Dangerously high temp USB battery bank charger!!! - Page 1
Forum section: electronics / beginners

author: edy
author_rank: Super Contributor
timestamp: June 14, 2014, 03:37:15 am
content: Hi folks,I bought one of those USB battery banks to top up my cellphone when it runs out of juice. It is called "Xtreme" 2600 mAh Portable USB Battery Bank.http://www.xtremecables.net/2600mAhPowerStickBatteryCharger-1-1.aspxI have attached a photo. When I am using it to charge my BlackBerry Z10, the end with the USB connectors gets up to 74 to 78 Celsius and runs this hot during most of the charge drain!!! See the attached photo where I put a thermocouple into the end of the USB port.Is this normal? What is going on? I usually just leave my phone in my pocket while it is charging up but I'm afraid to fry my gonads with this thing!!!!

author: KSP
author_rank: Regular Contributor
timestamp: June 14, 2014, 06:14:37 am
content: FUUUUUU.....No... Just no... I would throw it a mile personally. Batteries+heat=bad timesAnything that is too hot to touch (which 78c certainly is) should not be a portable/pocket device. I would call it faulty. I've never heard of the company but if they are a reputable brand then get hold of them and ask them wtf is going on

author: rob77
author_rank: Super Contributor
timestamp: June 14, 2014, 07:53:28 am
content: i assume there is a linear regulator inside - and that's the reason why it gets hot.take it apart if possible to verify that, but DO NOT damage the LiPo battery inside - if you puncture the LiPo it will catch fire (in most cases) - and the lipo fire is not the one which can be easily distinguished (water is making it even worse).you can eventually replace the linear regulator with a small switch mode regulator (you can buy ready-to-go small SMPS modules on ebay or DX - very cheap)

author: Legit-Design
author_rank: Frequent Contributor
timestamp: June 14, 2014, 08:02:39 am
content: Phone wants around 5V? LiPo/Li-ion are typically ~4.2V max? Probably not linear regulator inside. Throw it in the bin and get a working one.

author: rob77
author_rank: Super Contributor
timestamp: June 14, 2014, 08:21:38 am
content: Quote from: Legit-Design on June 14, 2014, 08:02:39 ami would bet on a 2 cell Lipo with a linear regulator inside

author: Psi
author_rank: Super Contributor
timestamp: June 14, 2014, 08:34:54 am
content: 78C externally = Internally a contender for the smallest pizza oven

author: Legit-Design
author_rank: Frequent Contributor
timestamp: June 14, 2014, 09:08:52 am
content: Quote from: rob77 on June 14, 2014, 08:21:38 amI would bet on single 18650 cell inside.

author: edy
author_rank: Super Contributor
timestamp: June 14, 2014, 11:05:40 am
content: I feel like making a USB-ended heat sink... one of those block finned aluminum ones you see on top of processor chips, and soldering a USB to it (just the outer ground) so they are thermally connected and plugging it into the battery bank when using it. At least it will draw heat off the unit.Just thinking it may be also that the particular phone I am charging draws a lot of current as well, whereas other phones may limit this. I know that when I used the Xtreme 1800 mAh with my phone it wouldn't charge at all and I returned it for this 2600 mAh version. The icon which indicates charging on the phone would light for maybe 5 seconds and then stop, or would say source not good enough to charge.Alternatively I can send it to Dave for a complete teardown and arse-kicking of the company for a piss-poor design and engineering. I wonder if it is even passing safety codes or if these things are being sold around the world by some underground network of distributors, or simply governments have no resources or interest in bothering with this stuff as it is lowest priority for them (like Dave's Apple charger teardown).

author: Legit-Design
author_rank: Frequent Contributor
timestamp: June 14, 2014, 11:36:29 am
content: Or just return the crap and never touch them again. If enough people return that crap maybe they will stop selling them. Crap is not worth touching. If you really want you will get one good cell out of it for some other projects. Ebay is full of working cheap battery banks with usb which you can add your own cells into.

