Aliexpress dodgy car charger

[matkar]

Time for a small rant. Not really worth the time but worth letting others know.
I recently bought a few car chargers for my tablet. I bought several different models because I expected not all will be usable. In fact only one proved to be almost up to spec.
But this is the story about the worst among them:
https://www.aliexpress.com/item/Micro-Auto-Universal-Dual-2-Port-USB-Car-Charger-For-iPhone-iPad-iPod-3-1A-Mini/32665128882.html?spm=2114.13010608.0.0.yChAdZ

This charger has a terrible ripple at the output (measured at 1A output current). Image below.
I didn't dare to connect my tablet to this source of evil. I opened a dispute on aliexpress explaining what the issue was. Aliexpress decided to release the payment to the seller. I asked them if they didn't understand the issue or didn't find the issue important enough and they responded:
Appeal Rejected
Reason for rejection:
Regarding this dispute, we found from the current evidence you provided we cannot judge the product defects. It is hard for dispute team to help our buyers if the evidence is not supported.That's why we reminded you to provide the detailed pictures or videos to verify your claim in the mail .Sadly you have not supplemented evidence and the dispute was closed.

Lesson learned. Don't fight aliexpress over technicalities. They didn't understand the problem. Luckily the lesson wasn't expensive.
I'm yet to leave feedback for this item but really don't know what to say...

Some modern DC-DC converters have a max input voltage of 5.5V. This charger clearly exceeds the specs on devices with such converters on board.

Does this charger rely on all devices having enough input capacitance to smooth the ripple?
Would you use it on your devices if you knew about this before?

[MagicSmoker]

Although I don't doubt that a charger from Aliexpress will suck six ways to Sunday, are you sure you are measuring ripple and not switching noise?

Ripple from an SMPS will always have a triangular shape (because of integration of the current performed by the inductor, and of the voltage by the capacitor). Switching noise, especially when radiated from high dV/dt nodes (as compared to high dI/dt loops), tends to look like thin spikes that match up precisely in time with the turn-on and/or turn-off event. Often this noise can be dramatically reduced with an additional small LC filter after the output capacitor (small defined here as a cutoff frequency about 10x higher than the main LC filter [note that the main output filter L in a flyback is the secondary winding]).

[Fraser]

Where power supplies and car adapters are concerned I take the view that my equipment is more valuable than any saving made buying cheap no-name units from China. I have had to repair many tablets and GPS units that have been damaged by cheap in-car adapters. They were for other people and I learnt from their mistakes. I tend to buy the OEM power supply units or those of another well known brand . Second hand is actually safer than new on eBay as so many fake units come out of China.

An example of a most serious failure follows......

Some high quality in-car 5V power adapters will often use a sense line on the output as well as the main supply conductors. This sense line samples the voltage at the DC connector as it enters the equipment and is used by the DC-DC converter to compensate for losses across the copper output cable. Some such cables are quite long in car applications and a voltage drop at high load currents becomes an issue. Some Chinese car adapters tried to copy this sense wire system. Unforunately they used very poor quality output cables and the sense wire was a very fine and fragile conductor. In normal use it would fracture. If it was a normal power rail conductor no real harm would occur. Sadly this is not so with the sense line. The DC-DC converter suddenly lost its sense voltage and its reaction was to increase the voltage output to try to bring the sense line back to 5V. The result...... a DC-DC car converter that had 12-14V input and supplied a solid 12-14V output ! The effect on the 5V input of the equipment can be imagined !

Overvoltage can be far more damaging to an equipment than reverse voltage as reverse voltage is often defended against with a protection system. Overvoltage cooks any component not intended to receive such an increased voltage. It can cause carnage in an equipment that uses what it expects to be a regulated 5V to power its processor circuits directly via some filtering and polarity protection.

TomTom were a victim of such poorly built DC-DC car converters when the first TomTom 'Classic' was released. The sense wire in the Chinese DC-DC adapter was very fragile and would fracture at the plug end where most flexing occurred. A recall and free repairs resulted. It cost TomTom a lot of money to sort out. A case of an OEM making a poor accessory purchasing decision.

Fraser

[matkar]

... are you sure you are measuring ripple and not switching noise?

Yes. Other chargers have ripple in the range of 100mV at most.

Where power supplies and car adapters are concerned I take the view that my equipment is more valuable than any saving made buying cheap no-name units from China.

I agree. That's why I bought several different ones and tested them all.
From the bunch this type is the most promising:
https://www.aliexpress.com/item/Dual-Port-USB-Car-Charger-For-Iphone-6-Plus-6s-6-5-4-For-ipad-Samsung/32765646819.html?spm=2114.13010608.0.0.IiSZOH

Other chargers can output only 600-700mA before the output voltage sags.

