Test/Review of Charger Keeppower L1

[HKJ]

[size=+3]Charger Keeppower L1[/size]

Keeppower is known for its LiIon batteries, but now they have also made a charger. It is a single cell charger with two charge currents and can handle sizes up to 26650, the charger is powered from usb.

I got the charger in a cardboard retail box with fairly limited printing on.

The box contained the charger, a bag and a usb cable, there was no instruction sheet.

The bag is for the charger and the cable.

The micro usb connector is placed on the front, just below the display.

The user interface is a display and a single button.
A press on the button will change between 500mA and 1000mA charge current, but only when there is a battery in the charger.
Holding the button down will turn off the display and disable the current change function, the charger will continue to charge with selected current. To turn display on again the button must be held down again.

The display has an animated battery icon, charge percent, voltage and selected current.

The charge uses the typical slider construction with a metal rail and it works smoothly from about 29.5mm to 71.5mm, i.e. the charger can handle any 18650 and 26650 cells both protected and unprotected.

The charger can easily handle 71 mm long batteries, including flat top cells.



[size=+2]Measurements[/size]

• Below 1 volt the charger will not detect a battery and the current will be zero, this means that it cannot reset protection circuits.
• Between 1.0 and 1.8 volt the charger will show empty battery with 0.00 volt, no charge current is applied.
• Between 1.8 volt and 3.0 volt the charger will charge with about 100mA at 500mA setting and 200mA at 1000mA setting.
• Above 3.0 volt the charger will use regular charging.
• The charger will not restart if battery voltage drops.
• Charge will restart charging after power loss, or battery insertion.
• Voltmeter works from 1.8 volt to about 4.3 volt and is within 0.03 volt. It will continue to update when charging is finished.
• When charging is finished the charger will discharge the battery with about 20uA.
• When charger is without power it discharge the battery with about 40uA.

The voltage scale on my charts is increased to 4.35 volt, because this charger over charges

At first glance this looks like a good CC/CV charge curve with 100mA termination, but there is one serious problem: The charger do not charge to 4.20 volt, but to 4.30 volt.

At 500mA charge current the problem is exactly the same.

The two other cells works the same way with CC/CV and over charge.

The charger has no problems with the older cell.

It looks like there is some small problems with the charging at 500mA for this cell. Due to this the end result is slightly better.

M1: 29,4°C, M2: 39,2°C, M3: 40,6°C, HS1: 45,3°C
The battery stays cool in this charger.

M1: 28,8°C, M2: 40,8°C, M3: 43,6°C, HS1: 44,1°C

The charger needs about 5 second to start.

The charger current can be switched at any time during charge (if the display is on).



[size=+2]Conclusion[/size]

The charger looks nice for a single cell charger and with two current settings it can handle most cell sizes, but the higher voltage makes it nearly useless (There is a few 4.3 volt batteries on the market).

Generally I will not recommend this charger, but if you have some 4.3 volt cells it can be very useful (Just remember to mark the charger clearly).

If Keeppower fixes the over charge and makes some way to recognize fixed chargers, it will be a good charger.



[size=+3]Notes[/size]

Using this charger will not make quality batteries explode, but it will reduce the lifetime of the batteries significantly.

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

 

[Dubois]

Thanks for the review. I'm surprised that Keeppower let this charger out the door. Looks like the QC department were sleeping on the job.

 

[ChrisGarrett]

I'll assume for the sake of this post, that Keeppower is reading this thread, so since they need to go in and redesign some of the internals, they might as well add a 250mA charge rate, so people can charge up their 16340s.

Otherwise, there are better chargers out there and better ones that do 2-4 bays.

How does a li-ion cell rebrander, one who's well respected, miss the boat on a proper CC/CV algorithm?

<mind blown>

Chris

 

[akhyar]

So good battery, bad charger?

 

[ChrisGarrett]

So good battery, bad charger?

If you like your 4.20v cells coming hot off the charger at 4.30v, then it's a great charger!

