Test/review of Tomo Power bank M2

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HKJ
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Test/review of Tomo Power bank M2

Tomo Power bank M2
DSC_9279
Official specifications:


  • Input: 5.0V/ 1A
  • Output: Dual USB: 5V/ 1A; 5V/ 2A
  • 2-in-1: 18650 Battery Charger + Smart Power Bank
  • Compatible Battery: 2 × 18650 battery (Not included)
  • Weight: 68g
  • Size: 130mm x 49mm x 25mm

I got it from Banggood
How does it look
DSC_9218 DSC_9219
The power bank is delivered in a cardboard box with a window and some specifications on the back.
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It contains the power bank, a usb cable and a “instruction sheet”.
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All connectors is placed at one end

  • Micro usb: Charge input.
  • 1A and 2A usb output.
  • Power on button.

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On the other end of the box is a display.
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There is no doubt when the power bank is turned on.
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This is the power status display,
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When charging a mains cord is shown to the left and the bars in the batteries are animated.
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When current is drawn the display will show voltage and current for each slot. The display will not indicate charging.
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The box do not include any batteries, it is up to the user to supply one or two batteries.
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 2.2mA
  • Power consumption from battery when on is 16mA
  • Power consumption from battery at 1.9V is 0.7mA
  • Limit for detecting current draw or not is about 45mA load on 2A usb and 60mA on 1A usb output.
  • The two 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 × 48.0 × 26.4mm
  • Weight: 52g (Accessories and batteries not included)

Tomo%20Power%20Bank%20M2%201A%20load%20sweep
The specification sheet says the box can deliver 1.5A on the 1A output, this is a bit optimistic, overload trips at 1.4A
Tomo%20Power%20Bank%20M2%202A%20load%20sweep
The 2A output is rated for 2.2A, but again the overload protection kick in a bit early at 2A and also a bit early for a 2.1A coding.
Tomo%20Power%20Bank%20M2%202A%20charging%20load%20sweep
The output looks the same with connected charge power.
Tomo%20Power%20Bank%20M2%20load%20sweep
Running both outputs in parallel gives slightly more current, but the current limit also works here.
Current
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.
Tomo%20Power%20Bank%20M2%20usb%20out%202A%2010ohm%20%28SA18650-33%29%20%231
Nice stable output voltage until the battery is about empty.
Tomo%20Power%20Bank%20M2%20usb%20out%202A%205ohm%20%28SA18650-33%29%20%231
AT higher current the output voltage is a bit lower, but again very stable until the battery is empty.
Tomo%20Power%20Bank%20M2%20usb%20out%202A%2010ohm%20%282xSA18650-33%29
Two batteries gives about double time.
Note: I am only measuring current and voltage on one battery.
Tomo%20Power%20Bank%20M2%20usb%20out%202A%205ohm%20%282xSA18650-33%29
Tomo%20Power%20Bank%20M2%20usb%20out%202A%202.5ohm%20%282xSA18650-33%29
At 2A the output voltage is fairly low, but stays stable until the batteries are empty.
10ohm
Noise is 8mV rms and 76mVpp
5ohm
Noise is 11mV rms and 85mVpp
2.5ohm
Noise is 16mV rms and 129mVpp, all noise values are very low.
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It uses a nice CC/CV charge algorithm, but do not really stop charging, instead it will pulse the current when the voltage drops slightly.
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The box will draw nearly 1A from usb when charging two batteries, this means about 0.4A for each battery.
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A 0.5ohm resistor in series with the usb supply to simulate a weak power supply or long cable do not prevent the box from charging at about the same speed.
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 on each port
  • Fairly low noise
  • Over load protection
  • Easy battery replacement, i.e. 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.
I will rate it as fairly good.
Notes
The power bank was supplied by Banggood for a review.
Read more about how I test USB power supplies and chargers

My website with reviews of many chargers and batteries (More than 1000): https://lygte-info.dk/

The Miller
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Thanks
The price is decent last time I saw it, good to know it is not a bad thing Wink

texas shooter
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Nice review. Can it be recharging while it is charging other items? I often use a power bank to quickly charge items while leaving it plugged into the USB to itself recharge at the lower .5amp rate.

HKJ
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texas shooter wrote:
Nice review. Can it be recharging while it is charging other items? I often use a power bank to quickly charge items while leaving it plugged into the USB to itself recharge at the lower .5amp rate.

Yes, but it depends on how much current you draw from it.

My website with reviews of many chargers and batteries (More than 1000): https://lygte-info.dk/

texas shooter
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HKJ wrote:
texas shooter wrote:
Nice review. Can it be recharging while it is charging other items? I often use a power bank to quickly charge items while leaving it plugged into the USB to itself recharge at the lower .5amp rate.

Yes, but it depends on how much current you draw from it.

Scary Ninja fast response! Thanks. Since most of us have more batteries than we know what to do with. The Power bank/battery charger is probably the best idea going. I really like the 2-4 cell line up from Tomo. Could you do more reviews of this style using loose cells?

