# Soshine SC-S2, Li-Ion Charger.



## march.brown (Mar 5, 2010)

Well at last my Soshine SC-S2 Charger has arrived ... It just happened that I had two Ultrafire 2400mAh protected 18650 cells that were discharged to exactly 3.8 volts to test the charger with.

I first checked to see if the charger had voltage present with no cells inserted ... It did and the voltages were 4.22V on the left hand slot and 4.23 on the right hand slot ... I put the cells in and started the charging process ... Eventually after 4 hours, the right hand slot showed blue, so the cell was removed and the voltage was 4.18 Volts ... after another 15 minutes, the left hand slot showed blue and the cells voltage was the same at 4.18 Volts.

The charger is supposed to be a fast-charger, though I don't think that I would class it as such ... The instructions say 2.9 hours for a 2400mAh and 3.5 hours for a 2800mAh but I don't know what voltage they started at in their charging sequence ... I monitored the charging voltage and it seemed to come up quickly for the first two hours then the last part of the charge took about the same length of time ... As far as I could tell, the last hour or so was not a fixed voltage (CV), it just gradually built up to the point where the blue LED came on.

Towards the end of the charge, I put my Avo 8 in series with one of the batteries to check the current ... It wasn't registering much on the 10 Amp range, so I switched to a lower range ... The Blue LED lit, so I went back to the 10 Amp range and the Red LED came back on ... It seems that the charger is very sensitive to any small extra resistance in series with the battery ... So, I can't check whether the charger actually switches the charging current off when the blue LED comes on.

During the first part of the charge, the charger reached 115 degrees F in one area and the cells reached 94F ... These temperatures dropped considerably during the last part of the charging process.

The charger seems to be well made, though as yet I haven't compared its function to my Trustfire TR-001 ... I will do a side by side comparison test in the next week or so, just to see which charger is quicker ... I suspect that they will be very similar in their charging times ... I will do the test from the same 3.8 volts as todays quick check ... I just wish that I could check the charging current with my Avo 8 ... I might try it with one of the DMMs to see if that will work better.
.


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## old4570 (Mar 5, 2010)

To measure charge current :

I put the 18650 battery in tail first and then use the MM to complete the circuit without actually putting the 18650 in all the way .


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## march.brown (Mar 5, 2010)

old4570 said:


> To measure charge current :
> 
> I put the 18650 battery in tail first and then use the MM to complete the circuit without actually putting the 18650 in all the way .


.
I have made a sort of three ply insert out of a central plastic membrane sandwiched between two pieces of sticky backed aluminium foil ... The insert goes between the positive end of the cell and the charger contact with the cell fully inserted ... The ammeter makes the connection between the two metal foils.

The problem seems to be that the charger can see the extra resistance of the ammeter when it is on ranges that are more sensitive than the ten amp range ... The charger Red LED shows that the battery is being charged OK when the Avo model 8 is on the ten amp range ... The moment that I try to go to the one amp or 200 milliamp ranges (or lower) the charger Blue LED comes on to say that the battery is charged ... When I go back to the ten amp range the red LED comes back on.

I think that it is due to the slightly higher resistance of the lower current ranges when the ten amp (shunt) is removed ... I don't know if you can understand my explanation.

I will try my method with the higher charge rate at the beginning of the charge just to see if it works.
.


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## old4570 (Mar 5, 2010)

No I understand .... 

The little insert U use may be the cause of the resistance , or more correctly adding to it ...

I was thinking of doing something similar , but then I started thinking if there would be much added resistance .. 

I went to the trouble of buying 2 1A amp meters , and then possibly making a sort of more permanent measuring system to read the charge rate for the entire charging cycle ... 

Im going to have to buy one of those 18650 cradles and some gator clips so as to monitor the charge rate I think ... 

I will be ordering the Soshine charger shortly , I look forward to you confirming if it shuts off on completion .


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## march.brown (Mar 5, 2010)

old4570 said:


> No I understand ....
> 
> The little insert U use may be the cause of the resistance , or more correctly adding to it ...
> 
> ...


.
The sticky-backed aluminium sheet is quite thick and is what I originally used for bodies/weight on trout flies ... I checked the DMM on ohms and the lead resistance was 0.3 ohms ... I put one of my 3 ply inserts in circuit and the resistance went up by 0.1 ohms.

