# Test/Review of Charger Xtar SV2 Rocket



## HKJ (Jun 5, 2016)

[size=+3]Charger Xtar SV2 Rocket[/size]















This Xtar charger can charge NiMH and LiIon batteries, it can handle fairly large cells and can also use a both low and fairly high charge current.



 

 

 

 

I got the charger in a retail cardboard box from. The box has a lot of specifications printed on the back.






The box contained the charger, a mains power supply, a car adapter a instruction sheet and a warranty card.






The charger has a DC input socket (5.5/2.1mm) where either the power supply or the car adapter can be connected.






The user interface is a display, two leds and one button.
A short press on the button will change charge current between 0.5A, 1A and 2A, a double tap (Why?) will change to 0.25A, a long press will turn the display off. With display off a short press or removing/inserting batteries will turn it on again.
The CH1/CH2 leds are red while charging and green at all other times.









The display shows selected current and how much the batteries are charged. After some time the brightness will be reduced, but it is still easy to read the display and a press on the button will return it to full brightness.









The charger uses the typical slider construction with a metal rail and works smoothly from about 30mm to 71mm, i.e. the charger can handle long protected 18650/26650/32650 cells.
Notice the long metal bar at the plus connection, this makes it possible to handle 32650 and D cells, it also means that flat-tops with very retracted plus pole may need a magnet to connect (The flat-top cells I tested worked directly).


















































The charger can handle 71 mm long batteries, including flat top cells. 
Many *high current* 18650 can be charged at 2A with only a minor impact on lifetime.



[size=+2]Measurements[/size]



When not powered a LiIon will discharge with about 2.3mA.
When not powered a NiMH will discharge with about 0.8mA.
When LiIon battery is full the charger will charge with 0.6mA.
The charger will restart if battery voltage drops below 3.94 volt.
Charge will restart charging after power loss, or battery insertion. 
Charger will charge from zero volt with about 100mA
Below 2 volt the charger assumes NiMH
Between 2 and 3 volt the charger uses 10% charge current
Above 3 volt regular LiIon charging is used.
Power consumption when idle is 0.6 Watt (0.9W with bright background light).


[size=+2]Charging LiIon[/size]






Nice and fast CC/CV voltage charging with 65mA termination.






It is the same on the other slot.










Other capacities are handled just as fine.






Also the old cell is handled as fast as possible, but due to the higher resistance it will spend more time in CV phase.






Again a good CC/CV curve and the termination current is lower at 35mA.






Also a good charge curve.






The charger easily handles two cells at 1A.






At 2A the temperature raises, but the charge curve is the same nice one.






M1: 45,3°C, M2: 45,8°C, M3: 48,0°C, HS1: 62,9°C
At 2A the charger is warm.






The charger needs 2 to 4 seconds to start, as can be seen the current slowly ramps up.






This is also the case when changing current, when increasing current it is ramped up, when reducing current drops immediately.



[size=+2]Charging NiMH[/size]






The charger start charging NiMH with a low current, then after about 10 minutes it goes to the selected charge current. Termination looks to be on voltage in this case here, followed by a two hour top-off/trickle charge at 50mA (Charger displays done).






It is the same on the other channel.














The 3 high capacity cells are also handled fine, two of them with -dv/dt termination.






I use a lower current here, this also means the top-off charge is done with slightly lower current.






With a 0.25A current there is no -dv/dt signal to termination on and it looks like the charger terminates on time.
This is not a fault with the charger, but use of wrong charge parameters for the cell. 






The charger takes some time to detect a full cell, first the 10 minutes with slow charging and then a few minutes with full current.
It do also use the top-off/trickle in this case.






Two cells at 1A is no problem.






Neither is two cells at 2A, but things are starting getting warm.






M1: 46,7°C, M2: 46,7°C, M3: 46,1°C, M4: 57,6°C,HS1: 63,2°C






The charger needs about 4 seconds, before it starts a low current charge.






10 minutes later it will switch to full current.






With NiMH the current do not ramp, but jumps directly to selected value.






The top-off/trickle charge is done with current pulses at the selected charge current. The pulse is 1 second wide each 21 second. This gives 47mA at 1A charge current.



[size=+2]Charging LiIon and NiMH at the same time[/size]

It is possible to charge one LiIon and one NiMH battery in the charger at the same time.
As usual the temperature sensor is on the opposite cell.






In this curve I recorded the NiMH battery, it looks the same as above.






The LiIon also looks the same as above.

Testing the mains transformer with 2500 volt and 5000 volt between mains and low volt side, did not show any safety problems.



[size=+2]Conclusion[/size]

This charger can handle from 10440 cells to 32650 cells or AAAA to D cells, the only requirement is that the user selects the correct charge current. The display is rather simple with only current and charge percent.

For a "simple" charger this is a very good charger for both LiIon and NiMH.



[size=+3]Notes[/size]

The charger was supplied by Gearbest for a review.

Here is an explanation on how I did the above charge curves: How do I test a charger
Read more about how I test USB power supplies/charger


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## sidecross (Jun 5, 2016)

It appears this is the replacement for the XTAR SP 2 charger.


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## scintillator (Jun 5, 2016)

Thanks for the detailed review HKJ very helpfull as usual.
I have been using this charger for about a month now and it is easy to use.


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## Gauss163 (Jun 5, 2016)

It would be interesting to compare the thermal imaging temperatures to other chargers, e.g. compare this to the Opus BT-C3100. But you don't seem to always list the conditions (e.g. current, ambient temp, etc) under which the thermal imaging was performed, so we could be comparing apples to oranges. Perhaps you could update the reviews with this info if you still have it (and maybe it would be useful to attempt to devise a "standard" context to make comparisons easier).


