# Test/Review of Charger Efest LUC V4



## HKJ (Dec 14, 2013)

[SIZE=+3]Charger Efest LUC V4[/SIZE]

[size=+2]Efest has modified this charger and a update review has been published[/size]



















Efest has been building a line of chargers from single cell to four cell with fixed and variable current, this is a 4 channel LiIon charger with 3 charge currents.










The charger comes in a brown cardboard box with a list of supported batteries.






In the box is the charger, a power supply and a manual.






The charger is powered from 12 volt and has an usb output. The usb output can only be activated when no power is connected to the input.






At 0.5 and 1A current the charger can charge 4 batteries. The two arrows are animated while charging.
The voltage display shows the battery voltage (The 8 is due to mixing of digits during long exposure, not because the display showed 8).
Below the display under the word "Charger" is the button, it is used to select charge current and to activate usb output (when possible).







At 2A current only the two center slots can be used, this is clearly illustrated on the display.






Usb output uses a icon in the center. This does not indicate what slot to use (It is slot #2).









The sliders for the battery work smoothly and can accept batteries from 30mm to 70.5mm.






Between the batteries is a list of supported battery sizes, but the 10440 size is only valid for IMR cells.





























The charger can handle 70 mm long batteries including flat top cells.
The charger is rated for 10440 batteries, but due to the charger current it is only recommended to charge IMR 10440.
Note: Using to high charge current will not make the batteries explode, but will reduce lifetime of the batteries.



[SIZE=+2]Measurements[/SIZE]

[SIZE=+1]LiIon at 4.2V (ICR/IMR)[/SIZE]



When not connected to power it will discharges with up to 0.09mA, except the USB out channel that will discharge with 0.15mA. 
When the battery is full the charger will discharge with about 0.1mA. 
If the voltage drops below 4.05 volt the charging will restart. 
Power cycling or reinsertion of the battery will restart charging. 
At about 0.65 volt the charger will detect a battery and start charging with 150mA 
The current will drop to 60mA at 3 volt, where the full charge current is applied. 
The voltmeter is limited to 4.2 volt, if the voltage get much above 4.2 volt it will show 0.0 volt. 
The voltmeter shows about 0.06 volt to low. 
The channels on the charger are independent, i.e. there are small differences between them. 







The charger does a good CC/CV charge curve with a good termination current, but it charger to 4.28 volt, not 4.20 volt (Maximum 4.25 volt), this is not good.






With 1A it is exactly the same, very good CC/CV charge curve, but to high a voltage.






It looks like the over charge protection in the 2600mAh cell tripped (The other cells I test with are unprotected).






The 3400mAh is exactly the same as the 3100mAh cell, to high charge voltage.






With 2A current and a Efest 26650, the result is again the same. The termination is slow, probably due to the high voltage.






With my old IMR 16340 cell the termination is also slow.














The other 3 slots looks close to the first slot, all slots are over charging.











M1: 39,1°C, M2: 40,9°C, M3: 40,2°C, M4: 40,2°C, M5: 41,5°C, HS1: 57,2°C

The heat from the charger is distributed fairly even across the batteries.











The charger does slowly ramp the current to the selected charger current, changing the selection will start a new ramp from 0.



[SIZE=+1]USB output[/SIZE]



When using usb output, the symbol will flash when the battery is nearly empty 
When usb output is on, but unloaded, it will draw about 12mA. 
Usb output turns off after about 30 seconds with a load below 30mA. 
It is not possible to turn off the usb output with the switch. 
When mains power is connected, the usb output is off. 
Usb output is coded as Apple 1A 
Usb output will turn off when overloaded 







As usual I do a load sweep first, to see how the output works at different loads. The LUC turns off at 1.15A, this is good for a 1A rated output.






Only one battery is used for usb output (Slot #2), here I am running with a 0.5A load, the output turns off when the battery is down to just over 3 volt. The efficiency is good at 85% to 90%.






2600mAh has shorter runtime.






3400mAh has longer runtime.






Increasing the load to 1A, show that the output has some trouble just before the battery is empty.






With 7mV rms noise and 108 mV peak-peak noise the output voltage is good.






