# Review of Charger Xtar XP4



## HKJ (Oct 12, 2013)

[size=+3]Charger Xtar XP4[/size]















Xtar is known for flashlights and a couple of good LiIon chargers. This time they have also included NiMH capabilities in the charger and together with 3 current settings and USB output it looks like a charger that can do just about everything (Except analyze).


















The charger comes in a cardboard box with lots of specifications on the outside.






The box contains the charger, a mains adapter, a car adapter (Probably optional), a manual and a warranty card.






The front/top of the charger contains 8 leds and one button:

3 blue leds to show the charger current, a short press on the button will select next charge current.
1 blue usb led, this led will be on when the usb output is active. To activate the output slot #4 must have a charged LiIon battery, power must be disconnected and the button must be pressed for some time.
4 red/green status leds. They are red when charging and green at other times. When slot #1 is discharging the led will flash red (Activated by a long press on the button).







The charger has a 12 volt input, this input can be supply from the main adapter or from the car adapter.
The usb output is rated at 1A and uses the battery in slot #4. It can only be activated when input power is disconnected.






Xtar uses this label to avoid fakes.









The battery + connection is slightly raised and worked with flat top batteries. The slider works fine.
The slider can work with batteries between 30.5 mm and 71.8 mm.












































The charger can easily handle 70 mm long batteries, including flat top cells. (See my Small LiIon comparison for length of different brands).


[size=+2]Measurements charger[/size]



When not connected to power it will discharges with up to 0.6mA, except slot #4 for usb output, it will discharge with up to 11mA.
When power is connected with a full battery, the charger will charge with 170uA (All slots with LiIon).
When power is connected with a full battery, the charger will charge with 10mA/30mA/50mA trickle charge (All slots with NiMH).
At 0 volt on the battery the charge current is 1.6mA (Green led is on).
At 0.22 volt the red led turns on and the current jumps to 90mA
At 1.22 volt the full charge current is turned on for NiMH.
At about 3 volt the full charge current is turned on for LiIon.
Any voltage drop, reinsertion of battery or power cycling will restart charging.
The led is flashing red when discharging. This only works on channel #1.
The channels on the charger are independent, i.e. there are small differences between them. 


[size=+1]Test with LiIon cells[/size]






Charging a 3100mAh cell with 0.25A is slow, but works perfectly. Notice the low terminations current, this is good. Lower would be even better, when charging small batteries.






Increasing the current to 0.5A does also look good. The termination current has increased slightly.






At 1A is also good, the termination current is about 100mA which is fine.














The other slots works just as well.






The charge time for 2600mAh is slightly shorter than 3100mAh






And 3400mAh has slightly longer charge time.






My old LiIon cell is handled perfectly at full charge current.






Charging a smaller cell with 0.25mA does, of course, also work.






Charging 4 LiIon batteries at the same time does generate some heat. My probe measures 41°C on the batteries.





M1: 51,5°C, HS1: 77,4°C

The USB port on the back of the charger gets very hot, it is not recommended to touch it.





M1: 50,3°C, HS1: 70,4°C

There is also some hot spots between the batteries and I measure 50°C on the batteries. This is at the limit.







After the charger is powered on it uses about 2 seconds on starting, then 1 second to sense battery type, before ramping up to charge current.






Changing from 0.25A to 0.5A takes about 4 seconds.






From 0.5A to 1A it takes about 8 seconds to ramp up. Reducing power is instantaneous.
Note: These times are neither good nor bad, it is just the way the charger works.



[size=+1]Test with NiMH cells[/size]






A very slow charge of a 2000mAh AA cell and something went wrong. It terminates at 1.40 volt and has only filled 1250mAh into the cell, but then the charge current is too low for this cell, lets test with a AAA cell.
Note: The risk with low charge current is usual overcharge, not premature termination.






Again it terminates early, only about 460mAh has been filled into the cell.






Let’s try 0.5A with a AA cell. Again I get about 1250mAh.
This is not very good.






With a AAA battery at 0.5A the charge is nearly ok.






What about 1A? Again it looks nearly ok, it terminates after about 2000mAh (This is a tad early for a 2000mAh NiMH). When the charge is finished the charger continues with trickle charge.
Notice the slow charge at the start of the curve, it is probably done to detect battery type. 














Here are 3. other channels. Looking at the voltage curve, it looks like #2 is terminating slightly early, #3 is good and #4 is early.






With a eneloop XX (2500mAh), the charge curve looks perfect. The voltage has reached a maximum and started to drop, before the charge is terminated.

My guess is that there is a bug in the "end of charge" detection algorithm, this means that it will not work correctly will all types/ages of NiMH batteries. A bit more work from Xtar will probably fit it.






Starting a charge with a full battery, is stopped very fast. First the charger uses two minutes to analyze the battery, then it charges 2½ minutes, before it detects the battery is full and changes to trickle charging.






With 4 batteries, there was also some premature termination, but as can be seen on the temperature curve, that battery did terminate properly. Even with one early termination I recorded a temperature of 51°C
Note: I was measuring volt and current on battery #1 and temperature on battery #3.






Let’s try once more, this time both the battery with voltage/current sensor and the battery with thermo sensor did terminate premature. This time, without proper termination, the temperature did only reach 43°C





M1: 51,1°C, HS1: 74,1°C

The USB port gets very hot with NiMH batteries.





M1: 50,9°C, M2: 51,8°C, M3: 51,2°C, M4: 45,7°C, HS1: 81,9°C

3 batteries at 51°C, the last is charging, but is not as hot.
Somewhere down on the PCB it gets really hot. It is probably not a problem for the electronic parts and it looks like the plastic can take it, but some heat is transferred to the batteries.