I put the Avo 8 on the 10 amp range and measured its resistance using the DMM and it was a virtual short circuit ... I could only see the lead resistance ... However with the ammeter on the 1 amp range, the resistance went up by 0.4 ohms ... The 100 milliamp range measured 4.0 ohms and the 10 milliamp range measured 40 ohms ... So even using the one amp range puts an extra 0.4 ohms in circuit ... The Avos leads together are about 0.1 ohms when measured on the DMM ... So using the one amp range on the Avo would put a total of 0.5 ohms in series with the battery ... I don't know how badly this extra resistance affects the results, but certainly it makes the charger change from red to blue LED ... Whatever voltage drop that occurs across the ammeter (during charging) would reduce the actual voltage across the cell ... Once the charger voltage across the cell and the extra resistance adds up to 4.18 volts or more, the charger LEDs turn to blue ... As such, I can't see a way of accurately checking that the current shuts off when the LEDs go to blue as the 100 milliamp range puts the extra 4.0 ohms into the circuit ... I need to do more research on this ... I will try checking on the ten milliamp range just to see if there is any current flow at all when the LEDs turn blue ... Due to the extra 40 ohms resistance the readings won't be accurate, but I should hopefully be able to see if the current drops to zero. 

The only other way I can think of is to leave the cells in the charger after the LEDs go to blue and see if the cell voltage goes up above the 4.18 volts that I measured earlier to about 4.22 volts which was the open circuit voltage of the charger.

I hope this sort of makes sense.

Any other suggestions please.
.


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## 45/70 (Mar 5, 2010)

Hey march. The easiest non EE way to tell if the SC-S2 is trickle charging after the LED turns blue, is to do as you suggested.

You need a cell that charges up to your 4.18 Volts. Most cells, unless they're really really new, will drop in voltage after 20 minutes, by 0.01 or more. So, if you have a cell that charges up to 4.18 volts, and 20 minutes after removing from the charger reads 4.17 Volts, put this cell in the charger and wait for the LED to turn blue. Let it remain on the charger for an additional 20 minutes. Then, take the cell out and measure the voltage. If the cell reads 4.17 Volts, or less, the charger is shutting down and not trickle charging. If the cell reads 4.18 volts, the charger is trickle charging.

Don't make things anymore complicated than necessary! 

Dave


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## old4570 (Mar 5, 2010)

https://www.candlepowerforums.com/posts/3304227#post3304227

I like to check :


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## 45/70 (Mar 6, 2010)

old4570 said:


> https://www.candlepowerforums.com/posts/3304227#post3304227
> I like to check :



Nothing wrong with that. I was just suggesting an easy way to tell if a charger trickle charges, or not. 

A lot of folks think that because their cells come off the charger at 4.20 Volts after leaving them on the charger after it indicates the charge is completed, that their charger doesn't trickle charge. In fact though, this usually means it does.

Dave


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## mfm (Mar 6, 2010)

march.brown said:


> As far as I could tell, the last hour or so was not a fixed voltage (CV), it just gradually built up to the point where the blue LED came on.
> .



So they lied when they said it was using the CC/CV algorithm, just like their other chargers. I wouldn't trust anything else they say either.



old4570 said:


> I like to check :



That is not going to work with chargers where you can put in a new cell to charge it (without cycling the power).


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## Tohuwabohu (Mar 6, 2010)

The LED turns blue when the charging current falls below approximately 30mA in the CV stage but the Soshine SC-S2 does not stop charging.

I bought 3 of these chargers some time ago but did not yet complete all the measurements and modifications that I had planned to do.

The chargers came in blister packs that I could only open with a knife.
Package contents: charger, wall wart with 12VDC output and12V car adapter cable.






Specification and instructions





Two of the chargers came with a 12V 1.2A wall wart, the third with a 12V 1.5A wall wart. 




The specification on the charger label differs from that on the instruction sheet or the Soshine website.

The two charging bays are long enough for all of my 18650s.





I did some measurements with an Agilent 66332A, a PSU that can act as current sink. 










I set the current limit to 5A and increased the voltage in small steps:




The Soshine SC-S2 is protected against short circuits but it does not have a low current precharge stage for deep discharged batteries.
The current in the CC stage is approximately 1A.
The off-load voltage of all 6 channels of my 3 units is a bit too high: between 4.240V and 4.254V

Enlarged view of the voltage range above 3.5V




The #3 Soshine is already modified to 4.20V off load voltage

The opened charger





The other side of the PCB





I don't understand the whole curcuit but each channel seems to be controlled by a MC34063 buck converter.
The HK324 quad operational amplifier could be used for current control and LED charging indicators.