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## HKJ (Jun 5, 2016)

Gauss163 said:


> It would be interesting to compare the thermal imaging temperatures to other chargers, e.g. compare this to the Opus BT-C3100. But you don't seem to always list the conditions (e.g. current, ambient temp, etc) under which the thermal imaging was performed, so we could be comparing apples to oranges. Perhaps you could update the reviews with this info if you still have it (and maybe it would be useful to attempt to devise a "standard" context to make comparisons easier).



I always use highest charge current for thermal imaging. For ambient look for the lowest temp., that will be very close to ambient (You can see it at the bottom of the scale).
I cannot do a standard ambient temperature, in our country air condition is fairly rare.


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## Gauss163 (Jun 5, 2016)

HKJ said:


> I always use highest charge current for thermal imaging. For ambient look for the lowest temp., that will be very close to ambient (You can see it at the bottom of the scale)...



How about an example. Using the images in your Opus BT-C3100 review, and based on what you know about your test environment, could you please explain how to infer which charger is heating the cells more, the Opus or this XTAR?


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## SG Hall (Jun 5, 2016)

Thanks for the detailed review HKJ. This charger is on my radar because of the high charge current.


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## HKJ (Jun 6, 2016)

Gauss163 said:


> How about an example. Using the images in your Opus BT-C3100 review, and based on what you know about your test environment, could you please explain how to infer which charger is heating the cells more, the Opus or this XTAR?



That would be the SV2, it charges with highest current and has no fan. The cells are around 45C in SV2 at 2A and only about 37C in C3100 (At 1A), both with an ambient around 21C-22C. This is also obvious when looking at the black lines on the charge charts, the temperature is not the same but again the SV2 is warmest.


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## FlashKat (Jun 6, 2016)

What happens if you charge an Eneloop AAA at 2 amps by mistake?


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## HKJ (Jun 6, 2016)

FlashKat said:


> What happens if you charge an Eneloop AAA at 2 amps by mistake?




Probably nothing (Except extra wear), eneloop are very robust. 
Anyway an exploding NiMH is not nearly as violent as an exploding LiIon cell. The problem with LiIon is that it will self ignite when above a certain temperature and they contains combustible chemicals.


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## FlashKat (Jun 6, 2016)

Now what happens if you charge a 10440 at 2 amps by mistake? Is there any safety features to prevent an accident.


HKJ said:


> Probably nothing (Except extra wear), eneloop are very robust.
> Anyway an exploding NiMH is not nearly as violent as an exploding LiIon cell. The problem with LiIon is that it will self ignite when above a certain temperature and they contains combustible chemicals.


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## HKJ (Jun 6, 2016)

FlashKat said:


> Now what happens if you charge a 10440 at 2 amps by mistake? Is there any safety features to prevent an accident.




I am not going to do that test and if you do I would suggest doing it outdoors. 

With most round cell chargers it is up to the user to select the correct current, there is no safety.


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## FlashKat (Jun 6, 2016)

Thanks HKJ 


HKJ said:


> I am not going to do that test and if you do I would suggest doing it outdoors.
> 
> With most round cell chargers it is up to the user to select the correct current, there is no safety.


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## Gauss163 (Jun 6, 2016)

HKJ said:


> That would be the SV2, it charges with highest current and has no fan. The cells are around 45C in SV2 at 2A and only about 37C in C3100 (At 1A), both with an ambient around 21C-22C. This is also obvious when looking at the black lines on the charge charts, the temperature is not the same but again the SV2 is warmest.



Thanks. Unfortunately that doesn't tell me enough to figure out in general how to use those images to do thermal comparisons. For example, at what time during the charge was the image taken? Do you always use the same cells? If not, big differences in IR could cause big thermal differences. One would have to design a carefully controlled standardized thermal test in order for any sort of _comparison _to be meaningful.


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## HKJ (Jun 6, 2016)

Gauss163 said:


> Thanks. Unfortunately that doesn't tell me enough to figure out in general how to use those images to do thermal comparisons. For example, at what time during the charge was the image taken? Do you always use the same cells? If not, big differences in IR could cause big thermal differences. One would have to design a carefully controlled standardized thermal test in order for any sort of _comparison _to be meaningful.



Instead of all your problems with my test, why don't you do your own.


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## Gauss163 (Jun 6, 2016)

My remarks were meant to be constructive. With just some minor changes, one could make a first step towards being able to do thermal comparisons of chargers. This would be very useful information to have given that heat plays a significant role both in cell health and safety matters.


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## THE_dAY (Jun 6, 2016)

HKJ, thank you for your time and effort on another great review!
Really wish Xtar would make 2A charger with voltage readout for charging/resting voltage instead of the percentage readout.


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## Bullzeyebill (Jun 6, 2016)

PM to Gauss163.

Bill


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## candle lamp (Jun 7, 2016)

Another excellent test review. Thanks so much for your time and effort. HKJ! :thumbsup:


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## markr6 (Jun 7, 2016)

THE_dAY said:


> Really wish Xtar would make 2A charger with voltage readout for charging/resting voltage instead of the percentage readout.



Yes. That's my requirement for any chargers moving forward. The percentage thing is useless to me. I love my VP2, being able to throw a cell in and do a quick voltage read. During charging it's obviously reading higher, but good enough.


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## newbie66 (Jun 7, 2016)

Thanks HKJ! Now I have decided that this charger is in my next to buy list.


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## cave dave (Jun 11, 2016)

> When LiIon battery is full the charger will charge with 0.6mA.



Is the after termination charge considered a safe rate to leave the battery on for a day or two if I forget?


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## HKJ (Jun 11, 2016)

cave dave said:


> Is the after termination charge considered a safe rate to leave the battery on for a day or two if I forget?



The NiMH top-off charge is time limited and do not affect how long you can leave the batteries in the charger.
The charger current when LiIon is finished is low enough that it will not damage batteries in a day or two.