With 1A load the rms noise increases to 9mV and the peak-peak to 110mV, again a good value. The trouble just before the battery is empty will, of course, have *much* higher noise.


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 uses the correct algorithm has a good termination current and I like the design, but the high charge voltage is not acceptable.
The usb output does also work fine, but I do not know how much use it is in this type of charger. If it had been power when the charger was powered, it would probably be more useful.

If Efest fixes the high charge voltage it will be a good LiIon charger, but before that happens it is not very good.



[SIZE=+2]Notes[/SIZE]

The charge was supplied by Efest for 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 and chargers


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## TEEJ (Dec 14, 2013)

Excellent review Sir!

Good catch on the over charging....hopefully they will reexamine that and make the appropriate changes, and then have you re-review it when the corrected version is available.

:thumbsup:


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## shelm (Dec 14, 2013)

HKJ does not do re-reviews 

:thumbsup:


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## HKJ (Dec 14, 2013)

shelm said:


> HKJ does not do re-reviews
> :thumbsup:



Sometimes I do, but for this problem here it is hardly necessary to do a new review.
The problem is probably due to random variations in the used reference and only a few percent of the chargers will be this much out of tolerance. This is, of course, not acceptable.

If Efest send me a message that they will be more careful with the voltage in the future, I will add it to the review.


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## candle lamp (Dec 15, 2013)

Another excellent review. HKJ! :thumbsup:

Thanks a lot.


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## cactus man (Dec 15, 2013)

Great review....
I wonder if they have a "calibration" potentiometer to adjust the charging voltage on 
their circuit board?

I wonder how they calibrate and quality control their chargers?

I understand component tolerances will vary slightly thus a variation on the voltage.

They also offer a similar two bay charger..I wonder if the excessive voltage 
is a challenge for that model too? Model LUC.

Cactus Man


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## dgrogers (Dec 16, 2013)

I bought this charger around the same time you posted your review. I had been looking for a review like this before making my purchase, but since it hadn't been posted yest I decided to take a chance. So far, I'm glad I did because I don't think I would have if I had read your review first. I checked a fully charged Efest 18650 battery with a volt meter and it metered out to exactly 4.20 volts about 12 hours after charging it on the Efest LUC V4. so now I have two questions....

1) How much of a voltage drop (if any) can be expected after charging a battery by letting rest for 12 hours or so? If there is a drop in voltage, is it the pre-rest or post rest voltage you want to be at 4.2 volts?

2) Is it possible the charger was designed for 120 volt electric service and 240 volt electric service could be throwing it off?

I must say I think my Xtar WP2 was overcharging my batteries now (never tested on a volt meter) because the volt meter on my electric cig reports freshly charged batteries on the Xtar at 4.2 volts and freshly charged batteries from the LUC V4 at 4.1 volts (my e-cig ssems to under report voltage).

I do wish there were a few more features on this charger (I absolutely hate that it charges all bays at the same rate instead of allowing me to customize each slot), but overall I'm pretty happy with it.


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## HKJ (Dec 16, 2013)

dgrogers said:


> 1) How much of a voltage drop (if any) can be expected after charging a battery by letting rest for 12 hours or so? If there is a drop in voltage, is it the pre-rest or post rest voltage you want to be at 4.2 volts?



The voltage drops depends on a lot of factors, some of them are battery age, actual battery chemistry (2600 and 3400 mAh batteries uses different chemistry), voltage (Battery will drop more when overcharged).

The voltage that has to be 4.20 volt (4.15 volt to 4.25 volt) is the charger voltage, when charging. This means that a correctly charged battery will be slightly below 4.20 volt.




dgrogers said:


> 2) Is it possible the charger was designed for 120 volt electric service and 240 volt electric service could be throwing it off?



No. Running a 120 volt appliance on 230 volt will usual kill the appliance and there might be fireworks involved.


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## dgrogers (Dec 16, 2013)

HKJ said:


> The voltage drops depends on a lot of factors, some of them are battery age, actual battery chemistry (2600 and 3400 mAh batteries uses different chemistry), voltage (Battery will drop more when overcharged).
> 
> The voltage that has to be 4.20 volt (4.15 volt to 4.25 volt) is the charger voltage, when charging. This means that a correctly charged battery will be slightly below 4.20 volt.
> 
> ...