In slot #1 the charger can also do a discharge. The battery I tested with was only half full. When charging there was no premature termination. When discharging the led is flashing red.






The current is fairly low, a 2000mAh cell will take nearly 7 hours to discharge and then 2 hours to charge, because the charger only has one slot with discharge function it will take at least 35 hours to cycle a pack of four cells.






At power on it takes two seconds before the charger starts at the low sense current.






Here it switches from sense to full charge current.






Manual switching between the currents happens instantaneous, with NiMH it does not use a ramp.



[size=+1]Test with both LiIon and NiMH cells[/size]






Charging both LiIon and eneloop does not change much. It looks like there is a bit more noise in the charge current.






The NiMH does also look fine.



[size=+2]Measurements USB output[/size]



The charger can only use one battery for the usb output and it has to be a LiIon battery.
USB out does not turn off when loaded with 200% of rated output
When battery is empty, the output will be turned off, but there is still drained about 5mA from the battery.
Output is turned off when battery voltage is slightly above 3 volt, making it useable for all 3.6/3.7 volt LiIon batteries.
Usb output is coded as Apple 1A








The output is rated at 1A and can easily deliver 2A (To not blow the usb output I stopped at 2A).






At 1A output it has a good efficiency and runs for about 1 3/4 hour. The output turns off when the battery is down to about 3.1 volt, but it still has a current drain of about 5mA from the battery.






Reducing the current to 0.5A improves the efficiency slightly and more than doubles the time it can run.






A 2600mAh gives shorter runtime.






And a 3400mAh gives longer runtime.






The usb output has very little noise, only about 7mV at 1A (67mVpp).






At 0.5A the noise is about the same (6mV and 65mVpp).



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



[size=+2]Conclusion[/size]

The charger has many functions of varying quality:

The LiIon charger is good and support a wide variety of cell sizes, this is as expected from Xtar.
The NiMH charger obvious has a bug in the "end of charger" detection and is not very useful.
The NiMH discharge function is too limited with only one slot and only a slow discharge.
The USB output delivers very good power, low noise and stable voltage, but do not leave a empty battery in slot #4 for days.
The charger gets hot while working at maximum current, the battery temperature is just at the allowable limit. I would have preferred both the box and the batteries where considerable cooler, this heat does wear the batteries down faster.


Generally it is a good quad LiIon charger, but the NiMH function is not very good before Xtar get it fixed.



[size=+2]Notes[/size]

The charger was supplied by Xtar for a review, I believe it is the second production batch.

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 and chargers


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## ChrisGarrett (Oct 12, 2013)

Thanks for your time and effort once again HKJ. You're starting to get an excellent database together. As for this charger, I'm an Xtar fan, but we can't 'always hit it out of the ballpark,' can we?

It seems that these 'all-in-one' multi-chemistry chargers are a bit problematic and live up to the 'jack of all trades, master of none' adage.

Chris


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## psychbeat (Oct 12, 2013)

So if you're charging regular Eneloops @1amp & u leave em to trickle a little bit this charger will work ok?

I wish it had 2amp for 18650 

Thanks for the review!!


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## HKJ (Oct 12, 2013)

psychbeat said:


> So if you're charging regular Eneloops @1amp & u leave em to trickle a little bit this charger will work ok?



The trickle charge is 50mA and you need it for up to 14 hours in the test I did above.



psychbeat said:


> I wish it had 2amp for 18650



2A is to much for many 18650 batteries.


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## gopajti (Oct 12, 2013)

Thank you HKJ! some pics and my results





VP1/WP2S (left) and XP4 (right) adapter

















my short "end voltage" test (I have 2pcs XP4)






I used cottonpickers voltage meter and I measured immediatly, after the leds changed red to green. Otherwise I don't care NiMH charging, so this is not problem for me (I have MH-C9000). I need good quality four bay real CC/CV li-ion charger with various charge current, not more. 

animations


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## Mr. Tone (Oct 12, 2013)

Thanks for the great review. I was waiting to see it and am glad I waited. I am curious if it is possible for an automatic charger to work for each chemistry properly. It will be interesting if the new Fenix multi-charger has similar issues.


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## HKJ (Oct 13, 2013)

Mr. Tone said:


> Thanks for the great review. I was waiting to see it and am glad I waited. I am curious if it is possible for an automatic charger to work for each chemistry properly. It will be interesting if the new Fenix multi-charger has similar issues.



It is possible to make a good charge with automatic selection between LiIon and NiMH. It is not that easy to make a prober termination on NiMH, when you have to handle all sizes and ages of NiMH also at low currents.

The Fenix charger looks like the Thrunite MCC-4.


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## yellow (Oct 13, 2013)

HKJ said:


> the usb output is active. To activate the output slot #4 must have a charged LiIon battery, power must be disconnected and the button must be pressed for some time.



which makes the "_USB-output_" as useless, as with the XP2
(which I have and like)
what mind does such an "output" come from?

XTar:

keep that joke of an USB output, for times when there is no wall outlet available AND
*ADD a real USB output when charger is connected to the grid*


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## HKJ (Oct 13, 2013)

yellow said:


> which makes the "_USB-output_" as useless, as with the XP2



Calling it useless is a bit hard, but it would be more useful if it was also powered when mains is connected.

You can get usb power boxes where the output is active when mains is connected and they are much easier to travel with, than this charger.


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## sbbsga (Oct 13, 2013)

Thank you both HKJ and gopajti. 

I have been using mine for about two weeks now. It is a relief to know that charging 18650's at 0.25A is okay because I sometimes still forget to change the setting at powering on - got used to WP2 II. I was afraid it could have wrong termination or over charging or something bad, because the lights turned green as soon as I switched to 1A when I finally realized the lower setting. But nothing got warm, battery voltages were okay, only awfully long charging time. 