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## recDNA (Jun 11, 2016)

So the if I read correctly at no time did the temperature of the device nor the batteries get dangerously hot?


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## HKJ (Jun 12, 2016)

recDNA said:


> So the if I read correctly at no time did the temperature of the device nor the batteries get dangerously hot?



Why would they do that?


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## recDNA (Jun 12, 2016)

HKJ said:


> Why would they do that?


No reason. It's just a problem I have sometimes had with other brand chargers. I don't like it to feel "hot" to my hands. Those numbers looked a little high to me but I didn't bother to do C to F conversion.


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## adirondackdestroyer (Oct 4, 2016)

I bought one of these to charge my keeppower protected 26650. I charged them at 2.0 and they charged up pretty quick. Just to be 100% sure, if charging 18650 I should charge at 1 amp, and charing 14500 I should charge at .5, right? Just wanna be sure before I do it. 
Thanks


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## HKJ (Oct 4, 2016)

adirondackdestroyer said:


> I bought one of these to charge my keeppower protected 26650. I charged them at 2.0 and they charged up pretty quick. Just to be 100% sure, if charging 18650 I should charge at 1 amp, and charing 14500 I should charge at .5, right? Just wanna be sure before I do it.
> Thanks




Correct. With *some* 18650 cells you can charge at 2A, but it will usual cost a little bit of lifetime. You can sometimes find maximum charge current listed in my reviews or else you need to find some datasheets.


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## Gauss163 (Oct 4, 2016)

HKJ said:


> Correct. With *some* 18650 cells you can charge at 2A, but it will usual cost a little bit of lifetime. You can sometimes find maximum charge current listed in my reviews or else you need to find some datasheets.



The impact on health / life is impossible to predict without knowing more info. It might be slight or great. There is a fundamental asymmetry in current Li-ion cells: charging at high rate causes _much _worse degradation than corresponding high rate discharges. Just how bad it will be will depend on many factors: chemistry and design of the cell, the average SOC of the charges, ambient temp, etc. In extreme cases doubling the charge rate can reduce life by a factor of 10 or more, but a corrseponding doubling of discharge rate may have only a slight impact. As such, if it is not inconvenient to charge at slower rates then you should do so, since it may yield much longer life. This is especially worth consideration for devices with cells that are not (easily) user replaceable.


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## HKJ (Oct 4, 2016)

Gauss163 said:


> In extreme cases doubling the charge rate can reduce life by a factor of 10 or more



Can you list any 18650 cells rated for 2A charge (or more) that will only last 30 to 50 cycles at 2A charge current?


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## Gauss163 (Oct 4, 2016)

HKJ said:


> Can you list any 18650 cells rated for 2A charge (or more) that will only last 30 to 50 cycles at 2A charge current?



There have been numerous studies of accelerated degradation caused by high rate discharges, some of which have been discussed here in the past, e.g. this NASA study Performance and Safety Testing of Panasonic 2.9 Ah Li-ion NCR 18650 Cells by Jon S. Read. The same degradation mechanism holds for all current Li-ion cells, but the exact results depend heavily on the specific parameters.


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## HKJ (Oct 4, 2016)

Gauss163 said:


> There have been numerous studies of accelerated degradation caused by high rate discharges, some of which have been discussed here in the past, e.g. this NASA study Performance and Safety Testing of Panasonic 2.9 Ah Li-ion NCR 18650 Cells by Jon S. Read. The same degradation mechanism holds for all current Li-ion cells, but the exact results depend heavily on the specific parameters.




I take that as a *no*.


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## Gauss163 (Oct 4, 2016)

HKJ said:


> I take that as a *no*.



Off the top of my head, I don't recall the specific cells tested or other specific parameters. The point of becoming familiar with these studies is that they help one develop some _qualitative _intuition about such matters. We might not be able to infer specific numbers for any particular case (without actually testing), but we will obtain a better understanding of the asymmetry between charging and discharging - how higher charger rates are much more detrimental than corresponding higher discharge rates, etc.

Anyone who sincerely desires to better understand the underlying science should read the studies. They are few and far between (since cycle testing is expensive), but they are really the only solid data we have to provide any foundation for making _educated _guesses about such matters.


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## Aggressor (Oct 5, 2016)

Gauss163 said:


> In extreme cases doubling the charge rate can reduce life by a factor of 10 or more



I suggest that in addition to reading studies, we should refrain from making definitive statements if the only thing we can back them up with is "intuition".


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## Gauss163 (Oct 5, 2016)

Aggressor said:


> I suggest that in addition to reading studies, we should refrain from making definitive statements if the only thing we can back them up with is "intuition".



The scientific studies are not based on "intuition". But the initial guesses that I critiqued most likely are.


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## Aggressor (Oct 5, 2016)

Gauss163 said:


> The scientific studies are not based on "intuition".



Where did I say scientific studies are based on intuition?
The study you referenced is great, but it contains NOTHING to substantiate your claim:



Gauss163 said:


> In extreme cases doubling the charge rate can reduce life by a factor of 10 or more



So, once again, can you substantiate your claim in any way?


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## Gauss163 (Oct 5, 2016)

Aggressor said:


> So, once again, can you substantiate your claim in any way?



Try reading the NASA study I linked above. And chase links to that to find related results.


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## Aggressor (Oct 5, 2016)

Gauss163 said:


> Try reading the NASA study I linked above. And chase links to that to find related results.



I read that study long time ago. It is very interesting, but It contains NOTHING to substantiate your claim.

Please provide exact quote from the study which you think supports your claim.

Or is it too much to ask?


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## Gauss163 (Oct 5, 2016)

Aggressor said:


> I read that study long time ago. It is very interesting, but It contains NOTHING to substantiate your claim.
> Please provide exact quote from the study which you think supports your claim. Or is it too much to ask?