author: amyk
author_rank: Super Contributor
timestamp: June 14, 2014, 11:59:04 am
content: Does the rest of the unit i.e. the cell get hot? I think it's just bad contact creating a high resistance. Try plugging in-and-out an unconnected plug a few times. If the device charges at e.g. 2A, even a 0.1 ohm resistance means 400mW dissipated in the contacts.

author: edy
author_rank: Super Contributor
timestamp: June 14, 2014, 01:55:50 pm
content: I can't tell if the cell gets hot... the entire thing is in a plastic housing. Only the metal ends I can touch (the micro USB) gets hot. I assume it is a component on the board attached on the end and NOT the batteries themselves.I will also have to test if this happens when charging a blue tooth earpiece, and iPhone. Perhaps blue tooth draws less power so it won't heat asmuch?

author: ConKbot
author_rank: Super Contributor
timestamp: June 14, 2014, 02:18:56 pm
content: I'd look into contact resistance also. I have a battery bank (easy ACC 12000mAh, tore one down, great build quality) And when I'm charging it with a 2A charger, the input usb gets warm (not that hot though, just warm) What is the output current for your battery pack? 0.5A 1A? 2A?

author: mcinque
author_rank: Unknown
timestamp: June 14, 2014, 04:44:49 pm
content: That's what I'm asking to myself why the hell I must go thru CE (or FCC) certification, studying EMC, ESD and related literature when who should supervise cares nothing about this sh*t products...

author: rob77
author_rank: Super Contributor
timestamp: June 14, 2014, 05:24:22 pm
content: Quote from: Legit-Design on June 14, 2014, 09:08:52 ambut then it have to have a step-up converter to make the 5V for the USB plug output. single 18650 cell is 3.7V - most of the devices wouldn't even start charging when connected to 3.7V.

author: edy
author_rank: Super Contributor
timestamp: June 14, 2014, 08:26:44 pm
content: I found some YouTube videos describing perhaps a similar charger. Mine looks a bit different case-wise, but the approximate shape is the same and the 2 USB ports at the end are the same (a standard USB and a micro USB). So I wonder if the inside also uses an 18650 Li-Ion rechargeable cell and a small IC that handles the rest, like here:PDF File of IC:http://escooter.org.ua/_fr/1/DW01A-DS-10_EN.pdfYouTube Videos:???: Portable Mobile Power Bank USB 18650 BatteryHere is my PowerBank:==================

author: edy
author_rank: Super Contributor
timestamp: June 14, 2014, 08:38:05 pm
content: I paid $20 for this thing from a local shop. Perhaps I should open it up and take a video, I don't mind destroying it. It may be worth the educational value... how NOT to design something or perhaps a call to enforce better control and safety. It seems you can get them for $3-5 shipped directly from Hong Kong via eBay all around the world, shipping included. All the retailers are stocking up their shelves by importers buying cases of these and nobody seems to be watching.I just found this link, unrelated company but perhaps a sign of more to come:http://news.asiaone.com/news/digital1/recall-power-banks-raises-concerns

author: ConKbot
author_rank: Super Contributor
timestamp: June 14, 2014, 09:46:14 pm
content: Quote from: rob77 on June 14, 2014, 05:24:22 pmAnd it charges from a 5v usb, which means you would have to have a boost converter for the 8.4v to charge a 2s lithium battery, so youre going to need one either way

author: rob77
author_rank: Super Contributor
timestamp: June 14, 2014, 09:56:11 pm
content: Quote from: ConKbot on June 14, 2014, 09:46:14 pmthat's correct, in one of the directions you need a boost converter, no doubts.the device in discussion produces excessive heat during powering some device through it's output. boost converters are not supposed to produce too much heat, therefore the assumption that there 2cells with a linear regulator (that would explain the excessive heat).in case of the cell producing the heat - the whole device would be warm/hot, but only the USB end is getting hot so apparently the electronics is producing the heat. probably it's an incredibly crappy boost converter with a single cell

author: sunnyhighway
author_rank: Frequent Contributor
timestamp: June 15, 2014, 01:01:22 pm
content: I can't believe nobody mentioned a piss poor soldering job on the USB connector as a probable cause.