My only tiny complain is, like my WP2 II's, the sliders were very rough out of the box, so I had to apply some lubricant and all is good now. :twothumbs


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## yellow (Oct 13, 2013)

thats correct, but I would have to bring them - as well as the charger I would also bring,
as well as the charger for the cellphone, and ...

If that USB output were a "real" one, it were only one device
(so I hope that feature will be added sometimes - but to the smaller XP2, or its following ones)


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## netprince (Oct 13, 2013)

Thanks for the very informative review.


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## Mr. Tone (Oct 13, 2013)

HKJ said:


> It is possible to make a good charge with automatic selection between LiIon and NiMH. It is not that easy to make a prober termination on NiMH, when you have to handle all sizes and ages of NiMH also at low currents.
> 
> The Fenix charger looks like the Thrunite MCC-4.



Yeah, I can see why it would be hard to handle the various nimh sizes/capacities automatically. I thought the Fenix looked familiar


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## samgab (Oct 13, 2013)

Your reviews are always outstanding, and getting even more so, with the thermal images etc. Good Work! Can't wait to see a review from you of the Maha C9000 and the SkyRC NC2500.


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## candle lamp (Oct 14, 2013)

Thanks a lot for another excellent review. HKJ! :thumbsup:

As far as I remember, you've first measured the temp. on the XP4 charger itself. Is it the deliverate attempt to measure the temp. or did you feel the necessity to measure it due to the unexpected temp. in your hand?

This is not all-around charger for Ni-MH batteries. Hope and believe they will release the upgraded version in the future.


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## HKJ (Oct 14, 2013)

candle lamp said:


> As far as I remember, you've first measured the temp. on the XP4 charger itself. Is it the deliverate attempt to measure the temp. or did you feel the necessity to measure it due to the unexpected temp. in your hand?



I saw a lot discussion on how hot chargers get and decided to include some temperature measurements in my reviews. 

First I made a adapter to measure battery temperature:




And then I got my hands on a thermal imager.

I have been very busy with this and Xtar XP4, Efest BIO V2 and ThruNite MCC-4 all got everything.
On request I am doing a few older chargers, but only with the thermal images, not with the logging and I do not change the review, only add the images (Until now I have only added thermal images to i4 V2).

They do each serve a purpose:
The sensor can be included in the logging and shows when the battery gets hot (With NiMH it also shows when the battery is full).
The thermal imager shows the temperature of everything, but only at discrete time intervals (I uses between 10 and 30 minutes) and then I pick the hottest one for my review.


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## candle lamp (Oct 14, 2013)

Thank you for your detailed reply.


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## netprince (Oct 25, 2013)

I have an xp4 and can confirm early termination on my eneloops. I tried restarting charger by power cycling the charger and it terminates quickly as if the cell is fully charged.


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## sbbsga (Oct 26, 2013)

I have been using mine daily since October 3rd. Unfortunately, I have to return it as the top and bottom panels, at the bottom right corner, have split apart. I suspect the strong springs caused it. 

According to my dealer, this is the second unit that has this issue.


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## shelm (Oct 26, 2013)

sbbsga said:


> the top and bottom panels, at the bottom right corner, have split apart. I suspect the strong springs caused it.



penals? at a corner? split apart? 


sure. 
whatever.


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## sbbsga (Oct 26, 2013)

shelm said:


> penals? at a corner? split apart?
> 
> 
> sure.
> whatever.









Here is the photo. Top and bottom panels, split apart at the bottom right corner. Sorry if this is still confusing. Anyway, the context was, the charger failed structurally, could be on any other side, photo or not. I hope yours will not end up like this if you have one or more.


Sent from mobile device.


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## Dirtbasher (Oct 27, 2013)

sbbsga said:


> Here is the photo. Top and bottom panels, split apart at the bottom right corner. Sorry if this is still confusing. Anyway, the context was, the charger failed structurally, could be on any other side, photo or not. I hope yours will not end up like this if you have one or more.
> 
> 
> Sent from mobile device.



The same thing happen with my NiteCore i4 charger due to tight tension on the springs , I just superglued mine.


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## sbbsga (Oct 27, 2013)

Dirtbasher said:


> The same thing happen with my NiteCore i4 charger due to tight tension on the springs , I just superglued mine.



I thought about that too. Anyway, if the replacement opens up, I would just fix it myself or I could just glue them right out of the box. 

We'll see.


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## shelm (Oct 27, 2013)

Now i am getting it. Of course. Thanks for sharing the photo!

Aren't the panels held together with 4 screws?


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## sbbsga (Oct 29, 2013)

shelm said:


> Now i am getting it. Of course. Thanks for sharing the photo!
> 
> Aren't the panels held together with 4 screws?



I thought the screw at that corner was undone but it was fully tightened. 


Sent from mobile device.


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## sbbsga (Nov 2, 2013)

Unfortunately, the replacement failed at the same corner too. :shakehead I will just glue them up this time.

[UPDATE: 13.11.2013]
It was the right side that split. Now, the left side. Not so apparent because the right corner has been glued but gap widens when that corner is loaded up. 

I hope XTAR responds to this issue, it cannot be an isolated case as this is my second unit which replaced the first one that have the same problem. Cost of shipping will be raking up if I am suggested to keep shipping damaged units back.


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## Ares (Nov 19, 2013)

Anyone know if they fixed the NiMH issue in the production model??


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## thedoc007 (Nov 19, 2013)

Ares said:


> Anyone know if they fixed the NiMH issue in the production model??





HKJ said:


> The charger was supplied by Xtar for a review, I believe it is the second production batch.



Um, this was a review of a production version, not a prototype or engineering sample.