Chris

 

[akhyar]

If you like your 4.20v cells coming hot off the charger at 4.30v, then it's a great charger!

Chris

Lol! Indeed, hot from the oven

 

[TL-Mike]

Interesting - I think the intended design was to charge the battery to 4.26V which from my understanding is considered a "safe maximum" although still not recommended since it's beyond 4.2. Perhaps your unit (or they all are) is slightly defective and accidentally goes a little over?

 

[markr6]

Too bad it's overcharging. It looks like a nice compact charger. I like the display info; everything you need.

The percentage is really nice, even though it's easy enough to look at the voltage and know about where it's at. Actually, maybe not? Maybe it's a better indicator of the charge. I know Xtar chargers report a much higher voltage while charging (i.e. 4.18v on screen when cell is actually around 4.12v or so)

 

[TinderBox (UK)]

I would check if the charger has a version number, then contact the manufacture and report the problem, maybe it`s a one off, or the problem has been fixed in an new version, but is 4.30v dangerous or is it just bad for the battery, if it`s dangerous the charger should have been recalled.

John.

 

[HKJ]

Too bad it's overcharging. It looks like a nice compact charger. I like the display info; everything you need.

Agree.

The percentage is really nice, even though it's easy enough to look at the voltage and know about where it's at. Actually, maybe not? Maybe it's a better indicator of the charge. I know Xtar chargers report a much higher voltage while charging (i.e. 4.18v on screen when cell is actually around 4.12v or so)

Neither Xtar or Keeppower report too high voltage while charging, they report voltage on the battery while charging. When you stop charging the voltage will drop and you will measure a lower voltage.

I would check if the charger has a version number, then contact the manufacture and report the problem, maybe it`s a one off, or the problem has been fixed in an new version, but is 4.30v dangerous or is it just bad for the battery, if it`s dangerous the charger should have been recalled.

It was not just my charger, I had already received a report from some other guy about over charging on this charger. I have also received a email from Keeppower stating they will fix it.

4.30 volt is not dangerous on a normal quality battery, it will just reduce the lifetime.

 

[markr6]

Neither Xtar or Keeppower report too high voltage while charging, they report voltage on the battery while charging. When you stop charging the voltage will drop and you will measure a lower voltage.

That's what I meant. The cell is 4.12v, but the screen says 4.18v. You remove it, put back in, and for 2 seconds it reports 4.12v, then back to 4.18v after charging starts. I wish it would give the voltage on the battery in real time, but maybe that's not possible. So the percentage is a good idea (if accurate)

 

[HKJ]

That's what I meant. The cell is 4.12v, but the screen says 4.18v. You remove it, put back in, and for 2 seconds it reports 4.12v, then back to 4.18v after charging starts. I wish it would give the voltage on the battery in real time, but maybe that's not possible. So the percentage is a good idea (if accurate)

The battery voltage while the charger is charging is 4.18 volt, not 4.12 volt.

 

[markr6]

The battery voltage while the charger is charging is 4.18 volt, not 4.12 volt.

Yes, but the important number is when I take if off the charger, correct? Like my VP2 I'll see it say 4.20v, but the charge indicator is still blinking (3 out of 4? blocks?) so I know it still has a ways to go. If I take it off at 4.20, I may only have a cell with a useable 4.15v charge (about 90%). Not a big deal, but not perfect for knowing what charge you have once it settles down.

 

[HKJ]

Yes, but the important number is when I take if off the charger, correct? Like my VP2 I'll see it say 4.20v, but the charge indicator is still blinking (3 out of 4? blocks?) so I know it still has a ways to go. If I take it off at 4.20, I may only have a cell with a useable 4.15v charge (about 90%). Not a big deal, but not perfect for knowing what charge you have once it settles down.

What is important, depends on what you are looking for. The voltage during charge shows when the charger enters CV phase (More or less). The voltage when you take the battery of the charger will vary with battery age and how long time you wait before you measure it.