author: edy
author_rank: Super Contributor
timestamp: June 27, 2014, 01:51:50 am
content: I tore open my power pack and have attached photos. I will write more about the components... please chime in on what is happening here. The 4R7 coil inductor is blazing hot. I will check the temperature of each device and see if I can figure out which is hottest.

author: edy
author_rank: Super Contributor
timestamp: June 27, 2014, 01:58:28 am
content: On one side I guess we have:SS24 - Schottky Barrier RectifierB628 - CMOS voltage detector2DLF -?4R7 - inductor coilAnd lots of resistors and 2 capacitorsOn the other side we have:DW01 - one cell LIPO battery protection IC8205A -?A couple resistors and a couple capacitors and a couple LEDs (under the USB)

author: XOIIO
author_rank: Super Contributor
timestamp: June 27, 2014, 01:59:44 am
content: Wait, is it just me or do those middle pins on the connector look like they are not even soldered? Sheesh.

author: edy
author_rank: Super Contributor
timestamp: June 27, 2014, 02:06:46 am
content: They wouldn't be soldered as they are data pins. The USB is only used for power in this case.Also I can't figure out what battery is being used... cannot find those numbers anywhere. Any ideas?

author: klr5205
author_rank: Regular Contributor
timestamp: June 27, 2014, 02:28:11 am
content: Even if they were no-connects I'd still expect them to be soldered... they just wouldn't be connected to any traces. I'm with XOIIO - Sheesh.

author: edy
author_rank: Super Contributor
timestamp: June 27, 2014, 02:40:07 am
content: Notice the PCB coating is still there under those pins so any reflow work would have nothing to solder to. There is no bare copper even available under those pins!I am also guessing the inductor is getting the hottest based on when I touch it, but maybe it is just because it has the most thermal mass.I don't know the voltage of the battery but the circuit would I assume step up the voltage to 5V from whatever the battery is (3.7v for Lipo?). I need to get out my CRO and probe around for fun!

author: XOIIO
author_rank: Super Contributor
timestamp: June 27, 2014, 02:55:48 am
content: Quote from: klr5205 on June 27, 2014, 02:28:11 amYeah. How much would you really save by doing that? They should at least be soldered for a bit more structural strength.

author: amyk
author_rank: Super Contributor
timestamp: June 27, 2014, 10:24:54 am
content: Here's the complete parts list I could gather from the pictures:R1 - 100R supply for DW01C1 - 0u1 supply for DW01R2 - current sense for DW01U1 -DW01lion protectorQ1 -8205Adual N-MOSFETU3 -XR1151boost converter.R5 - 20k pullup on enable pin of U3R8, R6(?) - 91k and 12k divider to set output of U3 (5.15V)U2 - unsure, it's a sot23-6 lion charger with 2 LED outputs, so probably something likeLP4061orHD7100or any of the many others with the same pinout...D1 -SS24 2A schottky diodeI guess the inductor is either saturating or underrated for the application - try pulling less current from it to see if it doesn't heat up as much.The bulk of the structural integrity of the USB connector comes from the soldering on the casing, so those small pins not being soldered won't make much difference.

author: XOIIO
author_rank: Super Contributor
timestamp: June 27, 2014, 11:26:13 am
content: Quote from: amyk on June 27, 2014, 10:24:54 amTrue but still just seems lazy, or maybe they saved half a cent doing that somehow.

author: ConKbot
author_rank: Super Contributor
timestamp: June 27, 2014, 11:37:23 am
content: Quote from: XOIIO on June 27, 2014, 11:26:13 amSeems lazy, but when there is only 6 solder joints on the board that will be done by hand (2 wires coming from the board, 2 on the housing of the usb, and the +5 and gnd lines of the usb) another 3 joints would be 50% more soldering for the assembly tech to doThough they could just blob the 4 pins on the left together since they are all connected to the same trace anyway, and that would be about as fast as doing one joint :p

