# Review of / Measurement on Xtar SP2 charger



## HKJ (Jun 23, 2012)

[size=+3]Charger Xtar SP2[/size]










Xtar has for some time made good chargers, this is their latest model. This model has selectable charge current, making it fast and safe to handle many different LiIon battery sizes.









It comes in a cardboard box that list the battery sizes that it is designed for.






The box contains the charger, a universal voltage (100-240V 50/60Hz) mains power supply, a car power adapter and a instruction manual.






The plus connection is slightly raised, this means that the charger can be used with flat top batteries.






The minus connection is a slider, making it possible to charge different size batteries without using a spacer. This slider is using a metal rail and works very smooth.






The connections for the power adapter is clearly marked.






The charger has one button that is used to select charge current. It always starts at 0.5A, a short press will move to 1A, next press to 2A, a third press will start over at 0.5A. This button can be used with or without a battery in the charge and will always affect both channels.
There is also a led for each charge channel. These leds are red when charging and green at other times, including fault conditions.























The charger can handle 70 mm long batteries including flat top cells. In addition to the batteries specified on the box the charger can also be used for shorter batteries, if a spacer is used.



[size=+2]Measurements[/size]

Below 1.3 volt the charger charges with 0.7mA, this is enough to reset a protection (led is green).
Between 1.3 and 2.8 volt the charger charges with 60 to 75 mA in 0.5A range (0.1A in 1A and 0.2A in 2A range) (led is red).
Above 2.8 volt the charger is applying regular charge current (See curve below).
Especially at the 0.5A current setting the termination voltage is slightly high (nearly 4.23 volt on #2 channel), this is within allowable limits.
When the charge current goes below the termination current the charging is stopped and it will charges with < 250 uA.
The charger will restart charging when the cell drops to 3.9 volt.
The charge will always restart charging when a battery is put into it or after a power loss.
When charger is disconnected from power, but with a battery in, it will draw up to 3.7 mA from the battery (The two channels does not draw the same amount of current).
Two batteries in the charger will not change the charge current, i.e. the channels are truly independent.
Because each channel is independent, the different voltages and currents vary between the channels with a small amount.














The charger uses CC/CV charging and the termination current changes with charge current. In the above curves the termination current is 100mA for 0.5A charge current, 130mA for 1A charge current and 180mA for 2A charge current. This is good values, but lower values would have been slightly better (i.e. 5% to 10% of charge current).
Due to some resistance in the charger (About 0.08 ohm, calculated from the charge curve), the CV (constant voltage) part of the curve is not completely flat and the termination voltage changes slightly with charge current.














The second channel looks very much like the first channel.






First channel, but also charging on second channel. The curve looks about the same as above.






This charge curve is with an old battery and due to the high charge current the charger goes into CV charge nearly immediately.






The charger is supposed to use soft startup and a check shows this to be correct.






Changing current while charging will trigger the same soft startup again. Here I press the button at 1s and 5s.



[size=+2]Conclusion[/size]

The charger uses CC/CV charging and soft charges nearly empty batteries, this is a very good. The possibility to select different charge current, makes the charger suitable for a wide range of battery sizes and still have a fast charge speed.
The two charge/error indicator lights could be better, I would have like a flashing error indication, instead of just a green, that does also mean "battery charged and ready".

I like this charger, it will charge most common LiIon battery sizes and not use too many hours for it. It is the best Xtar charger I have tested until now.


[size=+3]Notes[/size]

The charger was supplied by XTAR for a review.

Here is an explanation on how I did the above charge curves: How do I test a charger


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## Dubois (Jun 23, 2012)

Once again, HKJ, an excellent review, thank you. Is it too early to say this is better than the Pila? I don't see a review by you of that model on your site, so may be an unfair question.


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## HKJ (Jun 23, 2012)

Dubois said:


> Once again, HKJ, an excellent review, thank you. Is it too early to say this is better than the Pila? I don't see a review by you of that model on your site, so may be an unfair question.