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## ggroyal1117 (Dec 2, 2013)

This charger does a great job charging my Sanyo XX eneloop 2450ma AA nimh batteries. They are barely warm at end of charging. I charge them at .5 amps.
No problems charging 14350, 18650, and 26650 li-ion batteries. I have not tried the USB port.
I have not seen any cracks or separations on the case. Also, I have the Xtar VP1 and SP2 chargers.


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## shelm (Dec 2, 2013)

ggroyal1117 said:


> They are barely warm at end of charging. I charge them at .5 amps.



du
:shakehead


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## ggroyal1117 (Dec 2, 2013)

I charged my 160mah single cell lipo batteries for my nano quadcopter using a 4000mah 26650 4seven li-ion battery in slot four.
The Eflite single cell lipo charger plugs into the USB port.

Thanks for the excellent review of the Xtar XP4 charger.


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## lowks (Dec 2, 2013)

There is a new revision of this charger which has been released to the market and according to the marketing person, they have and I quote "XP4's inductance has been changed in new version and can be cooler about 10℃."

I believe this is rev 4


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## RI Chevy (Dec 3, 2013)

How would one know what version you are buying? Any markings on the box or on the charger itself?


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## shelm (Dec 4, 2013)

lowks said:


> There is a new revision of this charger which has been released to the market and according to the marketing person, they have and I quote "XP4's inductance has been changed in new version and can be cooler about 10℃."
> 
> I believe this is rev 4



can you please post a new review of the new version?


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## HKJ (Dec 4, 2013)

shelm said:


> can you please post a new review of the new version?



I do not have the new version, but maybe I will ask Xtar about it, but not right now (they have just shipped some other chargers to me).


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## lowks (Dec 4, 2013)

RI Chevy said:


> How would one know what version you are buying? Any markings on the box or on the charger itself?



From what I can see, I don't see any markings on the charger's casing itself indicating the version of the charger. Probably the PCB inside would have some sort of marking.


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## RI Chevy (Dec 5, 2013)

OK. Thank you for the heads up.


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## viperxp (Dec 6, 2013)

I will have the latest XP4 version hopefully within a week. I can post a review of the charger. It will not be as half as technical and profound as HKJ's one, but it will answer some interesting questions. Are you guys interested?


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## shelm (Dec 6, 2013)

viperxp said:


> I will have the latest XP4 version hopefully within a week. I can post a review of the charger. It will not be as half as technical and profound as HKJ's one, but it will answer some interesting questions. Are you guys interested?



a tear-down would be helpful to demonstrate that you have the latest production iteration


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## viperxp (Dec 6, 2013)

shelm said:


> a tear-down would be helpful to demonstrate that you have the latest production iteration



If I will make a review, I will surely disassemble the charger.


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## ggroyal1117 (Dec 7, 2013)

I use Dr. Marty's conductive grease to lubricate the slides.

http://www.bigsquidrc.com/dr-martys-easy-on-conductive-grease-review/


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## RI Chevy (Dec 7, 2013)

Also some diaelectric grease or Super Lube!


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## rlapporte (Jun 26, 2014)

I realize that this thread is a bit old, but I was trying to research the right current to use for charging my lithiums in my new XTAR VP2 and this thread touches on it. I assume I should be using 0.25A for 18350 and RCR123. The owner's manual states that you should use 0.25A up to 18700 but it takes forever to charge my 18650 at 0.25A.

Several concerns...

I'm most concerned with safety. Is there any risk to charging at 0.25A? As I understand it, it can be risky to undercharge a cell because the charger doesn't recognize when it's fully charged.

My next concern is long term battery life. If I charge at 0.50A or 1A, am I shortening the life expectancy?

Of course, I'd love to charge the batteries faster, but not if safety or battery life would be compromised.

And on the topic of charging faster, I'd love a 4-cell charger that is just as good. In reading the reviews, I'm not sure that anything else out there compares to the XTAR. Will the XP4 be the next best thing if I wanted to charge 4 simultaneously?

Thanks


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## HKJ (Jun 26, 2014)

rlapporte said:


> I realize that this thread is a bit old, but I was trying to research the right current to use for charging my lithiums in my new XTAR VP2 and this thread touches on it. I assume I should be using 0.25A for 18350 and RCR123. The owner's manual states that you should use 0.25A up to 18700 but it takes forever to charge my 18650 at 0.25A.



Check the VP2 review, it has a table with my recommendations for current settings for different battery sizes.




rlapporte said:


> I'm most concerned with safety. Is there any risk to charging at 0.25A? As I understand it, it can be risky to undercharge a cell because the charger doesn't recognize when it's fully charged.



That is for NiMH, with LiIon the only risk is that you fill the cell a bit more and get shorter battery lifetime due to that.



rlapporte said:


> My next concern is long term battery life. If I charge at 0.50A or 1A, am I shortening the life expectancy?



As long as you stay below the batteries rated charge current, it will last the rated 300 or 500 cycles.



rlapporte said:


> Of course, I'd love to charge the batteries faster, but not if safety or battery life would be compromised.



Batteries usual has two charge rating. A low one (Usual between 1A and 2A for 18650) that means it will last the rated number of cycles and the highest safe charge rate, but with reduced lifetime.



rlapporte said:


> And on the topic of charging faster, I'd love a 4-cell charger that is just as good. In reading the reviews, I'm not sure that anything else out there compares to the XTAR. Will the XP4 be the next best thing if I wanted to charge 4 simultaneously?



There is a couple of LiIon chargers that can works fine with 4 channels, XP4 is one of them.


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## ven (Jun 26, 2014)

I use 0.25 and 0.5A settings for my 16340 cells ,i would not use the 1A as imo a bit too much,however if you require a quicker charge 0.5A should be fine(has been for me).