author: edy
author_rank: Super Contributor
timestamp: June 27, 2014, 12:04:19 pm
content: I am charging a BlackBerry Z10... I will test with a Blue tooth earpiece and iPhone, and old phone which uses a smaller MA rated wall wart. The Z10 does best with a 2A charger.If you read the product info they say it is to charge your tablets like ipads which need 2A so this product is being used for what they are recommending for. They just cheapened out on something. If it can't handle the current draw for charging these larger devices it shouldn't be marketed for it. I still have no idea what battery capacity that is, as I cannot find anything on Google.Please note that during charging the battery using even a 2A wall wart, there is little heat produced. The burning hot reaction only occurs when the unit is being discharged to charge up my phone... so the boost conversion from what I assume to be a 3.7v Lipo to the 5A USB. I have to still check if the battery is a single cell or two in series. Based on what I read it looks like a switch mode power supply using the inductor and caps to boost up so should be a single Lipo. I don't know what the typical heat-source is in these types of circuits... the linear voltage reducers usually create heat in the resistors of the divider, but for switching supplies I don't know what typically heats the most.

author: edy
author_rank: Super Contributor
timestamp: July 05, 2014, 01:48:56 am
content: Quick update... I filled in and emailed an RMA to the company and received my replacement battery pack today! Let's see if it does the same thing! I still have the original, they didn't want it, just a copy of my receipt. So I can do a comparison video!

author: amyk
author_rank: Super Contributor
timestamp: July 05, 2014, 03:03:03 am
content: Note that according to the datasheet for the boost converter, the peak current is 2A and the recommended output diode is 2A but they suggest a target of 800mA for designs using it. Also, the efficiency will decrease the more current is drawn, meaning more power lost as heat within the circuit.

author: edy
author_rank: Super Contributor
timestamp: July 05, 2014, 04:41:28 pm
content: Thanks for reviewing the datasheet. Perhaps the company manufacturing these just re-purposed an existing design with lower current applications by changing some of the cheaper components, but did not bother with the more important parts. The unit is designed for 2600 mAh and I know my BlackBerry Z10 did not charge when I plugged it into their 1800 mAh version which is why I returned the 1800 mAh version to the store and then picked up the 2600 mAh one.This is strange in itself because as far as I know from various forums you can charge a BlackBerry Z10 with as little as 750 mA, and it will slowly charge even when plugged into my computer USB which theoretically should only give 500 mA. Perhaps I am confused about the units of measurement here because when it says 1800 mAh and 2600 mAh, I am assuming that it means these banks output 1.8 A and 2.6 A, respectively. However, the units are mA versus mAh... I don't believe we can just assume they mean the same thing. I will explain...For example, if a bank says it is 2000 mAh, that means it will let you draw 2000 mA for 1 hour? Or presumably if you connect a device that only needs 1000 mA of current, it will run for 2 hours (2h x 1000 mA = 2000 mAh). And if a device draws 4 amps, the bank will only last for 30 minutes???The standard battery LS-1 on a BlackBerry Z10 is a 1800 mAh. When I charge it up using the 2600 mAh battery pack, it will go from 0% only to about 60% maybe 70% tops. So where is all this extra energy going? Is it just turning my pocket into a small toaster oven?Given the 1800 mAh rating on the LS-1 BlackBerry battery, am I to assume that if I am getting about 10 hours use on average (from say 8am to 6pm before needing to charge up) then my phone is using about 180 mA per hour? Shouldn't this "2600 mAh" battery juice up the internal phone battery back to at least a full charge and have extra to spare?Perhaps there is a way I can measure and/or limit the current draw into the BlackBerry Z10? I have no idea what it is pulling in when I plug a charger into it. Any advice on how I can easily test it? Do I hook up my multimeter in series and let current pass through a modified USB cable that I have spliced into? Should I place a resistor in series inside the USB cable to limit the current? Maybe the heat generated in the resistor will be less than what is wasted if the battery bank is operating beyond it's efficient zone?