I have never tested/reviewed the Pila.
The SP2 has better functions than the Pila with the selectable current, but the Pila has shown good reliability for a couple of years. 
What is best depends on what you prefer.


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## Robert_M (Jun 23, 2012)

Great review! Thanks!!!


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## LEDAdd1ct (Jun 23, 2012)

Thanks for the review!


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## MattSPL (Jun 23, 2012)

Thanks for the review.

Is it ok to charge an 18650 at 1 or 2A every time, or is the 500mA setting better for cell life?

Cheers
Matt


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## HKJ (Jun 23, 2012)

MattSPL said:


> Thanks for the review.
> 
> Is it ok to charge an 18650 at 1 or 2A every time, or is the 500mA setting better for cell life?
> 
> ...



Generally a low charge current is better for the battery life, but I do not believe you will see much different between 1A and 0.5A. 2A is a bit high.


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## Shadowww (Jun 23, 2012)

MattSPL said:


> Thanks for the review.
> 
> Is it ok to charge an 18650 at 1 or 2A every time, or is the 500mA setting better for cell life?
> 
> ...



1A is OK for any high-quality (NOT UltraFire and similar) 18650's, 2A is only recommended for IMR 18650's (but if you're in hurry & have *high-quality* cells, 2A won't be deadly, at most - it'll just add some wear to the battery).


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## MattSPL (Jun 23, 2012)

Shadowww said:


> 1A is OK for any high-quality (NOT UltraFire and similar) 18650's, 2A is only recommended for IMR 18650's (but if you're in hurry & have *high-quality* cells, 2A won't be deadly, at most - it'll just add some wear to the battery).



Ok thanks for the reply.

I have Panasonic 18650 IMR 2250mAh, and Senybor protected(Panasonic) 3100mAh cells. I'm using an Xtar mp1 at the moment, and would like something faster.

Cheers
Matt


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## MattSPL (Jun 23, 2012)

HKJ said:


> Generally a low charge current is better for the battery life, but I do not believe you will see much different between 1A and 0.5A. 2A is a bit high.



Ok, thanks for the reply.

I'll have to look into getting one of these.

Cheers
Matt


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## Shadowww (Jun 23, 2012)

MattSPL said:


> Ok thanks for the reply.
> 
> I have Panasonic 18650 IMR 2250mAh, and Senybor protected(Panasonic) 3100mAh cells. I'm using an Xtar mp1 at the moment, and would like something faster.
> 
> ...


The 2250mAh Panasonic is *not* IMR. IMR is LiMn chemistry, ICR is LiCoO2, the 2250mAh Panasonic is a hybrid between those two. Panasonic recommends 0.7C and lower charge current for that cell, which is 1.575A or less.

For 3100mAh cells Panasonic *recommends* 850mA charge current, but 1A won't do them any harm (2A most likely will, though).


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## MattSPL (Jun 23, 2012)

Shadowww said:


> The 2250mAh Panasonic is *not* IMR. IMR is LiMn chemistry, ICR is LiCoO2, the 2250mAh Panasonic is a hybrid between those two. Panasonic recommends 0.7C and lower charge current for that cell, which is 1.575A or less.
> 
> For 3100mAh cells Panasonic *recommends* 850mA charge current, but 1A won't do them any harm (2A most likely will, though).



Thanks for the info, i didn't know that.

So the SP2 on the 1A setting should suit then.

Cheers
Matt


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## Colonel Sanders (Jun 24, 2012)

I have two of these chargers and *HIGHLY* recommend them. They are surprisingly compact and sleek and do a fine job charging. Using the 2a settings I can fully charge two pairs of completely depleted 18350s in 30 minutes.  

It will also charge Feilong 32650s.


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## candle lamp (Jun 24, 2012)

Another excellent review as laways. HKJ! :thumbsup:

Thanks a lot for your posting the great review.

Regarding the above graph relating to battery voltage (green) & charging current (red), Is the first graph for 0.5A charging selection?

It seems the final graph shows 1A & 2A charging current change at 1 sec. & 5sec. after starting 0.5A charging.


