkuti is just experimenting with an O-scope monitored charging setup. I think he said he plans to include a fail safe circuit to ensure safety. He's in experimenter mode right now. I'm confident that he will add sensing devices for safety. No one wants hot lithium battery electrolyte all over the workbench.

 

[Rossum]

@DaveP A USB voltage/current monitor shows you what your phone's charging circuit is pulling from the USB supply, not what's actually happening at the battery. The charging circuit needs some power from the USB source to keep itself "alive" even if it applying zero voltage or current to the battery.

Dedicated Li-ion chargers like your LUC and my XTARs work as follows:
1) They start in Constant Current Mode. In Constant Current Mode, they monitor the cell's voltage. When the cell reaches the selected terminal charging voltage (usually 4.2V, but some chargers do accommodate others), they switch to:
2) Constant Voltage Mode. In Constant Voltage Mode, the monitor the current that the cell will accept while maintaining terminal voltage. When that current drops below a certain threshold (usually 50-100 mA), they:
3) Stop charging entirely. At that point, they will normally continue to monitor the cell's voltage. If/when the cell's voltage drops below a certain threshold (generally around 4.0V) they will start the cycle over again.

The power supply Barkuti is using can do 1) and 2) perfectly well, but it will not do 3). He will have to do that manually.

I'm not going to go so far as to say it is dangerous to continue to apply Constant Voltage Mode indefinitely (because I really don't know whether it is or not) but it can't be good for the cells, because every spec-sheet I've seen for any of the cells we use demands that 3) should occur.

 

[DaveP]

@DaveP A USB voltage/current monitor shows you what your phone's charging circuit is pulling from the USB supply, not what's actually happening at the battery. The charging circuit needs some power from the USB source to keep itself "alive" even if it applying zero voltage or current to the battery.

Dedicated Li-ion chargers like your LUC and my XTARs work as follows:
1) They start in Constant Current Mode. In Constant Current Mode, they monitor the cells voltage. When the cell reaches the selected terminal charging voltage (usually 4.2V, but some chargers do accommodate others), they switch to:
2) Constant Voltage Mode. In Constant Voltage Mode, the monitor the current that the cell will accept while maintaining terminal voltage. When that current drops below a certain threshold (usually 50-100 mA), they:
3) Stop charging entirely. At that point, they will normally continue to monitor the cell's voltage. If/when the cell's voltage drops below a certain threshold (generally around 4.0V) they will start the cycle over again.

The power supply Barkuti is using can do 1) and 2) perfectly well, but it will not do 3). He will have to do that manually.

I'm not going to go so far as to say it is dangerous to continue to apply Constant Voltage Mode indefinitely (because I really don't know whether it is or not) but it can't be good for the cells, because every spec-sheet I've seen for any of the cells we use demands that 3) should occur.

I agree with all that you said. Barkuti's setup does need a cutoff device. Even at trickle charge the battery is undergoing ionization at a lower rate, but one that a cell shouldn't experience over long times.

I used to service Xerox equipment all over. In computer rooms, tech shops, and labs at major factories and electronics companies they'd always have a wall of chargers running 24/7 to supply workers' pagers, cell phones, radios, tools, and the like. I used to cringe at that, but it was necessary for maintaining a ready source of cells for the workers. You could feel a slight warmth as you walked by 50 chargers running at once. They were all national brand devices and AFAIK there was never an issue because they were UL listed devices with safety cutoffs built in.

 

[AttyPops]

Then why do all the cell manufacturers' specifications prohibit continuous charging?

Isn't this about heat dissipation and degradation of the electrolyte? After all, in the extreme reverse situation (short) that's where the explosions come in. Pauses would allow built up heat to disseminate in the material.

P.S.
I didn't really follow well, so please excuse the stupid question: Does this charger/charging method limit amps at the device, or is it counting on the internal resistance of the electrolyte to be that limiting factor? IDK what that rig is.

If it's just using the internal resistance of the battery, then that works in optimal conditions, but develop a problem over time, and watch that charging situation get nasty fast. Basing the charging on ideal condition of a battery only works well when the battery is in ideal condition.......

(Totally guessing here. Just crap-shooting).

Stay safe people! Consider charging in a vented metal box (with insulating liner if necessary to prevent shorts on the probes). Some people use old ammo boxes and such.

 

[Rossum]

I didn't really follow well, so please excuse the stupid question: Does this charger/charging method limit amps at the device, or is it counting on the internal resistance of the electrolyte to be that limiting factor? IDK what that rig is.

