Powerbank with dummy batteries

Preamble

A friend gave me an Eloop E10 powerbank to look at, as the USB (A) and USB Micro connectors had slipped out of place.

Investigation

This looked like it would be a simple job of opening the case and repositioning the two USB connectors flush with the casing.

Upon carefully cracking open the case, we discovered that it contained three 18650 Li-Ion batteries (One was a lilac colour an the other two were off pink).


However, only one of the batteries (the lilac battery) was actually connected to the charging circuit.


The remaining two 18650 batteries seemed to be employed purely for bulk and weight purposes… I wonder if they were defective and just included in the case to make it seem more substantial than it really was.


I connected the charging circuit (via the USB Mini to an iPhone charger. The red light came on, and is appeared to charge. A while later, the red light had gone out and I assumed that the battery was charged.

Upon connecting an iPhone thunderbolt connector, and then an iPhone 5, the SMD IC started to smoke and melt, I quickly unplugged the iPhone. The IC was fried and hot. I reconnected it to the iPhone charger. No LED, and the IC got very hot. The IC, and hence the charging PCB seemed to be, effectively, dead.

The damage can be seen below, with visible melting of the top of the IC. Note that the SS14 IC (Surface Mount Schottky Barrier Rectifier, Datasheet, PDF: ss12) was fine. The capacitor  (immediately above the 8 pin IC – towards the USB connector) showed some signs of burning on one of the solder pads (the upper solder pad), althogh it is not clear if the capacitor itself is damaged:

Damaged components
Damaged components

Now, I am not sure why the IC melted as it did not appear to be shorted up against anything. Maybe one of the corners had been touching one of the dummy batteries contacts, but as they did not form part of the circuit, it should not have mattered.

It was interesting to note that the IC remained very warm/hot to the touch, when not connected to the charger, nor iPhone.

Repair

I thought, that it would be a simple job to just replace the PCB charging circuit.

Now, the charging circuits appear to be ten to the penny on eBay, or more precisely two for £1.00, see here: 2PCS MICRO USB 1A Battery Charging Module TP4056 Precise NEW.  However, the PCB is not the same as the one in the E10 powerbank, it seems to be lacking the inductor, and it also lacks the all important USB A connector, to which the iPhone charging cable to the phone would be connected.

I also thought about just replacing the SMD IC. These ten for a £1.00 on eBay, 10pcs TP4056 SOP-8 TP Chips For Battery Charging Board Charger Module. However, the IC on the PCB is not a TP4056.  Unfortunately, the melting of the IC has obscured the etching on the surface. The only visible etchings were:

Top of IC

FM6316FE

Alternatively:

  • FH6316FE
  • EK6316FE
  • FX6316FE
  • 5U6316FE
  • 5116316FE

Bottom of IC

XXXX49.1K3

Rear of PCB

HKS-XS-828FE 20160623 (Serial number and date)

Now maybe a TP4056 would suffice, I don’t know, but I doubt it. A quick google, will show that there are a number of IC suppliers for battery charging ICs:

After correctly identifying the SMD IC as a FM6316FE (by just googling the visible 6316FE and seeing what came up), I then found the datasheet, (PDF: FM6316FE-FUMAN ELECTRONICS), which is in Chinese (unfortunately), but it does provide a PCB layout. See also, FM6316FE Datasheet PDF ETC (PDF: pdf-ETC-846782):

FM6316FE
FM6316FE

FM6316FE is applied to a mobile power, integrated lithium battery charge management, DC-DC step-up and load detection in one portable power Source management IC.

FM6316FE integrated include trickle charge, constant current and constant voltage charging charging charge of the whole process, and contains the end of the charging process and charging status indicator Lamp; charge current is programmed by an external resistor; the system will be shut down in the charged state output discharge path; when the external input power removed, FM6316FE to an external device powered by the battery, if the external device is not detected the access, the system enters the standby state, the standby current of the entire system 16uA.

I was unable to find the IC on eBay, but it is available on AliExpress: FM6316FE, $1.50-$1.80 for 10.

I was able to find the PCB on eBay, Lithium battery microUSB charge, 5V USB step up, all-in-one PCB board, $2.48 + $0.99 (p + p).

Description:

This PCB can step up a lithium ion battery to 5V for output to 5V devices. Normal USB output.
Just connect a lithium ion battery to the battery input source.
This PCB also support charging the battery. Simply supply a 5V source to the charging input (MicroUSB) and it will charge the connected battery to 4.2V.
Great for mobile power source using Lithium ion batteries
Connect multiple batteries to the battery input to increase the capacity power capacity

Never reverse the battery connection polarity.
Control IC: FM6316

Specifications:

  • Charging voltage input: 4.25V-6V 500mA
  • Stepup voltage output: 5.0V 350-450mA (max 450mA) Higher output current version 
  • 38mmX10mmX4mm
  • Operating temperature -40C to 85C

This device, while close and cheaper, 5V Lithium Battery Charging Protection Board Charger Boost Step Up Module 1A, $0.99, is not quite the same:

Similar PCB
Similar PCB

It is missing the second SMD IC SS14 (Surface Mount Schottky Barrier Rectifier, Datasheet, PDF: ss12), and it is not definitely using the 6316.

USB and Micro USB 5V Step-Up Module Boost Converter Battery Charging Protection For DIY Charger

Product Introduction:

  • Input Voltage:3.7V~5.5V
  • Charging Current:1A(max)
  • Output Current:1A(max)
  • Output voltage:5V
  • BAT Discharging Stop Voltage:2.9V
  • Discharging Efficiency:85%(input 3.7V output 5V/1A)

Features:

  1. Charging and discharging indication
  2. Internally installed charging and discharging power MOS
  3. Preset 4.2V charging voltage, precision ±1%
  4. Max 8uA standby current
  5. Integration charging management and discharging management
  6. Intelligent temperature control and overtemperature protection
  7. Integration output overvoltage protection,short coircuit protection,overload protection
  8. Integration overcharging and overdischarging protection
  9. Support trickle mode and zero voltage charging

For less, there is 2x-5V-Step-Up-Module-Boost-Converter-Battery-Charging-Protection-Lithium-Charger, two pieces for $1.40

One device using the TP5400, 5V Lithium Battery Charger Step Up Protection Board Boost Power Module Micro USB, $1.57

TP5400 Dual USB (A and micro)
TP5400 Dual USB (A and micro)

This device, one of the charger PCBs from 5V Lithium Battery Charging Board Boost Micro USB For 18650 Battery, shows a similar PCB ID code (HKS-MT-882 (the last number (2015-05-05)is the date of manufacture):

Similar PCB Serial number
Similar PCB Serial number

Additional Information

A great guide, from Digikey, A Designer’s Guide to Lithium (Li-ion) Battery Charging.

Videos

Not really related to the FM6316FE, there are two great videos for Julian Illet, which I have talked about before, see Building a Lithium battery charger:

Using the FM6316FE, there is this Power bank charging speed-up hack, which increases charging current from 580 mA to 1000 mA:

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