Test/review of Tomo Power bank M4

EDC Gear for Flashlight Carriers USB Power Devices
1

Tomo Power bank M4







Official specifications:

  • Input: 5V / 1.2A

  • Output: 5V / 1A, 2A

  • 2-in-1: 18650 Battery Charger + Smart Power Bank

  • Compatible Battery: 4 x 18650 battery (Not included)

  • Weight: 86g

  • Size: 10.00 x 8.40 x 2.70 cm / 3.94 x 3.31 x 1.06 inches


I got it from Gearbest

How does it look



The power bank is delivered in a cardboard box with a window and some specifications on the back.



It exist in black and in white.



It contains the power bank, a usb cable and a “instruction sheet”.



All connectors is placed at one end

  • Micro usb: Charge input.

  • 1A and 2A usb output.

  • Power on button.





On the other end of the box is a display.



When current is drawn the display will show voltage and current for each slot. The display will not indicate charging.



When charging a mains cord is shown to the left and the bars in the batteries are animated.





The box do not include any batteries, it is up to the user to supply them.
The length of the batteries can be from about 58mm to 69mm.



Measurements

  • Usb output 1A is coded as usb charger (DCP)

  • Usb output 2A is coded as Apple 2.1A

  • Power consumption from battery when off is 3.5mA

  • Power consumption from battery when on is 21mA

  • Power consumption from battery at 1.9V is 1.5mA

  • Limit for detecting current draw or not is about 65mA load on 2A usb and 65mA on 1A usb output.

  • The four battery slots are independent, i.e. no problem mixing full and empty batteries.

  • It is possible to use both outputs simultaneous, but the total current is only 2A, this is enforced.

  • Can be used as UPS

  • Size: 100 x 83.6 x 26.4mm

  • Weight: 87.7g (Accessories and batteries not included)





The 1A output can deliver nearly 1.4A before shutting down.



The 2A output can deliver 2A, but not the coded 2.1A



The current limit is not changed when charging.



At 0.5A load on the 1A output with a single cell in the power bank the curve looks fine.



Same with a 1A load.



The 2A output with a 1A load from a single cell.



With 4 cell the runtime is more than 4 times longer, here at 0.5A load.
Note: Current measurement is only for one cell.



And at 1A load.



At 2A load the boost converter has trouble when the batteries are about empty. This killed the power bank.



The current display is not a precision meter, but it will easily show if the connected device is charging and give a very good idea on how fast charging is.



Noise is 16mV rms and 159mVpp



Noise is 24mV rms and 227mVpp



Noise is 26mV rms and 335mVpp, all noise values are fairly very low.



Charging is with a CC/CV voltage charge curve.
Note: Current measurement is only for one cell.



A 0.5ohm in series with the power supply to simulate a long cable or weak power supply will slow down the charging, but not that much.


Tear down

With the power bank dead I decided to take a look inside.



The box was clipped together and could be opened without too much trouble.



There is a lot of electronic inside, lets take a closer look at it.
On each side of the display is a dual mosfet (Q3 & Q4) together with dual comparators (U9 & U10: LM393), this is the circuit that is used to select what battery that has to deliver power onto the internal power bus. This power bus can also get power from the usb input via a diode (D2), i.e. if the usb input voltage is a diode drop higher than battery voltage it will supply the boost converter.
Close to the display flat cable connection is a transistor (Q2) to control the backlight .
There is four linear charge ic’s (U1, U2, U3, U4), one for each battery.
In the center of the board is the microcontroller (U8:PIC16F1933), it has build-in LCD controller, ADC and lot of other stuff. The display must have a build in controller, the controller in the mcu is too small for this display.
The boost converter is one IC with rectification build in (U6: G5177C) and a inductor (L1).
Near the usb connectors is a dual transistor (Q5) to shut down the outputs and two resistors for current measurements (R41 0.05ohm & R42 0.1ohm). It looks like the ADC (Inside the microcontroller) has lowest range at 1V and I cannot see any amplification, this means the current measurement is only using 10% of the ADC range.



Only usb connectors, switch and battery connections on this side of the circuit board.







The LCD is controlled directly from the microprocessor, the red and black wires are used for a backlight module mounted on the back of the display.




Conclusion

This power bank has many good details:

  • Long battery slot, i.e. can handle some protected batteries.

  • Can be used as UPS

  • Independent slots

  • The display with current for each port

  • Overload protection

  • Easy battery replacement, this makes it possible carry spare batteries or use it as 18650 charger.


