Soshine SC-S2, Li-Ion Charger.

[Mr Happy]

Am I understanding correctly ?

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

 

[Tohuwabohu]

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

 

[old4570]

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

 

[Meterman]

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

 

[Tohuwabohu]

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.

 

[old4570]

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

 

[march.brown]

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 :-

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.

 

[Tohuwabohu]

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.

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.

 

[march.brown]

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.



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.

.
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.
.

 

[Tohuwabohu]

.
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.

 

[march.brown]

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.

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.
.

 

[mfm]

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.

 

[Tohuwabohu]

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.

 

[AlexLED]

Thanks Tohuwabohu, excellent review !!

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

 

[march.brown]

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.
.

 

[Ray_of_Light]

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

 

[old4570]

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 ?

 

[45/70]

10 ohm = 10 ohms

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

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



Dave

 

[45/70]

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

 

[Meterman]

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