Incorrect. The graphs on pp. 10 and 11 illustrate the qualitative effects I described above. Many other studies show analogous results.


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## Aggressor (Oct 5, 2016)

Gauss163 said:


> Incorrect. The graphs on pp. 10 and 11 illustrate the qualitative effects I described above. Many other studies show analogous results.



The graphs show reduced life by factor of 10 or more? Are you sure you know how to read a graph?


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## Gauss163 (Oct 5, 2016)

Aggressor said:


> The graphs show reduced life by factor of 10 or more? Are you sure you know how to read a graph?



Yes, and yes.


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## Aggressor (Oct 5, 2016)

Gauss163 said:


> Yes, and yes.



Perhaps you don't know what factor of 10 means? You really ought to google terms before using them in a sentence.


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## Gauss163 (Oct 5, 2016)

Aggressor said:


> Perhaps you don't know what factor of 10 means? You really ought to google terms before using them in a sentence.



I have no idea what lies at the source of your confusion. But if I had to make a guess, it might be related to the fact that cells are considered end-of-life when they reach 80% of nominal capacity. Keep that in mind when you are extrapolating data from the graphs.


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## Aggressor (Oct 5, 2016)

Gauss163 said:


> I have no idea what lies at the source of your confusion. But if I had to make a guess, it might be related to the fact that cells are considered end-of-life when they reach 80% of nominal capacity. Keep that in mind when you are extrapolating data from the graphs.



I have pretty strong idea what lies at the source of your confusion, but I am going to keep it to myself out of politeness. Who exactly (besides yourself) considers cells end-of-life when they reach 80% nominal capacity?


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## StandardBattery (Oct 5, 2016)

Aggressor said:


> I have pretty strong idea what lies at the source of your confusion, but I am going to keep it to myself out of politeness. Who exactly (besides yourself) considers cells end-of-life when they reach 80% nominal capacity?


Good idea, we already woke the enforcers a while back over something small, never thought they would visit this forum for such small stuff.


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## Gauss163 (Oct 6, 2016)

Aggressor said:


> Who exactly (besides yourself) considers cells end-of-life when they reach 80% nominal capacity?



That is the industry standard when doing cycle life tests. Some may go a bit lower, to 75% or 70%. But it doesn't matter much where you draw the line, because the degradation caused by high-rate CC/CV charging is a _nonlinear_ process, so one will see the same qualitative effects at some point.



Aggressor said:


> I have pretty strong idea what lies at the source of your confusion, but I am going to keep it to myself out of politeness.



What politeness? Your puerile jabs above ("Sure you know how to read a graph" ... "maybe you don't know what a factor of 10 means") are far from polite. You won't have much luck eliciting expositions form others if you continue to behave like that.


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## scintillator (Oct 6, 2016)

I am using this charger exclusively now.
About 2 months ago the spring broke on one of the sliders.
Rather than go to the hassle of returning the thing for a new one I decided to fix it.
Removed rubber feet,unscrewed the bottom and revealed the problem.
The little plastic post the spring fixes to broke.(this plastic post is way underdesigned flimsy very poor)
I was able to drill a hole in the PC board just behind the broken post and attached the spring in the hole.
Better than new.
Just my 2 cents


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## Aggressor (Oct 6, 2016)

Gauss163 said:


> That is the industry standard when doing cycle life tests. Some may go a bit lower, to 75% or 70%. But it doesn't matter much where you draw the line, because the degradation caused by high-rate CC/CV charging is a _nonlinear_ process, so one will see the same qualitative effects at some point.



The problem is, you made specific quantifiable claim which is not supported by this graph. You said: "In extreme cases doubling the charge rate can reduce life by a factor of 10 or more". Therefore, in the graph, we are looking to compare cases marked "C charge" with "C/2 charge", and "C/5 charge" with "C/10 charge". We are not looking to compare "C charge" with "C/10 charge", because that represents ten times the charge rate, not doubling.

And comparing relevant cases, graphs show life reduction nowhere near factor of 10, whether you make the cut at 80% remaining capacity, or at a more universally accepted 70%.



Gauss163 said:


> What politeness? You puerile jabs above ("Sure you know how to read a graph" ... "maybe you don't know what a factor of 10 means") are far from polite. You won't have much luck eliciting expositions form others if you continue to behave like that.



Maybe you don't know what sarcasm means?


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## StandardBattery (Oct 6, 2016)

scintillator said:


> I am using this charger exclusively now.
> About 2 months ago the spring broke on one of the sliders.
> Rather than go to the hassle of returning the thing for a new one I decided to fix it.
> Removed rubber feet,unscrewed the bottom and revealed the problem.
> ...


Thanks for the report. I've not used this charger yet, just have it for charging some 26650 cells a little faster than some of my other chargers I trust and easier than the hobby charger. I have not had time to make room for it with several other chargers in use or test, but I'll be recharging more 26650 cells now so I plan to get it hooked up soon.


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## scintillator (Oct 6, 2016)

Yes a 26650 battery is what caused the spring post to break in slot no one.
That is mainly what I use it for also.I charge my 18650`s at one amp unless I am in a hurry,then I use 2 amp function 
who knows using faster charge rate might cost me in battery life in the long run,but when you need it charged now it
is the price you pay.


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## Gauss163 (Oct 6, 2016)

Aggressor said:


> Therefore, in the graph, we are looking to compare cases marked "C charge" with "C/2 charge", and "C/5 charge" with "C/10 charge". We are not looking to compare "C charge" with "C/10 charge", because that represents ten times the charge rate, not doubling.



I don't recall anyone claiming to compare C vs C/10. In any case, the source of your misunderstanding was revealed above. There are many other studies which illustrate this fundamental asymmetry, some of which you don't even have to extrapolate to infer the results.