I did this table once:

I would like to redo the table with some of my never equipment (more precision) and a couple of different cells, but I always lack spare equipment and time to do the scripts for it.

 

[Gauss163]

That's what I meant. The cell is 4.12v, but the screen says 4.18v. You remove it, put back in, and for 2 seconds it reports 4.12v, then back to 4.18v after charging starts. I wish it would give the voltage on the battery in real time, but maybe that's not possible. So the percentage is a good idea (if accurate)

The charger cannot determine the actual resting (open-circuit) voltage of the cell without pausing to do so. Since this charger does not pause, the voltage it measures (and displays) is the cell's rest voltage plus an incremental voltage due to resistances (internal to the cell, in wires, contacts, etc). By Ohm's law, the voltage increment V caused by such resistances R is proportional to the current flowing V = I R. At the end of charge the current I is usually small, e.g. C/20, so such voltage gain will be small. When you remove the cell from the charger this incremental voltage disappears, hence the slight voltage drop you observe. If instead you removed the cell earlier when the charge current I was higher you would see a (propertionally) higher voltage drop when the cell is removed. Same if you use an older cell with higher internal resistance R, since increasing either I or R will increase V = I R. In particular this implies that older cells may not be completely charged by chargers using this method.

 

[Capolini]

THANKS FOR THE REVIEW!

I just ordered the "L2" version of this charger. I really hope they rectified the overcharge issue that that they had w/ L1!

I love the display,voltage/%/charge current and time charging! :twothumbs

 

[Octavian]

Hi Capolini, did you receive the Kepppower L2 version?

I also intend to order it, but I'm concern about high voltage, did they fix the bug ?

Thank you

 

[Capolini]

Hi Capolini, did you receive the Kepppower L2 version?

I also intend to order it, but I'm concern about high voltage, did they fix the bug ?

Thank you

Yes it is fixed,but it takes a long time to charge older batteries,, 2.5x to 3x longer than my Fenix ARE-C2 charger!

The ending voltage is never more than 4.16v. I believe the reason it takes so long with older batteries is that it struggles to terminate the charge. IT CAN BE AT 4.19V/99% For 3 hours or longer sometimes! What I Learned to do is after 3 hours I pull it off the charger and it is usually @ 4.14/15v. If I left it on it would literally take 2 more hours just to achieve another 0.01v!

So if that is not an issue for you I think you will like the charger,it charges newer batteries,,IMR,ICR at an acceptable rate.,,,,,,,,, 1.5h to 3 hours.

 

[Octavian]

4,14...4,15V out of charger (measured with a voltmeter) or 4,15 in the charger/what charger shows

Tanks for reply.

4,14 out of charger for me is more than enough for a full load.

 

[Capolini]

Out of charger w/ DMM. The charger is off by 0.08v to 0.10v until the last part of the charge. No big deal. I AGREE FINAL CHARGE IS OK,JUST NOT GREAT FOR CHARGING old BATTERIES!

A few examples below:


CYTAC 18650 3400mAh[2 YEARS OLD]- START:3.70V, ENDING: 4.16V. DURATION: 5H 50M!

Orbtronic 18650 3400mAh-3 years old. START:3.68V, ENDING:4.16V, DURATION:5H 10M!

EFEST 16340 700mAh[ 9 months old]. START: 3.72V, ENDING: 4.16V, DURATION: 4H 32M! This is NOT an older battery!

LG HG2[6 MONTHS OLD]-START:3.84V, ENDING:4.16V, DURATION: 2H 36M.

SONY VTC5 [8 MONTHS OLD] START:3.87V, ENDING: 4.16V, DURATION: 1H 04M. :thumbsup:


As you can see it took Four[4] times longer to charge a 16340 than it did an 18650[VTC5]!!!

EDIT: I have to add that it charged an IMREN IMR 16340[8 MONTHS OLD] START: 3.72V ENDING: 4.16V, DURATION: 1H 44M! :shrug:,,,,,WHO KNOWS!