Test/review of Charger ISDT C4

HKJ · 2018-03-11T19:14:51.000Z

Charger ISDT C4

This charger from ISDT has a lot of functions and can handle both NiMH and all 3 common LiIon types. It can also do NiZn.

The charger was in a cardboard box with specifications on the outside.

The box contains the charger, a power supply, a instruction sheet, a screen protector and some stickers.

I used the screen protector, but as can be seen on some of the photos I was not very lucky with putting it on.

The stickers.

The charger is powered from 12V and has a usb output and a micro usb “update connector” for new firmware releases.

The fan is a bit loud and will turn on/off frequently when the charger is working hard, this is rather annoying.

On the bottom is the specifications and air intake correctly placed at opposite end of air outlet.

The power supply is a standard 12V 2.5A model.

The user interface is a good looking color lcd display and a panel at the right. It is possible to touch up/down/select, there is auto repeat on up/down. The up/down function can also be done by sliding.

The touch button works mostly fine, except it sometimes believe I am sliding when I am not.

The charger will automatic recognize NiMH, 3.6V and 4.2V LiIon batteries, but for the two LiIon types this recognition do first take place around 3.6-3.7V, until then it will not specify what type LiIon it is charging. This also means that discharging or charging to storage voltage the automatic recognition will sometimes fail.

The charger has a lot of modes, I have tested most modes below.

Available chemistries: NiMH, NiCd, NiZn, Eneloop, Li-Ion, LiFePO4, LiHv (In my test I used NiMH, not Eneloop)

The display looks very nice and includes a lot of information.

There is no scale on the curve, but it gives a good idea of what is going on.

Even the input voltage and the usb output current is monitored.

Holding down on the select button will open the system menu where it is possible to see software/hardware version, reset to factory settings, select language (5), beeper volume (off-low-medium-high), backlight (low-medium-high), capacity limit (on-off), auto start after (off, 3s, 5s), cycle display (off-5s-10s)

The charger has fixed slots, this limits what size batteries it can handle:

AAA slot up to about 45mm

AA slot up to about 51.5mm

xx650 slot up to about 67mm

The slot marked AA/AAA can also handle LiIon batteries.

The charger cannot handle protected cell, but both button top and flat top will usual work. The charger is very limited in supported battery sizes, but with spacers it is possible to handle a few more sizes.

Measurements

Contents

4.2V LiIon charging

4.2V LiIon discharging

4.2V LiIon analyzing

4.2V LiIon storage

4.2V LiIon cycle

LiIon internal resistance

LiIon activation

4.35V LiIon charging

3.7V (LiFePO4) LiIon charging

NiMH charging

NiMH discharging

NiMH analyzing

NiMH internal resistance

NiMH activation

USB output

Power consumption is 1.5W when idle with display on and 0.9W with display off.
Charger do not assume chemistry on voltage alone.
Charger will sometimes automatic select between LiFePO4 and LiIon 4.2V
When not powered the charger will discharge LiIon with about 0.03mA
Voltmeter is within 0.03V
Voltmeter updates both during charge and when the charger is finished.
Charger will not restart if battery voltage drops
Charge will restart charging after power loss or battery insertion.

The charger has 4 channels and each has two set of terminals. The black numbers are the channels, the white numbers are the references I use in the test.

Test is done with firmware 1.0.0.8
After the testing I updated to firmware 1.0.0.11, it was easy on a Win10 computer. The description of the improvements was not very useful, it just said “optimization” for analysis and NiMH charge.

4.2V LiIon charging

The charger current for LiIon can be selected from 0.1A to 3A in 0.1A steps.

This charge is a good simulated CC/CV curve.
Display shows: 3214mAh 67mOhm 6:50:30

At higher charge current it goes faster and the voltage will go above 4.25V.
Display shows: 3274mAh 54mOhm 2:26:10

How much it goes above depends on the internal resistance of the cell.
Display shows: 3212mAh 46mOhm 2:25:03

This cell is not exactly new and the voltage goes above 4.30V, using a lower charge current would have improved this.
Display shows: 2630mAh 75mOhm 1:33:45

Two cells at maximum charge current, again the voltage is up tp 4.30V.
Display shows: 2842mAh 48mOhm 1:05:22 and 2821mAh 45mOhm 1:08:15

Using an external 12V supply it looks like the 2.5A input rating is exactly right, but 4.40V during charge is way to much.