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## Aggressor (Oct 6, 2016)

Gauss163 said:


> There are many other studies which illustrate this fundamental asymmetry, some of which you don't even have to extrapolate to infer the results.



Did anyone question the existence of this asymmetry? Where?
I have questioned this claim and asked you to provide any evidence:



Gauss163 said:


> In extreme cases doubling the charge rate can reduce life by a factor of 10 or more



As we have seen, the graphs in the referenced study do NOT provide such evidence (if one looks at the RELEVANT cases, with DOUBLE charge rate). Any other study you want to mention, or "there are many other studies" is all we are going to get as your "evidence"?


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## StandardBattery (Oct 6, 2016)

I think the cell charging discussion is now way OT for this thread. Let's get it back to this charger.


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## Bullzeyebill (Oct 6, 2016)

StandardBattery said:


> I think the cell charging discussion is now way OT for this thread. Let's get it back to this charger.



Good idea. Keep on track.

Bill


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## StandardBattery (Oct 9, 2016)

Did my first charge on this today. One battery 2A charge. 5200mAh rated 26650. Initial voltage was 3.8V (I think I forgot to record it, it would not drive Med level in my G20). It did pretty well on this simple charge. I probably would have pulled the cell earlier, but wanted to measure the exact termination voltage. This is a pretty simple charger, and you can set the charge rate before you insert the cell without issue. It would be nice if the bays could have just a couple more mm of length so that it would be easy to insert a current measurement shim probe in there with the battery. I bought this for 26650 cells, and while I could also use the BT-C3100 (v2.1) I guess I needed an excuse to try this XTAR charger and 26650 cells are the best I could come up with and leave the 3100 for analysis jobs. Termination was spot on so I'm happy, I'll just need to test the other slot and two cells at one next time. The estimated charge percentage seems accurate enough for my expectations, I don't really intend to rely on it that much, but I'll test more to see if it's accurate once it gets to 98% estimate or so, as at that level I'm happy to pull the cells early if I need them. 


*Start*20%55min42%115min70%164min96%175min99%*204min**100% (4.20V)

*


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## gteague (Oct 17, 2016)

anyone have a link to a chart where i can determine what current to charge at least the most popular batteries? if someone wants to just reply to a few, here's the ones i use the most. btw, i can never remember the li-on numbering system. apologies.

nimh 2400-2800mah
cr123r
18650 (i tested the 4, 2-3 year-old cells i have in my nitecore tiny monster by charging two of them at 2a using the sv2 and the other two at 500ma using the previous xtar charger which only goes to 1a. the cells were at approximately 3.2v (they are getting old--they lose charge more quickly as they age) and in the sv2 charger they charged to approx 4.2v in less than two hours. the two in the slower charger were still less than 50% after the two hours so i transferred them to the sv2 charger and they charged to full in about 45-60 minutes. a full charge of these 4 cells inside the flashlight with the nightcore charger can take 3-5 hours even when they are at about 3.4-3.6v to start with.)

at any rate, any current recommendations for max current and ideal current for those 3 batteries would be appreciated. }

tks, /guy


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## HKJ (Oct 17, 2016)

gteague said:


> anyone have a link to a chart where i can determine what current to charge at least the most popular batteries? if someone wants to just reply to a few, here's the ones i use the most. btw, i can never remember the li-on numbering system. apologies.



From the op:


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## ahill2 (Dec 3, 2016)

Between the xtar vc2 plus and xtar sv2 what would you choose?

I want it for charging 18650 and some eneloop pro 5th gen,nothing more.

Thank you.


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## StorminMatt (Dec 8, 2016)

ahill2 said:


> Between the xtar vc2 plus and xtar sv2 what would you choose?
> 
> I want it for charging 18650 and some eneloop pro 5th gen,nothing more.
> 
> Thank you.



That depends. Each of these chargers has its advantages and disadantages. The SV2 has more charging rates. Specifically, it can charge at .25A and 2A in addition to .5A and 1A. It can also charge 26650, 32650, C, and D cells should you eventually decide to expand your horizons. But the Plus Master works with USB power, can function as a powerbank, and is more compact. All in all, I consider the SV2 to be a better home charger and the Plus Master to be a better travel charger.

There are a couple of other things I should note. First of all, HKJ noted some termination problems with the Plus Master when charging NiMH batteries. I have never had a problem myself with this on my Plus Master. But it is possible that he either got a defective sample, was charging a defective battery, or was charging the battery under conditions that the charger couldn't handle. Or maybe I just got lucky. So be aware that this COULD be an issue if you get a Plus Master. Also, Illumination Supply is currently having a sale on Xtar chargers. The SV2 is currently going for about $18 and the Plus Master about $12. Why not get both for LESS than the regular price of the SV2 alone? That's what I did, and I'm glad I did.


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## kaptain_zero (Dec 8, 2016)

For the record, and barring my removal from the forum by Kelly for commenting on an Xtar product (aka Greta), I'm super happy with my SV2 charger! It works a treat and seems to charge all my lithium and NiMH cells just fine. 

Regards

Christian


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## vadimax (Dec 9, 2016)

markr6 said:


> Yes. That's my requirement for any chargers moving forward. The percentage thing is useless to me. I love my VP2, being able to throw a cell in and do a quick voltage read. During charging it's obviously reading higher, but good enough.



I do quick voltage reads with a DMM


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## vadimax (Dec 9, 2016)

Be aware of one "feature" of the charger: it has no memory. In case you charge a small battery that is capable of 0.25A charging current and power supply cuts off and then recovers, the charger defaults to 1A charging. In worst case scenario you may get fireworks... I guess  In any case that would be no good to the battery.


