Review: cheap 18650 mobile power bank

EDC Gear for Flashlight Carriers USB Power Devices
89

I just used one of the 2 "bad chargers" that I mentioned in the above post to charge a couple phones to see where it would cut off. Halfway through discharging the second phone, it stopped charging. It flashed the blue led when it cut off. My wife quickly disconnected it before I got a chance to check the voltage. I did check the voltage within one minute of it cutting off. The cell was at 3.3x volts.

The charger was definitely running hotter than seems appropriate. I had the lid off. I think it would have been too warm with the lid on. I didn't check temperature or current while it charged. I will try another run sometime this week and report back.

I don't know if good units also get hot discharging. I think I will pot mine with the first recipe from here anyway.

90

Good additional data esp. the nice photos, so looks like there may be several variants of this thing. IMO most/all(?) of the research/testing WRT FM6316CE-based ones should still hold…. E.g. think any FM6316CE-based ones that cease charge prior to nearly or fully discharging cell (e.g. to below 2.2v) are only doing so because the device being charged is ceasing charge due to low USB voltage.

91

Good point. I don't know why this one stopped yesterday. It would be nice to know the cell voltage under load just prior to it stopping. I'll try to capture more info next time. Maybe tomorrow.

92

I dug around a bit, and didn’t find any flat 4 18650 usb chargers less than this, in qty 1, but I did get a flat 2 x 18650 usb charger for a few bucks, and is on the way. I think there were some triangular 3s, and square 4s between $4 and $10 but the shapes weren’t interesting to me.

This may be a decent power bank for the price?

93

Received a blue one today from BIC. FM6316CE inside. It overcharges - I stopped when charging voltage was 4.4v, the battery measured 4.3v. It likely would go further. When I reinserted the battery something shorted and I saw smoke coming out the charger.
I’m glad I’ve ordered only one unit.

94

Now that I have that ENB 2x18650 that HKJ reviewed ($12 or so delivered) in hand & tested I offer this simple summary comparing to the FM6316CE-based ones:

The 2-cell ENB above is working very well as per HKJ’s review. Will say though that it seems better to use 2 reasonably matched cells in it. I found that although it does a nice job individually charging differing cells (e.g. both to 4.1Xv) it doesn’t discharge differing cells down to same voltage. But its still a safe/conservative cut-off voltage regardless, e.g. when it shutdown/ceased charging my iPod 2 the new green cell was at 3.5v and the old/differing purple cell at 2.9v when they were coupled. Also it takes a good long while to recharge the cells. But like it a lot - Thanks again HKJ!

95

You overpaid it for 50%, but still, u now have a decent power bank :stuck_out_tongue: http://www.buyincoins.com/item/25240.html

96

FYI - One of my white units has a bad chip as pictured in post #53’s 1st picture. :frowning:

Time the crack open the white units I closed up before the bad chips were discovered (better have a look at those boards. I have no clue what’s in them.) This should be fun. These things are closed up like tanks… :~

97

Yeah…sad that the chips suck…they are decently designed cases, close up really tight.

Ah well…I ordered some other charger and will retire these for sure, sucks these could have been pretty good little rigs

98

- The units’ (likely) cold solder joints on battery tab & spring can loosen when taking these all apart, be prepared to have to re-touch their solder joints.

- Again you don’t have to dissect them to confirm they’ve a “bad” design for charging your devices, you could check how it charges each device and avoid use for known high-draw ones (e.g. IPad 2). E.G. with power bank open during charging; 1) feel if USB jack is “too hot”, 2) use pack checking if battery voltage gets below 2.6v. IF you confirm/assure that ALL devices that would charged with it don’t pull > 1A (gets too hot) AND don’t pull battery below 2.6v, it may be OK to use.

  • I found not too hard to open using a small, thin blade putty knife in combo w/a thin blade screwdriver & knowing where the tabs were. The plastic sides give.

BTW my FM6316CE-based two are going in the trash. Not worth the hassle or risk, need at least 2x18650 to do any decent charging anyway.

99

FYI - In order to easily remove a closed case -> I carefully dremeled a hole in the back lid in order for me. Held in a bench vise with a rag & one usable hand this was still relatively easy.

100

It’s hard to see in this picture but the white bank with the bad chip is a lighter(newer?) shade of white then the white banks with the good chip. Perhaps this signifies that the bad chips were used in a new batch where there is a slight variation in the plastic used?

(it’s the 1st one on the left.)

here’s a pic of the white bank w/ the bad chip

Man, my batch order contained ~80% of the ones with bad chips. It seems the is much protection PCB soldering onto 18500 cells in my future (I might not even have enough of these.)

Anyway -> for the banks which I will keep for personal use I am contempting whether or not I want to make a notch in the lid (before closing) in order for future cell removal.

