car usb charger not durable

I have gone through several car usb chargers that plugs into cigarette lighter plug.

They usually die in a few months.

I just opened one up and it has a 34063a IC in it. The circuit is probably similar to this:

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When I plug this in it draws 3mA but the built-in LED doesn't light up. I assume the IC has fried.

Any idea why these chargers don't last long? Where can I buy one that last longer, and how is it made differently to make it last longer?

Reply to
bob
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Because they're junk?

What are you charging? I see some that are rated for 2A but I've fried a few of those, too. Some have two USB ports. Don't do it!

Reply to
krw

Didn't think too deeply about it, but it's a different circuit topology than the one shown on the first 34063 datasheet that I pulled up. I hope that the ifixit web site is wrong, because the inductor location seems wrong!

Reply to
Frank Miles

I passed out about 15 of those to various friends and customers last Christmas as "stocking stuffers". None have failed so far. Most are being used to charge phones. Unlike yours, these have two USB sockets. One wired for Apple, and one for the rest of the planet. Something like this one: I'll tear one apart today, if I can find where I put them.

The schematic looks odd. There's also no spike or reverse polarity protection on the 12V line. The automobile electrical system is a hostile environment, which is quite capable of delivering high voltage spikes to connected electronics from starter back-EMF and such. Extra credit for alternators that don't know what to do with a dead battery[1]. Since I can't seem to find a plague of similar problems, my guess(tm) is that your situation is unique. I suggest you plug an oscilloscope and DVM into your cigarette lighter jack and see what's coming out, especially when you toggle loads (lights, heater fan, radio, etc) and start/stop the engine.

Doing a post mortem might help, but you're probably correct. There's not much else to blow up except the IC.

Your vehicle might be killing them.

I bought some of these. on a recommendation by a friend. It seems to charge my Samsung tablet at the rated 2A, but I haven't bothered to measure it. No failures so far.

[1] I lost 3 alternators, several 2way radios, and the glow plug timer in my 1983 Dodge D50 before I figured out what was happening. Charging a good battery is fairly simple. What to do with a half-dead battery is not so simple.
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Jeff Liebermann     jeffl@cruzio.com 
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Reply to
Jeff Liebermann

Another approach would be to bodge in a PolyZen. They're brilliant.

Cheers

Phil Hobbs

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Dr Philip C D Hobbs 
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Phil Hobbs

ghter plug.

y

That website is the usual internet electronics site: junk. The schematics a re both obviously wrong in that the feedback to IN(-) requires a DC input a nd therefore should be connected to the output node and not the diode node. Other comments there are similarly smug and probably wrong.

assume

The thermal impedance of that IC package is rather high at about 90oC/W, wh ich means it's going to run hot, the Darlington output drive is the least e fficient way to use the 34063.

ake it

Reply to
bloggs.fredbloggs.fred

snip!

OT: Say Jeff, do they still have that big nude hot tub place in Santa Cruz?

I thought that was rather unique, when I was there... jb

Reply to
haiticare2011

Yeah. They're really slick. I'd use a bunch, except that they won't reset themselves when the fault is removed. I'm looking for a replacement for expensive TVS diodes. Thinking about a couple of nose-to-nose pass-fets with appropriate controls but they're not so good (or cheap) at high currents, either.

Reply to
krw

What I have done in the past, if I had a car battery that only wanted to sip a few mA from the 6 A or 10 A charger, was to stick the dumb 1 A charger on it and let it cook for a few hours. After that, I could put the "big" charger on it and it would actually charge at a decent rate (5 A to 10 A) and then taper off as normal. Maybe some alternators don't know to back off if the brute force approach isn't working?

By the time I had to do that trick to get it to charge, the battery was kinda beat, but doing that would get it to work as good as it could for a while - days to weeks, depending on the usage of the car.

If the battery still wouldn't take a good charge (more than a couple of amps) after cooking on the 1 A charger overnight, it was usually toast.