The voltage is set with the R13, R2 voltage divider at pin 5 of the MC34063 for channel 1 and R30, R19 for channel 2.
The MC34063 has an internal voltage reference of 1.25V.
The theoretical output voltage is
Vout = 1.25V (1 + R13/R2) = 1.25V (1 + 24k/10k) = 1.25V * 3.4 = 4.25V
The real value can differ quite a lot since the voltage reference only has a 2% accuracy and the resistors used for then voltage divider will add some more inaccuacy. 

An easy way to adjust the voltage is to put high ohm resistors parallel to the resistors.
A 10M resistor parallel to R13 will reduce the output voltage by approx. 7mV.
A 10M resistor parallel to R2 will increase the voltage by approx. 3mV.

To reduce the voltage from 4.25V to 4.2V a 1.3M or 1.5M resistor parallel to R13 is needed.

I simply soldered the additional resistors on top of the voltage divider resistors.

My preliminary rating:

+ two completely independent charging curcuits
+ 1A current in CC stage
+ CC/CV charging algorithm (although not perfect due to high output resistance)
+ wall wart type power supply (no dangerous voltage inside the charger - makes modifications easy and safe)
+ protection against short curcuit and reversed batteries


- voltage a bit too high
- does not stop charging when indicator turns blue
- DC connector plug a bit too loose in socket
- no precharge stage for deep discharged battries
- no safety timer
- no temperature control
- lid and sliding contacts flimsy
- springs at sliding contacts a bit weak
- wrong specification on the charger label


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## march.brown (Mar 6, 2010)

Done some more checking and the charger is definitely trickle charging ... I still get weird results on the different ranges of the Avo 8 though ... The trickle current is showing 4.0mA on the 100mA range and 0.8mA on the 10mA range ... I get different current readings with the DMMs, but it still shows that the charger doesn't switch off when the blue LED comes on ... I will just have to remove the cells when the blue LEDs come on ... At least I know that the cell voltages are then 4.18 for both channels ... If I leave them a few extra minutes inadvertantly, with this low trickle current, I will have to put up with perhaps a shorter cell life ... Three years or so instead of four.

My charger is almost identical to the pictures that "Tohuwabohu" posted ... My ac adaptor says input 100-240V , 50-60Hz *0.4A *, Output 12V *1.5A *, *Model No.ACTM-09.*

The charger label says input DC 12V *1200mA *, Output DC 4.2 Volts plus or minus *0.05* , *1000mA X 2*.

My charger on first glance looks exactly like the pictures other than a few differences in the printed labels ... It also came in a sealed plastic blister pack.

I will not bother with the mods to reduce the open circuit charger voltage , I will just take care with my charging techniques and watch for the blue lights ... I mean the blue lights on the charger not on the Fire-Engines (hopefully).

Tohuwabohu, thanks for the graphs and the pictures they are very informative .. You obviously have some very sophisticated test equipment ... I am waiting for delivery of a five volt reference so I can check both my cheap DMMs, at least then I will be able to remove the cells off charge at an accurately measured 4.2 volts or whatever lower point that I decide.

I'm giving up on all the charger current measurements in favour of a simple life ... In future, I will just remove the cells when the blue lights come on ... I will still religiously check the battery volts though.
.


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## march.brown (Mar 6, 2010)

Just looked at this graph in more detail and it looks as though the Soshine unmodified is still charging at about 400mA when the voltage is 4.18 V.

My chargers blue LEDs come on when my cells are up to 4.18 volts ... You said that your Soshine LEDs turn blue when the current drops to below approximately 30mA ... This is where the graph says that the voltage is about 4.24 to 4.25 volts ... The modified charger seems to be pushing out about 180mA when it gets up to the 4.18 volts point.

I am probably interpreting the graph wrongly, as I don't have experience with the Agilent unit.

I will check my Soshine again with a partially discharged battery to see if my blue LED comes in at a different voltage this time.


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## Meterman (Mar 6, 2010)

march.brown said:


> Just looked at this graph in more detail and it looks as though the Soshine unmodified is still charging at about 400mA when the voltage is 4.18 V.



@ march.brown

All these beautifully colored lines but black and brown (PSU and Pila) show the properties of chargers, which don't keep to the CC/CV directions exactly. Thus your observation is true. 