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## HKJ (Jun 24, 2012)

candle lamp said:


> Regarding the above graph relating to battery voltage (green) & charging current (red), Is the first graph for 0.5A charging selection?



When turning on power it will always start at 0.5A, I recorded that in the first graph.




candle lamp said:


> It seems the final graph shows 1A & 2A charging current change at 1 sec. & 5sec. after starting 0.5A charging.



In the second graph it was charging at 0.5A and I pressed the switch two times.


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## 45/70 (Jun 24, 2012)

Hi HKJ. Thanks for the, as usual, excellent review.:thumbsup:

I'm curious, from your charging graph it appears that the charger does not do voltage checking (other than at start up, of course). I see that it does still appear to use a pulsed charge, rather than an actual constant current, but the current seems to be smoothed out quite a bit. Has XTAR finally done away with constant voltage checking (which is totally unnecessary when charging Li-Ion cells) with this version charger?

One gripe I would have is the spring loaded negative posts. I find these cheesy on any charger. It'd be nice if they came up with something like the YOHO-122 had, ie. clips that can be pried up for the charging of shorter length cells. Also, does the electrical path to the negative posts pass through the springs, or is there a solid connection, such as a wire bypassing the spring? This is what I did to the NiCd chargers I rewired for use with my hobby chargers that had spring loaded contacts. It's still kinda flakey though, although electrical contact is solid and it works.

The other quality I'm not too keen on is the ability of this charger to charge over discharged cells. I can understand the need to reset a protected cell's protection circuit, but charging for example, an unprotected cell with an OC voltage of less than 1.5 Volt, could be a problem.

Other than the spring loaded contacts and the ability to potentially charge damaged cells, I agree that this XTAR looks like the best one yet. If your graphs show an accurate representation of the actual current deviation during charging (the non constant current part, LOL!), I think I could live with that.

Dave


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## HKJ (Jun 24, 2012)

45/70 said:


> I'm curious, from your charging graph it appears that the charger does not do voltage checking (other than at start up, of course). I see that it does still appear to use a pulsed charge, rather than an actual constant current, but the current seems to be smoothed out quite a bit. Has XTAR finally done away with constant voltage checking (which is totally unnecessary when charging Li-Ion cells) with this version charger?



It looks like a real CC/CV charger, there is no pulse charging. The variations in the curve is adjustment of the current generator, it looks very much like on a hobby charger.




45/70 said:


> One gripe I would have is the spring loaded negative posts. I find these cheesy on any charger. It'd be nice if they came up with something like the YOHO-122 had, ie. clips that can be pried up for the charging of shorter length cells. Also, does the electrical path to the negative posts pass through the springs, or is there a solid connection, such as a wire bypassing the spring? This is what I did to the NiCd chargers I rewired for use with my hobby chargers that had spring loaded contacts. It's still kinda flakey though, although electrical contact is solid and it works.



I prefer this type of spring loaded sliders, they make it easy to charge many different sizes. And as I wrote in the review, these sliders works well.
I do not know if there is a wire in addition to the spring.



45/70 said:


> The other quality I'm not too keen on is the ability of this charger to charge over discharged cells. I can understand the need to reset a protected cell's protection circuit, but charging for example, an unprotected cell with an OC voltage of less than 1.5 Volt, could be a problem.



It is a bit difficult to decide what is best, the charger rejecting batteries with low voltage or the charger supplying a small current to reset the protection. I am sometimes annoyed with my hobby charges, because they cannot reset a protection.



45/70 said:


> Other than the spring loaded contacts and the ability to potentially charge damaged cells, I agree that this XTAR looks like the best one yet. If your graphs show an accurate representation of the actual current deviation during charging (the non constant current part, LOL!), I think I could live with that.



Both voltage and current is logged each second and I am using a 10mOhm series resistance for current. I believe that gives a good representation of the current and voltage.


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## 45/70 (Jun 24, 2012)

HKJ said:


> Both voltage and current is logged each second and I am using a 10mOhm series resistance for current. I believe that gives a good representation of the current and voltage.