But the standby current is a bit on the high side, i.e. the batteries has to be charged every few months even when not using it. I would also have like a bit more current on the 2A port and auto coding.

It looks like this type of power bank has problems with delivering full power for long time: they die.

I will rate it as acceptable.



Notes

The power bank was supplied by Gearbest for a review.

Read more about how I test USB power supplies and chargers
2

Thank you for this review. I have three of the original version of this charger. And love them. I’ve put one through the ringer. I take to work with me. Its taken a beaten of you saw it in a recycle bin you wouldn’t even take it. Been dropped, plastic has chemical burns on it industrial bug repellant leaked in my bag and ate away at the plastic. I have to charge the batteries seperarly but these are great if you have piles of laptop pulls or tons of cells. The other two work around the house. I’d like to see a 2 amp charge rate. Instead of one amp.

I did have one die on me after one week of use, but imrbatteries took care of me in no time on it. I recommend if you want a cheap power bank you can swap cells on the go with. I’m not sure about the this new version. But the old one can take protected pana b. Its a tight fit but they fit and work.

3

Thanks for the review mate!

We can now call you HKJ the power bank killer :stuck_out_tongue:

4

My score is 3 for this year, two that could not handle maximum current and one that died at very low current.

5

So, how does this compare to the TLIFE?
Is there a difference in build quality, components?

6

Thanks a lot for the review. Looks just as bad as I have experienced. I don’t like how low the output voltage drops under load.

Also, if you happen to use this heap of mediocrity, you should never load the power bank with only one 18650. It heats up very much when discharged. Even with four batteries the efficiency is quite bad, I got 31.8 Wh out of four 18650GAs, which is about 67 %.

Just get a good 10000 mAh power bank like a Xiaomi, which is not only smaller but better in every way.

The only saving grace of the Tomo is that it’s very cheap and there’s not many like it.

7

I have the Tomo version of this power bank, and as said in the comment above the efficiency seems quite low a lot of power wasted as heat and not much getting into your phone/tablet.

The Xiaomi 10.000mah seems to be sold out on a lot of sites, It must be popular, Though i prefer power banks i can change the battery`s once the die.

John.

8

Thanks for the review.

I am not that familiar with these power banks other than the fact that several[3] could not take your test! :wink:

9

I have had 2 battery charger`s go bang from new, and another just die while charging so it must be catching.

John.

10

I like my Tomo Original very.

I don’t mind the low efficiency because you can recharge the bank and have infinite energy supply this way

11

The Tomo may not be perfect, but it have some advantages:

  1. Display of current
  2. Easy replacement of batteries (This makes it easy to carry spare batteries).

I do not use it because I want auto coding and preferable Quick Charge and I do not want to carry spare 18650 cells (Except two for my lights). This is personal choices and other people may have other preferences.

12

So what’s the difference between Tomo M4 and TLife TC-01 ?

13

The charge circuit must be different, but the boost converter looks to be about the same.

14

Just returned from a 3 week trip during which, what could go wrong did.

Butt I must say that my TOMO M4 worked as expected on my MP3 player, LG smartphone, a couple flashlights (Nitecore TIP, Astrolux S42), and provided extra 18650 batteries (and/or charging) for my Nitecore MH20GT. A single channel charger (XTAR in my case) powered by the TOMO covers most all my battery needs.

AA/AAA is another animal. Wish they would evolve.

15

I have TOMO S4 i accidentally connected its output terminal to input, now its not charging.

16

Just wondering, which is better: Tomo M4, T4 or S4?

17

SHOP - TOMO or SHOP - TOMO

18

What's the runtime of the powerbank when i connect a consumer with 0.5A?

I've got an USB fan, and i am going to

19

Depends on the capacity of the cells you put into the TOMO M4.

4x 3000mAh for example give you 44Wh capacity. A 0.5A fan needs 2.5W.
With the conversion losses the fan would run around 13 hours.

20

thanks @angerdan !

it's this graph, right?


With 4 cell the runtime is more than 4 times longer, here at 0.5A load.
Note: Current measurement is only for one cell.

I've got some old 4xNCR18650B for the test. Before going to bed, i'll pause the test, remove the batteries. I've got an omnicharge 4x18650B too, so i should do a runtime test with it too. Sounds like fair game. We will expect that the omnicharge has a longer runtime.