[SeanB]

I put some of those into an order on a whim, and of the 3 I got, one went up in flames on test ( I was powering it from a 12V SLA pack just to see if it actually worked) with only a 30ma load from the USB voltage monitor on it, and I decided the other 2 were probably going to have a similar fate, so took one apart to see why. Tiny ceramic capacitors inside, no fuse at all other than the traces, inductor that looked barely capable of 50mA let alone the 1A plus claimed, soldering that was really horrid ( even for the lowest cost shops) and generally shoddy thin board and a tiny 5 pin SMD switcher there.

I recycled an old Nokia charger, and simply grafted a micro USB plug onto the end in place of the Nokia plug, and it works perfectly for charging at 500ma for my needs. 5V 650ma rating, and can actually deliver it as well. Finnish tech at it's best.

[rsjsouza]

I wouldn't expect the folks at Aliexpress to understand the talk about ripple, noise, but instead a more practical proof of a non-workable unit: does not charge, iPad blown, etc.
As Fraser mentioned, the marginal gains of off-brand chargers are not worth if you have the option of buying a branded one - in certain countries or markets you have absolutely no choice other than these cheap units.

[Fraser]

Yes sadly car adapters appear to be a favourite for poor quality parts and performance. I even found one that contained only a resistive potential divider, and another that contained a resistor and zener diode. Total cr*p.

It must also be remembered that car supply rails can contain nasty voltage transients that destroy cheap DC-DC switchers and can even lead to the full potential being delivered to the output.

I buy Nokia, Sony, Motorola, Samsung, Nook and HP car adapters. All have been high quality products with input protection, over voltage and over current detection and decent build quality.

Fraser

[rsjsouza]

Your post also reminded me of a kit my dad gave me a few years ago: it was a very nice LED flashlight (similar to this one) that used a 18650 battery and charger. Not only the mAh rating of the 18650 was marked as larger than anything else from eneloop, panasonic or other brands, but the charger... ah, the charger. It looked really nice from the outside, but its internals were just a resistor, a LED and the barrel jack were both the plugpack and the cigarette lighter adapter could be connected. That is criminal, considering how dangerous lithium-ion batteries are.

[matkar]

When I bought from Ali I expected some of them would be of poor quality and not to spec. I was surprised to see most of them don't meet the specs even remotely.
A disassembled NOKOKO brand charger that is the best by performance. The picture is in the attachment. It can handle 1.6A for a short time with no ripple increase and no voltage drop (below 5V).
The chip gets very warm after a while and the voltage drops eventually due to overtemperature protection I suppose. I will mount a small heatsink to it. No input fuse or any other type of protection is present on the board.

[wraper]

I recall in the past receiving like 8 Nokia 6020 phones for repair from a single customer, all with blown TVS and/or fuse on the charging input. Turned out trucking company bought a bunch of car chargers for their drivers.

[amyk]

When I bought from Ali I expected some of them would be of poor quality and not to spec. I was surprised to see most of them don't meet the specs even remotely.
A disassembled NOKOKO brand charger that is the best by performance. The picture is in the attachment. It can handle 1.6A for a short time with no ripple increase and no voltage drop (below 5V).
The chip gets very warm after a while and the voltage drops eventually due to overtemperature protection I suppose. I will mount a small heatsink to it. No input fuse or any other type of protection is present on the board.

http://www.szssm.com/411.html
That IC is only rated for up to 1.2A, so 1.6A is beyond what it should be able to supply.

[thm_w]

Lesson learned. Don't fight aliexpress over technicalities. They didn't understand the problem. Luckily the lesson wasn't expensive.
I'm yet to leave feedback for this item but really don't know what to say...

Put some similar feedback as here so people know to avoid it if they are expecting 2A.
$1 for a car usb charger is absurdly cheap though. I see some Rock/Aukey ones for $5-6 which are probably much better quality, its not much money.

I see one comment already:

I thought these would be good , but on each one of them , if I have my galaxy , and tablet plugged up , they both charge for 10 to 30 seconds , stop for same amount of time , cycling, but when you only have one device pluged up , no problem , I guess you get what you pay for

[Fraser]

There is really one important question to ask before buying cheap Chinese power supplies of any sort..... is it good value for money if it fries my appliance? In most cases the answer is no.

There are times when buying really cheap gear from China makes sense, such as buying Arduino related stuff. If it fails there is no real harm done. The same cannot be said for power supplies used with expensive appliances. The old British saying, "penny wise, pound foolish" comes to mind.

We have likely all seen both good quality and appalling quality power supplies that come out of China. Usually the good ones come from known manufacturers and through reputable supply chains. A junk power supply, be it for mains or 12V car sources, is false economy.

Some people dismantle the power supply before use. Good idea but do they totally trust the markings on the switcher chip ? Is it genuine, within spec and fitted with the internal protection systems of a Genuine part ? If not, when it fails it can cause havoc.

Fraser

[JPortici]

i swear, there was a photo on piclist some years ago from a guy that opened a cheap chinese car charger, it contained only a zener and a resistor.