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## Gauss163 (Dec 13, 2016)

vadimax said:


> [...] it has no memory. In case you charge a small battery that is capable of 0.25A charging current and power supply cuts off and then recovers, the charger defaults to 1A charging. In worst case scenario you may get fireworks....



That's a fairly serious design flaw. If this can occur while charging Li-ion cells then that could prove to be quite dangerous, since charging Li-ion at too high current is one of the primary causes of thermal runaway.

It would be very helpful if reviewers tested charger behavior in exceptional cases like this. Typically reviewers do not perform such testing. Yet knowing how chargers handle such exceptions is essential knowledge required in order to properly assess their performance across the entire safety spectrum.

This is especially a concern for chargers like this that are designed to make automatic choices (for novices, or for convenience, etc). Often, as above, they do not have access to information required to make decisions, so they are forced to choose between making very conservative (but inconvenient) safe, default choices, vs. agressive (more convenient), but possibly dangerous default choices (e.g. default charge current). And, what's worse, in some cases the designer may not have even considered some exceptional conditions, which increases the chance that unsafe (default) choices might be made by the firmware.

With competent design you get a plug-n-play charger. But with incompetent design you get a plug-n-pray charger. To accurately distinguish the two requires much more extensive reviews that test performance in cases like these.

This is an area where everyone can contribute,since many such tests do not require any special knowledge or equipment. Rather, it requires only that we devise some standard safety test [procedures (tweaked as need be based on the features of each chargers).


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## StorminMatt (Dec 13, 2016)

vadimax said:


> Be aware of one "feature" of the charger: it has no memory. In case you charge a small battery that is capable of 0.25A charging current and power supply cuts off and then recovers, the charger defaults to 1A charging. In worst case scenario you may get fireworks... I guess  In any case that would be no good to the battery.



This is a BIG reason why it is a good idea to have multiple chargers. I feel like the Rocket is probably best reserved for rapid charging of larger cells. Although the Rocket has .25A and .5A settings, it is probably better used for cells that can tolerate a 1A or 2A charge. For smaller cells, something like the VP series might be better.


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## asleep (Dec 14, 2016)

So, would this be the charger to get for solely charging an 18650(AW protected 3400), if I can get one for under $20?

I've read nearly every @HKJ review.

This'll be my first charger, so safety and simplicity are important to me.


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## StorminMatt (Dec 14, 2016)

It would be a good charger for 18650 only, as 1A is perfect for them. And you can currently get this charger for under $20 at Illumn.


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## asleep (Dec 14, 2016)

StorminMatt said:


> It would be a good charger for 18650 only, as 1A is perfect for them. And you can currently get this charger for under $20 at Illumn.


Thanks, appreciate your help.

Now I just need to get up $50, otherwise the shipping from www.illumn.com adds about 60% back to the cost.


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## Sherbona (Feb 19, 2017)

scintillator said:


> I am using this charger exclusively now.
> About 2 months ago the spring broke on one of the sliders.
> Rather than go to the hassle of returning the thing for a new one I decided to fix it.
> Removed rubber feet,unscrewed the bottom and revealed the problem.
> ...


I just had this happen to me too. I was charging a pair of 18650s and a few minutes after the start I suddenly heard a loud click/pop from that direction that startled the heck out of me, and now the slider is completely loose (grrrr). Thank you so much for your great idea scintillator, I might try doing that myself.


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## scintillator (Feb 19, 2017)

[/IMG]


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## Sherbona (Feb 22, 2017)

Thanks for the picture scintillator, very helpful!

EDIT:
I ended up going back to Illumn.com with this (my purchase point) and they have shipped me a replacement (I'll be sending the broken one back to them, they'll take care of shipping). I'm satisfied with their resolution - next time I think I'll try what you did above, it would probably be easier.


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## FDP (Apr 23, 2017)

Just got my SV2. Very happy so far.


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## vadimax (May 2, 2017)

Some news from Xtar: asked them via e-mail regarding SV4 and the answer was "yes". But no details about "when".


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## vadimax (May 2, 2017)

And, by the way, I decided to use the authority of the CPF for the evil cause 


> Dear Michael,





> I am a CandlePowerForums member and there are a couple of issues detected with the SV2 model:
> 
> 
> 1. When there is a power outage the charger has no memory and defaults to 1A charging that is absolutely no good for small batteries.
> ...


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## FDP (May 20, 2017)

So I'm not very happy with my charger any more! The one slot spring also broke out while I was inserting a battery! 

I really hate it when manufacturers create a product with an excellent algorithim, but the construction is poor. 

I hope the retailer can sort this out for me.


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## Sherbona (May 20, 2017)

Yeah same thing with the replacement SV2 that I got (post 70). After about a month and a half a slot spring broke while inserting a battery. So now it's happened twice for me with two different units. Bad Xtar!


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## FDP (May 20, 2017)

I really hope they correct this on the new models going forward. Hearing stuff like this makes my hard earned money go somewhere else.


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## Gene (Aug 25, 2017)

I realize this is an older thread but I had a question maybe HKJ or someone could answer about this charger or has an opinion on this.

I purchased this SV2 Rocket primarily for NiMH c & D cells as I still use quite a few of them. Now I will admit my C & D NiMH cells are quite old, maybe almost 10 years but they've always charged up nicely. The D cells are Powerizer 9500mAh and the C cells are Powerizer 4500mAh. They continue to read right at 1.2V off the charger.

The first couple of times I charged them in the SV2 at 2A as recommended, at the end of the charging cycle, they were quite warm but not overly so. This last time I charged them in the SV2, at the end of the cycle, they were very, VERY warm. I noticed a couple of the C cells and a couple of the D cells negative bottoms were very slightly bowed out. I had never noticed this before. They still read 1.2V and still work fine in my devices but I know very, very warm is not good for any cells. It took them awhile to cool down. 