M1: 29,7°C, M2: 30,6°C, HS1: 37,0°C
The charger do not heat the batteries from internal heat, the fan handles this.

HS1: 36,0°C

The charger needs about 5 seconds to start, a few of these seconds are used to wait for the user, other are used to initialize and play a welcome melody.
The charger starts slowly and after a few seconds it will use the selected current.

While charging it will turn current off to do a voltage check each 3. second.

4.2V LiIon discharging

The discharge current can be selected from 0.1A to 1.5A in 0.1A steps.

The charger discharges to 3.1V and it looks like it is adjusting the current trying to keep the voltage at 3.1V.

Two cells at full discharge current.
Display shows 2685mAh 2:02:26 and 2677mAh 2:00:10

M1: 27,2°C, M2: 25,9°C, M3: 38,9°C, HS1: 44,2°C
The noisy fan is good at keeping the batteries and charger cool.

HS1: 42,1°C

4.2V LiIon analyzing

For analyzing LiIon the current can be selected from 0.1A to 3A in 0.1A steps. The time shown is for the total operation.

The batteries are charged, discharged and charged again. The charge is not done correctly it is missing the CV part (See below about software update).
Display shows 3260mAh 76mOhm 10:04:29

If the selected current is higher than the possible discharge current it will charge at selected current and use maximum discharge current.
Display shows 3021mAh 68mOhm 03:58:41

4.2V LiIon storage

For storage the current can be select from 0.1A to 2.5A in 0.1A steps.

First try at storage failed, the charger guessed it was a LiFePO4 cell and started discharging it, this was very fast!

This time I selected 4.2V LiIon and the storage worked much better, it charged the battery to 3.7V
Display shows: 1267mAh 57mOhm 01:01:23

Next storage test was with a full battery and it was discharged to 3.7V

4.2V LiIon cycle

This cycle the current can be select from 0.1A to 2.5A in 0.1A steps, there is only one current setting.
The number of cycles can be selected from 1 to 66.

In this test I did 3 cycles and the charger added a final charging. The CV part of the charge is missing.
Display shows 3074mAh 56mOhm, 21:10:48

LiIon internal resistance

The charger shows internal resistance while charging.

The first row is done with the same battery in all slots, there is some variation some of it due to varying contact resistance.
For all the other measurements the battery and connection is not touched.
The results looks good, the charger is fairly close to the correct resistance values most of the time.

LiIon activation

The selection said 2A, but the display said 0.1A at 0V (Current will increase at higher voltage).

The charger applies 0.1A for 2½ minute to try resurrect the battery. If the voltage increase the current will also be increased.

A closer look at the current shows it is pulses.

When activation fails the charger report “Battery type wrong”

4.35V LiIon charging

The charger has a special LiIon LiHv type that charges to 4.35V

The simulated CC/CV charging strikes again with too high voltage during charging.
Display show 2845mAh 154mOhm 03:07:29

3.7V (LiFePO4) LiIon charging

Usual the charger will automatic recognition this type of LiIon cell and stop the charger at 3.7V

Display show 1131mAh 92mOhm 00:57:03

Both cells are charged fine and looking at the start of the curve it can be seen that the charger uses a low current below 3V.
Display show 512mAh 118mOhm 00:39:25

NiMH charging

The charger current can be selected from 0.1A to 2.0A in 0.1A steps.

In the first curve I have selected way to low charge current for the cell and the charger failed to terminate when the cell was full, the termination was either on time or capacity (The 3001 in the display makes me suspect termination was on capacity).
Display show 3001mAh 52mOhm 30:56:17

A more sensible charge current and the charger uses a -dv/dt termination.
Display shows 1972mAh 51mOhm 2:02:01

It is the same on the 3 other channels (I used the same cell for these 4 test.