Matt Roberds

Reply to
mroberds

Did you have a meter on that 1A charger? Was it delivering 1A or just a few hundred miliamperes too? I suspect the big charger was using a 3-stage alg orithm and was knocked right into stage 3 float charge by the high terminal voltage, whereas the 1A charger was some simple 1-stage taper charge.

Reply to
bloggs.fredbloggs.fred

It didn't have a built-in one, but sometimes I used my DMM (20 A range) inline.

The 1 A nominal charger would deliver less than 1 A, but more than the

6 A or 10 A charger would. It was 15+ years ago, but I vaguely remember that the battery would initially draw something like 0.2 - 0.3 A from the "1 A" charger, but 0.0 - 0.1 A from the "6 A" or "10 A" charger.

The 1 A charger was indeed a taper charger, but so were both big chargers. Each one had exactly four pieces of silicon in it, no "smarts".

I have seen the effect you are talking about with smarter chargers and batteries that have a high terminal voltage for some reason. Sometimes you have to load the battery for a minute or two to drop its terminal voltage and get the charger to switch back to "bulk charge" mode.

Matt Roberds

Reply to
mroberds

The biggest problem is poor power management in the start up circuit, which for many have none.

One of the biggest problems of cheap unmanaged power for starting up these things is the fact that outlet power in the vehicle at times gets turned off/on abruptly, mostly during the starting cycle of the vehicle.

These cheap charging units do not provide an instant reset for a proper restart on the controlling chip and thus, could hang the MOSFET into full on, with no switching.

So if one has a vehicle that drops the voltage out or dips a lot at the accessory socket during start cycling, it's very conceivable for this to happen.

I've had several pass my bench just for an inspection of contents and found the fusible link or component to be opened but no shorted components, a couple did exhibit signs of escaping smoke. Most of them work fine after the fusible component was rectified.

Just some thoughts..

Jamie

Reply to
Maynard A. Philbrook Jr.

Okay, the simplest "old time" bulk chargers, like those manufactured by Mot orola e.g., were pretty bare with a heavy 60Hz step-down transformer drivin g some SCRs with a zener in the gate circuit. They were very reliable and l asted forever, no electrolytics used, the zener would taper the firing angl e to zero as the battery approached 2.4V/ cell. That type of charger has a very non-linear operating characteristic as a function of battery terminal voltage so a few hundred mA here or there, not too mention the difficulty o f measuring a true average DC charging current, is no big deal.

Your batteries were sulfated, not worth salvaging or risking a breakdown in the middle of nowhere. Replace them when they lose cranking power, you're not going buy yourself much time using a charger. The battery charger indus try is as much a ripoff as the exotic audio garbage.

Reply to
bloggs.fredbloggs.fred

Ooooh, $2.99- weren't you the big spender!

Reply to
bloggs.fredbloggs.fred

I overpaid. Here's a similar 5V 2A device for $1.74 including shipping from China:

They were for my friends as Christmas/Hanukkah gifts and are what we call "reefers", which are free or bargain marijuana cigarettes passed out by drug dealers to entice users into buying the more expensive hard drugs. In this case, my logic was to give away devices that are both addictive and of dubious quality, which would then inspire them to purchase a better device from me: Unfortunately, none have failed so far, making my holiday sales promotion a rather unprofitable affair.

Incidentally, the really good friends also got USB charge/sync cables with their adapters, most of which were either lost, loaned, or in some way destroyed. The geeks got one of these cables instead, which have so far proven to be nearly useless: $4 including tax and shipping.

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Reply to
Jeff Liebermann

Ouch.

