Test/Review of Charger Opus BT-C3100 software V2 update

Thanks man! First :stuck_out_tongue: So great! Reading it now!

I hoped for better news, but thanks anyway :slight_smile:

Thanks for the update, HKJ. Would you still say this is a good buy, for $40?

I’ve already bought mine, so will be finding a better power supply to get rid of some of the issues you noted.

Yes, it is much easier to use than a four channel hobby charger and much more compact (The hobby charger is a better analyzer & charger).

My power supply broke after one use. I now see why. I’m using a higher power PSU now with no issues.

Thank you for the review :slight_smile:

Helo. Where can i buy the white battery holder?

Thanks for the review, very good charger.

Fasttech has a bunch, just remember to check length, as some protected batteries don’t fit in certain holders.
http://www.fasttech.com/search?18650%20holder

Thank you HKJ, your reviews are awesome.
One question: Could it be possible to add a big input electrolytic capacitor to reduce that current spike? If not how should they modify the design to remove that spike?
Thanks.

I have the FT holders. They are small, cheap and poor.

I want white.

Plus FastTech holders are known to cause shorts with unprotected cells because the metallic part goes under the heatshrink on the positive side.
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I’m surprised to see that HKJ has a hobbyking power supply for his hobby charger. I would have immagined that he would use a more robust lab PSU or even a PC power supply as I’m sure he has many!

It is not produced any more.

Yes, it would have to be about 100000uF.

Keep the charge current pulses as low as possible and use a decent buck regulator on the input. Using a buck regulator on the input will reduce the peak input current draw to about half the peak charge current. I.e. 4x3A charger current is 12A and using half that from DC input would only be 6A from the 12 volt supply (Assuming the internal working voltage is 5 to 6 volt).

Stepping the charge pulses down to 2A would be even better and then using an extra transistor to parallel two charge circuits for high current charge.

My favourite would be real current regulation without pulsing, but it requires a more complex circuit.

Yes, I do have many lab power supplies, but they are MUCH larger. I do not really uses PC power supplies, except in PC's. I prefer that a power supply is in a closed box.

With that small supply I can take the charger and power supply out when I need them. This is not very often, usual my two iChargers are enough.

Ahahah ok.


Do you imply that this charger does not use a buck regulator? I doubt the fact that it’s using a linear regulator! Or is it?

The charger does have an inductor for each slot and I assume it does some sort of buck regulation, but it is not doing a good job.

One detail is that the input current pulse is about 10ms, but the charger pulse is closer to 20ms, i.e. the charger has to use double input current.

Thanks for the great review HKJ.

Is the EU plug of higher quality or i still need to replace it in order to achieve best results? thanks.

As you can see in my first review the EU supply did also have problems, but I did not analyze it as careful as I have done this time.

I understand. This is indeed a very bad design. If they bothered to include an inductor then it should not be that hard to make a nicer solution. Or even simpler they could change the phase of pulsing by 90° for each slot to avoid pulling all the current at the same time.
If I understand correctly, the charger sends a PWM current with 3A amplitude and changes the duty cycle according to the desired charge current. Isn’t that bad for a small AAA cell? 3A is way beyond a safe charging current.

Yes, using four phases would be a good solution, but I doubt the hardware supports it.

Due to the pulsing speed it will average out, but generate more heat than a constant current. Double current generates four times the heat and only having it on half the time will only reduce the heat to half.

I do wonder how much peak current the small cells can take, but all analyzing charger for NiMH batteries works this way.

Interesting. Thanks.


You have two icharger 208B? Are you a RC hobbyist? I would like to hear more about your setup. You should do some reviews about these hobby chargers, batteries, etc.

Yes and no. I bought the iChargers after my first battery test and was planning to use them for the next one. But a couple of trial runs showed me that they where not suitable for it.

Instead I upgraded to electronic load and lab power supply, both controlled from a computer.

I do have a lot of equipment: Power supplies, electronic loads, DMM's, oscilloscopes, waveform generator, component testers/analyzers, etc.. A lot of it can be computer controlled.

At the bottom of most of my reviews, you can find a link showing what equipment I uses for that test. The listed equipment is not always 100% correct and often substitute with another unit that has the same function.

Maybe one day, hobby charger do take a long time to analyze and test.