On the ones intended for gifts -> I haven’t decided if I want to do this. + Using protected cells in the “bad” chipped ones only partially addresses one of it’s downfalls. I would not use high drain devices on the such as tablets. I fear the drain will be too high for some of the components. Unless one had already ordered these I would recommend getting a different type of power bank. What a hassle.

Heck I might not even gift the ones I have here if the “good” banks still turn out to be junk in repeated usage. I’ll think it over before giving these out.

101

I’m awaiting a shipment of five of these as well (from BIC). Did you guys contact them and ask for a compensation?

102

I bought another two from another ebay seller.

I got a black and a white one and sadly both contain the FM6316CE-based circuit inside. But something else is different to the one that broke down for me before, they contain SS34 diodes instead of SS24, maybe something else is different too?

Can anyone confirm that the ones with SS34 diodes are also bad for them? (over discharging possible?) If not I will probably just try to use it normally and get a refund if it breaks.

But before really using them I will measure some things before they break again. Maybe just parts of the circuit are missing, as there are quite some free pads on these small boards(?). In my opinion, what also looks suspicious is this 0 ohm resistor.

103

I’ll pop mine open tonight and check em out

104

My unit (blue from BIC) has ss34. It was overcharging and shorted and burned before I did a discharge test.

105

OK, and I also re-read these thread and dchomak’s also did over-discharge, from his pictures he also has SS34….

I will then start experimenting I guess, trying to replace the 000 Ohm (which actually connects the GND of the device) with 1…5 Ohm or something and see what this does, or rather thinking more about what could help….

But I probably should ask for a refund anyway.

The best would be to get the real circuit diagram or board layout of these little CHD-XS V1.1 board / pcb as it might contain some missing parts for these unpopulated soldering pads. Someone good at googling this? Maybe it can be found…

106

Just a heads up -> BIC’s CS responded to my partial refund request very promptly & just offered me a refund of more than 50% of my order total (consisting solely of these power banks.)

As this pretty much seemed to be a cut and dry case of this power bank’s manufacturer opting to now produce the units with unsafe chips -> BIC goes on my list for good vendors.

For the record, I am not affiliated with them in any way and I have sent very little $ overall towards their way.

107

All 20 of mine arrived today…and all 20 have the 6136 chip. Brilliant. To those who have said they have no overcurrent protection, I shorted a usb cable through my multimeter and it was trying to push 5A. I only wanted to test one but the results were certainly concerning. My Ruinovo 6x-18650 box cuts before the multimeter refreshes past 1.5A, and requires a push of the hardware button to reset the breaker.

Dissappointed

EDIT: Also, no over-charge protection either, I’m filing a dispute with the vendor so I’m sacrificing a laptop pull and I want to see how high it will charge it.

108

Hm interesting one of the new FM3616CE based ones (with SS34 diodes in my case versus my previous with SS24) does have the blue led become more and more dim after the battery reached 2,5V. After that with a multimeter I saw it going down to about 2,38V when I disconnected it. By now the cell has recovered to 3,72V (still rising, this was just minutes ago…).

To say something positive, the FM3616CE might actually try to keep the cell at 2,5V, by cutting-off at 2,5V - but with a bad implementation that already begins to discharge again at 2,50…01 V so you could say, disregarding production variance and temperature dependence that maybe means something between 2,45 or 2,55V for that barrier…
Anyway, this would mean, each time the battery goes above 2,5V, it will again be discharged for at least one pulse of the FM3616CE’s internal boost converter, grinding down the battery to a certain voltage, until it won’t even recover to 2,5V anymore! Then it will probably really stop to discharge… but that might maybe be too late for the cell, I know electronics but I am not a battery specialist. Maybe someone else who knows more about batteries can even say that this is perfectly fine? But I am suspecting it is not, as the current will be quite high, for a 5V 1A discharge, this will already mean a cell discharge current of at least 2A, not counting the conversion losses.

To those who don’t know what I mean with “pulse”: The FM3616CE is very probably doing a DC/DC buck conversion for charging and a boost conversion for discharging, these kind of converters have a certain operation frequency in which they operate, for more details, see [1] below - basic electronic understanding is still required though.

In the end:
Maybe (just maybe) this is also just a lack of circuitry and the FM3616CE itself is actually quite good: Some resistors, diodes, capacitors, whatever might be missing…. When looking at the CHD-XS V1.1 circuit board, there are still multiple unpopulated parts and one 0 Ohm resistor. Maybe it would actually work if all/the correct parts would be populated……

Additional Information: I did only check for discharge cut-off doing all this, not for overcurrent protection so far!

Maybe I am experimenting more at another time. This is already over the limit of my time making sense to me (expect if I would buy 100+ and rework them, which I won’t be doing…), at least at the moment it is still fun as a short pastime :wink:

[1] DC-to-DC converter - Wikipedia

EDIT:
Ok I also verified that it is not overcurrent protected at all :-/