I use the 0.25A setting for my 10440 cells mainly.


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## rlapporte (Jun 27, 2014)

Thanks to both of you for your quick replies. So it looks like I can safely go up to an amp, even up to 1.7 amps if the charger allows for it. Very different from the chart in the Xtar manual. So HKJ, do you have a favorite 4-bay unit? I don't really care if it also does NiMH, as I already have a Maha. I'm looking for a way to quickly (and safely) charge my 18650s, 18350s, and CR123s. Considering the Xtar XP4 and the Jetbeam i4 pro, but I'm open to others. Thanks for all of your help on this.
Best,
Rob


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## HKJ (Jun 27, 2014)

rlapporte said:


> Thanks to both of you for your quick replies. So it looks like I can safely go up to an amp, even up to 1.7 amps if the charger allows for it. Very different from the chart in the Xtar manual. So HKJ, do you have a favorite 4-bay unit? I don't really care if it also does NiMH, as I already have a Maha. I'm looking for a way to quickly (and safely) charge my 18650s, 18350s, and CR123s. Considering the Xtar XP4 and the Jetbeam i4 pro, but I'm open to others. Thanks for all of your help on this.



Take it easy, 1.7A may be to high, depending on the battery.

Generally I like Xtar very much for LiIon chargers, they may not always be perfect, but they are never bad.
Soshine has a 4 bay unit, but due to temperature it might be best to limit it to 3 cell.
ThruNite (And Fenix) does also have a decent 4 bay unit.

There is also a Opus 4 bay analyzing charger (BT-C3100), it is not perfect and definitely not a perfect charger, but the total package is acceptable, due to the analyzing function.

I have done a review of all of them, where you can see more details.


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## rlapporte (Jun 27, 2014)

thanks. I read your reviews, and they are amazing...but I'm still left wondering which one I should get  I'll reread them and figure it out. I see you didn't mention the i4. Is it not in the same league as the others you mentioned?

The reason I mentioned 1.7 amps is because I read that 0.5c is acceptable and I have some 3400's.

Best,

Rob


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## HKJ (Jun 27, 2014)

rlapporte said:


> I see you didn't mention the i4. Is it not in the same league as the others you mentioned?



Generally I do prefer non pulsing LiIon charger.
I am working on the 2014 version off the i4, look for the review in a few weeks.



rlapporte said:


> The reason I mentioned 1.7 amps is because I read that 0.5c is acceptable and I have some 3400's.



0.5C is not acceptable for all cells, for Panasonic 3400mAh it is acceptable, but not for 2900 and 3100mAh cells.


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## rlapporte (Jun 27, 2014)

I see. So there's obviously not a general rule that will allow you to calculate the ideal charge current based on the capacity. Bummer.
Looking forward to your review


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## HKJ (Jun 27, 2014)

rlapporte said:


> So there's obviously not a general rule that will allow you to calculate the ideal charge current based on the capacity.



No. Once it was 1C and that is still a good guess for smaller cells. For 18650 the safe value is 1A.
Reading some data sheets may increase the charge current significantly for many cells, some high current cells can be charged at 2C (Price is reduced lifetime).


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## rlapporte (Jun 30, 2014)

HKJ said:


> No. Once it was 1C and that is still a good guess for smaller cells. For 18650 the safe value is 1A.
> Reading some data sheets may increase the charge current significantly for many cells, some high current cells can be charged at 2C (Price is reduced lifetime).



Thanks so much.


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## Sethaas (Sep 15, 2014)

viperxp said:


> I will have the latest XP4 version hopefully within a week. I can post a review of the charger. It will not be as half as technical and profound as HKJ's one, but it will answer some interesting questions. Are you guys interested?


Hi Viperxp

This thread has probably been abandoned for good, but I'm interested to know if your unit has the problems that HKJ pointed out? Thanks!


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## espresso (Sep 27, 2014)

I received the charger today and noticed Sanyo XX was getting too warm at 1A. It had 57°C (134F) when I decided to terminate the charge. I'll see how NiMH batteries do in the following days. 

Efest IMRs worked fine with 4,16V just after the charge finished, followed by a drop to 4,15V moments later. They had around 40°C at 4x1A which is 2-3 degrees hotter then Intellicharger i4 at 4x375mA. That looks ok.


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## HKJ (Sep 27, 2014)

espresso said:


> I received the charger today and noticed Sanyo XX was getting too warm at 1A. It had 57°C (134F) when I decided to terminate the charge. I'll see how NiMH batteries do in the following days.



You will often get a fairly hot battery just before the charger terminates, due to the way -dv/dt works.


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## kreisl (Sep 27, 2014)

HKJ said:


> You will often get a fairly hot battery just before the charger terminates, due to the way -dv/dt works.



with some chargers the cell gets hot around the top part because of plain heat conduction lambda from the hot positive terminal to the cold battery


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## espresso (Sep 27, 2014)

Ok, it has just finished charging four Eneloops at 1A and the temperatures at the end of the charge were 71C (160F) in the upper half of each of the first three cells, vs 64C (147F) in their lower halves. An exception was the cell furthest to the right which had 64C in the upper half (didn't get the lower half of it).

So this charger will destroy your NiMH cells, in short. I'm certainly never going to use it again on 1A with NiMH cells. I will try lower modes with AAA and AA, however.

The problem is that the positive terminals, as kreisl mentioned, transfer insane amount of heat to the batteries. The terminals are still very hot minutes after removing the cells... 
I'm just not sure how this heat transfer doesn't affect Li-ions... It could be that the electronics don't get as hot when the charger outputs higher voltages needed for li-ion (due to reduced power dissipation of some sort), or the larger 18650s simply absorb the heat better with their volume. 