@ Tohuwabohu

A very surprising idea to show current over voltage instead of the usual way to show current and/or voltage over time. So quite a different aspect - current at (even very) low voltage becomes visible.

Interesting to see the foldback in voltage of the Pila in your graph, it really (probably solely) cuts off the current completely. You find this behaviour as well in the _familiar_ sort of graph of a Pila I happen to have at hand.







May be that helps others to understand your unusual graph more easily.

Wulf


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## Tohuwabohu (Mar 6, 2010)

Wulf,
thanks for the explanation. I'm sure it will help others to understand the graphs.
It is easier and faster to do this type of measurement than to monitor voltage and current when charging a battery.
When I have done some more measurements on the Soshine I will start a thread in the Messerforum and we can discuss it there.

The Pila charger is indeed very special, I have never before seen a charger with a negative output impedance.
The Pila does completely stop charging when the charging current drops below 70mA and the resting voltage of the battery is high enough.
When the resting voltage is below 4.08V it will go into a sort of error mode (red LED on, green LED off) and continue to charge with very low current.
This can happen when the contact are dirty or the battery resistence is too high.

march.brown,
in the CV stage the Soshine does not push a current into the battery.
It is a constant voltage source with an output impedance of approx. 180 milliohm.
The current is a result of the voltage difference between the off-load voltage of the charger, the resting voltage of the battery and the sum of the resistences of charger, battery contacts and internal resistence of the battery.
When you put an amperemeter in the curcuit you increase the resistence and thus decrease the charging current.

The Agilent 66332A that I used as an electronic load has a very low impedance when it is in constant voltage mode - much lower than the internal resistence of a 18650 lithium ion battery.
This will lead to higher currents at the same voltage.


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## Mr Happy (Mar 6, 2010)

Tohuwabohu said:


> Enlarged view of the voltage range above 3.5V
> 
> 
> 
> ...



With the modified Soshine charger (green line) the current drops to zero by the time the voltage reaches 4.20 V. This seems to mean it would take a nearly infinite time to fully charge a cell since the voltage will asymptotically approach 4.20 V but never reach it.

I wonder if the original preset voltage of 4.25 V was deliberately set slightly high like that in order to allow charging to 4.20 V to complete in a reasonable time...?


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## Tohuwabohu (Mar 6, 2010)

Mr Happy,
of course you are right, a battery in the modified charger will never reach 4.20V. 
But I prefer to have a charger that will never charge beyond 4.2V over one that will charge up to 4.25V when the batteries are left in the charger too long.
The battery voltage will be lower than 4.2V when I remove them form the charger as soon as the indicator turns to blue but that's ok for me.


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## 45/70 (Mar 6, 2010)

Excellent posts by Tohuwabohu, also the comments from Meterman which helped me better understand the graphs. :thumbsup: You guys are way ahead of most of us and are better equipped, when it comes to testing and explaining the results of these tests.



march.brown said:


> ... I get different current readings with the DMMs, but it still shows that the charger doesn't switch off when the blue LED comes on ... I will just have to remove the cells when the blue LEDs come on ... At least I know that the cell voltages are then 4.18 for both channels ... If I leave them a few extra minutes inadvertantly, with this low trickle current, I will have to put up with perhaps a shorter cell life ... Three years or so instead of four.



Leaving cells on charge after the charge should have been terminated, for a short time, is probably not a big issue with this charger. The danger is forgetting to remove the cells, and leaving them to trickle for long periods. The big problem with trickle charging beyond a fully charged state, isn't so much the shortening of cell life, but the danger of the plating out of metallic lithium. From B.U.'s Charging Lithium-ion batteries page:



> [FONT=Verdana, Arial, Helvetica, sans-serif]No trickle charge is applied because lithium-ion is unable to absorb overcharge. A continuous trickle charge above 4.05V/cell would causes plating of metallic lithium that could lead to instabilities and compromise safety.[/FONT]


I don't think most Li-Ion users are aware of this. Most are more concerned with how trickle charging, or overcharging Li-Ion cells, shortens cell life. To me anyway, the plating out of metallic lithium is a bigger concern. The effect is cumulative, is irreversible, and the cells become unstable. The more a cell is subjected to trickle, or overcharging, the more likely a "venting with flame" incident could occur.

