Teardown of a classic 4-slot battery charger made by Duracell. This innovative charger also works as a USB powerbank supplying 5V at 500mA.
By Julian
Youtuber, shed dweller, solar charge controller aficionado
Good morning all…
Youtuber, shed dweller, solar charge controller aficionado
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I've got 2 of these. Both won't turn on USB output unless the accus are FULLY charged. However when they are, let's say 50% charged, there's a way to "trick" the charger by pluging it to 230V and then turn on USB output, unplug it, and it works until accus are depleted. Strange, isn't it? Overall my favourite charger.
I have duracel cef23 any body tell methe number of switching regulte controler ic.
no tis not because it doesnt turn off instantly
Interesting video, I like how it gives the ability to plug in a USB such as the flashlight or a charging cable… maybe Duracell has created something more recent? Your videos are very informative
Seems like a very nice design for its time a short while ago, thanks for sharing.
Can you run USB mode when it's plugged into the wall, or USB mode plugged into the wall and no batteries? That way it would fit the description of a "universal charger" a tad more.
Would it be iterating voltage down the line? Like PWM, but instead of turning off the voltage, it switches rails? So at any one time there will be a potential difference? Does a RMS reader read different?
It is possible that the battery charging voltage gets passed as series to the USB. That means it does no smart charge, just sticks a voltage on the the tabs, all of them pulse width modulated out of phase with each other, so it will still add up together to produce the voltage for the USB.
Heyy Julian! Ypu probably didn't watch the Varta battery charger teardown of Dave Jones 😉 I think this works exactly the same way. The batteries are charged by one constant current source (that is probably clamped to some voltage) and all the active (<- that's the keyword, so not the empty) slots of the bank are put in series. The empty/fully charged slots are simply bridged out. This way you need you constant current source and it's easy to tap the battery or the charging voltage and just step it down to USB 5V.
I'd try shorting one battery and putting it in usb mode to see if it passes ~3.6V out the USB port or tries to step it up somehow.
I've been watching your stuff for quite some time now and I've learned so much and enjoyed every video you have put out! I was wondering if you could do your own kit build that your viewers could order and do at home with your videos? Or at least round up the parts and solve a simple problem.
Perhaps they're charged in series too, and they're just shorting out the missing cell bays with the FETs. Your voltage measurements with 2 cells would make sense that way.. The two points on the same end are electrically the same as measuring a single cell.
I wonder if you shave the DC plug whole just a little wider on the case, then maybe you won't need the DC cable spitter. You shouldn't have to shave much off to widen the diameter.
Fascinating teardown.
From your voltage measurements, I think the cells are charged in series and the transistors just switch in to bypass empty slots and they're still in series for the USB output. I wouldn't be too surpised if those inductors and caps in the corner are a DC-DC converter for the USB output.
I have something similar but it works with 18650 lithium ion batteries. its both a 4 slot 18650 charger and it has 2 usb ports on the back to used the charged cells as a power bank. Dunno if id trust AA's to do a power bank job though.
I was told that 500ma charging is better for batteries, when compared to faster, higher amp charging.
The cells are probably in series, with a FET switched bypass for each. EEVBlog (#811,#812) did a teardown of an other charger with similar construction a few months ago.
It looks like a nightmare trying to manufacture this circuit board…