Intellicharger i4 still remains the safer charger out of the two. But I just can't tolerate slow charging speed so I can put XP4 to better use.


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## HKJ (Sep 27, 2014)

espresso said:


> The problem is that the positive terminals, as kreisl mentioned, transfer insane amount of heat to the batteries. The terminals are still very hot minutes after removing the cells...



The charger often heat the cells, but the 71C temperature you get would probably be from the -dv/dt termination.
But the XP4 do get fairly warm when charging.



espresso said:


> Intellicharger i4 still remains the safer charger out of the two. But I just can't tolerate slow charging speed so I can put XP4 to better use.



Because i4 is charging at a low current the temperature raise will be lower and it does also use voltage termination with eneloop.


The best way to keep the batteries cool at the end of the charger is to termination before the batteries are full as a lot of chargers do. I.e. if you want cool batteries go after a charger with voltage termination, if you want full batteries go after a charger with -dv/dt termination.
A charger with a fan can keep the temperature lower, but a -dv/dt termination will still get warm.


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## espresso (Sep 27, 2014)

While I do agree that dv will cause higher temperatures than peak voltage termination, I cannot accept that 0,5C charging rate with properly implemented dv can cause temperature as high as 70ºC.

For instance, GP "Smart 2" charger that applies 2A to the cells, plus transfers a great deal of it's own heat to them, leaves the same cells at 60ºC at the end of charge. And this is a complete charge (maybe 50mAh less than the full capacity which is acceptable for 1 hour charger).

But XP4 takes it to a new level, it toasts cells 10ºC hotter at half the rate


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## espresso (Sep 28, 2014)

Here are my final observations about this charger. 

Charger terminals at 1Amp are very hot to the touch (no matter what battery you're charging). You'll burn your finger if you keep it on the terminal for longer than a second. This is definitely the reason why it heats up batteries so badly.

The only thing stopping 18650 from getting toasted is 18650's big volume. It's a massive cell which spreads heat across itself very good so contact area between charger's positive terminal and battery pole just isn't enough to transfer more heat. 
But that cannot be said for smaller AA batteries. They're unable to get rid of the heat transferred by the charger, plus they warm up more than Li ions during charging. 
I suppose, if you tried charging smaller li ions at the highest current setting, things would not look so good.

Why is it so hard to make a charger that doesn't heat up the batteries. They could have used wires to connect the terminals to the pcb instead of directly soldering terminals onto pcb. That's what's killing this otherwise great charger. 


One more observation is that when a li ion cell is charged alone, it will receive a slightly more complete charge (4,19 vs 4,17 in the charger). If more than one cell is being charged, the charger is not able to maintain 4,19V constant voltage, and terminates at 4,17.

Charging four AA Eneloops at 500mA produced safe temperatures - around 40C at the end of the charge. But this charging rate is useless because I also experienced early termination. Eneloops charged this way yielded 1170, 1350, 1450, 1420 mAh (tested by c9000). I must say that my BC700 completely charges Eneloops at 500mA without a problem. 

As for 4xAAA (eneReady) at 500mA, the hottest one had 57C at the end. If I charge only one AAA, the temperature is 37-40C. 

I really hoped this charger could be the one. 
But instead of making a charger that helps take away heat from the cells, they made one that feeds the heat. I have no choice but to continue piling up chargers in search for the ideal one.


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## kreisl (Sep 28, 2014)

i have the XP4 too, i like its compact size, fits in my pocket, so i gave it to my neighbor. the last time i checked there was a crack in the plastic and she didn't know what had happened there. thanks for the report, i agree it is pretty the ideal one if it were any better.


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## teacher (Nov 14, 2014)

I know this is an old thread, but I have a question. 
Is the XP4 Panzer an upgrade to the XP4 that this review concerns? In other words have the NIMH concerns mentioned in this review been addressed in the XP4 Panzer model?
I realize Xtar now has a XP4c model but I am wondering about the "Panzer" model.
Thanks in advance............


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## HKJ (Nov 14, 2014)

teacher said:


> I know this is an old thread, but I have a question.
> Is the XP4 Panzer an upgrade to the XP4 that this review concerns? In other words have the NIMH concerns mentioned in this review been addressed in the XP4 Panzer model?
> I realize Xtar now has a XP4c model but I am wondering about the "Panzer" model.
> Thanks in advance............



The XP4 was updated after my review according to Xtar.


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## espresso (Nov 14, 2014)

teacher said:


> I know this is an old thread, but I have a question.
> Is the XP4 Panzer an upgrade to the XP4 that this review concerns? In other words have the NIMH concerns mentioned in this review been addressed in the XP4 Panzer model?


I bought it two months ago, they haven't touched it. It's a wreck when it comes to NiMH. You can read my observations, too.


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## magellan (Nov 14, 2014)

Awesome review, thanks. Looks like I'm about to buy my fifth Xtar charger, despite the few problems, such as with the NiMH cells which I'm not worried about since I use my SkyRC charger with the remote iPhone app for those.


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## magellan (Nov 14, 2014)

Hi HKJ,

Unless I have detailed knowledge of the particular cell (a work in progress ) I usually just charge at 1/4C or less as others here have said. Even considering most capacities are overstated that means I'm unlikely to be charging at more than 35 or 40% of C and hopefully less if the capacity rating is more or less accurate. I don't need to "hot rod" the charger because I always have extra backup cells. I'm okay if it takes four hours for a charge. Do you see anything wrong with this approach as a general rule?



HKJ said:


> No. Once it was 1C and that is still a good guess for smaller cells. For 18650 the safe value is 1A.
> Reading some data sheets may increase the charge current significantly for many cells, some high current cells can be charged at 2C (Price is reduced lifetime).