author: amyk
author_rank: Super Contributor
timestamp: July 06, 2014, 12:42:14 am
content: Quote from: edy on July 05, 2014, 04:41:28 pmYes, you're confusing the units of charge (mAh) with current (mA/A).QuoteThat is likely the capacity of the battery inside, and you're correct that abattery rated for 2000mAh will (approximately) contain enough energy to sustain a 2A discharge (also known as "1C") for 1 hour. In reality battery capacities may be specified at smaller discharge rates, and the Chinese like to overspec capacities anyway, so a "2600mAh" battery might have closer to 2000~2200mAh. Due to internal resistance, at higher discharge rates the effectivecapacity also decreases.Even good Japanese cells might be somewhat below advertised capacity.There's also a limit to the amount of current you can safely draw from the cell, usually 1-2C (e.g. 2600 ~ 5200mA for a 2.6Ah unit.)The other important part is the boost converter, which also has its own currentlimit. As most devices that charge from USB don't consume more than 500mA ~1A as per the specification, with some rarer ones up at 2A, it doesn't makeeconomic sense to use a boost converter that can supply more current than that.QuoteAlthough the charge/discharge process for lion batteries is highly efficient (that's why the cell itself doesn't heat up signifcantly), no system is 100% efficient and in this case the majority of the losses are in the circuitry between - the boost converter is probably not more than 80%, and the charger in the phone is likely of a linear type so it will also waste quite a bit of energy as heat. Don't forget that the other components e.g. the processor, display, RF amps, etc. are also drawing current during the charging process.QuoteYes.Quote

author: edy
author_rank: Super Contributor
timestamp: July 06, 2014, 01:43:05 am
content: Thanks for the clarification, that is what I thought.I conducted a few more tests... I used the battery bank to charge an iPhone 5s from about 50% up to full charge. I also used the battery bank to power some portable USB-powered laptop speakers.In both of these cases the battery bank got hot. It took a bit longer but still managed to get up there near the 78 degrees experienced when charging up my BlackBerry Z10. I think the issue then lies in the amount of current these devices are willing to accept during charging.... or the amount required.Given a chance, the phones will probably draw a large amount. The speakers wouldn't because they have a set internal resistance and will only take what they need. Both phones will also charge on a 1 A source but slower, but if you give it 2 A it will charge faster.Somehow the battery bank is not current limited or the limit is set to higher than the ideal efficiency level... so it overheats. I haven't tried to short the bank to see if maybe even it has no short protection, or it is defective. But given the chance to get up there the bank will keep pumping out current even if it means overheating.So again, heat is also generated to a burn on an iPhone 5s charge up, and burning hot on the BlackBerry Z10. Then again the iPhone has a 1560 mAh battery inside while BlackBerry has 1800 mAh. Could also be the charge circuits in the phones differ and they have different current limits based on the stage of charging. Either way we shouldn't be getting a USB port that measures 78 degrees C.UPDATE: The iPhone did not heat up as much... Only a short burst and then fairly cool running all the way up to 100% when I tried it several times. Looks like it has to do with the BlackBerry.

author: amyk
author_rank: Super Contributor
timestamp: July 06, 2014, 09:45:22 am
content: It's a very simple design; there is no current limit. However, USB devices aren't supposed to draw more than the spec allows.

author: edy
author_rank: Super Contributor
timestamp: July 06, 2014, 01:09:22 pm
content: I was suggesting to put my multimeter in the circuit to check the amperage being drawn... I should have a cable I can cut into and connect the ammeter in series. Someone I think said no to that suggestion... I can put my meter in the high amp mode, because on the regular setting it only goes up to about 200 MA and then blows a fuse.Couldn't that help me determine what is going on? I could compare the various devices to see what current they run at and if they vary with time as well.Any thoughts?

author: edy
author_rank: Super Contributor
timestamp: July 06, 2014, 09:08:38 pm
content: I've attached a profile of the charge as indicated by the phone settings. The first picture shows 12 hours... overnight plugged in wall, so started at 100% then drains through day and the last rise up to 50% is my 2600 mAh battery bank which overheats. It never got over 50% which is fairly poor performance.... probably so inefficient due to overheating.I decided to look back 24 hours... notice the second picture. the overnight charge curve when it is plugged into a mains plug rated at 750 mA is about the same slope as when it is plugged into the battery bank (the last rise on the curve to 50%). So am I to assume the phone is drawing the same current both times?Another question is can I easily limit the current capable of drawn out from the battery bank for example by placing a resistor (as you would for an LED) and if not, why?