Review of / Measurement on ML-102 Charger

HKJ

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[size=+3]Charger ML-102[/size]

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This charger is a very small 18650 charger, it need an external USB power source to charge, and can also work as a USB charger. It only charges one battery at a time.

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Only a USB cable is included with the charger, I did also order some spacers, making it possible to charge smaller batteries.

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The charger is powered from any USB source that can supply 1A, sadly it uses the mini and not the micro USB connector (The micro USB is much stronger and is the common charge connector on phones). Because the connector is on the side of the charger it is not possible to place a couple of these chargers beside each other.

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The charger also has a full size USB connection for power out, it can be used to charge a phone or other USB equipment.

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The charger has a couple of leds, one is placed on top of the charger and some other inside the charger.
The light is red when charging, both red and green when nearly full, green when finished and blue when supplying USB power.

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The plus connection is slightly raises, making it possible to charger flat top batteries, the spring at the minus connection is rather short, but long enough to support unprotected 18650 batteries.

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With the two spacers (Each 15.9 mm long) I included in my order the charger can also handle xx500 and xx340 cell, but the charger current is too high for many of these batteries.

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supportedBatterySizes.png
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The charger can handle 69.6 mm long batteries, including flat top cells. Not all 26650 can be charged, it depends on the size and shape of the plus pole on the battery. With the spacers it is also possible to use smaller batteries, but watch the maximum charge current for the battery type!



[size=+2]Measurements[/size]

Below 2.8 volt the charger charges with 130 to 170 mA (Highest current at lowest voltage).
Between 2.8 volt and 4.2 volt the charger is applying regular charge current (See curve below).
When the charge current goes below 70mA the charging is stopped and it will discharge with less than 75 uA.
The charger will restart when the battery drops to 4.12 volt or power is cycled.
Reinserting the battery will not restart charging.
When charger is disconnected from power, but with a battery in, it will draw below 75uA from the battery.

ML-102%20(AW18650-26).png


The charge curve does not look like a CC/CV charger, but the only disadvantage with this type of curve is the slower charge speed, the final result will be just as good as a CC/CV charger. The termination current is around 80mA, this is a good value.
The above curve is done with a USB power supply (or more correctly a lab power supply adjusted to 5 volt).

ML-102%20(AW18650-26)%20Vusb=PC.png


Using a laptop as power supply does not change the charge curve significantly. The charger is using nearly 1A from the USB connector, this is more than allowed in the USB specifications, but nearly always works fine.

ML-102%20(AW18650-26)%20Vusb=4.5V.png


What happens if a weak USB power supply is used or long cables, to simulate that I turned the power supply down to 4.5 volt. The charger continues to charge and stops when the battery is full, but it takes considerable longer time (nearly 10 hours).

ML-102%20(AW16340-IMR).png


The charger also handles my old IMR cell without any problems.

Measurements on USB power

The charger can supply USB power while discharging the battery. It is possible to connect a USB power supply to the charger and connect the charger to some USB equipment and charge both at the same time.

USB specification says the voltage must be between 4.75 and 5.25 volt, I have placed a yellow line at 4.75 volt in the charts.

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The first curve is with a 20 ohm load, this gives a load current of 250 mA, the usb output stays exactly at 5.13 volt, until the battery is empty. It keeps a very good efficiency at about 90%.
The power is turned off when the battery is down to 3 volt and it does not turn on again when the battery voltage increases, this is a good design.

ML-102%20USB%20out%2010%20ohm%20(AW18650-26).png


Reducing the resistor increases the current to 500 mA and drops the voltage to 5.1 volt (probably due to cable losses). The efficiency is still very good at 85% to 90%.

ML-102%20USB%20out%209.1%20ohm%20(AW18650-26).png


Reducing the resistor again increases the current to 550 mA, the efficiency is starting to drop now, but the voltage is stable.

ML-102%20USB%20out%207.7%20ohm%20(AW18650-26).png


This time I have increased the current to 650 mA and this is at the limit of the circuit, the voltage is not stable anymore, but it can still supply this current for two hours and stay within the USB specifications.



Conclusion

This charger is a very compact LiIon charger with dual functionality (Can both charger USB devices and 18650 batteries), the charging profile is good, but not optimal for speed. I can see two obvious applications for this charger, one is for people with only a few 18650 batteries, the other is in a travel kit, where the ability to charger USB equipment from an 18650 battery can be very useful.
I like this charger and is going to add it to my traveling kit.


[size=+3]Notes[/size]

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

Norm

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Great review, I have a couple of these, a good cheap charger, it works as described. I have successfully charged 18650s using a 300mA USB charger, obviously it charges more slowly.
Norm
 
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candle lamp

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Another excellent review. HKJ! :thumbsup:

Thanks a lot for introducing a good charger & your effort as always.
 

sidness

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Thanks for another great review, i use a ML-102 charger and was hoping for a review just for extra piece of mind.

ps the forum could do with a thanks button, :D
 

Norm

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Thanks for another great review, i use a ML-102 charger and was hoping for a review just for extra piece of mind.

ps the forum could do with a thanks button, :D

:thanks: :goodjob: :wow: :hitit: :welcome: :thumbsup:
 

kosPap

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This charger's e;ectronics look "suspiciously alike" those found on the 4x18650 battery banks found on eBay and discussed here some moths ago
 

Norm

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This charger's e;ectronics look "suspiciously alike" those found on the 4x18650 battery banks found on eBay and discussed here some moths ago

You can see my internal photos from another thread here click twice for hi res.