Display shows 2092mAh 44mOhm 2:09:25
Display shows 2067mAh 48mOhm 2:07:55
Display shows 2096mAh 55mOhm 2:09:43

This high capacity cell is handled fine.

Display shows 2658mAh 68mOhm 02:44:28

The charger could not really terminate on this cell, but due to the 3000mAh limit, the charging is fine (Or as fine as can be expected with this old cell).

Display shows 3001mAh 202mOhm 03:05:38

Nice charging.

Display shows 799mAh 95mOhm 01:38:55

A full cell was discovered in 10 minutes.

Display shows 171mAh 57mOhm 00:10:37

Four NiMH at full charging current, this time the charger was a bit slow to terminate.

Display shows 1997mAh 63mOhm 01:01:49, 1992mAh 44mOhm 01:01:40, 1997mAh 41mOhm 01:01:49, 1992mAh 40mOhm 01:01:40

This time the charging looks perfect. The charger uses less than 2A from the power supply.

M1: 28,4°C, M2: 30,2°C, M3: 30,7°C, M4: 28,4°C, HS1: 37,6°C

Not much heat in this picture.

The charger need some time to initialize and wait for any user interaction, before starting charging.

While charging it will turn current off to do a voltage check each 3. second.

NiMH discharging

NiMH discharge current can be selected from 0.1A to 1.5A in 0.1A steps.

A NiMH discharge is to 0.9V and with a final low current discharge.

Display show 1895mAh 2:01:52

These discharge are done with the same cell as I charged above.
Display show 1882mAh 2:01:27
Display show 1919mAh 2:03:48
Display show 1927mAh 2:03:46

M1: 27,0°C, HS1: 38,9°C

The fan keeps the charger cool.

NiMH analyzing

NiMH analyzing current can be selected from 0.1A to 2A in 0.1A steps.

The analyze cycle is a charge, a discharge and a final charge again.

Display show 2175mAh 47mOhm 13:02:55This is a super eneloop cell with more than 2000mA?

NiMH internal resistance

The charger shows internal resistance while charging.

The first row is done with the same battery in all slots, there is some variation some of it due to varying contact resistance.

For all the other measurements the battery and connection is not touched.

The results looks good, the charger is fairly close to the correct resistance values most of the time.

NiMH activation

The selection said 2A, but the display said 0.1A at 0V (Current will increase at higher voltage).

The charger applies 0.1A for 2½ minute to try resurrect the battery. If the voltage increase the current will also be increased.

A closer look at the current shows it is pulses.

When activation fails the charger report “Battery type wrong”

USB output

Power consumption is 1.5W when idle with display on and 0.9W with display off.
Usb output is auto coding with DCP, Samsung and Apple 1A

The current display has good precision.

The usb output can deliver just above 2.3A before overload protection trips.

And it is exactly the same on 230VAC (As expected).

No problem running for one hour with 2.1A output.
The temperature photos below are taken between 30 minutes and 60 minutes into the one hour test.

M1: 38,4°C, M2: 36,3°C, HS1: 43,1°C

M1: 37,4°C, HS1: 57,1°C
I found a hot spot on the charger or at least a warm spot (The charger did not use the fan when I used the usb output).

M1: 37,6°C, HS1: 43,0°C

Noise is 172mV rms and 567mVpp

Noise is 206mV rms and 850mVpp

Noise is 148mV rms and 673mVpp

With the fairly high noise level I decided to check what it contained.

New firmware V1.0.0.11

While I was testing a new firmware was release. I did first update when testing was finished and then I did a few extra checks on the areas where the new release was supposed to improve the charger (Analysis and NiMH charge).

The low current NiMH charging was not improved, it still do not terminate.
Display shows 3001mAh 40mOhm 30:56:17

Normal NiMH charge looks similar.
Display shows 2075mAh 61mOhm 02:08:22

A CV voltage has been added to the initial charge in analysis mode and the discharge mode do not slowly reduce current anymore, instead it drops to 0.5A from there sloly reduce current. It looks like the charge failed, there is no CV phase.
The fan did not stop when the charger was finished, but continued to run.
Display shows 3138mAh 106mOhm 06:10:25

Testing with 2500 volt and 5000 volt between mains and low volt side, did not show any safety problems with the power supply.