Cells with metallic lithium present, can "vent with flame" at any time, when they become unstable. It could happen while, charging, in use, in your pocket, or stored in your dresser drawer. This is an event that is not limited to occurring while charging.

Dave


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## march.brown (Mar 6, 2010)

Good evening everyone, I have just carried out a "top-up" charge on another Ultrafire 2400mAh protected cell ... My two DMMs read slightly different, for example this 18650 cell read 4.03V on one meter and 4.02 on the other ... Through this particular test the difference between the two readings was 10 millivolts with occasional flickers to 20 millivolts before settling to the lower difference ... When my five volt reference arrives, I will know which one is the more accurate meter and I will be able to correct both their readings.

At 1424hrs , the top-up charge started and the charger applied 4.18 volts to the cell.
At 1450hrs , the voltage was 4.21 volts.
At 1500hrs , the voltage was 4.22 volts.
At 1515hrs , the voltage was 4.23 volts.
At 1530hrs , the voltage was 4.23 volts and the blue LED came on ... I assume that this was the time when the current dropped to below 30 milliamps.
The higher of the two meters is quoted in the above figures.

I removed the cell and checked the voltage immediately ... It was 4.18 on one meter and 4.19 on the other meter... That was at 1530hrs.
At 2000hrs the reading was 4.17 and 4.18 volts.

The battery didn't heat up, so I never took its temperature.

To bring the cell up from 4.03 volts to 4.19 volts took 66 minutes.

I think I can live with this charger OK, assuming that I don't leave it trickle charging on the "blue" for too long ... I also think that the manufacturers charging times for 18650 cells are rather optimistic if you want to attain the full 4.20 volts.
.


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## old4570 (Mar 6, 2010)

Am I understanding correctly ?


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## march.brown (Mar 6, 2010)

old4570 said:


> Am I understanding correctly ?


.
R13 and R30 was quoted.


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## Mr Happy (Mar 6, 2010)

old4570 said:


> Am I understanding correctly ?


I read it the same as you do. Hence your circled resistor does appear to be R13.


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## Tohuwabohu (Mar 7, 2010)

old4570,
yes, that is R13.

Here is a better photo of that part of the curcuit:





You can read the marking on the resistors:
_2402_ on the 24 kΩ resistor R13
_1002_ on the 10 kΩ resistor R2


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## old4570 (Mar 7, 2010)

Just double checking , dont want to build a bomb by mistake ... 
Was planning on buying this charger ... 

If only I could mod my shekor charger to terminate @ 4.18 or 4.19v


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## Meterman (Mar 7, 2010)

old4570 said:


> Just double checking , dont want to build a bomb by mistake ...



But you have seen, that R13 is only for channel 1 and *R30* (not R31, as you had marked in the picture) is the corresponding resistor for channel 2?

Wulf


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## Tohuwabohu (Mar 7, 2010)

old4570,
I didn't notice that you had marked R31.
I didn't even look at that part of the photo.

Thanks for your help Wulf.

R30 is close to the other MC34063 at the edge of the PCB.


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## old4570 (Mar 7, 2010)

Thanks , I thought it was R30 but for some reason had R31 on the brain ...
I must be seeing things ....


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## march.brown (Mar 7, 2010)

My previous quote was :-
_*"*My chargers blue LEDs come on when my cells are up to 4.18 volts ... You said that your Soshine LEDs turn blue when the current drops to below approximately 30mA ... This is where the graph says that the voltage is about 4.24 to 4.25 volts ... The modified charger seems to be pushing out about 180mA when it gets up to the 4.18 volts point*."*_

When the Blue LED comes on, my charger is at 4.23 volts and when the cell is removed its voltage is 4.18 volts ... So the difference between the charger voltage and the resting cell voltage is 0.05 volts ... I assume with only this 50mV difference, the charge current has dropped to below 30mA hence the Blue LED being lit at that point.

Your reply was :-


Tohuwabohu said:


> march.brown,
> in the CV stage the Soshine *does not* push a current into the battery.
> It is a constant voltage source with an output impedance of approx. 180 milliohm.
> The current is a result of the voltage difference between the off-load voltage of the charger, the resting voltage of the battery and the sum of the resistences of charger, battery contacts and internal resistence of the battery.


 
From your graph, it seems that the charger is still "pushing out" about 180mA during the constant voltage part of the charge ... I realise that the charge current is due to the charger voltage being greater than the cell voltage and that the internal resistances of the charger and battery etc do have a contributary effect on limiting the current, but the charger is still supplying the current and when this current reduces to less than 30mA the Blue LED should come on.