There are two in Santa Cruz that I know of: They're both about 50 meters from each other, so you can easily walk over and try both if you're so inclined. There are also the usual assortment of massage parlors, spas, and medical marijuana dealers. If you can survive in cold water and morning fog, try the nude beaches:

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Jeff Liebermann

With all due respect for your instant judgement, I think you'll find that iFixit is one of few sites on the internet that offer help to the shrinking minority of people that have a genuine interest in fixing things. This is largely a self-defense effort against manufacturers (and possibly designers) who favor throw-away electronics and unrepairable devices. The web page above is a user contributed page, which lacks the benefits of a proper editorial review. I would not judge the entire web site on the basis of one web page.

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Jeff Liebermann     jeffl@cruzio.com 
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Reply to
Jeff Liebermann

Is that your ad?

That thing is ridiulous, dunno who would make use of it unless they think c lutter is beautiful.

The OP's charger could be made to last forever if he tacks a P-FET in there to deliver the bulk of the current. If you look at some of the Chinese des ign notes, they're more obsessed with the package, and the electronics is m erely an afterthought, they refer to the regulator as the 12-to-5V conversi on circuit and represent it as a very small block of negligible importance- probably a bunch of "industrial" engineer/designer types. Let's hope and p ray they stay out of the coffeemaker business.

Reply to
bloggs.fredbloggs.fred

No. I sometimes resell stuff I buy on eBay for those who do not like to buy things online. There's an amazingly large number of people who live in morbid fear of hackers, cyber criminals, crooks, Chinese vendors, and resellers like me.

It's an improvement over carrying a tangle of cables or seperate chargers for each device.

That's correct. It's the package that sells, not the electronics. A few cents spent on attractive package will yield far more sales than the same amount spent on overvoltage and spike protection. When you're building something to sell for $1.74, there's no room in the budget for frills like protection circuity. Adding a P-FET might cost $0.30 more, which would price the device out of the market.

Next time I draw a schematic, I'll try to remember to draw blocks of importance somewhat larger.

What do you have against industrial engineers and designers? Or do you prefer products that have a miserable user interface, are clumsy o use, that don't fit together, are a pain in the posterior to manufacture, and look awful? Without industrial engineers and designers, everything you own and use would be drab, ugly, clumsy, ugly, dangerous, ugly, boxy, ugly, non-ergonomic, ugly, overly utilitarian, ugly, ugly, ugly, etc, and probably more expensive.

I switched to tea, but I see your point. For examples of your future coffee hell, see: Some are design concepts, but many are available for purchase today. Some may even produce drinkable coffee.

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Jeff Liebermann     jeffl@cruzio.com 
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Jeff Liebermann

Like a complete idiot, I decided take apart one of my cheapo USB car chargers and see what makes it work. I know they are junk, but I never expected them to be this bad. Start here:

What's inside:

They ground off the numbers from the switcher chip so I couldn't identify it. I *ASSUME* that it is a common MC34063A, but that's apparently not the case because there's a heat sink on the bottom of the chip that is suppose to be sweat soldered to the PCB. I therefore have the wrong chip number. (Sorry about the focus problem but you can see the metal bottom on the chip). Of course, it's not soldered, so heat dissipation will suffer.

I'm still not sure it's an MC34063A, but if that's the chip, it's only rated to 1.5A, not 2.1A. Argh. Duz anyone have a clue as what other chip it might be?

So, I then traced out the schematic. It's not an MC34063A because it doesn't oscillate and the schematic is somewhat different from the test circuits in the app notes and data sheet. The LTspice simulation results in zero output. I'm also not certain of some of the part values. The resistors are probably correct, but the small cap and inductor are bad guesses since my LRC meter is not available.

I then noticed something odd in the resistor network around the USB connector. If you look at R3, R4, R5, and R6, on the schematic, it makes no sense. The traces between the data pins on the two connectors should have been seperated (or cut). The way it shows on the PCB and schematic, the pins are shorted together. No way is that going to work for both Apple and Non-Apple products.

To be continued, possibly with some measurements, as time permits.

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Jeff Liebermann     jeffl@cruzio.com 
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Jeff Liebermann

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