Conclusion

This charger has many functions and is easy to use, but it also has a few faults:
Auto recognition of LiIon 4.2V and 3.6V(LiFePO4) do not always work. I have seen 4.2V LiIon stopping at 3.6V and discharge/storage is also likely to fail if started with a partial full 4.2V LiIon.
First version of analysis missed the CV part, next version is better in that respect, but charger malfunctioned, this will probably be fixed in a later software update.
LiIon charge algorithm use way to high charge voltage, but the battery will not be overcharged.
There is also the limit on battery size, some common LiIon sizes requires spacers to be charged in this charger.

Do this charger match the top analyzing charger? The answer is no, it is far behind in settings and precision, but it is much easier to use.

For now I will only rate the charger acceptable.

Notes

The charger was supplied from Banggood for review.

Here is an explanation on how I did the above charge curves: How do I test a charger
Read more about how I test USB power supplies and chargers

ImagioX1 · 2018-03-13T03:38:47.000Z

Thanks for the review. I’ve been looking at the MC3000 but I feel like color touchscreen cylindrical battery chargers are right around the corner and I don’t want to be stuck with an expensive outdated charger LOL. Was hoping this one would fit the bill but it has too many short comings for me. Probably will have to pass.

Andrew_Debbie · 2018-03-15T11:07:47.000Z

Thanks for posting. Your excellent review is an accurate description of the features and shortcomings.

Do you think that no sliders makes the C4 better at measuring internal resistance? I wondered if sliders are part of the reason why the Lii-500 is poor at measuring internal resistance.

I’ve been using my C4 for several weeks now. It works well to charge a pair of 18650s. I also updated to firmware V1.0.0.11. The fan stops on mine after completing an analysis cycle. I’m trying it again with a 26650 5Ah cell.

The fan cycles on and off during the discharge portion of analysis. That is annoying. I can tune out a constant-on but not on and off.

I hope that ISDT will post another firmware update soon that fixes the flaws you uncovered. A low speed for the fan would be nice but maybe that isn’t possible.

My conclusion:

This could be a very good engineering charger after the next firmware update. Too limited be a general purpose charger. It is expensive but maybe that helps pay for the firmware updates.

HKJ · 2018-03-15T11:31:46.000Z

Andrew_Debbie:

Do you think that no sliders makes the C4 better at measuring internal resistance?

Depends on how the sliders are made, but no slider will often be better. This will only be related to the first line in my IR test table, in the other lines I do not move the slider.
Slider solutions (5 is best, 1 is worst for measuring IR):

Only rail is connected to charge current
Rail and spring connected to charger current.
1. - a wire connected directly to slider with charger current
1. - a wire connected directly to slider with charger current
Only a wire connected directly to slider with charger current

Some add a wire to improve their charger.

gregor · 2018-03-15T12:23:11.000Z

Thank you for this nice review.

stephenk · 2018-03-15T21:03:46.000Z

Looks good, but needs a few firmware updates and ability to handle longer batteries. Thanks for the review HKJ!

LichtAn · 2018-03-20T18:57:58.000Z

The display is so beautiful but the negative points are too overwhelming sadly. The high charging voltage is a no-no for me.

meeshu · 2018-07-28T06:26:30.000Z

Just received an iSDT C4 charger ordered from Banggood.

Charger posted the day after my order. According to tracking, charger was "held up" for several days somewhere
between China and NZ while in transit between the two countries. Slight delay in NZ Customs of a day or two.
Charger arrived 14 days after date of order.

Charger within its box was wrapped in black plastic bag for shipping! No extra protection for the charger/box was
provided (ie no foam, no bubble wrap etc) which was of some concern. Because on opening the black shipping
bag, one corner of the charger box had been "squashed" somewhat leaving about an inch long split along the
edge of the box by the corner which was squashed!

I thought the charger may have been damaged (during transit), but fortunately the charger was (partially) enclosed
within a plastic "carrier" inside its box and there was no damage to the charger! Phew!!