Obviously you have studied this technology to a much higher level than the vast majority of us and you have extremely good test equipment and data logging devices, but I am still of the opinion that the charger is supplying current even when in the CV part of the charge algorithm ... I base this on the fact that I have read on CPF that the ideal charger, with the perfect CC/CV algorithm should cut off the charge when the (CV) charging current drops below 30mA.

I hope this post makes sense to you, though it wouldn't be the first time that my views were slightly different to others ... It is merely the view of an elderly engineer ... Maybe I should have said very elderly.


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## Tohuwabohu (Mar 7, 2010)

march.brown,
probably I was just using the wrong words.
It's more than 25 years ago that I learned English at school and I don't speak or write English very often.
I spend more time looking up words than actually writing.
That's why I like to add photos or graphs to my posts.



march.brown said:


> From your graph, it seems that the charger is still "pushing out" about 180mA during the constant voltage part of the charge ... I realise that the charge current is due to the charger voltage being greater than the cell voltage and that the internal resistances of the charger and battery etc do have a contributary effect on limiting the current, but the charger is still supplying the current and when this current reduces to less than 30mA the Blue LED should come on.



Of course the charger is supplying current in the CV part of the charge algorithm. When I wrote that it's not _pushing out a current_ I only wanted to say that the current is not controlled or regulated by the charger as it is in the CC stage. 
In the CV stage the current is determined by the voltage difference and the sum of the resistances of charger, battery contacts, protection curcuit and battery. 

The internal resistance of the charger is quite high, that is why the voltage measured at the contacts of the charger is not really constant during the CV stage. I would call the whole region above 4.05V the CV stage.

I'm just discharging a 18650 and will post a "normal" charging graph soon. I hope that will help to clear up any misunderstandings.


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## march.brown (Mar 7, 2010)

Tohuwabohu said:


> march.brown,
> probably I was just using the wrong words.
> It's more than 25 years ago that I learned English at school and I don't speak or write English very often.
> I spend more time looking up words than actually writing.
> ...


.
My apologies to you Tohuwabohu, from your written English I would never have guessed that it was not your first language ... It would seem that my poor choice of words "pushing out a current" was misleading.

Many Thanks for taking the trouble to reply so soon and I look forward to reading more of your posts about Li-Ion cells and chargers.

It would seem (to me) that some of the cheaper Li-Ion chargers work on this difference in voltage (between the charger and the cell) to charge the cell ... A higher current at the beginning of the charge when the battery volts are low then as the battery volts build up to about 4.2 volts, the charging current reduces to a point of equilibrium where the battery volts gradually becomes the same as the charger volts ... The battery volts will never actually reach the charger volts but gets within a few millivolts ... Obviously a charger with the proper algorithm (CC/CV) is ideal, but these seem to be at the high end of the prices ... I think that most people are willing to accept a charger that is not quite a perfect model as long as the charger works safely ... I was hoping that the Soshine would be better than my Trustfire TR-001, though the Trustfire seems to charge my 18650s OK ... I do always keep checking the volts regularly and I also switch off the charger as soon as I can after the Blue LED comes on.

Again, many thanks for your quick response and the excellent pictures and graphs.
.


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## Tohuwabohu (Mar 7, 2010)

march.brown said:


> .
> It would seem (to me) that some of the cheaper Li-Ion chargers work on this difference in voltage (between the charger and the cell) to charge the cell ... A higher current at the beginning of the charge when the battery volts are low then as the battery volts build up to about 4.2 volts, the charging current reduces to a point of equilibrium where the battery volts gradually becomes the same as the charger volts ... The battery volts will never actually reach the charger volts but gets within a few millivolts ...


That does not only apply to cheap charger but also to the good and expensive ones because there is always the internal resistance of the battery.
A high output resitance of the charger will lengthen the duration of the CV stage.
A good bench power supply has an output resistance near zero and will need far less time for the CV stage than the Soshine.
But the Soshine is already much better than the HXY-042V2000A "Digital Li-Ion 18650 Battery Charger".

