Review of / Measurement on Soshine SC-S7 Charger

[size=+3]Charger Soshine SC-S7[/size]



This is a smart charger that can handle both LiIon and NiMH batteries, it can charge one battery at a time and is rated for a 1A charge current.



I did not get the charger in a full retail package, but instead in a envelope.



The envelope contained the charger, a universal voltage (100-240V 50/60Hz) mains power supply and a usb cable.



The plus connection is slightly raised, this means that the charger can be used with flat top batteries.




The minus connection is a slider that can be manually moved . This gives a span from 26 mm to 70 mm long batteries.
I would have liked a spring in one of the ends, this would have made the adjustment easier.
The negative end can be used as a spring, but then it must be moved in, before the battery is placed in the charger.



Power can be supplied from a 12 vold adapter or from a usb power supply, in both cases it requires a 1A power supply.



Instead of the typical red/green leds, this charger uses a display to show status information on.



When no battery is in the charger it shows this standby display. There is a faint clicking sound from the charger in this mode.



While charging it shows the voltage and the time used, with LiIon it will also show an estimate of how many percent capacity is charged into the battery.
The voltmeter has some limitations, for LiIon it will not show below 3.3 volt or above 4.2 volt, it will stay at these voltages.




When done the display will show a battery full message, then show the time used and the capacity charged into the battery, these 3 displays will cycle. The capacity is not a precision measurement, but good enough to compare LiIon batteries and see when it is time to replace a battery (Remember the battery must be empty to measure the capacity).
For NiMH the value will be way above the battery capacity, these batteries need some extra current when being charged.





The charger can handle 70 mm long batteries including flat top cells.



[size=+2]Measurements[/size]

Below 0.7 volt the charger reports standby and is pulsing 130mA current to test for a battery, this will also reset a protected battery.
Between 0.7 volt and 2.3 volt the charger assumes it is a NiMH battery.
Above 2.3 volt the charger will assume LiIon.
When a battery is put into the charger it will start with about 300mA and after some time switch to full charge current.
When charger is disconnected from power, but with a battery in, it will discharge with 2 mA from a NiMH and 7mA from a LiIon.
When the charge current goes below the termination current the charging is stopped and it will discharge with 2 mA from a NiMH and 10mA from a LiIon, but due to pulsing the battery will stay charged.
The charge will always restart charging when a battery is put into it or after a power loss and for NiMH it might charge a significant amount of current.



The first test is with a 18650 battery, the charger does a CC/CV charge profile, but when it report battery full (At the yellow line) it starts doing some very strange pulses.



Same battery, this time with usb power. The charger starts at full current, but reduces the current during charge, maybe because it cannot supply full current with the lower voltage difference between battery and usb voltage?
It does look like the pulses stops after some time. The pulses will not damage the battery, but the battery will be charged slightly higher.





A smaller LiIon battery works exactly like the 18650 I tried first.



My old IMR cell, did not work as expected, after a short time the "Poor cell" text turned on and it showed "FAIL" on the display. The charger has a point about the cell.
I have also seen the charger only show "Poor cell", but continue to charge.





When charging NiMH the 300mA current on for much longer time, than when charging LiIon and this makes it visible in the charts (My guess is that this current is used to detect a LiIon battery with). The charge current is the same on 12 volt and usb power.
This charger might use -dv/dt terminations for NiMH.
The charger also has the pulsing after the charge is terminated and it does not look like it will stop, this is perfectly fine for a NiMH battery.



This is the charge current, just after a NiMH battery is put into the charger, it is pulsing with 300mA current.



After some time (about 10 minutes) it switches to the full 1A charge current, but still pulsing. During the low part of the pulse it is discharging the battery (The red curve is below the 0.0 line)



This is the charge current, just after a LiIon battery is put into the charger, it is pulsing with 300mA current, it will after a few seconds change to the full current.



Full charge current into a LiIon battery. This does not do any discharge in the pulses.



The LiIon battery is full and the charger is pulsing and also doing a weak discharge in between the pulses. The average will continue to charge the battery. Note: I have changed scale.



[size=+2]Conclusion[/size]

The charger has many interesting features: Charges both LiIon and NiMH, shows charged capacity, detect bad batteries, shows charge state for LiIon.
But all these features are only interesting, if the charger does a good job. It looks like it does a good job on NiMH and an acceptable job on LiIon, but I am not impressed with the pulsing when the charge is supposed to be finished. The discharge of a few mA is not really significant, except if leaving the batteries in the charger for days.



[size=+3]Notes[/size]

The charger was supplied by illuminationGear.com for a review.

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

Excellent review!

Excellent review. HKJ!

Thanks for your effort & good information. :thumbsup:

I bought one after reading your review, paid just under A$15, had it a few weeks now very pleased.

Great review, but your costing me $$$

Norm

Thanks for the review, HKJ!

I bought one and now I am expecting anxiously that arrive. Seems to be almost my dreamed charger: small, functions with Ni-Mh and Li-Ion, USB, digital display... :thumbsup:

What happens with if charge it from a USB computer with only 500 mAh ?

BlackhawkB said:

What happens with if charge it from a USB computer with only 500 mAh ?

Click to expand...

If the USB port shuts down, the charger will be stopped.

hi HKJ!

i purchased this charger for lack of a 18700 compatible one AND tis usefulness in measuring charged mA.

the question is what is the voltage one would expect a NiMh and Li-ion battery to be 100% discharged? (to be used as a starting point)
1.2 and 3.2V respectively?

kosPap said:

the question is what is the voltage one would expect a NiMh and Li-ion battery to be 100% discharged? (to be used as a starting point)
1.2 and 3.2V respectively?