I don't doubt your test equipment and methods. Your test equipment alone is likely worth more than my car! I'd question that statement if it were my light collection though. Sometimes however, I do question your interpretation of the results, not this time. When the current level constantly jumps between zero and xxx mA, as seen in other tests however, and you refer to this as "constant current", for example....... LOL!

Peace, and thanks again for the review. This does look like a "good one".

Dave


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## HKJ (Jun 25, 2012)

45/70 said:


> I don't doubt your test equipment and methods. Your test equipment alone is likely worth more than my car! I'd question that statement if it were my light collection though.



Generally I like equipment where I can trust the result.




45/70 said:


> Sometimes however, I do question your interpretation of the results, not this time. When the current level constantly jumps between zero and xxx mA, as seen in other tests however, and you refer to this as "constant current", for example....... LOL!



Even if you switch a constant current generator on and off, it will continue to be a cc generator.


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## iron potato (Sep 16, 2012)

Hi, I also really liking this SP2 charger along with their WP6 II, but recently my SP2 were a bit strange





Whenever after it charged a battery off the right slot with 18650 at 1A or 26650 at 2A, the led will blinks red/green continuously after I removed the battery.

I tried cycle the input or let it rest for 10-15mins, power on its still the same, until out of sudden, it return to solid green (w/o battery in the slot)

At first I assumed is the heat or something, so I try again with another 26650 @ 2A, while I stand up the charger, after it charged, red/green blinks again after battery removal



this doesn’t happen on the left slot ever.

As while it was blinking red/green, I put in a battery & it will still charge it (solid red till green, and blinks again when battery removed).

Does any one having this symptom ? or should I return to the seller for replacement ?


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## Robert_M (Sep 16, 2012)

iron potato said:


> Hi, I also really liking this SP2 charger along with their WP6 II, but recently my SP2 were a bit strange
> 
> 
> 
> ...



Mine has the exact same problem. Its annoying when it happens, but doesn't seem to affect the ability to charge. I've had mine for several months and that's the only issue I've had with it.


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## iron potato (Sep 16, 2012)

Robert_M said:


> Mine has the exact same problem. Its annoying when it happens, but doesn't seem to affect the ability to charge. I've had mine for several months and that's the only issue I've had with it.



Correct, it doesn't affect the function tho, I'll just keep it then, guess I'm not alone afterall


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## iron potato (Sep 19, 2012)

It all came down that the right channel on my SP2 slot were not charging anymore.

So I took the risk & opened it up to have a look on the charger pcb, especially on the right channel area.

Found a SMD component near to C10 had sort of cold-solder, the left channel sides also not to my liking. (sorry, forgot to take photos)

Switched on my hot air gun with small nozzel to correct it & wicked up extra solder, after both channel sides seems satisfied, close it back & have a try.

Surprisingly it was charging again, also doesn't blinks red/green after a charge anymore, no matter with 26650 @ 2A or 18650 @1A setting, great to actually solved it.


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## 45/70 (Sep 19, 2012)

That's great that you managed to "fix" your SP2, Iron. I guess "you get what you pay for" applies to QC, as much as anything else, when it comes to the less expensive chargers.

I wish XTAR would incorporate the SP2's electronics (and thus the algorithm) into their WP6 version. I've been tempted to get one, but the quasi CC/CV charging algorithm has held me back from doing so. That, and the potential QC issues, such as you have had to deal with, as well as the relatively slow charge rate. As it stands, the only XTAR charger I would consider, is the SP2, as it's the only one in the line that appears to actually utilize a CC/CV algorithm. I'm not saying the others are bad, just "not quite right", IMO.

Again, glad you got your SP2 working.:thumbsup:

Dave


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## Robert_M (Sep 19, 2012)

iron potato said:


> It all came down that the right channel on my SP2 slot were not charging anymore.
> 
> So I took the risk & opened it up to have a look on the charger pcb, especially on the right channel area.
> 
> ...



