Test/Review of Charger Xtar SV2 Rocket

[newbie66]

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

 

[cave dave]

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?

 

[HKJ]

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.

 

[recDNA]

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

 

[HKJ]

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?

 

[recDNA]

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.

 

[adirondackdestroyer]

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

 

[HKJ]

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.

 

[Gauss163]

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.

 

[HKJ]

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?

 

[Gauss163]

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.

 

[HKJ]

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.

 

[Gauss163]

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.

 

[Aggressor]

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".

 

[Gauss163]

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.

 

[Aggressor]

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:

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?

 

[Gauss163]

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.

 

[Aggressor]

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?

 

[Gauss163]

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.

 

[Aggressor]

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?