I realize this is a fast charger and has no cooling fan and cells will get warm using it but even though these cells seem to charge up to just about 100% and still work fine, I'm wondering if the charger may be defective and charging at a higher rate or maybe the cells are just wearing out. Any thoughts?


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## terjee (Aug 25, 2017)

I'm not HKJ, but...
I'd order some replacement cells.
It's more likely the cells than the charger. Charging at a significantly higher rate is unlikely. Some heating towards the end of the charging cycle is normal (terminating on temperature rise has actually been suggested for NiMHs), but it's hard to comment over the 'net on if the heating is normal or not. It sounds likely to be more heating than expected though. Bulging of the bottom isn't exactly a good sign either. ;-)
It could even be simplified: after 10 years, they've had a good run. No matter how you look at this, their life is probably nearing an end.


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## HKJ (Aug 26, 2017)

I can guess at two reasons for the cells getting warm:
1) The internal resistance has increased over age, this will generally mean a warmer cell when charging at the same current.
2) The -dv/dt signal is very weak due to age/wear and the charger has problem detected the full cell. This means it will continue to charge for some time on a full cell where all the energy is converted to heat.


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## Gene (Aug 27, 2017)

terjee said:


> I'm not HKJ, but...
> I'd order some replacement cells.
> It's more likely the cells than the charger. Charging at a significantly higher rate is unlikely. Some heating towards the end of the charging cycle is normal (terminating on temperature rise has actually been suggested for NiMHs), but it's hard to comment over the 'net on if the heating is normal or not. It sounds likely to be more heating than expected though. Bulging of the bottom isn't exactly a good sign either. ;-)
> It could even be simplified: after 10 years, they've had a good run. No matter how you look at this, their life is probably nearing an end.





HKJ said:


> I can guess at two reasons for the cells getting warm:
> 1) The internal resistance has increased over age, this will generally mean a warmer cell when charging at the same current.
> 2) The -dv/dt signal is very weak due to age/wear and the charger has problem detected the full cell. This means it will continue to charge for some time on a full cell where all the energy is converted to heat.



Good info and thanks so much!


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## vadimax (Aug 28, 2017)

I guess, those cells aren't that expensive that you decide to either be hit with a shrapnel or put your house on fire 

Personally for me it was enough of more than normal heating and chemical odor to dump a cell. Well, there was a headache as well to be true. That chemical smell was poisonous I guess.


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## TinderBox (UK) (Sep 21, 2017)

Question can each channel be set to a different charge rate, say 250ma for an AAA nimh and 2000mah for an 3400mah 18650 or do both channels have to be the same rate??

thanks

John.


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## HKJ (Sep 21, 2017)

TinderBox (UK) said:


> Question can each channel be set to a different charge rate, say 250ma for an AAA nimh and 2000mah for an 3400mah 18650 or do both channels have to be the same rate??



No, both channels use same charge rate.


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## TinderBox (UK) (Sep 22, 2017)

HKJ said:


> No, both channels use same charge rate.



Thanks Henrik, saved me again.

John.


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## david57strat (Sep 22, 2017)

scintillator said:


> I am using this charger exclusively now.
> About 2 months ago the spring broke on one of the sliders.
> Rather than go to the hassle of returning the thing for a new one I decided to fix it.
> Removed rubber feet,unscrewed the bottom and revealed the problem.
> ...



The same thing happened to me, after about six months of daily use of that charger (I had two of them), and on two separate occasions (both times, with a 26650 battery in the well). 

The first time, I just went into the store, with the charger, in all of the original packaging, and they immediately exchanged it, no questions asked. 

The second time (maybe with the other unit..who knows), they were out out of stock, but set me up with a loaner charger, apologized for the problems, said they would advise XTAR of the problem; and a few weeks later, I had the replacement unit (Which I also picked up at the store, when they still had a storefront to go to lol.

These guys have always taken care of me, so I've never had any reservations about buying XTAR chargers.

Now, I'm enjoying four of these babies - among others


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## joelbnyc (Nov 29, 2017)

Just wanted to give a big thanks to HKJ for taking the time to purchase lab equipment to make all these charger and battery measurements, and presenting the data in such a hugely useful format: the battery comparator and sortable round cell charger table. Such an immense un-remunerated contribution shows quite a passion and is much appreciated.

Thinking of picking this charger up as a non-pulse-charging backup/complement to my Opus 3100, esp at cyber-week sale price. I have had a few older Xtars without displays.

I don't fully understand the difference between simulated cc/cv (is this what pulse charging is?) and actual cc/cv, but I take it this charger does not use the pulse charging that was noted as a possible downside to the Opus?


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## Gauss163 (Nov 29, 2017)

joelbnyc said:


> I don't fully understand the difference between simulated cc/cv (is this what pulse charging is?) and actual cc/cv, but I take it this charger does not use the pulse charging that was noted as a possible downside to the Opus?



The OPUS "pulse" charging works fine for 99.999% of consumer applications. There are no scientifically backed studies that prove otherwise - only old-wives tales that have no scientific basis.


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## HKJ (Nov 29, 2017)

Gauss163 said:


> The OPUS "pulse" charging is works fine for 99.999% of consumer applications. There are no scientifically backed studies that prove otherwise - only old-wives tales that have no scientific basis.



I do not believe that you have yet shown a study that shows it is fine to charge a battery with 10 times rated charge current (The Opus do that with 10440 batteries).

Simulated CC/CV is not about the current, but because the charge algorithm is CC and current is adjusted depending on battery voltage with current off, this is not the same as CC/CV, but may look similar in many cases. The difference will often show up with old batteries, where the simulated CC/CV may go above 4.2V


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## Gauss163 (Nov 29, 2017)

HKJ said:


> I do not believe that you have yet shown a study that shows it is fine to charge a battery with 10 times rated charge current (The Opus do that with 10440 batteries).