Thanks for sharing the details of the repair. Mine still charges properly ... for now. I still get the occasional red/green light show though.


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## iron potato (Sep 20, 2012)

45/70 said:


> That's great that you managed to "fix" your SP2, Iron. I guess "you get what you pay for" applies to QC, as much as anything else, when it comes to the less expensive chargers.
> 
> I wish XTAR would incorporate the SP2's electronics (and thus the algorithm) into their WP6 version. I've been tempted to get one, but the quasi CC/CV charging algorithm has held me back from doing so. That, and the potential QC issues, such as you have had to deal with, as well as the relatively slow charge rate. As it stands, the only XTAR charger I would consider, is the SP2, as it's the only one in the line that appears to actually utilize a CC/CV algorithm. I'm not saying the others are bad, just "not quite right", IMO.
> 
> ...



Actually were on edge whether to send it back to HK for claim or I try my luck open it up to have a look, luckily second option paid off.

So far my WP6 II behaved normally, if I'm not using all 6 slots, I''ll slot in no.1/3/5 or 2/4/6 slot to prevent the quasi CC/CV algorithm u mentioned, correct me if I'm wrong.

Fred


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## iron potato (Sep 20, 2012)

Robert_M said:


> Thanks for sharing the details of the repair. Mine still charges properly ... for now. I still get the occasional red/green light show though.



No problem Robert, just share what I did, I also not 100% sure it will solve it too, just take chances, that's why I didn't take any photo on the particular area to post it up


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## 45/70 (Sep 20, 2012)

iron potato said:


> So far my WP6 II behaved normally, if I'm not using all 6 slots, I''ll slot in no.1/3/5 or 2/4/6 slot to prevent the quasi CC/CV algorithm u mentioned, correct me if I'm wrong.



Hi Fred. I was referring to how the WP6 II, as well as most of the rest of XTAR's chargers, apply the charging current in pulses, rather than a constant current. So far, the SP2 is the only one that doesn't.

I wasn't going to bring it up again, but a few posts back HKJ stated......



HKJ said:


> Even if you switch a constant current generator on and off, it will continue to be a cc generator.



This is true, concerning the current generator. However, it seems to me that a charger that switches the current generator on and off, is not supplying a constant current. How this could be interpreted as CC, is beyond me, LOL!

Cheers,

Dave


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## Isaiah6113 (Oct 10, 2012)

Thank you HKJ for this wonderful review.

About 16340 batteries. Your chart shows the charger working with 16340s, however the product literature does not explicit state it supports 16340.

Can we use the SP2 to charge 16340s?

Thank you,

Matthew

EDIT:

Oh I think I see, the packaging shows three battery ranges:
1) 14500/14650/17670 (with 16340 falling in this range)
2) 18500/18650/18700
3) 22650/25500/26650 

Correct?


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## HKJ (Oct 10, 2012)

Isaiah6113 said:


> Thank you HKJ for this wonderful review.
> 
> About 16340 batteries. Your chart shows the charger working with 16340s, however the product literature does not explicit state it supports 16340.
> 
> Can we use the SP2 to charge 16340s?



Not directly, you need to add a spacer (That is probably the reason it is missing from the specifications).
Also note that the charge current is at the upper limit of charge current for many 16340 batteries, this might wear you batteries down a bit faster.


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## Isaiah6113 (Oct 10, 2012)

HKJ said:


> Not directly, you need to add a spacer (That is probably the reason it is missing from the specifications).
> Also note that the charge current is at the upper limit of charge current for many 16340 batteries, this might wear you batteries down a bit faster.



Understood, thank you.

That's where some will use rare earth magnets to take up the space.


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## ptolemy (Oct 13, 2012)

From what I can tell the power supplied to charger maxes out at 2A, so when you have 2 channels running and select 2A setting, it won't work but just do 1A max per channel?


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## HKJ (Oct 13, 2012)

ptolemy said:


> From what I can tell the power supplied to charger maxes out at 2A, so when you have 2 channels running and select 2A setting, it won't work but just do 1A max per channel?