I meant could the difference be caused by the transformer supplying the 12 volts DC to the charger.


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## HKJ (Dec 16, 2013)

dgrogers said:


> I meant could the difference be caused by the transformer supplying the 12 volts DC to the charger.



The transformer is supplying 12 volt with both 120 volt and 230 volt input.


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## applevalleyjoe (Dec 17, 2013)

Another excellent review! So, bottom line...the xtar VP1 and Nitecore Intellicharger i4 are more effective and better buys? Thanks.


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## HKJ (Dec 17, 2013)

applevalleyjoe said:


> Another excellent review! So, bottom line...the xtar VP1 and Nitecore Intellicharger i4 are more effective and better buys? Thanks.



It looks like Efest will be fixing the voltage issue, making this a good charger.


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## psychbeat (Dec 20, 2013)

Gonna have to pick one of these up I think if they really have fixed the voltage issue 
Love the 2amp option!
My WP6 II is glitching out on me.


Ill test the terminating V & report back when I get it.


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## psychbeat (Jan 6, 2014)

I received my LUC V4 yesterday & have charged 6 cells in it. 

Checking with my Cottonpickers mini volt meter (my decent dmm isn't here) all cells have terminated @4.20-4.22 

So I suppose mine is a little on the hot side but not as hot as HKJs test version. 

The two IMR 18350 I charged were the ones that came off @4.22

I think I got lucky with the tolerance variation on this one. 

I LOVE the 2amp option & having the voltage displayed etc. 

So far so good 


Thanks again for the review HKJ!


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## psychbeat (Jan 17, 2014)

UPDATE!

So I just received some bare NCR18650PF and they're showing 4.25 immediately after termination. 
Again that's testing with my little Cottonpickers volt meter. 

Not sure if I want to send it back to Efest or what to do. 

I think my other cells have more internal resistance so they're coming off @420-422

I don't think .05v is danger level but it's probably going to shorten the life of my poor little cells 

I guess that just means I get to upgrade earlier?!

(spoken like a true flashaholic)


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## beamis (Feb 6, 2014)

Short of buying it and testing, how would somebody be able to tell the difference between an older version with the voltage issue and a newer one without?


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## psychbeat (Feb 12, 2014)

Update #2

I've brought my GE dmm home from the studio & have been seeing .02V less than my little Cottonpickers VM. 

So the IMR cells are coming straight off @~4.21 or 4.22 & most of my regular @4.19-4.20

Some of my older 16340 have high internal resistance probably & come off around 4.16

I'm not sure if there's a way to tell if u get a revised version or the old one - maybe wait a couple of months for inventory to sell off. 
Mine is most likely the 1st version but it's really not overcharging all that much. 
I'm sure there's a bit of tolerance between units tho.


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## cvedrick (Feb 26, 2014)

Everything being equal, I have had my LUC for about 2 months now and after resting a bit, my batteries are reading 4.1v

However my one dislike over the Nitecore I have shelved is I have to get off my butt and walk across the room to see if it is done charging. The nitecores LEDs are visible from the couch.

I DO like the fact that the LUC gives me a readout of the voltage when I put the battery in for charging though.


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## LastRide (Apr 15, 2014)

I just picked up one these Luc V4. My batteries are coming off charged at 4.16 or 4.15 . I charged a 26650 with it. I also put in 2 batteries that were charged 2-3 days ago. The charger said they were charged and when I check them with a multimeter the 18500 and 18650 were at 4.15 so it appears something has changed and the charger is no longer overcharging batteries. There are no stickers or version numberas that I have found on the unit or box. The bar code on the box is 958946 200654 . 

I also have a Nitecore I2 and a Xtar SP2. Both these units put my batteries at 4.19 to 4.2 . The thing I like about the Nitecore I2 is that when left plugged in there are no lights to the unit. Both other units stay powered on with no batteries installed. Luv v4 and SP2 I unplug. Other than that all seem to perform well.