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## BillSWPA (Nov 14, 2014)

HKJ, I just followed the link in your signature to your website. It is now bookmarked for a lot of future reading the next time I need to buy something. Thank you for putting all of this information together.


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## HKJ (Nov 15, 2014)

magellan said:


> Hi HKJ,
> 
> Unless I have detailed knowledge of the particular cell (a work in progress ) I usually just charge at 1/4C or less as others here have said. Even considering most capacities are overstated that means I'm unlikely to be charging at more than 35 or 40% of C and hopefully less if the capacity rating is more or less accurate. I don't need to "hot rod" the charger because I always have extra backup cells. I'm okay if it takes four hours for a charge. Do you see anything wrong with this approach as a general rule?



No, it is a good rule as long as you have the time.
1/4C will usual be around 4½ to 5 hours due to the CV phase.
Quality batteries is fairly accurate in their capacity specification, but you might not run them empty when using them.


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## magellan (Nov 15, 2014)

Thanks, HKJ, I appreciate the help as I'm still figuring all this stuff out. Plus I'm thinking a 1/4C charge shouldn't present much of a thermal problem, especially since the thermal issues discussed here marred what otherwise seemed an excellent charger.

I also find it eye opening that not all Pannie's or Sanyo's can handle 1/2C or more. I just thought it was the Chinese cheapo's you had to worry about. I'm going to have to start taking notes on each cell type I own.

I also try to prematurely terminate the charge since the final topping charge phase is stressful for a lithium ion battery and they don't have memory problems like other chemistries if you do this. That means reduced run time but then I usually recharge every night or other night so that's not a problem. I rarely run a cell below 30% of capacity before recharging.


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## teacher (Nov 15, 2014)

Thanks for the replies HKJ & magellan..........


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## WhitedragonBC (Feb 27, 2015)

Were the nimh bugs in this ever fixed?


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## HKJ (Feb 27, 2015)

WhitedragonBC said:


> Were the nimh bugs in this ever fixed?



According to Xtar they did improve it, but I did never get a new one for review.


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## SVT-ROY (Jun 1, 2015)

I purchased on about 2 months ago. It was taking forever to charge the Duracell ion core AAs so I decided to look it up and found this thread. Should I use the factory Duracell charger ? I'm thinking that would be smart....


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## HKJ (Jun 1, 2015)

SVT-ROY said:


> It was taking forever to charge the Duracell ion core AAs so I decided to look it up and found this thread.



If the cells gets warm after some time, it has missed termination.




SVT-ROY said:


> Should I use the factory Duracell charger ? I'm thinking that would be smart....



There is no reason to get a charger from the same brand as the batteries.

I do not know how good Duracell chargers are, but I may look at them later on.
Energizer makes some bad chargers, Panasonic makes some good chargers.


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## SVT-ROY (Jun 1, 2015)

You are definitely on top of your game and we are lucky to have you. I'll do some research on a kick butt nimh charger. My thoughts were anything is better than getting half my mah. Am I reading the chart correctly? I see that .5 amps is OK for aaa, would 1a be OK for aa? I would like to get close to the 2000mah of the cell. 

This just got me thinking on the XP4c that somehow (OK probably me), got powered by my dirt devil power ac cord trying to charge a single olight 18650. The charger stays on red light always now and I'm afraid to use it. It wasn't hot and the battery was charged but I didn't check voltage like an idiot. I'm thinking of testing it to see if it's putting out volts, amps, whatever. Thoughts? Other than my stupidity haha.


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## HKJ (Jun 1, 2015)

SVT-ROY said:


> Am I reading the chart correctly? I see that .5 amps is OK for aaa, would 1a be OK for aa?



Yes and yes.



SVT-ROY said:


> This just got me thinking on the XP4c that somehow (OK probably me), got powered by my dirt devil power ac cord trying to charge a single olight 18650. The charger stays on red light always now and I'm afraid to use it. It wasn't hot and the battery was charged but I didn't check voltage like an idiot. I'm thinking of testing it to see if it's putting out volts, amps, whatever. Thoughts? Other than my stupidity haha.



That power supply cannot be used with Xtar chargers, it will prevent them from working properly and it might damage them.
The problem is the "Output: 7-25V", it must be "Output: 12V" and current must be between 1A or more, not 130mA (That is the same as 0.13A).


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## Octavian (Jul 28, 2015)

My xp4 does not charge at 4.2V, it stops at 4.15V. Till now I charged few IMRs 16340 and a 14500, all cells were charged only at 4.14-4.15V...
With IMRs I tried all currents but the result is the same.
Has anyone noticed this or my charger have a problem? 

With Trustfire TR001 takes a eternity to charge a 18650 cell, but always finish at 4.2V (also with 16340 or 14500 )


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## HKJ (Jul 28, 2015)

Octavian said:


> My xp4 does not charge at 4.2V, it stops at 4.15V.



Does it?
Most people takes the battery out when charging is done and then measures the voltage, that value is not the charge voltage!

Even if you measured the voltage with charge current on it is within acceptable limits.


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## kreisl (Jul 28, 2015)

Octavian said:


> Has anyone noticed this or my charger have a problem?
> 
> With Trustfire TR001 takes a eternity to charge a 18650 cell, but always finish at 4.2V (also with 16340 or 14500 )



You're taking the 18650 cell out of TR001 and your multimeter reads 4.2V offline voltage?
You're taking the 18650 cell out of XP4 and your multimeter reads 4.14V offline voltage?
So *same procedure*, just different charger, and you're getting a 0.06V difference in the offline readings - that's what you're saying? :thinking:


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## Octavian (Jul 29, 2015)

Yes, after charge with TR001, the multimeter read exactly 4,2V (like a said, take an eternity to charge a 18650 cell, but fully charged multimeter read 4,2V).