Yes, it does. The power supply he's using has both an adjustable current limit and and adjustable voltage. It can be set up to do a perfect job of charging, except for one thing: It will not stop automatically like a dedicated charger would.

 

[Barkuti]

Being a lot older than you I can pull that “old school” stuff at any time. It means nothing though. You can use any tech you want but I don’t “need” anything to tell me a damn thing.
…
Lastly, don’t ever assume you know how I do things here. I use five CC/CV supplies for all my personal charging and most of my other charging except when testing cells that need consistent charging with a fixed termination current level.

Someone felt attacked, or so it seems to me. If you felt attacked by me, rest assured it was not my intention. I even got you to swear…
I preferred not to continue this discussion by that time. Sorry fellows.

Oh! I know current flow doesn't stops. It just keeps tapering down indefinitely. Anyway I have to check out this PSU, because the current meter zeroes below a certain value (<6 - 7mA) when in CV mode…

Cheers

 

[r77r7r]

Wow, thought that I was in the Outside for a bit there.

 

[stols001]

The only argument I want to make is that I don't think "Damn" is really a swear word. Not in our current culture anyway, DAMN. LOL.

Good luck with the new charger and etc. It's astonishing enough that I Guess Folks Have Opinions.

Mine is that (especially with 15 batteries) it looks like some sort of spider or insect. I couldn't have it in my house for that reason alone, but I also likely wouldn't be able to operate it safely although I am NOT going to dispute whether it CAN be safely operated because I am entering a realm where it is all:


Happens often with electronics,

Anna

 

[AttyPops]

Wow, thought that I was in the Outside for a bit there.

Pffffft. Lightweights for sure.

 

[BillW50]

Dedicated Li-ion chargers like your LUC and my XTARs work as follows:
1) They start in Constant Current Mode. In Constant Current Mode, they monitor the cell's voltage. When the cell reaches the selected terminal charging voltage (usually 4.2V, but some chargers do accommodate others), they switch to:
2) Constant Voltage Mode. In Constant Voltage Mode, the monitor the current that the cell will accept while maintaining terminal voltage. When that current drops below a certain threshold (usually 50-100 mA), they:
3) Stop charging entirely. At that point, they will normally continue to monitor the cell's voltage. If/when the cell's voltage drops below a certain threshold (generally around 4.0V) they will start the cycle over again.

The power supply Barkuti is using can do 1) and 2) perfectly well, but it will not do 3). He will have to do that manually.

I'm not going to go so far as to say it is dangerous to continue to apply Constant Voltage Mode indefinitely (because I really don't know whether it is or not) but it can't be good for the cells, because every spec-sheet I've seen for any of the cells we use demands that 3) should occur.

Back when I started to use lithium cells back in the late 90's, chargers will always slowly ramp up to charging current. My two RC Triton chargers are like this too (they are like 15 years old now). And say I wanted to charge 18650s at 2A, it would take 10 minutes to ramp up from 100ma to 2A. This was done because we were told this extends the lifespan of the cells.

This was a PIA to simulate this when I was using CC/CV supplies. Every 30 seconds you bumped up the current by 100ma until in 10 minutes you would be up to 2A. I sure would like to know why this old practice was done away with in modern chargers. Maybe @Mooch knows something about this?

And using CC/CV supplies as chargers isn't really that bad of a deal. Sure the first couple times I did so, I babysat them. Monitored battery temps and everything. But after a few times, it becomes routine. Then it becomes super easy. And it is easy to calculate how long it should take to charge. So I just set a timer in case I'm not watching the time. All of my watches has timers, so one is always with me anyway. And I see no point waiting for the current to drop below 100ma. Just take it off anytime when it drops below 250ma. As trying to squeeze in that last little bit of capacity just seems to be a waste of time to me.

 

[BillW50]

There it goes!

Cheers

How in the world are you attaching alligator clips to 18650s?

 

[Mooch]

This was a PIA to simulate this when I was using CC/CV supplies. Every 30 seconds you bumped up the current by 100ma until in 10 minutes you would be up to 2A. I sure would like to know why this old practice was done away with in modern chargers. Maybe @Mooch knows something about this?

I don’t think it actually offers any measurable benefits. At least not with the cells we have available now. It might have been done previously to prevent charging very high internal resistance (low amp rated) cells accidentally at high charge rates? A slow ramp up gave them time to detect any problems?

Just guessing here though.