Connecting the charger to the mains power supply was straight forward. Noted that the firmware version of the
charger was at 1.0.0.17. I had already downloaded the latest firmware for the charger at version 1.1.0.6. I
immediately tried to update firmware to 1.1.0.6, but had trouble because the flashing software ONLY runs under
64 bit systems. Fortunately I have Windows 7 64 bit as well as other operating systems, so I was able to flash the
charger to firmware version 1.1.0.6 successfully in the end.

The reason for updating the firmware was to address some concerns about fan noise and other miscellaneous
issues.

I found the user interface fairly intuitive and didn't have to refer to the charger manual again (I did read a
downloaded pdf copy of the manual a day or two before the charger arrived).

I set the C4 charger to "cycle" a couple of NiMH cells. And one good aspect of this charger is that the charge and
discharge currents are independent of each other and can be set to whatever value you prefer. Many other
chargers such as the Opus series of chargers for example have their charge and discharge currents linked.
Usually their discharge currents are half that of the charge current, and this ratio can't be changed.

The C4 charger cycled the NiMH cells for about 12 hours plus, and there was no fan noise noticed, probably
because the fan didn't switch on at the low cell temperatures while cycling. Cell temperature didn't exceed about
24° C according to the C4 charger display.

The main good point about this charger is that is displays all cell parameters (voltage, current, capacity,
temperature, internal resistance, charge/discharge time) at once without having to push buttons to see other
parameters. Additional button presses are more common on other chargers (such as the Opus chargers for
example) in order to see other cell parameters.

Now there are a couple of minor issues, especially when running the cell "cycle" program. The number of cycles
can be adjusted up to 66 before starting the program, the default setting is 3 cycles. The problem is that the
charger doesn't show which cycle number it is presently running in. For example, the number of cycles could be
set to, say, 17, but the present cycle number could be 11, or 8, or 16, or ? So, I would like to see the addition of a
cycle counter to the display; it could show the total number of cycles that have been set, and also show the
present cycle number.

Another issue is that the early cell capacities (in mAh) are not shown in the display. Only the present cell capacity
is shown (while cycling). For comparison, I would like to see the previous cell capacities displayed so that their
capacities can be compared to the present cell capacities. This way we can see what changes, if any, are being
made to cell capacities.

Considering this was a relatively expensive purchase, I would like to have seen better protection for the charger
during shipping. The addition of shipping foam or plastic bubble wrap or even newspaper would have been
preferred (or even mandatory?) for such higher value shipments!?

A good point is that Banggood included a plug adapter free of charge for converting the default "Euro" power
adapter plug to the NZ power plug configuration.

Overall though, the C4 is a very good charger and is now my primary charger.

teacher · 2018-07-28T07:08:16.000Z

Thank you HKJ!!

meeshu · 2018-09-01T21:41:41.000Z

After using the iSDT C4 charger a bit more, a few issues were noted.

The touch screen 'buttons' were found to be a bit 'twitchy' and did not always respond, or there was a delayed response.

The 'terminals' or contacts for charging AAA cells are basically just a piece of bent wire! It was found that placing AAA cells with button top was a bit tricky to ensure the button top contacts the 'wire' terminal properly. I would like to see wider/flat charging terminals for AAA cells so that contact (with button tops) would be no longer be an issue.

Would like to see an AUTO mode option for charging current so that the charging current is dynamically adjusted according to the cells internal resistance (like the Miboxer series of chargers). This could probably be accomplished by updating the firmware.

Because of these "issues", the C4 has been demoted and is no longer my primary charger.

Andrew_Debbie · 2018-09-12T14:11:50.000Z

I just updated my C4 to firmware 1.1.0.9. There were three interim updates since HKJ tested the C4 with 1.0.0.11.

The end of analysis fan bug is fixed.

Requesting a 1.5A discharge rate gives a slightly lower current until about 3.7V. (see photo)

Andrew_Debbie · 2019-08-06T09:28:42.000Z

May 2019: The latest firmware is now V1.1.0.13

Most of the release notes are in Chinese. The release notes mention improved LiIon and NiMH charging. NiMH full charge voltage is now 1.55V.

I’m still using 1.1.0.9. but will update to 1.1.0.13 soon.