Extremely tiny Li-ion cells that may possibly be more quickly degraded by the Opus are rarely used by consumers. That's why I said 99.999%



HKJ said:


> Simulated CC/CV is not about the current, but because the charge algorithm is CC and current is adjusted depending on battery voltage with current off, this is not the same as CC/CV, but may look similar in many cases. The difference will often show up with old batteries, where the simulated CC/CV may go above 4.2V



It's not clear what you are trying to say. How does that have anything to do with the Opus? [EDIT: Ah, the above seems to be a reply to the OP's earlier question, not to my comment on the Opus. It would be better to reply directly to the OP so as not to cause further confusion between the Opus charge algorithm and others].


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## HKJ (Nov 29, 2017)

Gauss163 said:


> Extremely tiny Li-ion cells that may possibly be more quickly degraded by the Opus are rarely used by consumers. That's why I said 99.999%



10440 is not extremely tiny, AA sized flashlight are popular and some of them uses LiIon.
16340/14500 is also charged with a rather high current, compared to their rating.




Gauss163 said:


> It's not clear what you are trying to say. How does that have anything to do with the Opus? [EDIT: Ah, the above seems to be a reply to the OP's earlier question, not to my comment on the Opus]



Opus uses simulated CC/CV, that is easy to see when it is charging old cells.


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## Gauss163 (Nov 29, 2017)

HKJ said:


> Opus uses simulated CC/CV, that is easy to see when it is charging old cells



"simulated cc/cv" is not standard terminology, so it wasn't clear what you meant. I thought you were referring to some of the more recent algorithms which dynamically adjust the charge current.



HKJ said:


> 10440 is not extremely tiny, AA sized flashlight are popular and some of them uses LiIon ...



Such small Li-ion cells are (relatively) rarely used by consumers so I think they fall into the 0.001% category in general consumer usage.

Furthermore, I am not aware of any scientific studies proving that the Opus algorithm will cause (significant) degradation even for those smaller cells. It makes no sense to attempt to apply parameters from _pure_ CC/CV algorithms to other variants such as that used by Opus. There can be dramatic differences in cell behavior under pulsed vs. constant current cases, so completely separate analyses need to be applied to obtain meaningful results. Even experts on Li-ion electrochemistry have made wrong guesses on related matters.


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## joelbnyc (Nov 29, 2017)

Oops, didn't mean to set off this little spat again.

I do charge 350mAh 10440 frequently, for my keychain light. I'd previously been using the Xtar XP1 Hummingbird at 0.25A for 10440 and 14500, so I will stop using the Opus 3100 for these small cells then.

*Edit*, looking at the curves, I may go with the Enova Gyrfalcon all-44 for a "pure" cc/cv simple charger (one of these days I will get a SkyRC 3000), because of 0.1A min and curves look to terminate right about 4.19V for 18650:





Whereas my Xtar WP2 II charges 18650 to ~4.15V and this SV2 Rocket seems to reach ~4.22-4.25V during charging, though perhaps this will have a negligible effect on lifecycle?


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## Bullzeyebill (Nov 30, 2017)

joelbnyc said:


> Oops, didn't mean to set off this little spat at again.



Yes, it is happening again. Good if it could be done via PM's. Speaking as a mod.

Bill


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## HKJ (Nov 30, 2017)

joelbnyc said:


> *Edit*, looking at the curves, I may go with the Enova Gyrfalcon all-44 for a "pure" cc/cv simple charger (one of these days I will get a SkyRC 3000), because of 0.1A min and curves look to terminate right about 4.19V for 18650:
> 
> 
> Whereas my Xtar WP2 II charges 18650 to ~4.15V and this SV2 Rocket seems to reach ~4.22-4.25V during charging, though perhaps this will have a negligible effect on lifecycle?



The actual charge voltage may vary between copies of the same charger, i.e. do not base you decision on that.
Higher voltage when charging is finished means more energy in the battery and it will also lower the lifetime a bit.


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## start90a (Nov 30, 2017)

Incredibly many thanks to HKJ for his tests.
The Optus pulse charge of 1 time at 2.2 A and 10 times at 0 A although there's no study to tell with no doubt isn't good for cell's life, common sense would say that a cell rated of little capacity should avoid useless charging patterns.
I prefer a co stand charge of 0.25 A instead of that loop.


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## TinderBox (UK) (Nov 5, 2020)

I want to run two of these charger`s side by side, Does anybody know if it will run without damage on a 15v 5a power supply, It does come with a car lighter socket adaptor and the voltage from a car lighter socket can be quite high with the engine running.

I have a splitter cable on order to power both charger from the same power supply.

The power supply is from an old SkyRC MC3000 the only part i kept when it died.

*EDIT: I decided to order an 12v 5a power brick for £11.66, Better safe than sorry.
*
Thanks

John.


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## xxo (Nov 7, 2020)

vadimax said:


> And, by the way, I decided to use the authority of the CPF for the evil cause
> 
> 
> 
> ...




I've had two SV2 rockets break like that, all four spring posts - it's a shame that the construction is so poor.


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## TinderBox (UK) (Nov 12, 2020)

I opened my new Rocket`s and they use PCB REV A-3 but they still use the plastic poles that the spring clip around, The poles then enter holes in the back cover when it`s fitted so there fixed at both ends.

I took some photo`s if they are of use.

John.


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## asleep (Oct 13, 2021)

xxo said:


> I've had two SV2 rockets break like that, all four spring posts - it's a shame that the construction is so poor.


Three broke for me, and I use them _very_ infrequently.

Only reason I got three was at time of purchase it was ~$5 more to order three with free shipping than one and paying for shipping. Looking for something more durable now.


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