Test/Review of Charger Klarus CH4s

[HKJ]

@ferongr

At some point during the charge with the older cells the voltage overshoots the 4.2V mark. Is this reflected on the display?

I do not look at the display during test and did not simulate it either, i.e. I do not know.

[light-wolff]

Thanks for your revier, HKJ.

One question that arises on every charger/analyser review:
How accurate is the capacity display for charging and discharging?

You always write down displayed capacity, which is fine, but this doesn’t tell much because we don’t know the actual value for comparison. One would have to read it from the charge graphs, but this is difficult and inaccurate.

Would it be possible to add actual capacity in the text, like “Display shows 717mAh, actual value is 780mAh”?

Im my experience, the simple analyzer/charger with better than 10% capacity accuracy under all conditions does not yet exist. Soshine, LiitoKala, Kingpower, Foxnovo, none of them did a good job at measuring capacity. They’re all just “guessing” capacity, for some cells it works better, for others worse. XTAR I didn’t test.

[HKJ]

@light-wolff

One question that arises on every charger/analyser review: How accurate is the capacity display for charging and discharging? You always write down displayed capacity, which is fine, but this doesn’t tell much because we don’t know the actual value for comparison. One would have to read it from the charge graphs, but this is difficult and inaccurate. Would it be possible to add actual capacity in the text, like “Display shows 717mAh, actual value is 780mAh”?

The problem is getting a good accuracy, my shunts used to measure charge/discharge currents are only within a few percent and I do not wish to maintain calibration factors for each of my shunts.

Another way was to use batteries with known capacity, but that would mean I had to check them all the time with some of my more precise equipment.

I would expect that most chargers are build with standard 5% or 10% parts and without any calibration, i.e. there will be significant difference between copies of the same model. This means there are no reason for precise measurement in the test.

For now I do not really see a good reason to spend the extra time getting precise measurements.

[light-wolff]

Ok, I see.

Some chargers seem to have algorithmic or systematic problems measuring charge.
Like at 1A set discharge current (actual current 1.04A) after exactly 1h displaying only 870mAh.
Or like using a PWMed 0.8 Ohm resistor for discharge, resulting in current pulses of 4A peak at 13% duty cycle when 0.5A is set.
Etc.

[HKJ]

@light-wolff

Some chargers seem to have algorithmic or systematic problems measuring charge. Like at qA set discharge current (actual current 1.04A) after exactly one 1h displaying only 870mAh.

These type of errors you can usual see on my curves.

@light-wolff

Or like using a PWMed 0.8 Ohm resistor for discharge, resulting in current pulses of 4A peak at 13% duty cycle when 0.5A is set. Etc.

That is 0.5A discharge current, but I do prefer constant current.

You can also see this on my oscilloscope pictures, but the current will usual be a bit to low because I uses a 0.1ohm resistor to measure across.

[light-wolff]

@HKJ

@light-wolff

Some chargers seem to have algorithmic or systematic problems measuring charge. Like at qA set discharge current (actual current 1.04A) after exactly one 1h displaying only 870mAh.

These type of errors you can usual see on my curves.

Maybe some people can, but most can’t.

@HKJ

@light-wolff

Or like using a PWMed 0.8 Ohm resistor for discharge, resulting in current pulses of 4A peak at 13% duty cycle when 0.5A is set. Etc.

That is 0.5A discharge current, but I do prefer constant current.

You can also see this on my oscilloscope pictures, but the current will usual be a bit to low because I uses a 0.1ohm resistor to measure across.

Problem is: PMWing this way makes it very hard to impossible for the charger to measure current accurately (using the sampling ADC of the µC). And even if it did: what is a measurement of 1C-capacity worth if it’s actually carried out with 8C pulses, even if at some 10kHz?

I believe it’s worth mentioning that the displayed capacity on all these charger/analyzers, though having 1mAh resolution, is at best an educated guess. Ok to roughly compare some cells, but almost useless for absolute measurements or to verify manufacturer’s specification. On one charger I tested (not a Klarus CH4s) I’ve seen systematic errors from –20 to +15%, but this one here seems to be better.

I agree it’s not easy to measure exact charge and discharge mAh in the process. I also have no means to do this without influence on the process (like using a shunt).

[maniac]

I just wonder if there is a simple way to measure battery capacity .

With powerbanks , tablets & phones I just put a USB Volt/ amp tester , my version even had the mAh reading !!!.

Tested it to be pretty accurate !!! ( In some/ most case I couldn’t even find a 5-10% error!!! )

But with batteries I think u need a HOBBY charger kit to accurately measure it capacity , that’s from my limited knowledge , please correct me if I am wrong!!!