Thanks again, Paul

HKJ
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texas shooter wrote:
Could you do more reviews of this style using loose cells?

I am also working on a 4 cell Tomo, but it will be some time before I publish that, I have a few other power bank reviews I need to publish first.

My website with reviews of many chargers and batteries (More than 1000): https://lygte-info.dk/

EasyB
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The two slots in this power bank are independent apparently. How does it handle two cells that have different voltages while charging or discharging to the USB output? In another power bank you tested it only charged/discharged one cell at a time and just switched between them. But this one doesn’t seem to have that behavior. Thanks.

jimahi
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Is it safe to use unprotected cells in it (LVP)? I’m guessing the answer is no if it draws 0.7mA from a battery at 1.9v

EasyB
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jimahi wrote:
Is it safe to use unprotected cells in it (LVP)? I’m guessing the answer is no if it draws 0.7mA from a battery at 1.9v

The power bank will stop discharge when the cell reaches ~3.2V, so it does have LVP. But you’re right there is still a small parasitic drain so you can’t leave cells in there and just forget about it for months. Most power banks have some parasitic drain.

HKJ
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EasyB wrote:
The two slots in this power bank are independent apparently. How does it handle two cells that have different voltages while charging or discharging to the USB output? In another power bank you tested it only charged/discharged one cell at a time and just switched between them. But this one doesn’t seem to have that behavior. Thanks.

It uses from the cell with highest voltage first and it is independent charge circuits for each cell.
In my review of M4 I do open it up and take a look at the circuit: http://lygte-info.dk/review/Review%20USB%20battery%20box%20Tomo%20M4%20U...

jimahi wrote:
Is it safe to use unprotected cells in it (LVP)? I’m guessing the answer is no if it draws 0.7mA from a battery at 1.9v

Depends. It will turn off output when the cells are discharged, but the standby drain will damage the cell if you leave it discharged for some time.

My website with reviews of many chargers and batteries (More than 1000): https://lygte-info.dk/

EasyB
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HKJ wrote:

It uses from the cell with highest voltage first and it is independent charge circuits for each cell.
In my review of M4 I do open it up and take a look at the circuit: http://lygte-info.dk/review/Review%20USB%20battery%20box%20Tomo%20M4%20U...

So it switches between the (balanced) cells quickly as they discharge? In your test with 2×18650 you measure the current and voltage of just one cell, and the curve looks very smooth.

Just bought one of these power banks along with a couple more Lii 100 chargers from gearbest.

HKJ
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EasyB wrote:

So it switches between the (balanced) cells quickly as they discharge? In your test with 2×18650 you measure the current and voltage of just one cell, and the curve looks very smooth.

Just bought one of these power banks along with a couple more Lii 100 chargers from gearbest.

Switches may be the wrong work, it opens up for the cells when the voltage is the same. Because I started with two full cells they where both uses simultaneous.

My website with reviews of many chargers and batteries (More than 1000): https://lygte-info.dk/

EasyB
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I think I understand now, thanks.

EasyB
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Just got my M2 powerbank. I’m satisfied with the overall apparent build quality. It seems to work fine. The cell capacity meter is a little odd/inaccurate. I measured the following:

5 bars: >3.87V
4 bars: 3.74V-3.87V
3 bars: 3.54V-3.74V
2 bars: —-
1 bar: 3.05V-3.54V
0 bars: <3.05V

I first was testing with a power supply with 0.1V resolution and it went right from 3 bars to 1 bar. I then made a voltage divider with an adjustable resistor to get finer resolution and I was still not able to get 2 bars. So, it roughly works; the 4 to 3 bar transition means you have approximately 50% left, and the 3 to 1 bar transition means you have approximately 25% capacity left (with a sanyo GA cell).

EasyB
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I just noticed a peculiarity. While the powerbank is outputting current a not-very-hard tap to the end with the ports causes a restart. This doesn’t happen when the powerbank is on but not outputting current.

SIGShooter
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This powerbank has reverse polarity protection as my daughter found out when she put in one of the batteries backwards and then tried to charge them. The one that was reversed showed as empty while the other one showed the correct charge state. However neither charged when connected to a USB charger which is a good thing in my opinion.

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ChrisGarrett
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I have the Tomo V8 and just leave the cells out of it until I need it.

I guess it works as intended.

Chris

avt
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What’s the difference between the M2 and the V8 – 2 ? Are they newer and older versions? GearBest even has them at different prices, and the V8 is more expensive. They appear similar though.
angerdan
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I have a TOMO K2 coming someday. Looking to replace my XTAR PB2 which didn’t work out well.

….Looks like it made it here, to San Francisco ISC anyway

Danglerb
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I“ve had a M2 for a month or so, put in good new cells, and it seems to work fine, BUT I notice the green back light is often on with nothing connected just sitting on the desk. A few seconds and it says poweroff and goes dark, but later I see it back on again..

Still a bit dim

avt
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That’s the V8-4. Apparently it’s an older version of the M4, also small difference in size. But, i’m talking about the V8-2, which could also be discontinued, but it’s still sold in a few places.