Here is a charging graph of my #2 Soshine:




The charger is not modified, I measured an off-load voltage of 4.247V
The battery I used is a black and red Trustfire 2400mAh that I discharged to 3.0V.
To avoid any additional resistance I measured the current as voltage drop accross the internal current sense resistors of the charger (~198mV/A).
After 250 minutes the LED turned blue and I removed the battery from the charger but kept it connected to the voltmeter for two more minutes.
The maximum voltage at the end of charge was 4,238V.
The voltage dropped to 4.230V within the two minutes after taken out of the charger.
Half an hour later it measured 4,227V.
At the end of the CC stage, after 103 minutes, the battery is already charged to nearly 70%. The last 30% take much loger to charge.


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## march.brown (Mar 7, 2010)

Tohuwabohu said:


> That does not only apply to cheap charger but also to the good and expensive ones because there is always the internal resistance of the battery.
> A high output resitance of the charger will lengthen the duration of the CV stage.
> A good bench power supply has an output resistance near zero and will need far less time for the CV stage than the Soshine.
> But the Soshine is already much better than the HXY-042V2000A "Digital Li-Ion 18650 Battery Charger".
> ...


 
Many Thanks for putting this latest graph on CPF.

It seems that my charger has a slightly lower voltage than yours ... Presumeably this is due to the tolerences of the resistors used in the potential dividers.

My left hand charging slot, open circuit voltage reads 4.22V and the right hand reads 4.23V

I charged a single 18650 cell and when the Blue LED came on, I removed the battery and its open circuit voltage was 4.19V.

I checked again after 4 hours 30 minutes and the battery voltage was 4.18V.

At these voltages, I don't think it would be wise to alter the resistor ratios as I am happy with them.

Again, thank you very much for providing this valuable information, photographs and graphs.

Based on your findings, it looks to me that the model SC-S2 Soshine is one of the better Li-Ion chargers, particularly if the user is willing to adjust the voltage by adding the extra (high value) shunt resistors (if needed) ... Though in my case the voltages seem to be OK ... Naturally the cells should still be removed as soon as possible after the Blue LED comes on. 
.


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## mfm (Mar 8, 2010)

Tohuwabohu said:


> But the Soshine is already much better than the HXY-042V2000A "Digital Li-Ion 18650 Battery Charger".



Just because the curve is prettier? In the real world my XXC (Euro version of HXY) has exactly 4.20 volts open voltage on both terminals (so no modding needed) and charges an 18650 cell in four hours just like the Soshine.


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## Tohuwabohu (Mar 8, 2010)

mfm said:


> Just because the curve is prettier? In the real world my XXC (Euro version of HXY) has exactly 4.20 volts open voltage on both terminals (so no modding needed) and charges an 18650 cell in four hours just like the Soshine.


The curve isn't prettier, its better.
The Soshines charge much faster than *my* HXY.
I can deduce it from the current vs. voltage graph and I know it from real worl experience because I used to charge my 18650s quite often with the HXY charger.
But there are quite a lot of chargers that look like the HXY but differ in some details. So your XXC may be better.
The two bays of the HXY chargers are not fully independent, they will always have the same open voltage on both terminals.
But the voltage can vary from charger to charger.

I'll try to take charging graphs like the one in my last post with the Pila and the HXY charger and my bench power supply, all with the same battery dischargerd to the same level.
It will take some time but I think it will be interesting to see a direct comparison.


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## AlexLED (Mar 11, 2010)

Thanks Tohuwabohu, excellent review !!

I was thinking of buying that charger, so maybe I'll copy your modification.


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## march.brown (May 1, 2010)

I have just been charging and topping up a few 18650s with my Soshine SC-S2 and I found that the charger open circuit volts has gone up slightly from my earlier figures.

Initially the left hand channel was 4.22 volts and today it read 4.25 volts ... The right hand channel has also risen from 4.23 volts to 4.25 volts ... It is possible that this is due to components aging or possibly a slight difference in the house a/c supply voltages ... I will have to check this in future each time I use the charger ... The cells came off at 4.21 volts and settled at 4.20 volts after resting.

My Trustfire TR-001 open circuit voltages are 4.25V and 4.24V ... The cells came off at 4.22/4.21 volts shortly after the green lights came on and settled to 4.21/4.20 volts after resting for an hour or so.

My DMM is spot-on when compared to my five volt reference voltage , so I know that the readings are right.

The chargers are within limits , but I will still have to keep an eye on them.
.


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## Ray_of_Light (May 18, 2010)

From my experience, the almost totality of the cheap 18650 chargers are using *current limited - constant voltage - no charge termination* method.
Basically, the cell is fully charged four to six hours after the visual indicator changes colour (usually, around 4.20 Volt). After that, the cell MUST be removed from the charger.