The power supply is 2A as you say, but with 12 volt, i.e. it can deliver 24 watt. To charger two LiIon batteries with 2A each you only need 16.8 watt, i.e. a power converter with more than 70% efficiency will work.
The SP2 does charger two batteries with 2A each, i.e. it must have at least 70% efficiency.


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## ptolemy (Oct 13, 2012)

HKJ said:


> The power supply is 2A as you say, but with 12 volt, i.e. it can deliver 24 watt. To charger two LiIon batteries with 2A each you only need 16.8 watt, i.e. a power converter with more than 70% efficiency will work.
> The SP2 does charger two batteries with 2A each, i.e. it must have at least 70% efficiency.



Thanks for the explanation


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## candle lamp (Oct 23, 2012)

This charger is very good! I like it. Thanks a lot for your excellent review again. HKJ! :thumbsup:

By the way, your mail box is full. 

KyeongHo,


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## HKJ (Oct 23, 2012)

candle lamp said:


> By the way, your mail box is full.



I will fix that later today.


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## HistoryChannel (Mar 28, 2013)

Hi,

I just started taking volt readings for batteries coming off the SP2. I found that when the light turns green, I take a reading and it reads around 4.15v consistently on all my 18650 batteries. Am I supposed to leave the batteries in the charger for a bit longer after the light turns green for it to reach 4.2v?

Thanks!


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## Robert_M (Mar 28, 2013)

I have two SP2 chargers. One charges to 4.20V (1A setting) and the other to 4.23V (1A setting). Depending on the accuracy of the voltmeter and the accuracy of the SP2, its not surprising that your SP2 is terminating at 4.15V which is only 0.05V low. I have a Pila charger which terminates at 4.17V. However, you may want to leave your battery on the charger for an extra hour after the LED indicator turns green ... it should NOT make any difference, but since you're curious try it anyway! That's the only way you'll know for sure! I've also noticed that the termination voltage varies some depending on whether its on the 0.5, 1 or 2 Amp setting. 



HistoryChannel said:


> Hi,
> 
> I just started taking volt readings for batteries coming off the SP2. I found that when the light turns green, I take a reading and it reads around 4.15v consistently on all my 18650 batteries. Am I supposed to leave the batteries in the charger for a bit longer after the light turns green for it to reach 4.2v?
> 
> Thanks!


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## HistoryChannel (Mar 28, 2013)

I'll try leaving it in the charger for a couple hours after it turns green just to see. I'd rather it undercharge than overcharge past 4.2v for safety and longevity of the batteries. 

Thanks for the response. I'll post back on here what I find after I leave it charging after green.


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## HistoryChannel (Mar 28, 2013)

Ok, left a battery in the SP2 after green and after an hour it's still spot on at 4.15v so that's what it's terminating at. No biggie, it's only .05v, this must be the +\- .05v they list.


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## HKJ (Mar 29, 2013)

HistoryChannel said:


> Hi,
> 
> I just started taking volt readings for batteries coming off the SP2. I found that when the light turns green, I take a reading and it reads around 4.15v consistently on all my 18650 batteries. Am I supposed to leave the batteries in the charger for a bit longer after the light turns green for it to reach 4.2v?



That sounds fine. The 4.2 volt is charge voltage, not battery voltage, take a look at this chart:






Just before the yellow line (Charge termination) the red voltage line is above 4.2 volt, at the yellow line it drops maybe 0.03 volt (How much depends on the age and type of battery and termination current). You are measuring after the drop and it is the voltage before the drop that is supposed to be 4.2 volt (between 4.15 volt and 4.25 volt).

For a good charger the voltage is not supposed to increase after charge termination.


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## bobstay (Dec 2, 2014)

Hello HKJ,

Did you take any temperature measurements of this charger? I would be interested to know if it gets hot during charge or not.


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## HKJ (Dec 2, 2014)

bobstay said:


> Did you take any temperature measurements of this charger? I would be interested to know if it gets hot during charge or not.



This review is from before I started with the temperature measurements.


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