Click to expand...

I have written an article about LiIon.

For NiMH you need to load the battery before measuring the voltage, but I do not have a table.

I have written an article about LiIon.

Click to expand...

Great resource, thanks

For NiMH you need to load the battery before measuring the voltage, but I do not have a table.

Click to expand...

The question is what kind of load. I guess you can do it with a resistor and i have been meanign to ask about this.

A look at the Eneloop datasheet shows that full caapcity is used at 1.2Volt with a 400mA....So to measure if the battery is dead we duplicate that current draw with a resistor of proper value and wait to see a 1.2V reading..correct?

kosPap said:

The question is what kind of load. I guess you can do it with a resistor

Click to expand...

A resistor is usual a fine load.

kosPap said:

A look at the Eneloop datasheet shows that full caapcity is used at 1.2Volt with a 400mA....So to measure if the battery is dead we duplicate that current draw with a resistor of proper value and wait to see a 1.2V reading..correct?

Click to expand...

Looking at the curve, you got energy down to about 1.1 volt even at 400mA and the battery is declared empty at 1.0 volt.
With a load you will probably have to wait a little time, before the voltage has dropped.

one more question....
How accurate is the chargers voltmeter? Mine's is off by more than a volt.
Strangely the charge percent status is acurate.
i.e. I am getting a 90% reading and 4.2Volts at the same etime

I have been using my sc-s7 for a week now with only one issue. A eagletac 3100 i bought from *bay is showing poor cell. I wounder if it has something to do with its a protected cell. None of my un protected cells have any issues.

firemedic said:

I wounder if it has something to do with its a protected cell. None of my un protected cells have any issues.

Click to expand...

I purchased this charger because of this thread, so I must have had it for 8 or 9 months most of my cells are protected and so far have never had any problem.

Norm

I have a question and hopefully someone will read this thread, otherwise I'll post a new thread...

I got this charger recently with some green-label ncr18650A cells. The charger says it charges up to 4.2v, but my DMM says 4.10v. For comparison, I get between 1.603 and 1.609v from a pack of fresh alkalines, so I think my DMM is OK. I understand that 4.1v will protect my cells, but is it low enough that I should return the charger? I might open it up and see if I can maybe replace the chip with a better version. Is it the chip that controls final charge voltage, or some accessory resistor or something?

Also, one of the cells came with a slightly bent button top. Is this reason to worry or is it normal? Both cells were at 3.6+ when I received them.

Thanks! Dan

From here.

HKJ said:

With a good LiIon charger the charging voltage is 4.2 volt (+/- 0.05 volt, i.e. between 4.15 volt and 4.25 volt). This does not mean the battery will end up with 4.2 volt when finished charging, usual it will be slightly below.

This chart slows a typical charge cycle, it is in a couple of phases:
1) Constant Current (CC), where the charge current is constant and the voltage will rise.
2) Transition from CC to CV, on the above curve it is absent, because the charger is very good.
3) Constant Voltage (CV), where the voltage is constant (at 4.2 volt) and the current slowly declining.
4) When the current has declined to the termination current (At the yellow line), the charge is terminated and the current turned off. This will always lead to a instant voltage drop (Notice that the red line drops when current is turned off).
5) The resting phase, this can be from seconds to months, depending on when the battery is going to be used. There will always be a slight voltage drop over time. During the first few hours the drop will be fairly rapid (But it usual not more than 0.0x volt).

How much the voltage drop will be, depends on a couple of factors. The termination current is important, but also temperature, battery age, actual chemistry.


Some chargers use simulated CC/CV (WP2II, i2, i4) or constant current puls charging (Fenix, WF139), these will often charger the battery to a slightly higher voltage, before terminating (Because they measure the voltage with the charge current off, for simulated CC/CV the difference is small).

Click to expand...

Yeah, I had seen the +/- 0.05v spec before, and was concerned that -0.1v was too low. According to this excellent site: http://lygte-info.dk/info/BatteryChargePercent UK.html, an NCR1865A (Panasonic 3100mah) retains 94% of charge at 4.1v. I think I will not worry about it, since I have heard that lower charging voltages give more cycles.

Thanks, Dan

hmmmm where are yuo gwetting your 4.2V figure? From the charger's screen of from yuor multimeter?
I ask becuase I have observed a 1+V difference between the two in my case, though I do get cells around 4.2V from the charger when done (DMM measured).

schizeckinosy said:

Yeah, I had seen the +/- 0.05v spec before, and was concerned that -0.1v was too low.

Click to expand...

Don't forget your meter also has an error spec which will influence the Voltage reading.

Norm

kosPap said:

hmmmm where are yuo gwetting your 4.2V figure? From the charger's screen of from yuor multimeter?
I ask becuase I have observed a 1+V difference between the two in my case, though I do get cells around 4.2V from the charger when done (DMM measured).

Click to expand...

The charger display says 4.2v when it terminates, and my DMM shows 4.10-4.11 (+/- 2% of reading or +/- .2% full scale which is 40v so about +/- 0.08v - cheap DMM) I have checked voltage while charging and my DMM and the charger are consistently 0.1v off. If I can find a quality DMM to try I will check again.

The more I read about Li-ion cells, the happier I am that the charger appears to be under-volting thecells. Batteryuniversity indicates that there should be a doubling of life for ever 0.1 less volts that the charger puts in, for not a lot less mah.

So, your charger indicates that it is charging the cells to 5.2 or 3.2v? That would scare me more. At least my charger *thinks* it is giving the correct charge!