Norm
 

rufus001

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I recently purchased a couple of these chargers and I have one concern. I was charging a battery and it seemed to be on red/green for longer than normal so I took it off. It was 4.22V. I put it back on the charger and it was still red/green. So I put it in my other ML-102 charger and it stayed green as you would expect. Finally I unplugged then plugged back in the original charger I used and it stayed green! Very strange.
 

roadkill1109

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I recently purchased a couple of these chargers and I have one concern. I was charging a battery and it seemed to be on red/green for longer than normal so I took it off. It was 4.22V. I put it back on the charger and it was still red/green. So I put it in my other ML-102 charger and it stayed green as you would expect. Finally I unplugged then plugged back in the original charger I used and it stayed green! Very strange.

Could it be the protection circuit of your battery which didn't kick in so it kept on charging? Maybe after taking it out then putting it back, that was when it realized it was already up to 4.22V. But I read somewhere that the cut off for these cells are in the 4.25volt range.
 

rufus001

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Could it be the protection circuit of your battery which didn't kick in so it kept on charging? Maybe after taking it out then putting it back, that was when it realized it was already up to 4.22V. But I read somewhere that the cut off for these cells are in the 4.25volt range.

It could be. One of the other batteries I ordered from the same place was DOA.
 

roadkill1109

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It could be. One of the other batteries I ordered from the same place was DOA.

Ouch! At least the charger's working.

It's cool that with one Panasonic 3100mAh, i am able to fully charge my Blackberry Bold 9900, and charge my Nokia 5800XM to 75% before the battery croaks! :) Dropped down to a safe 3volt just right for re-charging. :)
 

roadkill1109

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i might just order more of these chargers...so handy and efficient! i opened up the bottom and checked the circuitry, it was well made and will small components reminicent of motherboard parts.
 

Teobaldo

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A very good review, HKJ, congratulations.

I have two ML-102 and I am very satisfied with the purchase, both function well so much upon charging the battery as upon delivering energy by the USB port. I expect that arrive quickly the Blue Led Panel Meter to be able to weld them to him the charger. My intention is to use them in my next trip to the desert in bicycle to maintain charged the batteries of the flashlights.
 

gravelmonkey

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I recently purchased a couple of these chargers and I have one concern. I was charging a battery and it seemed to be on red/green for longer than normal so I took it off. It was 4.22V. I put it back on the charger and it was still red/green. So I put it in my other ML-102 charger and it stayed green as you would expect. Finally I unplugged then plugged back in the original charger I used and it stayed green! Very strange.

I've got two of the chargers and have found exactly the same results! One always charges to 4.22V while the other charges to 4.20V. I can't work it out, but then again, I'm a bit of an ape when it comes to these things. I wonder if the discharge cut-off is 0.02V different too... :thinking:

GM
 

Norm

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I've got two of the chargers and have found exactly the same results! One always charges to 4.22V while the other charges to 4.20V. I can't work it out, but then again, I'm a bit of an ape when it comes to these things. I wonder if the discharge cut-off is 0.02V different too... :thinking:

GM
Is your meter accurate?

Norm
 

HKJ

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I've got two of the chargers and have found exactly the same results! One always charges to 4.22V while the other charges to 4.20V. I can't work it out, but then again, I'm a bit of an ape when it comes to these things.

This kind of difference is expected, there will always be some tolerance on a cheap charger chip.
 

roadkill1109

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I paired this charger with the Solar Panel with USB power output. Now I can get to charge 18650's even in the middle of nowhere. I'm ready for the zombie apocalypse! :)
 

gravelmonkey

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This kind of difference is expected, there will always be some tolerance on a cheap charger chip.

Thanks HKJ! As a related point, would it be stupid to daisy-chain 2 chargers together? I'm thinking of linking my Cottonpickers solar 1000ma panel to a ML-102 with a salvaged panasonic CGR18650 charging a second ML-102 with an AW 14500 or 18650. Thinking that the panasonic in the first charger would provide a 'buffer' when the sun goes in.

Thanks,

GM
 

HKJ

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Thanks HKJ! As a related point, would it be stupid to daisy-chain 2 chargers together? I'm thinking of linking my Cottonpickers solar 1000ma panel to a ML-102 with a salvaged panasonic CGR18650 charging a second ML-102 with an AW 14500 or 18650. Thinking that the panasonic in the first charger would provide a 'buffer' when the sun goes in.

That will not really get your anything, except some wasted power (Boosting voltage from a LiIon up to 5 volt looses power).

It can be good idea to have a battery between the solar system and the charger, to get stable power for the charger, this is especially important with NiMH batteries, not as much with LiIon.
But for the first battery, I will recommend a battery/charger that is designed for exactly this purpose, i.e. buffering solar cells.
 
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