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## OneBigDay (Apr 5, 2015)

It's been almost a year since the last post in this thread. I notice they have these at illumination supply and I am considering it.

*Any more reports from the field in the last year about overcharging on this charger since they have claimed to fix it?* I already have a couple older single cell batteryspace chargers that I really like for their compactness and portability, but I never use them because they charge my cells to 4.25v.

Anything else similar I seriously need to consider? Requirements are it must be able to charge 26650s, and other "likes" are the screen readout while charging and 2 amp charge option.

Oveready has stopped carrying the XTAR VP2/4 I see, I wonder why?

TIA


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## psychbeat (Apr 6, 2015)

I'm still stoked on mine - which is one of the early ones that overcharges a bit. 
I'm not worried about it - some of my cells come off at 4.23 on occasion. 
It's nice having the 2amp charge setting for times when I need a quick partial charge up to ~4v 
I use mostly unprotected Panny cells.
No problems to date with weekly use since I've bought it.


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## OneBigDay (Apr 6, 2015)

Thanks psychbeat, appreciate the comments. I am still leaning towards this charger over the XTAR VC4 (I guess XTARs newest 4 bay). The 2 amp charge option is very appealing.


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## Octavian (Feb 27, 2016)

I bought recently Efest LUC V4 (verified serial number, 100% genuine) I think is not from the first series (the charger plug is purple, not yellow) , till now I'm very happy with it, the cells came out of charger at *4,17-4,18V* , I think this is how should be at a good charger.
I bought this charger because I'm little disappointed with Xtar XP4...it undercharge the LiIon cells (max 4,05...4,07 out of charger) .

Two minuses: has no grip on the back, no rubber to stay stable on the table, and the other minus, the cells don't stay very good, specially the cells 18650 with small button top. 
The termination phase maybe is a little to long. 

I like the lcd screen (very accurate when you put the cells in charger), I like also the possibility to charge at 2 Amps, maybe in future I will have in my collection some 26650 flashlights )


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## tripplec (Feb 27, 2016)

Just to clarify. You are referring to a possible over spec charge of .02 -.03V assuming 4.28VDC was detected. To me is appear pretty minute 3/100 th's of a volt if it does that everytime to everyone. I use protected batteries only so it may not be a factor if I bought one.

When are you measuring that voltage?
- in the charger when its shows finished
- pulling it out and testing it then immediately


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## Octavian (Feb 28, 2016)

I made some measurements, cell in the charger - 3,92V on charger display, same 3,92V to my voltmeter. 4,15Vcharger display- 4,15V my voltmeter, 4,19V charger display-4,19 my voltmeter. 4,2V charger display-4,2V voltmeter.

I didn't see any value over 4,20V with the *cell in charger* (charging).
*Cell out of charger* measured after 3-4 minutes 4,17-4,18V, after 30 minutes same value.

Seems that last series does not overcharge the cells.
Even with protection cells, if the charger overcharge, you will see values over 4,2V in the cell (out of charger). For example the Olight omni-dok from S30-R , even with protection cell, out of charger the cell measure 4,24V...not dangerous, but to high voltage.


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## tripplec (Feb 28, 2016)

Thanks for clarifying. I'll check my chargers next time I am charging some cells for curiosity.


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## Capolini (Jun 15, 2016)

From what I have read this charger[original] would over charge it batteries,,,now it under charges them! I guess that is better but this is one of my least favorite chargers.

Here are results of resting voltages From EFEST LUC 4 and FENIX ARE-C2.

Battery:KEEPPOWER 18650 3400mAh protected.FOUR BATTERIES

EFEST LUC 4 *AFTER 3 HOURS REST!*

Batt. #1-4.15V-acceptable
Batt. #2-4.14V-NOT HAPPY!
Batt. #3-4.13V-UNACCEPTABLE
Batt. #4-4.12V-UNACCEPTABLE

Now my favorite charger FENIX ARE-C2

*AFTER 5 DAYS REST!!!*

BATT #1-4.19V
BATT. #2-4.19V
BATT. #3-4.18V
BATT.#4-4.17V.....................:twothumbs


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