With XP4 read 4,14-4,15V . I measured the cell and was 4,15V ok...I put it again in charger, I know that can charge even if the led is green, after aprx one hour was 4,11V... 

And one more thing, without cell, charger XP4 measure 4,75V to all slots. At TR001 and one more no name charger also 4,2V (also this no name LiIon charger finish at 4,2V)


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## Octavian (Jul 29, 2015)

HKJ said:


> Does it?
> Most people takes the battery out when charging is done and then measures the voltage, that value is not the charge voltage!
> 
> Even if you measured the voltage with charge current on it is within acceptable limits.



I describe how I make the measurements.

I dont have the possibility to measure the capacity, there is any chance that voltage to be lower but the capacity to be greater after charging with XP4...?


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## HKJ (Jul 29, 2015)

If the batteries are on 4.2 volt after been taken out of the charger, the charger is overcharging them a bit.


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## Octavian (Jul 29, 2015)

Mmmmm... I didn't know this. 
Thank you for this info, because it came from you I take it as a reliable information.

PS: like many others I read a lot of your reviews (some of them two-three times ) , great job ! :thanks:


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## HKJ (Jul 29, 2015)

Octavian said:


> Mmmmm... I didn't know this.
> Thank you for this info, because it came from you I take it as a reliable information.



If you check my battery and charger reviews you will always see the battery voltage drops when the charger is done, how much varies.
The nominal charge voltage for LiIon batteries is 4.20 volt, i.e. the cannot be on 4.2 volt when charging is finished, except the charger finish at a higher voltage. It might be within the allowable limit: 4.25 volt (A few batteries do have a stricter limit).


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## kreisl (Jul 31, 2015)

HKJ said:


>



For the 'Average current' line, do you create an Excel moving average column in your spreadsheet?
How many preceding data points does it average, or also succeeding ones?

Great graphs, great charger!


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## HKJ (Jul 31, 2015)

kreisl said:


> For the 'Average current' line, do you create an Excel moving average column in your spreadsheet?
> How many preceding data points does it average, or also succeeding ones?



I do not use Excel for this, but I uses a moving average, usual about 1 minute or 60 date point.


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## kreisl (Jul 31, 2015)

HKJ said:


> moving average, usual about 1 minute or 60 date point.



my logger record 2 date point per seconds, so i'll try moving average of 120 date point thank.

OT on--

EDIT: here is my result, 
MovingA21 = moving average for time t, with 10 date points before (5sec), 1 date point at t proper, and 10 date points after (5sec); basically a "10.5sec average".
MovingA121 = moving average for time t, with 60 date points preceding (30sec), 1 date point at t proper, and 60 date points succeeding (30sec); basically a "60.5sec average"





















Prize question is: If the user sets the discharge current to -500mA and hence believes that the charger discharges with 0.500A, could the above erratic *graph of the actual discharge current* (as measured by a logging multimeter in series) be classified as "acceptable/good"? Assume that the charger uses this current to determine the discharge capacity.

--OT off


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## WarriorOfLight (Oct 20, 2015)

I read the thread and also the Feature description on the Xtar site, but my question is not answered. 

Does the XP4 Support charging @1A on all 4 channels at the same time?


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## HKJ (Oct 20, 2015)

WarriorOfLight said:


> I read the thread and also the Feature description on the Xtar site, but my question is not answered.
> 
> Does the XP4 Support charging @1A on all 4 channels at the same time?



Yes, if you check my curve with 4xPA18650-31 it says 1A charging.


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## TinderBox (UK) (Oct 22, 2015)

Hi. Henrik

Not to be patronizing, but i saw this yesterday and thought i would share it, you most likely already know.

*How NOT To Blow Up Your Oscilloscope! *

https://www.youtube.com/watch?v=xaELqAo4kkQ

John.



HKJ said:


> Yes, if you check my curve with 4xPA18650-31 it says 1A charging.


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## HKJ (Oct 22, 2015)

TinderBox (UK) said:


> Not to be patronizing, but i saw this yesterday and thought i would share it, you most likely already know.
> 
> *How NOT To Blow Up Your Oscilloscope! *




When working with electronic you better learn that kind of stuff very fast or it can be expensive. There is a couple of ways to get around it, some of them very unsafe.
One of the simple ways is to use my picoscope with a battery powered laptop, but it is only safe for low voltage.
For higher voltages I have probes with galvanic isolation.


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## hammerjoe (Nov 30, 2015)

Is this Vp4 and the VP4 Panzer the same charger?

I am looking for a charger that can be used in the car and I was considering the VC4 that allows two slots at 1A when I found this VP4 panzer that can do 1A on all four slots.

HJK you wouldnt know if the [email protected] also works with a car charger? I am guessing that it does but better get the answer from someone that knows about this stuff.
Also this review of yours show really bad performance for NIMH batteries. Has this been corrected or was it just a glitch with your unit?


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## Octavian (Jan 24, 2016)

The chargers are one and the same ( XP4 Panzer or simple XP4).

It was never fixed, its like in HKJ review regarding NiMh, AA are nearly ok charged at 1A and AAA nearly ok at 0,5A and because of high current the batts became real hot and the charger have a melting smell...

Even for LiIon from my view is not the best charger, usually the LiIon (all types) batts freshly charged measure somewhere between 4,08V-4,11V...not even close to 4,2V.

Half an year ago (when was almost new) the cells freshly charged measured about 4,14V, now after half an year (not hardly used !) I'm happy when I see 4,11..4,12V... *Usually it stops at 4,08V* when I charge 4x18650 eben with 0,5 even with 1A, same result. :scowl:


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