In my "quest for knowledge", and under controlled conditions, I left two cells in the charger for a very long time. After two months, one cell delivered half capacity. The other cell, after three months, was totally bricked.

I tried to identify the mechanism of failure. By cutting open the cells in lab conditions, I was expecting to find some plating. Instead, I found the cells had the safety vent open and the electrolyte evaporated. With no electrolyte in them, the batteries were an open circuit.
This happened with two cells of different manufacture and age.

All in all, leaving the batteries few hours more in the charger is not producing any measurable damage. 
Nor, from what I can see and notice, there isn't any likelyhood of cell overheating or fire events, if you supervise the charging. 

Don't quote me on that - because a sample of two batteries and one HXY charger -is not enough of a sample to set a generalised procedure. Under different circumstances, some nastier conseguences, other than bricked cells, may develop.

It is my idea to replace, sooner or later, all my "cheap" Li-Ion chargers with the Pila IBC chargers. 

Regards

Anthony


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## old4570 (Jun 17, 2010)

10M resistor = 10ohm ? 

I want to use a variable resistor to get mine tuned to 4.2v , but on ebay I only see ohm's and K listed , there are no resistors marked as 10m or 1.5m , unless m = ohm ..... In which case a 100ohm variable resistor should work ok ?


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## 45/70 (Jun 18, 2010)

10 ohm = 10 ohms

10k ohm = 10 kilo ohm, or 10,000 ohms

10M ohm = 10 Mega ohm, or 10,000,000 ohms



Dave


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## 45/70 (Jun 18, 2010)

I'm not saying that it's a bad idea to modify a charger so that the end voltage of the cell(s) is reduced to 4.20 Volts, if it presently charges cells to an end voltage _higher_ than 4.20 Volts. That's acceptable, although keep in mind that the generally accepted end voltage is 4.15-4.25 Volts. That said, limiting the end voltage to 4.20 Volts will reduce the chance of causing unnecessary damage to the cell, to some extent.

On the other hand, I wouldn't modify a charger that charges cells to a voltage _lower_ than 4.20 Volts, just to obtain 4.20 Volts, particularly chargers that "trickle" charge, or otherwise use an improper charging algorithm. In this case, you're fixing one problem and creating another. For example, possibly forcing a cell that is aged, or otherwise damaged to a higher voltage level than would normally be obtained, or trickle charging at a higher voltage than before. Chargers that trickle charge the cell are best left alone if the ending voltage of the cell is <4.20 Volts. This way you have a pseudo safety margin, but should still remove the cells when charge completion is indicated. I often wonder if this is why many of the inexpensive chargers seem to charge to a voltage lower than 4.20 Volts.

Also, keep in mind that the proper termination of charge for any Li-Ion cell chemistry, is the cessation of current through the cell when the charging current drops to a level during the CV stage of no lower than 0.03C of the charging current. The actual termination point has nothing to do with voltage, other than as relates to the predetermined voltage of the the CV stage of the algorithm (again, _ideally_ 4.20 Volts for LiCo cells). As has already been mentioned, a charger using a proper algorithm, setup with a 4.20 Volt CV stage, can never actually charge a cell to exactly 4.20 Volts. 

Dave


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## Meterman (Jun 18, 2010)

It seems to me that most often in the 4.2V discussion is forgotten that the commonly used cheap DMM very seldom is capable to measure 4.20V *with the indispensable precision to one hundreth of a volt or even better.* So I think that before any modification is planned, the accuracy of the measurement should be clarified. :thinking:

Wulf


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## old4570 (Jun 18, 2010)

I have a expensive MM and a cheap one , I have used the expensive one to verify the cheap one ..

My Soshine charges to 4.23v on one channel and 4.2v even on the other , thats why I want to use a variable resistor , so I can tune it to get 4.2v out of the one that goes a little high ..

I like the soshine charger , for 18650's I think its great , and fast , its only downside is it needs monitoring for completion and to tweak the voltage down on one channel . 

It charges about twice as fast as the WF-139 , the WF-139 charges faster than the TR-001 , so the Soshine has its place in my charger collection .


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## Roger7 (May 12, 2011)

Hi 
I know it's all China but is it a better charger than Ultrafire WF-188 ?
I hesitate which one to choose

Thanks


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